Motor Protection

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Application                               12/2
SIPROTEC 4 7SK80 Motor Protection Relay   12/9

                 12 Motor Protection


     Comprehensive motor protection func-
     tions are available in our overcurrent relays
     and in the machine protection units. No
     separate relay family is required for this ap-
     The examples in part 2 illustrate that relay
     selection depends on the type and size of
     the motor and on the protection functions
     required (see Fig. 2/60 to 2/63).
     The following table shows which motor
     protection functions are available in the
     different relays (partly, functions are op-

                                                      Fig. 12/1

                                                      Fault                               Protection                              ANSI No.
                                                      Stator thermal overload             Stator thermal overload protection      49
                                                      Rotor thermal overload during       2 protection principles for the rotor
                                                      start                               overload protection
                                                         too long or blocked                 Motor starting time supervision      48
                                                         too frequent                        Restart inhibit                      66, 49R
                                                      Earth fault (ground fault)          Earth-fault protection                  50G, 64G, 67G
                                                                                          (I0>; V0>;<(V0, I0))
                                                      Short-circuit                       Overcurrent-time protection             50, 51
                                                                                          Current differential protection         87
                                                      Loss of phase                       Negative-sequence protection (I2/IN)    46
                                                      Bearing overload                    Temperature monitoring                  38
                                                      Overheating of plant on             Undercurrent protection                 37, 32U
                                                      unloaded drivers                    active-power protection (P<)
                                                      (pumps, compressors)
                                                      Undervoltage                        Undervoltage protection                 27
                                                      (starting torque not reached
                                                      M ≈ V2 or start too long)
12                                                    Asynchronous operation              Underexcitation protection              40
                                                      (of an asynchronous motor)
                                                      Sudden high mechanical load         Load jam protection                     51M

                                                      Protection functions for various types of motor faults

     12/2                                                                                                                              Siemens SIP · 2008
                                                                                           12 Motor Protection

















                     Protection functions
                     Stator overload protection         49         n         n         n       n        n        n         n          n
                     Starting time supervision          48         n         n         n       n        n        n         n          n
                     Locked-rotor protection            48         n         n         n       n        n        n         n          n
                     Restart                            66,                  n         n       n        n        n         n          n
                     inhibit                            49R
                     Load jam protection                51M        –         –         n       n        n        n *)      –          –
                     Earth-fault protection
                     non-directional                    64G                  n         n                n        n         n          n
                                                        50G        n         n         n       n        n        n         n          n
                     directional                        67G                  n         n                n        n         n          n
                     Overcurrent-time protection        50, 51     n         n         n       n        n        n         n          n
                     Current differential protection    87                                                                            n
                     Negative-sequence protection       46         n         n         n       n        n        n         n          n
                     Temperature monitoring             38                   n         n                n        n         n          n
                     (via thermo-box)
                     Undercurrent protection            37                   n         n       n        n        n         n          n
                     Active-power protection (P<)       32U (37)                       n                n        n *)      n          n
                     Undervoltage protection            27                             n                n        n         n          n
                     Underexcitation protection         40                                                                 n          n
                     Frequency protection               81                             n                n        n         n          n
                     Breaker-failure protection         50BF                 n         n       n        n        n         n          n
                     Freely programmable logic (PLC)                                   n       n        n        n         n          n
                     Control functions                             n         n         n       n        n        n         n          n
                     Measuring transducers                                                                       n                    n
                     Flexible interfaces                           –         1         2       2        2        2/3       2          3
                     *) 7SJ64 only
                     Scope of motor protection functions provided by SIPROTEC devices


Siemens SIP · 2008                                                                                                                        12/3
                12 Motor Protection

      Selection table                 Asynchronous motor                                 Synchronous motor

                                      100 kW - 500 kW                                    < 2 MW
                                      7SJ60                 7SJ61 or 7SK80               7UM61
                                      Basic device          + more I/Os                  (Option:
                                                            + control functions          Generator Basic)
                                                            + flexible interfaces
                                                            + better local HMI
                                                              (larger display; digital

                                      500 kW - (1-2) MW                                  < 10 MW
                                      7SJ62 or 7SK80        7UM61                        7UM62
                                      Basic device          + more I/Os (7UM612)         (Option:
                                      + control functions   + control functions          Generator Basic)
                                                            + high accuracy
                                                            + high sensitivity
                                                            + operating range in a
                                                              wide frequency band
                                                              (11 Hz - 68 Hz)

                                      or with control functions via
                                      bay mimic diagram in graphic display

                                      7SJ63                 7SJ64
                                      Basic device          + synchro-check function
                                                            + high sensitivity
                                                            + extensive control func-
                                                            + 1 serial interface more

                                      > 2 MW                                             > 10 MW
                                                            7UM62                                           + 7UM61
                                                            + differential protection                         (Option:
                                                            + control functions                               Generator Basic)
                                                            + high accuracy              7UM62                or with control functions
                                                            + high sensitivity           (Option:             via bay mimic diagram in
                                                            + operating range in a       Generator Basic)     graphic display
                                                              wide frequency band
                                                              (11 Hz - 68 Hz)                                 7SJ64
                                                                                                              Maximum functionality
                                                                                                              + synchro-check)


     12/4                                                                                                            Siemens SIP · 2008
                                                            12 Motor Protection


Application example:
Protection of a small motor 100 kW - 500 kW
l Stator thermal overload protection   49
l Starting time supervision            48
l Earth(ground)-fault protection       50G
l Overcurrent-time protection          50, 51
l Negative-sequence protection         46

                                                Fig. 12/2


Siemens SIP · 2008                                                                12/5
                12 Motor Protection


     Application example:
     Protection of a small motor 100 kW - 500 kW
     in isolated or compensated systems
     l Overcurrent-time protection          50, 51
     l Sensitive earth (ground) fault       50G
       (non-directional,                    64G
       directional)                         67G
     l Negative-sequence protection         46
     l Stator thermal overload protection   49
     l Restart inhibit (rotor protection)   66, 49R
     l Starting time supervision            48
     l Undercurrent protection              37
     l Breaker-failure protection           50BF
     l Temperature monitoring either        38
       internally (max. 5 RTD-inputs)
       or externally via RTD-boxes
       (max. 12 RTD-inputs)
     l Load jam protection                  51M

                                                      Fig. 12/3


     12/6                                                         Siemens SIP · 2008
                                                             12 Motor Protection


Application example:
Protection of a medium-sized motor
500 kW - (1-2) MW
l Stator thermal overload protection   49
l Restart inhibit

  (rotor protection)                   66, 49R
l Starting time supervision            48
l Earth-fault protection               50G
  (non-directional,                    64G
  directional)                         67G
l Overcurrent-time protection          50, 51
l Negative-sequence protection         46
l Undervoltage protection              27
l Undercurrent protection              37
l Breaker-failure protection           50BF
l External temperature monitoring      38
  box (RTD-box)
  7SK80 offers alternatively an
  internal card with up to
  5 RTD-inputs
l Load jam protection                  51M1)

                                                 Fig. 12/4


1) not for 7SJ63

Siemens SIP · 2008                                                                 12/7
                12 Motor Protection


     Application example:
     Protection of a large motor > 2 MW
     l Stator thermal overload protection   49
     l Restart inhibit

       (rotor protection)                   66, 49R
     l Starting time supervision            48
     l Earth-fault protection               50G
       (non-directional,                    64G
       directional)                         67G
     l Differential protection              87M
     l Overcurrent-time protection          50, 51
     l Negative-sequence protection         46
     l Undervoltage protection              27
     l Undercurrent protection              37
     l Active-power protection              32U
     l Frequency protection                 81
     l Breaker-failure protection           50BF


                                                      Fig. 12/5

     12/8                                                         Siemens SIP · 2008
                                                                                                                   12 Motor Protection / 7SK80

SIPROTEC Compact 7SK80
Motor Protection Relay
                                                                                                            Function overview

                                                                                                           Protection functions
                                                                                                           • Time-overcurrent protection
                                                                                                             (50, 50N, 51, 51N)
                                                                                                           • Directional overcurrent protection, ground
                                                                                                           • Sensitive dir./non-dir. ground-fault
                                                                                                             detection (50Ns, 67Ns)
                                                                                                           • Displacement voltage (64)
                                                                                                           • Inrush restraint
                                                                                                           • Motor protection
                                                                                                             – Undercurrent monitoring (37)

                                                                                                             – Starting time supervision (48)
                                                                                                             – Restart inhibit (66/86)
                                                                                                             – Locked rotor (14)
                                                                                                             – Load jam protection (51M)
                                                                                                           • Overload protection (49)
                                                    Fig. 12/6                                              • Temperature monitoring
                                                    SIPROTEC 7SK80                                         • Under-/overvoltage protection (27/59)
                                                    motor protection relay                                 • Under-/overfrequency protection (81O/U)
                                                                                                           • Breaker failure protection (50BF)
                                                                                                           • Phase unbalance or negative-sequence
                                                                                                             protection (46)
                                                          Highlights                                       • Phase-sequence monitoring (47)
 Description                                                                                               • Lockout (86)
                                                          Removable current and voltage terminals
The SIPROTEC Compact 7SK80 is a multi-                                                                     Control functions/programmable logic
                                                          provide the ideal solution for fast and
functional motor protection relay. It is de-              secure replacement of relays.                    • Commands for the ctrl. of CB, disconnect
signed for asynchronous induction-type                                                                       switches (isolators/isolating switches)
motors of all sizes. The relays have all the              Binary input thresholds and current taps         • Control through keyboard, binary
functionality to be applied as a backup relay             are software settings. There is thus no need       inputs, DIGSI 4 or SCADA system
to a transformer differential relay.                      to ever open the relay to adapt the hardware     • User-defined PLC logic with CFC
                                                          configuration to a specific application.           (e.g. interl.)
The 7SK80 features “flexible protection
                                                          The relay provides 9 programmable func-          Monitoring functions
functions”. 20 additional protection func-
tions can be created by the user. For exam-               tion keys that can be used to replace push-      • Operational measured values V, I, f
ple, a rate of change of frequency function               buttons, select switches and control switches.   • Energy metering values Wp, Wq
or a reverse power function can be created.                                                                • Circuit-breaker wear monitoring
                                                          The battery for event and fault recording        • Minimum and maximum values
The relay provides circuit-breaker control,               memory can be exchanged from the front           • Trip circuit supervision
additional primary switching devices                      of the relay.                                    • Fuse failure monitor
(grounding switches, transfer switches and                The relay is available with IEC 61850 for        • 8 oscillographic fault records
isolating switches) can also be controlled                incredible cost savings in applications (e.g.    • Motor statistics
from the relay. Automation or PLC logic                   transfer schemes with synch-check, bus           Communication interfaces
functionality is also implemented in the                  interlocking and load shedding schemes).         • System/service interface                     12
relay. The integrated programmable logic                                                                     – IEC 61850
(CFC) allows the user to add own func-                    This compact relay provides protection,
                                                                                                             – IEC 60870-5-103
tions, e.g. for the automation of switch-                 control, metering and PLC logic functional-
                                                                                                             – PROFIBUS-DP
gear (including: low voltage starting, auto-              ity. Secure and easy to use one page matrix
                                                                                                             – DNP 3.0
matic restart, interlocking, transfer and                 IO programming is now a standard feature.
                                                                                                             – MODBUS RTU
load shedding schemes). The user is also                  The housing creates a sealed dust proof          • Ethernet interface for DIGSI 4
allowed to generate user-defined messages.                environment for the relay internal elec-         • USB front interface for DIGSI 4
The communication module is independ-                     tronics. Heat build up is dissipated through     Hardware
ent from the protection. It can easily be                 the surface area of the steel enclosure. No      • 4 current transformers
exchanged or upgraded to future commu-                    dusty or corrosive air can be circulated         • 0/3 voltage transformers
nication protocols.                                       over the electronic components. The relay        • 3/7 binary inputs (thresholds
                                                          thus will maintain its tested insulation           configurable using software)
                                                          characteristic standards per IEC, IEEE,          • 5/8 binary outputs (2 changeover/
                                                          even if deployed in harsh environment.             Form C contacts)
                                                                                                           • 0/5 RTD inputs
                                                                                                           • 1 live-status contact
                                                                                                           • Pluggable current and voltage terminals

Siemens SIP · 2008                                                                                                                                12/9
               12 Motor Protection / 7SK80


     Fig. 12/7 Function diagram

     The SIPROTEC Compact 7SK80 unit is a            Line protection                                Reporting
     numerical protection relay that can perform     The 7SK80 units can be used for line pro-      The storage of event logs, trip logs, fault
     control and monitoring functions and            tection of high and medium-voltage net-        records and statistics documents are stored
     therefore provide the user with a cost-effec-   works with grounded, low-resistance            in the relay to provide the user or operator
     tive platform for asset protection, monitor-    grounded, isolated or a compensated            all the key data required to operate modern
     ing and management, that ensures reliable       neutral point.                                 substations.
     supply of electrical power to the motors or
     other plant assets. The ergonomic design        Motor protection                               Switchgear cubicles for
     makes control easy from the relay front                                                        high/medium voltage
     panel. A large, easy-to-read display was a      The 7SK80 relay is specifically designed
     key design factor.                              to protect induction-type asynchronous         All units are designed specifically to meet
                                                     motors.                                        the requirements of high/medium-voltage
     Control                                                                                        applications.
                                                     Transformer protection
12   The integrated control function permits                                                        In general, no separate measuring instru-
     control of motors, contactors, disconnect       The relay provides all the functions for       ments (e.g. for current, voltage, frequency,
     devices, grounding switches or circuit-         backup protection for transformer differ-      …) or additional control components are
     breakers through the integrated operator        ential protection. The inrush suppression      necessary.
     panel, binary inputs, DIGSI 4 or the control    effectively prevents unwanted trips that
                                                     can be caused by inrush currents.              Typically the relay provides all required
     or SCADA/automation system (e.g. SICAM,
                                                                                                    measurements, thus negating the use of
     SIMATIC or other vendors automation sys-
                                                     Backup protection                              additional metering devices like amp, volt
     tem). A full range of command processing
                                                                                                    or frequency meters. No additional control
     functions is provided.                          The 7SK80 can be used as a stand alone         switches are required either. The relay pro-
                                                     feeder protection relay or as a backup to      vides 9 function keys that can be config-
     Programmable logic                              other protection relays in more complex        ured to replace push buttons and select
     The integrated logic characteristics (CFC)      applications.                                  switches.
     allow the user to add own functions for
     automation of switchgear (e.g. interlock-       Metering values
     ing) or switching sequence. The user can        Extensive measured values (e.g. I, V),
     also generate user-defined messages. This       metered values (e.g. Wp, Wq) and limit
     functionality can form the base to create       values (e.g. for voltage, frequency) provide
     extremely flexible transfer schemes.            improved system management.

     12/10                                                                                                                     Siemens SIP · 2008
                                                                                                                   12 Motor Protection / 7SK80


ANSI No.         IEC                               Protection functions

50, 50N          I>, I>>, I>>>, IE>, IE>>, IE>>>   Instantaneous and definite time-overcurrent protection (phase/neutral)

51, 51N          Ip, IEp                           Inverse time-overcurrent protection (phase/neutral)

67N              IEdir>, IEdir>>, IEp dir          Directional overcurrent protection, ground (definite/inverse)

67Ns/50Ns        IEE>, IEE>>, IEEp                 Directional/non-directional sensitive ground-fault detection

–                                                  Cold load pick-up (dynamic setting change)

59N/64           VE, V0>                           Displacement voltage, zero-sequence voltage

50BF                                               Breaker failure protection

46               I2>                               Phase-balance current protection (negative-sequence protection)

47               V2>, phase-sequence               Unbalance-voltage protection and/or phase-sequence monitoring

48                                                 Starting time supervision

49                   ϑ>                            Thermal overload protection

51M                                                Load jam protection

14                                                 Locked rotor protection

66/86                                              Restart inhibit

37               I<                                Undercurrent monitoring

38                                                 Temperature monitoring via internal RTD inputs or external device (RTD-box),
                                                   e.g. bearing temperature monitoring

27, 59           V<, V>                            Undervoltage/overvoltage protection

32               P<>, Q<>                          Forward-power, reverse-power protection

55               cos ϕ                             Power factor

81O/U            f>, f<                            Overfrequency/underfrequency protection

81R              df/dt                             Rate-of-frequency-change protection


Siemens SIP · 2008                                                                                                                               12/11
              12 Motor Protection / 7SK80

      Construction and hardware

     Connection techniques and
     housing with many advantages
     The relay housing is 1/6 of a 19" rack. The                                                               Illuminated 6-line display
     housing is thus identical in size to the 7SJ50
     and 7SJ60 relays that makes replacement                                                                   Navigation keys
     very easy. The height is 244 mm (9.61").
     Pluggable current and voltage terminals                                                                   Numerical key pad/9 function keys
     allow for pre-wiring and simplify the ex-
     change of devices. CT shorting is done in                                                                 8 programmable LEDs
     the removable current terminal block.
                                                                                                               Control keys
     It is thus not possible to open-circuit a
     secondary current transformer.
                                                                                                               Standard battery exchangeable from the front
     All binary inputs are independent and the
     pick-up thresholds are settable using soft-                                                               USB front port
     ware settings (3 stages). The relay current
     transformer taps (1 A/5 A) are new soft-
     ware settings. Up to 9 function keys can be
     programmed for predefined menu entries,
     switching sequences, etc. The assigned
     function of the function keys can be shown

     in the display of the relay.

                                                                                                                   Current terminal

                                                                                                                                                    Voltage terminal

                                                                                                       Fig. 12/8       7SK80 Front view, rear view, terminals

      Protection functions

     Time-overcurrent protection                      Available inverse-time characteristics
     (ANSI 50, 50N, 51, 51N)                          Characteristics acc. to                                      ANSI/IEEE                    IEC 60255-3
     This function is based on the phase-             Inverse                                                      •                            •
     selective measurement of the three phase
     currents and the ground current (four            Short inverse                                                •
     transformers). Three definite-time over-
                                                      Long inverse                                                 •                            •
12   current protection elements (DMT) are
     available both for the phase and the             Moderately inverse                                           •
     ground elements. The current threshold
     and the delay time can be set in a wide          Very inverse                                                 •                            •
     range. Inverse-time overcurrent protection       Extremely inverse                                            •                            •
     characteristics (IDMTL) can also be se-
     lected and activated.
                                                      the reverse movement of the Ferraris disk                    Cold load pickup/dynamic setting change
     Reset characteristics                            of an electromechanical relay (disk emula-                   The pickup thresholds and the trip times
                                                      tion).                                                       of the directional and non-directional
     Time coordination with electromechanical
     relays are made easy with the inclusion                                                                       time-overcurrent protection functions can
                                                      Inrush restraint
     of the reset characteristics according to                                                                     be changed via binary inputs or by setable
     ANSI C37.112 and IEC 60255-3 /BS 142             The relay features second harmonic re-                       time control.
     standards. When using the reset character-       straint. If second harmonic content is
     istic (disk emulation), the reset process is     detected during the energization of a trans-
     initiated after the fault current has disap-     former, the pickup of non-directional and
     peared. This reset process corresponds to        directional elements are blocked.

     12/12                                                                                                                                              Siemens SIP · 2008
                                                                                                        12 Motor Protection / 7SK80

 Protection functions

Directional overcurrent protection, ground
(ANSI 67N)
Directional ground protection is a separate
function. It operates in parallel to the non-
directional ground overcurrent elements.
Their pickup values and delay times can be
set separately. Definite-time and inverse-
time characteristics are offered. The trip-
ping characteristic can be rotated by
± 180 degrees.
For ground protection, users can choose
whether the direction is to be calculated
using the zero-sequence or negative-
sequence system quantities (selectable).
If the zero-sequence voltage tends to be
very low due to the zero-sequence imped-
ance it will be better to use the negative-                                                                     Fig. 12/9
                                                                                                                Directional determination
sequence quantities.                                                                                            using cosine measurements
                                                                                                                for compensated networks
(Sensitive) directional ground-fault detec-
tion (ANSI 64, 67Ns, 67N)
For isolated-neutral and compensated net-
works, the direction of power flow in the       (Sensitive) ground-fault detection             Breaker failure protection (ANSI 50BF)
zero sequence is calculated from the zero-      (ANSI 50Ns, 51Ns / 50N, 51N)                   If a faulted portion of the electrical circuit
sequence current I0 and zero-sequence
                                                For high-resistance grounded networks, a       is not disconnected when a trip command
voltage V0.
                                                sensitive input transformer is connected       is issued to a circuit-breaker, another trip
For networks with an isolated neutral, the      to a phase-balance neutral current trans-      command can be initiated using the breaker
reactive current component is evaluated;        former (also called core-balance CT).          failure protection which trips the circuit-
for compensated networks, the active cur-                                                      breaker of an upstream feeder. Breaker fail-
                                                The function can also be operated in the
rent component or residual resistive cur-                                                      ure is detected if, after a trip command is
                                                normal mode as an additional short-
rent is evaluated. For special network                                                         issued and the current keeps on flowing into
                                                circuit protection for neutral or residual
conditions, e.g. high-resistance grounded                                                      the faulted circuit. It is also possible to make
                                                ground protection.
networks with ohmic-capacitive                                                                 use of the circuit-breaker position contacts
ground-fault current or low-resistance                                                         (52a or 52b) for indication as opposed to
                                                Phase-balance current protection (ANSI 46)
grounded networks with ohmic-inductive                                                         the current flowing through the circuit-
                                                (Negative-sequence protection)
current, the tripping characteristics can be                                                   breaker.
rotated approximately ± 45 degrees.             By measuring current on the high side of
                                                the transformer, the two-element phase-
Two modes of ground-fault direction             balance current/negative-sequence protec-
detection can be implemented: tripping          tion detects high-resistance phase-to-phase
or “signalling only mode”.                      faults and phase-to-ground faults on the
It has the following functions:                 low side of a transformer (e.g. Dy 5 or                                                           12
                                                Delta/Star 150 deg.). This function provides
• TRIP via the displacement voltage VE.         backup protection for high-resistance faults
• Two instantaneous elements or one             through the transformer.
  instantaneous plus one user-defined
• Each element can be set to forward,
  reverse or non-directional.
• The function can also be operated in
  the insensitive mode as an additional
  short-circuit protection.

Siemens SIP · 2008                                                                                                                       12/13
                12 Motor Protection / 7SK80

      Protection functions

     Flexible protection functions
     The 7SK80 enables the user to easily add
     up to 20 additional protective functions.
     Parameter definitions are used to link
     standard protection logic with any chosen
     characteristic quantity (measured or calcu-
     lated quantity) (Fig. 12/10). The standard
     logic consists of the usual protection ele-
     ments such as the pickup set point, the set
     delay time, the TRIP command, a block
     function, etc. The mode of operation for
     current, voltage, power and power factor
     quantities can be three-phase or single-
     phase. Almost all quantities can be oper-     Fig. 12/10 Flexible protection functions
     ated with ascending or descending pickup
     stages (e.g. under and over voltage). All
     stages operate with protection priority.
     Protection functions/stages available are     Trip circuit supervision (ANSI 74TC)           Protection of motors require an additional
     based on the available measured analog        One or two binary inputs can be used for       time constant. This is used to accurately
     quantities:                                   monitoring the circuit-breaker trip coil       determine the thermal heating of the stator
                                                   including its incoming cables. An alarm        during the running and motor stopped con-
     Function                  ANSI No.            signal occurs whenever the circuit is gener-   ditions. The ambient temperature or the
                                                   ated. The circuit breaker trip coil is moni-   temperature of the coolant can be detected
     I<                        37
                                                   tored in the open and closed position.         either through internal RTD inputs or via
     I>, IE>                   50, 50N                                                            an external RTD-box. The thermal replica
                                                   Interlocking features can be implemented
     V<, V>, VE>               27, 59, 64          to ensure that the beaker can only be closed   of the overload function is automatically
                                                   if the trip coil is functional.                adapted to the ambient conditions. If nei-
     3I0>, I1>, I2>, I2/I1     50N, 46                                                            ther internal RTD inputs nor an external
     3V0>, V1><, V2><          59N, 47
                                                   Lockout (ANSI 86)                              RTD-box exist, it is assumed that the ambi-
     P><, Q><                  32                                                                 ent temperatures are constant.
                                                   All binary output statuses can be memo-
     cos ϕ (p.f.)><            55                  rized. The LED reset key is used to reset      Settable dropout delay times
     f><                       81O, 81U            the lockout state. The lockout state is also
                                                   stored in the event of supply voltage fail-    If the relays are used in conjunction with
     df/dt><                   81R                                                                electromechanical relays, in networks with
                                                   ure. Reclo- sure can only occur after the
                                                   lockout state is reset.                        intermittent faults, the long dropout times
     For example, the following can be imple-                                                     of the electromechanical relay (several
     mented:                                                                                      hundred milliseconds) can lead to prob-
                                                   Thermal overload protection (ANSI 49)
     • Reverse power protection (ANSI 32R)                                                        lems in terms of time coordination/grad-
                                                   To protect cables and transformers, an         ing. Proper time coordination/grading is
     • Rate-of-frequency-change protection         overload protection function with an           only possible if the dropout or reset time is
       (ANSI 81R)                                  integrated warning/alarm element for           approximately the same. This is why the
                                                   temperature and current can be used.           parameter for dropout or reset times can
12                                                 The temperature is calculated using a          be defined for certain functions such as
                                                   thermal homogeneous body model                 time-overcurrent protection, ground
                                                   (per IEC 60255-8), it considers the energy     short-circuit and phase-balance current
                                                   entering the equipment and the energy          protection.
                                                   losses. The calculated temperature is con-
                                                   stantly adjusted according to the calculated
                                                   losses. The function considers loading his-
                                                   tory and fluctuations in load.

     12/14                                                                                                                   Siemens SIP · 2008
                                                                                                               12 Motor Protection / 7SK80

 Protection functions

n Motor protection
Restart inhibit (ANSI 66/86)
If a motor is subjected to many successive
starts, the rotor windings or rotor bars can
be heated up to a point were the electrical
connections between the rotor bars and the
end rings are damaged. As it is not possible
to physically measure the heat of the rotor
we need to determine the heat by mea-
suring the current the rotor is drawing
through the stator to excite the rotor. A
thermal replica of the rotor is established
using a I2t curve. The restart inhibit will
block the user from starting the motor if the
relay determined that the rotor reached a
temperature that will damage the rotor
should a start be attempted. The relay will
thus only allow a restart if the rotor has a
sufficient thermal reserve to start (Fig. 12/11).
                                                    Fig. 12/11
Emergency start-up
If the relay determines that a restart of the
                                                    for I > IMOTOR START                              Load jam protection (ANSI 51M)
motor is not allowed, the relay will issue a
block signal to the closing command, effec-             ⎛I ⎞
                                                             2                                        Load jam is activated when a sudden high
                                                    t = ⎜ A ⎟ ⋅ TA                                    load is applied to the motor because of me-
tively blocking any attempt to start the mo-            ⎝ I⎠
tor. The emergency startup will defeat this                                                           chanical failure of a pump for example. The
block signal if activated through a binary          I            = Actual current flowing             sudden rise in current is detected by this
input. The thermal replica can also be reset                                                          function and can initiate an alarm or a trip.
                                                    IMOTOR START = Pickup current to detect a
to allow an emergency restart of the motor.                        motor start                        The overload function is too slow and thus
                                                    t            = Tripping time                      not suitable.
Temperature monitoring (ANSI 38)
                                                    IA           = Rated motor starting current
The relay can be applied with 5 internal                                                              Phase-balance current protection (ANSI 46)
RTDs. Two RTDs can be applied to each               TA           = Tripping time at rated motor       (Negative-sequence protection)
bearing (the cause of 50% of typical motor                         starting current
                                                                                                      If a rotating flux is set up in the stator that
failures). The remaining RTD is used to             The relay equation is optimally adapted           turns in the opposite direction of rotation
measure the ambient temperature. Stator             based on the state of the motor. The value        of the rotor. This flux will cause eddy cur-
temperature is calculated in by the current         applied on TA is dependant on the state of        rents in surface of the rotor bars and subse-
flowing through the stator windings. Up             the motor, cold or warm. This warm or             quently heat will be generated causing the
to 12 RTDs can be applied using external            cold state of the motor is determined by          rotor to heat up. This unwanted rotating
RTD modules. The RTDs can also be used              the thermal model of the rotor.                   flux is caused if the supply voltage are un-
to monitor the thermal status of trans-                                                               symmetrical. This unsymmetrical supply
                                                    Because the flow of current is the cause of
formers or other pieces of primary equip-
                                                    the heating of the motor windings, this           will cause a negative sequence current to         12
ment. (see “Accessories” , page 12/26).                                                               flow causing a rotating flux in the opposite
                                                    equation will accurately calculate the start-
                                                    ing supervision time. The accuracy will not       direction to the machine rotation.
Starting time supervision/Locked rotor
protection (ANSI 48/14)                             be affected by reduced terminal voltage
                                                    that could cause a prolonged start. The trip      Undercurrent monitoring (ANSI 37)
Starting time supervision protects the mo-          time is an inverse current dependant char-        A sudden drop in current, which can occur
tor against unwanted prolonged starts that          acteristic (I2t).                                 due to a reduced load, is detected with this
might occur in the event of excessive load                                                            function. This may be due to shaft that breaks,
torque or excessive voltage drops within            Block rotor can also be detected using a
                                                                                                      no-load operation of pumps or fan failure.
the motor, or if the rotor is locked. Rotor         speed sensor connected to a binary input
temperature is calculated from measured             of the relay. If activated it will cause an in-
                                                                                                      Motor statistics
stator current. The tripping time is calcu-         stantaneous trip.
lated according to the following equation:                                                            Essential statistical information is saved by
                                                                                                      the relay during a start. This includes the
                                                                                                      duration, current and voltage. The relay will
                                                                                                      also provide data on the number of starts,
                                                                                                      total operating time, total down time, etc.
                                                                                                      This data is saved as statistics in the relay.

Siemens SIP · 2008                                                                                                                              12/15
              12 Motor Protection / 7SK80

      Protection functions                            Customized functions (ANSI 51V, etc.)          Switching authority
                                                      Additional functions, which are not time       Switching authority is determined by set
     n Voltage protection                             critical, can be implemented using the CFC     parameters or through communications to
                                                      measured values. Typical functions include     the relay. If a source is set to “LOCAL”,
     Overvoltage protection (ANSI 59)
                                                      reverse power, voltage controlled over-        only local switching operations are possi-
     The two-element overvoltage protection           current, phase angle detection, and zero-      ble. The following sequence for switching
     detects unwanted network and machine             sequence voltage detection.                    authority is available: “LOCAL”; DIGSI
     overvoltage conditions. The function can                                                        PC program, “REMOTE”.
     operate either with phase-to-phase, phase-
     to-ground, positive phase-sequence or                                                           There is thus no need to have a separate
     negative phase-sequence voltage. Three-           Control and automatic functions               Local/Remote switch wired to the breaker
     phase and single-phase connections are                                                          coils and relay. The local/remote selection
                                                      Control                                        can be done using a function key on the
                                                      In addition to the protection functions, the   front of the relay.
     Undervoltage protection (ANSI 27)                SIPROTEC Compact units also support all
                                                      control and monitoring functions that are      Command processing
     The two-element undervoltage protection
                                                      required for operating medium-voltage or       This relay is designed to be easily integrated
     provides protection against dangerous
                                                      high-voltage substations.                      into a SCADA or control system. Security
     voltage drops (especially for electric ma-
     chines). Applications include the isolation                                                     features are standard and all the function-
                                                      The main application is reliable control of
     of generators or motors from the network                                                        ality of command processing is offered.
                                                      switching and other processes.
     to avoid undesired operating conditions                                                         This includes the processing of single and
     and a possible loss of stability. Proper oper-   The status of primary equipment or auxil-      double commands with or without feed-
     ating conditions of electrical machines are      iary devices can be obtained from auxiliary    back, sophisticated monitoring of the con-
     best evaluated with the positive-sequence        contacts and communicated to the 7SK80         trol hardware and software, checking of
     quantities. The protection function is ac-       via binary inputs. Therefore it is possible    the external process, control actions using
     tive over a wide frequency range (45 to 55,      to detect and indicate both the OPEN and       functions such as runtime monitoring and
     55 to 65 Hz). Even when falling below this       CLOSED position or a fault or intermedi-       automatic command termination after
     frequency range the function continues to        ate circuit-breaker or auxiliary contact po-   output. Here are some typical applications:
     work, however, with a decrease in accu-                                                         • Single and double commands using 1,
     racy.                                            The switchgear or circuit-breaker can be         1 plus 1 common or 2 trip contacts
     The function can operate either with             controlled via:                                • User-definable bay interlocks
     phase-to-phase, phase-to-ground or posi-         – integrated operator panel
                                                      – binary inputs                                • Operating sequences combining several
     tive phase-sequence voltage, and can be                                                           switching operations such as control of
     monitored with a current criterion.              – substation control and protection system
                                                      – DIGSI 4                                        circuit-breakers, disconnectors and
     Three-phase and single-phase connections                                                          grounding switches
     are possible.
                                                      Automation / user-defined logic                • Triggering of switching operations,
     Frequency protection (ANSI 81O/U)                With integrated logic, the user can create,      indications or alarm by combination with
                                                      through a graphic interface (CFC), specific      existing information
     Frequency protection can be used for over-
     frequency and underfrequency protection.         functions for the automation of switchgear
                                                      or a substation. Functions are activated       Assignment of feedback to command
     Electric machines and parts of the system
     are protected from unwanted frequency            using function keys, binary input or           The positions of the circuit-breaker or
     deviations. Unwanted frequency changes           through the communication interface.           switching devices and transformer taps are
     in the network can be detected and the                                                          acquired through feedback. These indica-
12   load can be removed at a specified fre-                                                         tion inputs are logically assigned to the
     quency setting.                                                                                 corresponding command outputs. The
                                                                                                     unit can therefore distinguish whether the
     Frequency protection can be used over                                                           indication change is a result of switching
     a wide frequency range (40 to 60 (for                                                           operation or whether it is an undesired
     50 Hz), 50 to 70 (for 60 Hz). There are                                                         spontaneous change of state.
     four elements (individually set as overfre-
     quency, underfrequency or OFF) and each
     element can be delayed separately. Block-
     ing of the frequency protection can be per-
     formed by activating a binary input or by
     using an undervoltage element.

     12/16                                                                                                                       Siemens SIP · 2008
                                                                                                             12 Motor Protection / 7SK80

                                                                                                  There is no exact mathematical method to
                                                  Further functions
                                                                                                  calculate the wear or the remaining service
                                                                                                  life of a circuit-breaker that takes arc-
                                                 Measured values
                                                                                                  chamber’s physical conditions into account
                                                 The r.m.s. values are calculated from the        when the CB opens. This is why various
                                                 acquired current and voltage along with          methods of determining CB wear have
                                                 the power factor, frequency, active and          evolved which reflect the different operator
                                                 reactive power. The following functions          philosophies. To do justice to these, the
                                                 are available for measured value process-        relay offers several methods:
                                                                                                  •   I
                                                 • Currents IL1, IL2, IL3, IE, IEE (67Ns)         • Σ I x, with x = 1... 3
                                                 • Voltages VL1, VL2, VL3, VL1L2, VL2L3, VL3L1    • Σ i 2t
                                                 • Symmetrical components                         The devices also offer a new method for
                                                   I1, I2, 3I0; V1, V2, V0                        determining the remaining service life:
                                                 • Power Watts, Vars, VA/P, Q, S                  • Two-point method
                                                   (P, Q: total and phase selective)
                                                                                                  The CB manufacturers double-logarithmic
                                                 • Power factor (cos ϕ),                          switching cycle diagram (see Fig. 12/12) and
                                                   (total and phase selective)                    the breaking current at the time of contact
                                                 • Frequency                                      opening serve as the basis for this method.
                                                                                                  After CB opening, the two-point method
                                                 • Energy ± kWh, ± kVarh, forward and
                                                                                                  calculates the remaining number of possible
Fig. 12/12 CB switching cycle diagram              reverse power flow
                                                                                                  switching cycles. Two points P1 and P2 only
                                                 • Mean as well as minimum and maximum            have to be set on the device. These are speci-
Chatter disable                                    current and voltage values                     fied in the CB’s technical data.
The chatter disable feature evaluates            • Operating hours counter                        All of these methods are phase-selective
whether, in a set period of time, the num-       • Mean operating temperature of the over-        and a limit value can be set in order to ob-
ber of status changes of indication input          load function                                  tain an alarm if the actual value falls below
exceeds a specified number. If exceeded,                                                          or exceeds the limit value during determi-
the indication input is blocked for a certain    • Limit value monitoring
                                                                                                  nation of the remaining service life.
period, so that the event list will not record     Limit values can be monitored using pro-
excessive operations.                              grammable logic in the CFC. Commands           Commissioning
                                                   can be derived from this limit value indi-
                                                   cation.                                        Commissioning could not be easier and
Indication filtering and delay
                                                                                                  is supported by DIGSI 4. The status of
Binary indications can be filtered or de-        • Zero suppression                               the binary inputs can be read individually
layed.                                             In a certain range of very low measured        and the state of the binary outputs can be
                                                   values, the value is set to zero to suppress   set individually. The operation of switch-
Filtering serves to suppress brief changes in      interference.                                  ing elements (circuit-breakers, disconnect
potential at the indication input. The indi-
                                                                                                  devices) can be checked using the switch-
cation is passed on only if the indication       Metered values                                   ing functions of the relay. The analog
voltage is still present after a set period of
                                                 For internal metering, the unit can calcu-       measured values are represented as wide-
time. In the event of an indication delay,
                                                 late an energy metered value from the            ranging operational measured values. To
there is a delay for a preset time. The infor-
                                                 measured current and voltage values. If an       prevent transmission of information to
mation is passed on only if the indication
voltage is still present after this time.
                                                 external meter with a metering pulse out-        the control center during maintenance,            12
                                                 put is available, the 7SK80 can obtain and       the communications can be disabled to
Indication derivation                            process metering pulses through an indica-       prevent unnecessary data from being trans-
                                                 tion input.                                      mitted. During commissioning, all indica-
User-definable indications can be derived                                                         tions with test tag for test purposes can be
from individual or a group of indications.       The metered values can be displayed and
                                                                                                  connected to a control and protection
These grouped indications are of great           passed on to a control center as an accu-
value to the user that need to minimize the      mulated value with reset. A distinction is
number of indications sent to the system         made between forward, reverse, active and        Test operation
or SCADA interface.                              reactive energy.
                                                                                                  During commissioning, all indications can
                                                 Circuit-breaker wear monitoring                  be passed to a control system for test pur-
                                                 Methods for determining circuit-breaker
                                                 contact wear or the remaining service life
                                                 of a circuit-breaker (CB) allow CB mainte-
                                                 nance intervals to be aligned to their actual
                                                 degree of wear. The benefit lies in reduced
                                                 maintenance costs.

Siemens SIP · 2008                                                                                                                          12/17
              12 Motor Protection / 7SK80

                                                      System interface protocols (retrofittable)
                                                      IEC 61850 protocol
     The relay offers flexibility with reference to   Since 2004, the Ethernet-based IEC 61850
     its communication to substation automa-          protocol is a global standard for protection
     tion systems and industrial SCADA or             and control systems used by power utili-
     DCS systems. The communication module            ties. Siemens was the first manufacturer to
     firmware can be changed to communicate           implement this standard. This protocol
     using another protocol or the modules can        makes peer-to-peer communication possi-
     be changed completely for a different con-       ble. It is thus possible to set up masterless
     nection or protocol. It will thus be possible    systems to perform interlocking or transfer
     to move to future communication proto-           schemes. Configuration is done using
     cols like popular Ethernet based protocols       DIGSI.
     with ease.
                                                      IEC 60870-5-103 protocol
     USB interface
                                                      The IEC 60870-5-103 protocol is an inter-
     There is an USB interface on the front of        national standard for the transmission of
     the relay. All the relay functions can be        protective data and fault recordings. All        Fig. 12/13
     set using a PC and DIGSI 4 protection            messages from the unit and also control          IEC 60870-5-103: Radial fiber-optic connection
     operation program. Commissioning tools           commands can be transferred by means of
     and fault analysis are built into the DIGSI      published, Siemens-specific extensions to
     program and are used through this inter-         the protocol. As a further option a redun-
     face.                                            dant IEC 60870-5-103 module is available
                                                      as well. With the redundant module it will
     Interfaces                                       be possible to read and change single
     A number of communication modules                parameters.
     suitable for various applications can be
     fitted at the bottom of the housing. The         PROFIBUS-DP protocol
     modules can be easily replaced by the user.      PROFIBUS-DP is a widespread protocol
     The interface modules support the follow-        in industrial automation. Through
     ing applications:                                PROFIBUS-DP, SIPROTEC units make
     • System/service interface                       their information available to a SIMATIC
       Communication with a central control           controller or receive commands from a
       system takes place through this interface.     central SIMATIC controller or PLC.
       Radial or ring type station bus topologies     Measured values can also be transferred
       can be configured depending on the cho-        to a PLC master.
       sen interface. Furthermore, the units can
       exchange data through this interface via       MODBUS RTU protocol
       Ethernet and the IEC 61850 protocol and        This simple, serial protocol is mainly
       can also be accessed using DIGSI.              used in industry and by power utilities, and     Fig. 12/14
       Alternatively up to two external tempera-      is supported by a number of relay manu-          Bus structure for station bus with Ethernet and
       ture monitoring boxes with a total of 12                                                        IEC 61850, fiber-optic ring
                                                      facturers. SIPROTEC units function as
       measuring sensors can be connected to          MODBUS slaves, making their informa-
       the system/service interface.                  tion available to a master or receiving in-
12   • Ethernet interface                             formation from it. A time-stamped event
       The Ethernet interface was implemented         list is available.
       for fast access to a number of protection
       units using DIGSI. It is also possible to
       connect up to two external temperature
       monitoring boxes (RTD-box for
       Ethernet) with a total of 12 measuring
       sensors to the Ethernet interface.

                                                                                          Fig. 12/15
                                                                                          Optical Ethernet communication module
                                                                                          for IEC 61850 with integrated Ethernet-switch

     12/18                                                                                                                          Siemens SIP · 2008
                                                                                                       12 Motor Protection / 7SK80


DNP 3.0 protocol
Power utilities use the serial DNP 3.0 (Dis-
tributed Network Protocol) for the station
and network control levels. SIPROTEC
units function as DNP slaves, supplying
their information to a master system or
receiving information from it.

System solutions for protection and station
Units featuring IEC 60870-5-103 interfaces
can be connected to SICAM in parallel via
the RS485 bus or radially by fiber-optic
link. Through this interface, the system is
open for the connection to other manufac-
turers systems (see Fig. 12/13).
Because of the standardized interfaces,
SIPROTEC units can also be integrated
into systems of other manufacturers or in
SIMATIC. Electrical RS485 or optical in-
terfaces are available. The best physical
data transfer medium can be chosen thanks
to opto-electrical converters. Thus, the         Fig. 12/16
RS485 bus allows low-cost wiring in the          System solution/communication
cubicles and an interference-free optical
connection to the master can be estab-
For IEC 61850, an interoperable system so-
lution is offered with SICAM. Through the
100 Mbits/s Ethernet bus, the units are
linked with SICAM electrically or optically
to the station PC. The interface is stan-
dardized, thus also enabling direct connec-
tion to relays of other manufacturers and
into the Ethernet bus. With IEC 61850,
however, the relays can also be used in
other manufacturers’ systems (see Fig. 12/14).


                                                 Fig. 12/17
                                                 Connection of two RTD units to 7SK80 using Ethernet

Siemens SIP · 2008                                                                                                                   12/19
             12 Motor Protection / 7SK80

      Typical connections

     n Connection of current
       and voltage transformers
     Standard connection
     For grounded networks, the ground cur-
     rent is obtained from the phase currents by
     the residual current circuit.

                                                   Fig. 12/18
                                                   Residual current
                                                   circuit without direc-
                                                   tional element

                                                   Fig. 12/19
                                                   Sensitive ground-
                                                   current detection
                                                   without directional


                                                   Fig. 12/20
                                                   Residual current
                                                   circuit with direc-
                                                   tional element (no
                                                   directional element
                                                   for phase)

     12/20                                            Siemens SIP · 2008
                                              12 Motor Protection / 7SK80

 Typical connections

Connection for compensated networks
The figure shows the connection of two
phase-to-ground voltages and the VE volt-
age of the broken delta winding and a
phase-balance neutral current transformer
for the ground current. This connection
maintains maximum precision for direc-
tional ground-fault detection and must
be used in compensated networks.

                                                             Fig. 12/21
                                                             Sensitive directional
                                                             ground-fault detec-
                                                             tion (no directional
                                                             element for phase)

Fig. 12/22 shows sensitive directional
ground-fault detection.

                                                             Fig. 12/22
                                                             Sensitive directional
                                                             ground-fault detec-

Connection for all networks
The figure shows the connection to three
current transformers and two voltage                                                 12
transformers in V-connection. Directional
ground overcurrent protection is not pos-
sible since the displacement voltage cannot
be calculated.

                                                             Fig. 12/23

                                                             Residual current
                                                             circuit with voltage
                                                             functions (no direc-
                                                             tional element for

Siemens SIP · 2008                                                           12/21
              12 Motor Protection / 7SK80

      Typical applications

     Overview of connection types
     Type of network                      Function                            Current connection                       Voltage connection
     (Low-resistance) grounded network    Time-overcurrent protection         Residual circuit, with 3 phase-current   –
                                          phase/ground non-directional        transformers required, phase-balance
                                                                              neutral current transformer possible
     (Low-resistance) grounded networks   Sensitive ground-fault protection   Phase-balance neutral current            –
                                                                              transformers required
     Isolated or compensated networks     Time-overcurrent protection         Residual circuit, with 3 or 2 phase      –
                                          phases non-directional              current transformers possible
     (Low-resistance) grounded networks   Time-overcurrent protection         Residual circuit, with 3 phase-current   Phase-to-ground connection or
                                          phases directional                  transformers possible                    phase-to-phase connection
     Isolated or compensated networks     Time-overcurrent protection         Residual circuit, with 3 or 2 phase-     Phase-to-ground connection or
                                          phases directional                  current transformers possible            phase-to-phase connection
     (Low-resistance) grounded networks   Time-overcurrent protection         Residual circuit, with 3 phase-current   Phase-to-ground connection
                                          ground directional                  transformers required, phase-balance     required
                                                                              neutral current transformers possible
     Isolated networks                    Sensitive ground-fault              Residual circuit, if ground current      3 times phase-to-ground connection
                                          protection                          > 0.05 IN on secondary side, other-      or phase-to-ground connection with
                                                                              wise phase-balance neutral current       open delta winding
                                                                              transformers required
     Compensated networks                 Sensitive ground-fault protection   Phase-balance neutral current            Phase-to-ground connection with
                                          cos ϕ measurement                   transformers required                    open delta winding required

      Technical data

     For detailed information regarding the
     technical data of the 7SK80 protection
     device, please visit us on the Internet at:


     12/22                                                                                                                             Siemens SIP · 2008
                                                                                                          12 Motor Protection / 7SK80

 Selection and ordering data   Description                                                              Order No.
                               7SK80 motor protection device                                            7SK80oo – ooooo – oooo
                               Housing, binary inputs and outputs
                               Housing 1/6 19’’, 4 x I, 3 BI, 5 BO (2 changeover/Form C),
                               1 live status contact                                                             1
                               Housing 1/6 19’’, 4 x I, 7 BI, 8 BO (2 changeover/Form C),                                            see next page
                               1 live status contact                                                             2
                               Housing 1/6 19’’, 4 x I, 3 x V, 3 BI, 5 BO (2 changeover/Form C),
                               1 live status contact                                                             3
                               Housing 1/6 19’’, 4 x I, 3 x V, 7 BI, 8 BO (2 changeover/Form C),
                               1 live status contact                                                             4
                               Housing 1/6 19’’, 4 x I, 3 BI, 5 BO (2 changeover/Form C), 5 RTD inputs,
                               1 live status contact                                                             5
                               Housing 1/6 19’’, 4 x I, 3 x V, 3 BI, 5 BO (2 changeover/Form C), 5 RTD inputs,
                               1 live status contact                                                             6

                               Measuring inputs, default settings
                               Iph = 1 A / 5 A, Ie = 1 A / 5 A                                                       1
                               Iph = 1 A / 5 A, Iee (sensitive) = 0.001 to 1.6 A / 0.005 to 8 A                      2

                               Rated auxiliary voltage
                               24 V / 48 V DC                                                                            1
                               60 V / 110 V / 125 V / 220 V DC, 115 V, 230 V AC                                          5

                               Unit version
                               Surface-mounting housing, screw-type terminal                                                 B
                               Flush-mounting housing, screw-type terminal                                                   E

                               Region-specific default and language settings
                               Region DE, IEC, language German (language selectable), standard front                             A
                               Region World, IEC/ANSI, language English (language selectable), standard front                    B
                               Region US, ANSI, language US-English (language selectable), US front                              C
                               Region FR, IEC/ANSI, language French (language selectable), standard front                        D
                               Region World, IEC/ANSI, language Spanish (language selectable), standard front                    E
                               Region World, IEC/ANSI, language Italian (language selectable), standard front                    F
                               Region RUS, IEC/ANSI, language Russian (language selectable), standard front                      G


Siemens SIP · 2008                                                                                                                               12/23
             12 Motor Protection / 7SK80

      Selection and ordering data          Description                                                    Order No.                       Order
                                           7SK80 motor protection device                                  7SK80oo – ooooo – oHoo L 0 o
                                           Port B (at bottom of device, rear)
                                           No port                                                                    0
                                           IEC 60870-5-103 or DIGSI 4/modem, electrical RS232                         1           see
                                           IEC 60870-5-103, DIGSI 4/modem or RTD-box, electrical RS485                2           following
                                           IEC 60870-5-103, DIGSI 4/modem or RTD-box, optical 820 nm, ST connector    3
                                           PROFIBUS-DP Slave, electrical RS485                                        9                  L0A
                                           PROFIBUS-DP Slave, optical, double ring, ST connector                      9                  L0B
                                           MODBUS, electrical RS485                                                   9                  L 0D
                                           MODBUS, optical 820 nm, ST connector                                       9                  L0 E
                                           DNP 3.0, electrical RS485                                                  9                  L0G
                                           DNP 3.0, optical 820 nm, ST connector                                      9                  L0H
                                           IEC 60870-5-103, redundant, electrical RS485, RJ45 connector               9                  L0P
                                           IEC 61850, 100 Mbit Ethernet, electrical, double, RJ45 connector           9                  L0 R
                                           IEC 61850, 100 Mbit Ethernet, optical, double, ST connector                9                  L0 S

                                           Port A (at bottom of device, in front)
                                           No port                                                                        0
                                           With Ethernet interface (DIGSI, RTD-box, not IEC 61850), RJ45 connector        6

                                           Measuring/fault recording
                                           With fault recording                                                               1
                                           With fault recording, average values, min/max values                               3


     12/24                                                                                                                    Siemens SIP · 2008
                                                                                                                            12 Motor Protection / 7SK80

 Selection and ordering data                     Description                                                              Order No.
                                                 7SK80 motor protection device                                            7SK80oo – ooooo – o H o 0
                                                 Designation                      ANSI No.          Description
                                                 Basic version                    50/51             Time-overcurrent protection phase I>, I>>, I>>>, Ip
                                                                                  50N/51N           Time-overcurrent protection ground IE>, IE>>, IE>>>, IEp
                                                                                  50N(s)/51N(s)1)   Sensitive ground fault protection IEE>, IEE>>, IEEp
                                                                                  49                Overload protection
                                                                                  74TC              Trip circuit supervision
                                                                                  50BF              Circuit-breaker failure protection
                                                                                  46                Negative-sequence protection
                                                                                  37                Undercurrent monitoring
                                                                                  86                Lockout
                                                                                  48                Starting time supervision
                                                                                  66/86             Restart inhibit
                                                                                  14                Locked rotor protection
                                                                                  51M               Load jam protection
                                                                                                    Motor statistics
                                                                                                    Parameter changeover
                                                                                                    Monitoring functions
                                                                                                    Control of circuit-breaker
                                                                                                    Flexible protection functions (current parameters)
                                                                                                    Inrush restraint                                         D
                                                 Basic version + directional (sensitive) ground fault, voltage and frequency protection
                                                 n                                67N               Directional overcurrent protection ground
                                                                                                    IE>, IE>>, IEp
                                                                                  67N(s) 1)         Directional sensitive ground fault protection
                                                                                                    IEE>, IEE>>, IEEp
                                                                                  64/59N            Displacement voltage
                                                                                  27/59             Under-/overvoltage
                                                                                  81U/O             Under-/overfrequency, f<, f>
                                                                                  47                Phase rotation
                                                                                  32/55/81R         Flexible protection functions (current and voltage
                                                                                                    parameters): Protective function for voltage, power,
                                                                                                    power factor, frequency change                          E


n   Basic version included
1) Depending on the ground current input
   the function will be either sensitive (Iee)
   or non-sensitive (Ie).
2) Only if position 6 = 1, 2 or 5.
3) Only if position 6 = 3, 4 or 6.

Siemens SIP · 2008                                                                                                                                          12/25
             12 Motor Protection / 7SK80

      Sample order                         Position                                                                Order No. + Order code

                                           6          I/O’s: 3 BI/5 BO, 1 live status contact, 5 RTD inputs              5
                                           7          Current transformer: Iph = 1 A / 5 A, Ie = 1 A / 5 A                   1
                                           8          Power supply: 60 to 250 V DC, 115 V AC to 230 V AC                         5
                                           9          Unit version: Flush-mounting housing, screw-type terminals                     E
                                           10         Region: US, English language (US); ANSI                                            C
                                           11         Communication: System interface: DNP 3.0, RS485                                        9                L0G
                                           12         Communication: Ethernet interface (DIGSI, not IEC 61850)                                   6
                                           13         Measuring/fault recording: Extended measuring and fault records                                3
                                           14/15      Motor protection function package: Basic version                                                   HD

      Accessories                          Description                                                                                   Order No.

                                           DIGSI 4
                                           Software for configuration and operation of Siemens protection units
                                           running under MS Windows 2000/XP Professional Edition/Vista.

                                           Basis           Full version with license for 10 computers, on CD-ROM
                                                           (authorization by serial number)                                              7XS5400-0AA00
                                           Professional DIGSI 4 Basis and additionally SIGRA (fault record analysis),
                                                         CFC Editor (logic editor), Display Editor (editor for default
                                                         and control displays) and DIGSI 4 Remote (remote operation)                     7XS5402-0AA00
                                           Professional + IEC 61850
                                                         Complete version:
                                                         DIGSI 4 Basis and additionally SIGRA (fault record analysis),
                                                         CFC Editor (logic editor), Display Editor (editor for default
                                                         and control displays) and DIGSI 4 Remote (remote operation)
                                                         + IEC 61850 system configurator                                                 7XS5403-0AA00

                                           IEC 61850 System configurator
                                           Software for configuration of stations with IEC 61850 communication under
                                           DIGSI, running under MS Windows 2000/XP Professional Edition/Vista.
                                           Optional package for DIGSI 4 Professional
                                           License for 10 PCs. Authorization by serial number. On CD-ROM                                 7XS5460-0AA00

                                           SIGRA 4
                                           Software for graphic visualization, analysis and evaluation of fault records.
                                           Can also be used for fault records of devices of other manufacturers (Comtrade format).
12                                         Running under MS Windows 2000/XP Professional Edition/Vista.
                                           (generally contained in DIGSI Professional, but can be ordered additionally)
                                           Authorization by serial number. On CD-ROM.                                            7XS5410-0AA00

                                           Temperature monitoring box (RTD-box) for RS485 connection
                                           24 to 60 V AC/DC                                                                              7XV5662-2AD10
                                           90 to 240 V AC/DC                                                                             7XV5662-5AD10

                                           Temperature monitoring box (RTD-box) for Ethernet
                                           24 to 240 V AC/DC                                                                             7XV5662-7AD10

                                           Manual for 7SK80
                                           English                                                                               E50417-G1140-C344-A1
                                           German                                                                                E50417-G1100-C344-A1

                                           Mounting rail for 19" rack                                                                    C73165-A63-C200-4

     12/26                                                                                                                                           Siemens SIP · 2008
                                                             12 Motor Protection / 7SK80

 Connection diagram

                      Fig. 12/24 7SK801 connection diagram


Siemens SIP · 2008                                                                         12/27
             12 Motor Protection / 7SK80

      Connection diagram

                                           Fig. 12/25 7SK802 connection diagram


     12/28                                                                        Siemens SIP · 2008
                                                             12 Motor Protection / 7SK80

 Connection diagram

                      Fig. 12/26 7SK803 connection diagram


Siemens SIP · 2008                                                                         12/29
             12 Motor Protection / 7SK80

      Connection diagram

                                           Fig. 12/27 7SK804 connection diagram


     12/30                                                                        Siemens SIP · 2008
                                                             12 Motor Protection / 7SK80

 Connection diagram

                      Fig. 12/28 7SK805 connection diagram


Siemens SIP · 2008                                                                         12/31
             12 Motor Protection / 7SK80

      Connection diagram

                                           Fig. 12/29 7SK806 connection diagram


     12/32                                                                        Siemens SIP · 2008