# Iec Guide to Cable Sizing Calculation

Document Sample

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1. INTRODUCTION

 From Ecodial2 to Ecodial3 :

 Windows 3.11, 95, 98 and NT

 New products :
 Contactors , Circuit breakers (Telemecanique),
 Thermal relays, Soft starters, Variable speed drives,
Capacitors

 A new calculation standard : CENELEC (R0064-003)
 Installation standards : IEC364, C15-100

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The main steps of a study

   General characteristics
   Drawing
   Definition of circuit characteristics
   Power sum
   Calculation
   Results
   Output

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General characteristics
Calculation / General characteristics

 Un Ph-Ph (415V) : sets the LV network voltage. This value corresponds to a
phase-phase voltage

 Earthing arangement (TNC) : sets the earthing arrangement at the transformer.
This value can only be changed in a network after an LV/LV transformer, or from
TNC to TNS.

 Cascading (YES) : authorises Ecodial to use reinforced breaking capacity to
choose downstream breakers. This can help reduce the cost of an installation.

 Discrimination (YES) : displays the discrimination results and chooses breakers
giving better discrimination results.

 Smax (240mm²) : sets the maximum cable CSA that Ecodial can use when sizing
cables (multiple cables in parallel can always be used though)

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General characteristics
Calculation / General characteristics

 CSA N / CSA Ph (1) : sets the minimum ratio between phase and neutral
conductors. This is used to allow half neutrals (1/2) or require full neutrals (1).

 Tolerance (5%) : Ecodial calculates the theoretical Phase CSA. Tolerance can be
included to allow the choice of cable slightly smaller than the theoretical value.

 Standard (IEC947-2) : Allows the user to choose a default product standard
(IEC947-2 or IEC898) according to which the breaking capacity of the circuit
breakers are given. If the standard is set to IEC898, Ecodial automatically chooses
IEC947-2 if no IEC898 are available

 Target power factor (0.96) : this is the value Ecodial will use to size the required
capacitor bank. It corresponds to the power factor downstream of the transformer.

 System frequency (50Hz) : enables users to choose products that are suitable for
60hz applications (capacitors, …).

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Drawing the network - the symbol toolbox
Display / Symbol Toolbox

   Sources : Transformer, Generator, Undefined, (Bus coupler)
   Busbar : Busbar, (interlock)
   Outgoing circuits
   LV transformer (isolating, step-up, step-down)
   Standard diagrams

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The first study

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Definition of circuit characteristics
Network / Circuit description

 select circuit and F4, or double-click on circuit
• Name all the circuits :
– Supply, Switchboard, Main Load, Main Motor, Main Lighting
• Enter circuit parameters:
– Main Load : 35m, 238A
– Main motor : 39m, 110kW (mechanical),
– Main Lighting :15m cable, 30m busbar, 20x150W Incandescent
lights, 10 identical circuits

 Useful tools
• Network / Item lists …
– faster input of circuit characteristics once the circuits are named.
• Display / Network tree (F2)
• Network / Logical check (F3)

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The Power Sum
Calculation / Power Sum

 Automatically calculates the theoretical power of transformer and generator.
(400kVA)

 Automatically calculates the currents in the different branches of the circuits. (ex
Total Switchboard feeders = 436.36A)

 Ku and Ks coefficients can be used to optimise design.

 Ecodial will recommend a transformer size.

Power sum should be run after every modification !

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The Power Sum
Calculation / Power Sum

 The Power Sum is not compulsory.

 But then the user must manually define the currents in every circuits.
• Advantage : quicker calculations :
– Do not have to draw/enter all the circuits.
– Enter only the circuits one wants to calculate, and expected current.
• Disadvantage : results can be sometimes surprising !

POWER SUM IS RECOMMENDED IN BIG PROJECTS !

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The Power Sum

 When single phases are connected to a three phase board, Ecodial can
automatically suggest a phase distribution solution
 The automatic distribution can be modified.
 The logic applied is the following
• Ecodial sorts the loads by decreasing intensity.
• Starting from the highest load, Ecodial will place the loads onto the first phase
until the sum of these loads is equal to 33% of the total load
• Ecodial then tries to load the second phase until the sum of these loads
reaches 50 of the remaining loads.
• All the loads that remain are then allocated to the third phase.
 This systems gives the best possible distribution in most cases. It is always
possible to modify the result.

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The Calculation
Calculation / Calculate

 Automatic mode
– equipment is selected automatically.
– No additional entry is required, Ecodial uses default values (installation
method, cable type, …)
 Manual mode
– parameters can be defined by user, and then theyare checked to see if
they verify all the safety criteria.
– An unsafe choice will not be allowed to be validated.

 Equipment calculated
– Circuit breakers (and fuses) and isolators
– Contactors and relays
– Cable, BTS, and busbar

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The Calculation
Calculation / Calculate

 Load current and breaking capacity identifies circuit breaker

 Choice of circuit breaker sets thermal setting

 Thermal setting defines minimum theoretical cable CSA

 Verification of cable (Sp, Sn, Spe theoretic)
• voltage drop
• protection against indirect contact
• short circuit currents

 Sizing constraint (overload, voltage drop, user, …)

Division - Name - Date - Language                                                                     15
The Calculation
Calculation / Calculate

 Busbar sizing :
• For main busbar, size is defined by the circuit breaker protection which is
defined by the nominal current of transformer (and not the sum of the load
currents !)
• For other busbar (sub DB) : sizing according to circuit breaker protection,
which is defined by the load current.

 Short circuit currents
• Ik max : cold short circuit (copper is cold-low resistivity)
• Ik min : warm short circuit (copper is warm - high resistivity)
• Ik3 : three phase ‘bolted’ fault
• Ik2 : phase - phase fault
• Ik1 : phase - neutral fault
• Earth fault : phase-earth fault

Division - Name - Date - Language                                                                                      16
The Calculation
Resistivity values

 ro : resitivity at 20 degrees Celcius (IEC909)
• copper : 18,51
• aluminium : 29,41
 At different temperatures :
• PVC
 r1= 1,2x ro at 70 degrees
 r2= 1,38x ro at 115 degrees (if S <= 300 mm²)
 r2= 1,34x ro at 105 degrees (if S > 300 mm²
 r3= 1,30x ro at 95 degrees (if S <= 300 mm²)
 r3= 1,26x ro at 85 degrees (if S > 300 mm²)
• PR
 r1= 1,28x ro at 90 degrees
 r2= 1,60x ro at 170 degrees
 r3= 1,48x ro at 140 degrees
 Linear reactance (non armoured cables)
• multi core or single core in trefoil : l = 0,08
• single core, flat touching : l = 0,09
• single core, spaced : l = 0,13

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The Calculation
Short circuit currents (values of resistivity to be used)

 Ik3max, Ik2max and Ik1max :
ro
 Ik2min and Ik1min
• for circuit protected by fuses : r2
• for circuits protected by circuit breakers : r1
 If (earth fault current)
• TNC :
– for circuit protected by fuses : r2
– for circuits protected by circuit breakers : r1
• Multicore, PE included
– for circuit protected by fuses : r2
– for circuits protected by circuit breakers : r1
• PE separate
– for circuit protected by fuses : r2
– for circuits protected by circuit breakers : r1
 Voltage drop :
• r1

Division - Name - Date - Language                                                                 18
The second study

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Modify the circuit

 Define new circuits :
• Emergency DB feeder : 45 m , (I = ???)
• Emergency DB
• Emergency supply
• Vital Motor (75m, 18,5 kW mechanical)

 Run Power Sum
• Transformer : 400 to 630 kVA
• Generator : 160 kVA (only supplies Emergency board !)

 Run Calculation

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 Zoom : drag a box around the area to zoom into

 Grid

 Alf F3 = search for a particular circuit based on its name or ID

 Circuit selection (multiple) : keep SHIFT button pressed while selecting multiple
circuits, or draw a box around the circuits to select.

 Moving circuits : drag and drop the selection

 Copying circuits (including the characteristics)
• select circuit to be copied
• CTRL+C and then CTRL+V
• Edit / Copy and then Edit / Paste

 Enlarge busbars : select busbar, click on          , enlarge bars.

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Circuit description
Transformer

 Power (kVA) : the nominal rating of the transformer. It is usually calculated and set
in the power sum, nonetheless it can be manually set by the user here.

 Earthing arrangement : a reminder of the earthing arrangement set in the general
characteristics. Modifying the earthing arrangement here does not modify the
earthing arrangement of all the downstream circuits.

 Distributed neutral : identifies networks that have or have no neutral conductor.

 Un Ph-Ph : a reminder of the system voltage. As for the earthing system, changing
the voltage here does not automatically change the voltage of all the other circuits.

 Short circuit voltage : parameter which is used to calculate the impedance of the
transformer (Z). The resistance and reactance are estimated using the CENELEC
guide lines.

Division - Name - Date - Language                                                                                         22
Circuit description
Transformer (2)

 HV Psc : short circuit level on the medium voltage side of the transformer. Enables
Ecodial to calculate the impedance (Z) of the medium voltage network

 Connection : the different windings of the MV/LV transformer

 Power factor : a result of the Power Sum. The power factor at the downstream
terminals of the transformer.

 System frequency

 HV operating time : time used to size the transformer to circuit breaker connection
(refers to Electrical Installation Guide table H1-63)

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Circuit description
Transformer (3)

 Results :

• R and X of MV network (using CENELEC R064-003 formulas)
– XQ= 0,995 x ZQ        RQ=0,1 x XQ

• R and X of transformer (using CENELEC R064-003 formulas)
– RT=0,31 x ZT           XT = 0,95 x ZT

• Ib : rated current of the transformer (In)

• Isc max (maximum short circuit current at the terminals of the transformer)

• Copper losses (heat loss)

Division - Name - Date - Language                                                                                       24
Circuit description
Generators

 Power (kVA) : see previous

 Earthing arrangement : see previous

 Distributed neutral : see previous

 Un Ph-Ph : see previous

 Power factor : see previous.

 System frequency : see previous

 X’o : Zero phase impedance

 X’’ : Transient impedance, used to calculate the short circuit current

Division - Name - Date - Language                                                                              25
Circuit description
Source

 Un Ph-Ph : see previous

 Isc max (kA) : maximum short circuit current (Ik3max) at the point of the LV
connection from which the study will start.

 Power factor : see previous.

 System frequency : see previous

 Energy supplier : Private substation is the only value.

 Distributed neutral : see previous

 I service connection (A) : Intensity of the connection, in other words the current
rating of the upstream protection device (not drawn on the diagram).

Division - Name - Date - Language                                                                                          26
Circuit description
Source (2)

 Isc min upstream (kA) : value of the Ik1min short circuit at the point of
connection. This value is used to calculate the ‘warm’ impedance of the
Phase/Neutral loop.

 Earthing arrangement : see previous.

 dU initial (%) : The voltage drop from the transformer to the LV connection from
which the study starts. This used to calculate the cumulative voltage drop
downstream of the LV connection.

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Circuit description
Capacitor

 Power factor before compensation : value of the power factor calculated in the
Power Sum (the Power Sum must be run to calculate a Capacitor bank)

 Power of the Harmonic sources : In order to take into account the effect of
harmonics on the capacitors, Ecodial needs the power of all the harmonic
generating (non-linear) loads on the network. This value is used in conjunction with
the transformer size to identify the type (Standard, H or SAH) of capacitor used by
Ecodial.

 Power (kvar) : Total power of the capacitor bank needed to attain the target power
factor.

 Type of compensation

 Step : resolution of the automatic capacitor bank : ex 5x50kvar means the
capacitor bank can go from 0 to 250kvar in steps of 50 kvar (controlled by the
regulator)
 Ib : current drawn by the capacitor bank (inclusive of possible harmonic currents
and manufacturing tolerances)

Division - Name - Date - Language                                                                                          28
Circuit description
Capacitor

Ih                                              Vh       L,w                            C,w

Harmonic current
Transformer        Capacitor
injection
(PT)             (Q)
 Equivalent impedance of L-C circuit (resistances ignored)
• Z= j.L.w / (1-L.C.w²)

 Resonance when w²=(2.p.f)²=1/LC (Zmax induces to Voltage max)
• order of resonance :

• if order of resonance is close to harmonic current injection, filtering devices
could be required.

 Harmonic voltage created across the equivalent impedance of the transformer and
capacitor, which causes circulating currents in the L-C loop, which can be a cause
of nuisance tripping in transformer or capacitor protection devices.

Division - Name - Date - Language                                                                                            29
Circuit description
Circuit breaker (distribution)

 Range : Product range from which the circuit breaker is to be chosen. If Ecodial
cannot find a breaker in that range it will look for a breaker in a predefined range
(function of the demand current)
 Designation : name of circuit breaker
 Trip unit / curve : name of the trip unit or curve of the circuit breaker
 Nb of poles protected : polarity of the circuit breaker that is required.
 Earth leakage protection : if earth leakage protection (RCD) is required (by user,
or for a particular application, switch this characteristic to YES).
 Fire protection : this is a characteristic that will force an earth leakage device, and
set it to ensure that a leakage current will not be able to cause a fire (threshold <
300mA)
• Integrated with the protection device : certain RCDs are integrated (NS Vigi,
…) and certain are separated (RH***). The user can choose the type of RCD
required. By default, Ecodial looks for integrated RCDs, and then separated
RCDs if unsuccessful.
• Class : (A / AC ) defines the sensitivity of the RCD to continuous and pulsed
DC signals.
• Earth leakage protection device : name of the device ensuring the function of
RCD.

Division - Name - Date - Language                                                                                           30
Circuit description
Circuit breaker (distribution) (2)

• Sensitivity (mA) : pickup current of the RCD device
• Delay (ms) : time delay before disconnection under earth fault conditions
   I thermal setting (A) : Thermal setting of the circuit breaker. This value is set to be
greater or equal to the demand current, and is used to size the cable.
   I magnetic setting (A) : magnetic setting of the circuit breaker. This setting s made
to ensure protection against indirect contact in TN, and to ensure correct motor
starting based on start-up currents.
   Frame rating (A) : maximum rating of the circuit breaker frame
   Trip unit rating (A) : maximum setting of the trip unit.
   Ir : position of the thermal adjustment on the trip unit
   Io : position of the thermal adjustment on the trip unit
   Im/Isd : position of the magnetic adjustment on the trip unit
   Motor mechanism : breakers must be able to be fixed with a motor mechanism

Division - Name - Date - Language                                                                                            31
Circuit description
Circuit breaker (distribution) (3)

• YES : circuit breaker is chosen using cascading with the upstream device (only
the device directly upstream)
• NO : circuit breaker is chosen based on its stand-alone breaking capacity.

 Discrimination requested :
• YES : circuit breakers that have better discrimination potential are selected

 Installation : Fixed breakers or withdrawable breakers

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Circuit description
Circuit breaker (motor)

   Range : see previous
   Designation : see previous
   Trip unit / curve : see previous
   Contactor : name of contactor to be used according to the co-ordination tables
   Thermal protection : name of thermal overload (if needed) according to co-
ordination tables.
   Soft starter : name of soft starter (if needed) according to co-ordination tables.
   Earth leakage protection : see previous.
   Fire protection :see previous with the added safety that the tripping time is
delayed by at least 60ms to ensure there is no nuisance tripping on start-up.
   Number of poles protected : always 3P3T, as Ecodial does not cover single
phase motors
   I thermal setting (A) : Thermal setting of the circuit breaker. This value is set to be
greater or equal to the demand current, and is used to size the cable.
   I magnetic setting (A) : magnetic setting of the circuit breaker. This setting s made
to ensure protection against indirect contact in TN, and to ensure correct motor
starting based on start-up currents.

Division - Name - Date - Language                                                                                            33
Circuit description
Circuit breaker (motor) (2)

 Frame rating (A) : maximum rating of the circuit breaker frame
 Trip unit rating (A) : maximum setting of the trip unit.
 Ir : position of the thermal adjustment on the trip unit
 Io : position of the thermal adjustment on the trip unit
 Im/Isd : position of the magnetic adjustment on the trip unit
 Motor mechanism : breakers must be able to be fixed with a motor mechanism
• YES : circuit breaker is chosen using cascading with the upstream device (only
the device directly upstream)
• NO : circuit breaker is chosen based on its stand-alone breaking capacity.
 Discrimination requested :
• YES : circuit breakers that have better discrimination potential are selected
 Installation : Fixed breakers or withdrawable breakers

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Circuit description

 Number of identical circuits : instead of drawing multiple feeders having
EXACTLY the same characteristic, just draw one !

 Ib : demand current of the load (calculated from the power and polarity)

 Circuit polarity : polarity of the load

 Earthing arrangement : see previous

 Power (kVA) : demand power (calculated from the current and the polarity)

 Power factor : power factor of the load (.8 is default value)

 Fixed / Mobile :
• Fixed : permanent connection from installation to load.
• Mobile : terminal load is fed through a power socket (special earth leakage
conditions are then applicable : 30mA and Instanataneous protection is
required)

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Circuit description
Motor

   Number of identical circuits : see previous
   Mechanical power (kW) : rated mechanical power of motor
   Type of starting : for Direct on Line or Soft Starting applications
   Motor efficiency : ratio between mechanical and electrical power (in kW)
   Ib (A) : full load current of motor
   Power factor : full load power factor of the motor
   Circuit polarity (always 3P)
   Earthing arrangement : see previous
   Power (kW) : demand power (calculated from the efficiency)
   Type of co-ordination : Type 1 or Type 2
   Starting class : Standard / Long
   Start-up current : sets the magnetic setting of the breaker

Division - Name - Date - Language                                                                                  36
Circuit description
Lighting

   Number of identical circuits
   Lighting Source : type of lamp
   Individual lamp power :
   Number of lamps per light : for each lighting point there can be several lamps
   Nb of lights (A) : total number of lamps on the Canalis lighting line
   Ib : full load current at the origin of the Canalis lighting distribution
   Ballast power : for lamps using ballasts (fluo tubes, …)
   Circuit polarity
   Earthing arrangement
   Power (kW) : total demand power (calculated)
   Power factor

Division - Name - Date - Language                                                                                        37
Circuit description
Variable Speed Drive

   Reference : name of VSD
   Nominal power of the VSD (kW) : characteristic of VSD
   Ib : current drawn by VSD (including harmonics)
   Absorbed power : total power drawn by VSD (motor power and heat loss)
   Torque (A) : starting torque : High or standard
   Form factor : ratio between total RMS and 50Hz signal (characteristic of VSD)
   Is permanent : output current
   Is max permanent : maximum permanent output current (characteristic of VSD)
   Is max 60s : maximum 60s output current (characteristic of VSD)
   Earthing arrangement
   Circuit polarity

Division - Name - Date - Language                                                                                       38
Circuit description
Cable

 Length : length of the cable (Short circuit and voltage drop calculations)
 Installation method : code for the type of installation. Defines the standard
derating factors and the type of conductors used.
 Insulation : sets the insulation material of the cable (impedance calculation)
 Type of conductor : output from the Installation method, not an input !
 Neutral loaded : source of derating on 3P+N networks
 Conductor arrangement : calculation of the linear reactance of the cable
 Type of PE : influences the type of cables selected by Ecodial
 Number of additional circuits : cable derating
 Number of layers : cable derating
 K user : additional cable derating (over and above the standards)
 Ambient temperature : cable derating
 Delta U max on circuit (%) : maximum voltage drop allowed on the cable
 Reference : name of cable

Division - Name - Date - Language                                                                                      39
Circuit description
Cable (2)

   Nb Ph conductor : calculation result
   CSA Ph conductor : calculation result
   Nb N conductor : calculation result
   CSA N conductor : calculation result
   Nb PE conductor : calculation result
   CSA PE conductor : calculation result
   Phase metal : cable characteristic (input)
   Neutral metal : cable characteristic (input)
   PE metal : cable characteristic (input)
   Safety voltage : 50V or 25V

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Ecodial and the earthing schemes
Implementing protection against indirect contact

 TT
• Earth fault current (leakage) calculated using the impedance of the source and
earth electrodes, and the Phase-Earth conductor impedance
• Standards require an RCD device on the main incomer
 the earth and source electrodes must not be interconnected !
 TN
• Earth fault current calculated using the Phase-Earth conductor impedance
• Protection against indirect contact insured by setting the magnetic under the
Earth fault current
• Trip units can be changed to ensure accurate magnetic threshold is used
• RCDs can be implemented
 IT (2nd fault)
• identical calculations as for the TN system
• Earth fault current is calculated assuming both fault occur at the same point.
This ensures ‘worse case scenario’ as if the second fault appears further away,
the real fault current on the 2nd fault would be greater than the calculated fault
current corresponding to the 2nd fault location, and ensuring tripping by the
2nd fault location protection device.

Division - Name - Date - Language                                                                                           41
Calculation rules
Phase CSA

 Theoretical Phase CSA : calculated by a formula, where (IEC 60364-5-523-B):
• K is the total derating (temperature laying method, cables in parallel, …)
• Irth : is the thermal setting of the upstream breaker
• m and a : parameters defined by the laying method and the type of cable
(metal, insulator) andthe number of loaded conductors in the circuit)

 Choice of Phase conductor
• based on cable database supplied
• based on theoretical phase CSA and tolerance
• based on installation rules (ex TNC Smini = 10mm²)
• based on limits implied in the standards (ex Smini for multicore conductors on
perforated tray = 25mm²)
• based on maximum phase CSA allowed

 Voltage drop is calculated on this cable using demand current
• CSA could be increased

Division - Name - Date - Language                                                                                      42
Calculation rules
Neutral CSA

 Theoretical calculation made by Ecodial
• minimum theoretical CSA equal Ph or Ph/2

 Warning : the Neutral as any cable should be sized according to the upstream
protection setting (this is to ensure safety, not continuity !).
• With 4p4t CB, the neutral can be of the same CSA of the Phase
• With 4p3t 1/2N, the neutral can be half
• With 3p devices (Neutral not protected), there is an unknown, as there is no
direct protection on the neutral…

 Phase unbalance can lead (worse case scenario) to a phase current equal to
neutral current, so Neutral should be at least equal to Phase

 Triplen Harmonics (3rd, 9th, …) add up on the neutral. Therefore, if the phase is
ONLY 3rd harmonics, neutral current = 3x phase current. In reality, the neutral
current will usually be less than 1.7-1.8 times the phase current, example ;
• Irms (phase) = (I1, I3 (80%), I5(45%), I7(12%)) = 1.36x I1
• Irms (neutral) = 3x I3 = 2.4x I1 = 1.76 Irms (phase)

Division - Name - Date - Language                                                                                        43
Calculation rules
Neutral CSA

 Recommended actions :
• use half neutrals
– when there is a 4p3t N/2 circuit breaker protecting the circuit,
– and if there is no possibility of excessive phase unbalance and/or triplen
– Note : 3p3t are acceptable solutions, but 4p3t N/2 offer more safety
under unexpected conditions

• use full neutrals
– when there is a 4p4t circuit breaker protecting the circuit
– and if there is a possibility of excessive phase unbalance, or limited
triplen harmonic (max allowed = 33% triplen in the RMS)
– Note : 3p3t are acceptable solutions, but 4p4t offer more safety under
unexpected conditions

• use double neutrals
– with 3p3t circuit breakers
– when there is a high risk of excessive triplen harmonic

Division - Name - Date - Language                                                                                       44
Calculation rules
PE CSA

 Automatic minimum PE :
• if Ph  16mm², PE = Ph x kph/kpe
• if Ph  35 mm², PE = 16mm² x kph/kpe
• if Ph > 35 mm², PE = Ph/2 x kph/kpe
• where kph and kpe function of the type of phase and earth conductor (metal,
insulation, single/multi core, …)
• in TT, max PE = 35mm²

 Theoretical minimum PE : the theoretical minimum PE cross section should only
verify the I²t < k²S² condition, as no current is ever expected to flow on the PE (as
it is an equipotential link). This condition usually implies small PE cross sections
(+/- 4mm² in TN and 1mm² in TT). Using such small cables has two bad
consequences :
• reducing Earth fault current (due to higher impedance), which could require the
use of earth fault protection devices or lowering the magnetic thresholds to
non efficient levels (motor starting and discrimination problems)
• creating a higher voltage differential on the PE due to natural leakage currents
 Ecodial chooses automatically the CSA given above, but allows smaller
cables to be selected by the user.

Division - Name - Date - Language                                                                                        45
Calculation examples
the effect of long cables

 Network
• General characteristics
– TNC
– 400V
• Transformer
– 800kVA transformer
– Incomer cable length = 0
– 3P+N
– 100A
– Installation method EJ(1)

 Calculate the network with :
• Load cable length =30m, 100m, 140m, 170m
• Info needed : Irm, If, Sph, Spe, DeltaU, CB, Sizing criteria

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Calculation examples
the effect of long cables

 Cable sized on load current

 Cable sized on voltage drop

 Setting of trip unit to cater for low earth fault current
(protection against indirect contact)
• To ensure disconnection in sufficient time, Ecodial verifies that the earth fault
current is higher than the magnetic setting of the breaker (including tolerance).
• Trip units can be changed to ensure this :
– C curve to B curve
– TM to STR
• cable size can be increased
• If no solution is found Ecodial interrupts the calculation requesting the user to
manually place an RCD on the circuit breaker to ensure disconnection, and
therefore protection against indirect contact.

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Calculation examples
Prefabricated busbar trunking

• the Icc and DeltaU can be calculated at each tap-off point, or for worst case
scenario (Icc at source)
• Calculation method to be used for distribution systems having loads that vary
substantially in power and location.

• the Icc is calculated at the beginning of BTS.
• The voltage drop is estimated as a function of the number of tap-offs
power and location)

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Calculation examples
Prefabricated busbar trunking (2)

 Uniformly and Non-uniformly distributed load.
• 800kVA
• 100A tapoffs
• D=5,10,15,20,25
• Total length 30m
• Info needed :
– Icc, deltaU per tap/off.

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Calculation parameters
Diversity and usage coefficients

 Ku : usage coefficient
• applicable to a CIRCUIT
• example :
– motor +/- 80%
– Light 100%

 Ks : diversity coefficient
• applicable to a DISTRIBUTION BOARD
• chance of all feeders drawing maximum load at any given time
• relative to the number of feeders on DB.
• See Electrical Installation Guide

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Calculation parameters
Diversity and usage coefficients - example

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Calculation parameters
Diversity and usage coefficients - example

 Apartment blocks :
Consumers        4          9      14         19         24        29    34    39    49
Ks               1          .78    .63        .53        .49       .46   .44   .42   .41

 Distribution Boards (IEC439) :
Circuits           3               5                     9               10+
Ks                 .9              .8                    .7              .6

 Circuits (Ks or Ku ?):
• Lighting                                 1
• Heating, air conditioning                1
• Socket outlet circuit        .1 to .2 (higher in industry)
• Lifts/hoists                             1 / .75 / .6

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Calculation parameters
Diversity and usage coefficients - example

 Problem with Ku and Ks
• Responsibility of the user
• Personal experience
• Knowledge of installation
• Database of existing installations

 Advantage of Ku and Ks
• more cost effective installation
• not oversized
• Example
– total installed power : 144kVA
– maximum expected demand : 80 kVA

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Calculation guides
Special help file

 The algorithms used by Ecodial

 Formulas, constants
• impedance
• Icc, voltage drop, ..

 Reference to standards

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Output

 Different types of information :
 The front page
 The device lists
 Equipment display
 Calculation notes
 The single-line diagram
 Printing :
 Customise the setup
 Choice of language

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Special

   Open and save a project
   How to make a link between projects ?
   Choice of interface language
   The summary
   Different kinds of exports :
 DXF
 RTF
 ECD

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Guides and tools
 Circuit breaker and busbar selection
 Tripping curves

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Limitations

 Maximum number of circuits in a project : 70
 Maximum number of copied circuits : 20
 Maximum number of transformers : 4

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Special applications

 Normal and emergency sources
• Ecodial uses the worst case scenario to select equipment :
– max short circuit level from Transformers
– min earth fault current from Generators

 Complex networks
   It is not always possible to draw the exact network. It can be necessary to
draw a simplified network, and define the final network based on these
calculations.

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