Iec Guide to Cable Sizing Calculation

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Iec Guide to Cable Sizing Calculation Powered By Docstoc
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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
                                       Loads : receiver, motor, lighting, variable speed drive
                                       LV transformer (isolating, step-up, step-down)
                                       graphic links - project links
                                       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
            Load distribution


                                     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.
                                     The upstream circuit is sized on the highest phase loading.




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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, …)




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            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




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            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


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            The second study




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            Modify the circuit

                                     Define new circuits :
                                       • Emergency DB feeder : 45 m , (I = ???)
                                       • Emergency DB
                                       • Emergency supply
                                       • Vital Load (36m, 135A)
                                       • 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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            Advanced editing

                                     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.




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            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)




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            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




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            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).




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            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)


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            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.

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            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.


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            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




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            Circuit description
            Circuit breaker (distribution) (3)


                                     Cascading requested :
                                       • 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
                                          instead of normal circuit breakers

                                     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.




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            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
                                     Cascading requested :
                                         • 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
                                            instead of normal circuit breakers
                                     Installation : Fixed breakers or withdrawable breakers




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            Circuit description
            Load


                                     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




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            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




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            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




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            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




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            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.



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            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




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            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)


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            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
                                              harmonic loading on the circuit.
                                           – 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

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            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.

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            Calculation examples
            the effect of long cables


                                     Network
                                       • General characteristics
                                           – TNC
                                           – 400V
                                       • Transformer
                                           – 800kVA transformer
                                           – Incomer cable length = 0
                                       • Load
                                           – 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




Division - Name - Date - Language                                                                       46
            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


                                     Non-uniformly distributed load
                                       • 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.

                                     Uniformly distributed load
                                       • the Icc is calculated at the beginning of BTS.
                                       • The voltage drop is estimated as a function of the number of tap-offs
                                       • Calculation adapted for distribution systems having evenly distributed loads (in
                                          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
                                       • % full load current when load is running
                                       • 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




Division - Name - Date - Language                        51
            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




Division - Name - Date - Language                                                                                 52
            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




Division - Name - Date - Language                                      54
            Output

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




Division - Name - Date - Language                                        55
            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




Division - Name - Date - Language                                               56
            Guides and tools
                                     Circuit breaker and busbar selection
                                     Discrimation and cascading tables
                                     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.




Division - Name - Date - Language                                                                                         59

				
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