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Contents

 [hide]

1- Use of

formulae

2- Simplified

table

3- Examples

Use of formulae

Figure G27 below gives formulae commonl used to calculate voltage drop in a given circuit per

!ilometre of length "copper cable with #$%E insulation&'

(f)

(*) +he full load current in amps

$) $ength of the cable in !ilometres

,) ,esistance of the cable conductor in .!m

  for copper 

  for aluminium

/ote) , is negligible above a c's'a' of 0 mm2

#) inductive reactance of a conductor in .!m

/ote) # is negligible for conductors of c's'a' less than 0 mm2' (n the absence of an other

information ta!e # as being eual to '4 .!m'

) phase angle between voltage and current in the circuit considered generall)ϕ

(ncandescent lighting) cos5 6 1

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$ed lighting) cos 7 '8ϕ

9luorescent with electronic ballast) cos 7 '8ϕ

:otor power)

 ;t start-up) cos5 6 '30

(n normal service) cos5 6 '4

Un) phase-to-phase voltage

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=alculations ma be avoided b using Figure G2 which gives with an adeuate approximation

the phase-to-phase voltage drop per !m of cable per ampere in terms of)

>inds of circuit use) motor circuits with cos5close to '4 or lighting with a cos5close to 1'

+pe of circuit? single-phase or 3-phase

x (* x $

> is given b the table

(* is the full-load current in amps

$ is the length of cable in !m'

+he column motor power @cos5 6 '30A of Figure G2 ma be used to compute the voltage drop

occurring during the start-up period of a motor "see example no' 1 after the Figure G2&'

c!s!a! in mm2 Single"p#ase circuit $alanced t#ree"p#ase circuit

otor po&er 'ig#ting otor po&er

ormal service Start"up ormal service Start"up

Cu * cos + , -! cos + , -!./ cos + , 0 cos + , -! cos + , -!./

1'0 2B 1'C 3 2 8'B

2'0 1B'B C'B 14 12 0'D

B 8'1 B'1 11'2 4 3'C

C 1 C'1 2'8 D'0 0'3 2'0

1 1C 3'D 1'D B'0 3'2 1'0

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1C 20 2'3C 1'10 2'4 2'0 1

20 30 1'0 'D0 1'4 1'3 'C0

30 0 1'10 'C 1'28 1 '02

0 D '4C 'BD '80 'D0 'B1

D 12 'CB '3D 'CB '0C '32

80 10 'B4 '3 'BD 'B2 '2C

12 140 '38 '2C '3D '3B '23

10 2B '33 '2B '3 '28 '21

140 3 '28 '22 '2B '20 '18

2B B '2B '2 '18 '21 '1D

3 0 '21 '18 '10 '14 '1C

Fig. G28: Phase-to-phase voltage drop ΔU for a circuit, in volts per ampere per km

1amples

1ample 0 "see Fig! G23&

 ; three-phase 30 mm2 copper cable 0 metres long supplies a B < motor ta!ing)

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1 ; at a cos 5 6 '4 on normal permanent load

0 ; "0 (n& at a cos 5 6 '30 during start-up

+he voltage drop at the origin of the motor cable in normal circumstances "i'e' with the distribution

board of Figure G23 distributing a total of 1 ;& is 1 < phase-to-phase'

hat is the voltage drop at the motor terminals)

(n normal serviceF

Guring start-upF

Solution)

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General rules of electrical installation

design

Connection to the MV utility distribution

network 

Connection to the LV utility distribution

network 

MV and LV architecture selection guide for 

 buildings

LV Distribution

Protection against electric shocks and

electric fires

Sizing and protection of conductors

Conductor sizing and protection

Conductor sizing:

methodology and definition

Oercurrent !rotection

 !rinci!les

Practical alues for a

 !rotectie scheme

Location of !rotectie deices

Conductors in !arallel

Practical method for determining the

smallest allowable cross-sectional area of

circuit conductors

General method for cable

sizing

"ecommended sim!lified

a!!roach for cable sizing

#izing of busbar trunking

systems $busways%

Determination of voltage drop

Ma&imum oltage dro! limit

Calculation of voltage drop

in steady load conditions

Short-circuit current

#hort'circuit current at the

secondary terminals of a MV(LVdistribution transformer 

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ww.electrical-installation.org/enwiki/Practical_values_for_a_protective_schemehttp://www.electrical-installation.org/enwiki/Location_of_protective_deviceshttp://www.electrical-installation.org/enwiki/Conductors_in_parallelhttp://www.electrical-installation.org/enwiki/Practical_method_for_determining_the_smallest_allowable_cross-sectional_area_of_circuit_conductorshttp://www.electrical-installation.org/enwiki/Practical_method_for_determining_the_smallest_allowable_cross-sectional_area_of_circuit_conductorshttp://www.electrical-installation.org/enwiki/Practical_method_for_determining_the_smallest_allowable_cross-sectional_area_of_circuit_conductorshttp://www.electrical-installation.org/enwiki/General_method_for_cable_sizinghttp://www.electrical-installation.org/enwiki/General_method_for_cable_sizinghttp://www.electrical-installation.org/enwiki/Recommended_simplified_approach_for_cable_sizinghttp://www.electrical-installation.org/enwiki/Recommended_simplified_approach_for_cable_sizinghttp://www.electrical-installation.org/enwiki/Sizing_of_busbar_trunking_systems_(busways)http://www.electrical-installation.org/enwiki/Sizing_of_busbar_trunking_systems_(busways)http://www.electrical-installation.org/enwiki/Determination_of_voltage_drophttp://www.electrical-installation.org/enwiki/Maximum_voltage_drop_limithttp://www.electrical-installation.org/enwiki/Short-circuit_currenthttp://www.electrical-installation.org/enwiki/Short-circuit_current_at_the_secondary_terminals_of_a_MV/LV_distribution_transformerhttp://www.electrical-installation.org/enwiki/Short-circuit_current_at_the_secondary_terminals_of_a_MV/LV_distribution_transformerhttp://www.electrical-installation.org/enwiki/Short-circuit_current_at_the_secondary_terminals_of_a_MV/LV_distribution_transformer

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)'!hase short'circuit current

$*sc% at any !oint within a LV

installation

*sc at the receiing end of a

feeder as a function of the *sc at its

sending end

#hort'circuit current su!!lied

 by a generator or an inerter 

Particular cases of short-circuit

current

Calculation of minimum leels

of short'circuit current

Verification of the withstand

ca!abilities of cables under short'circuit

conditions

Protective earthing conductor (PE)

Connection and choice for

 !rotectie earthing conductor 

#izing of !rotectie earthing

conductor 

Protectie conductor between

MV(LV transformer and the main

general distribution board $MGD+%

,-ui!otential conductor 

he neutral conductor

#izing the neutral conductor 

Protection of the neutral

conductor 

+reaking of the neutral

conductor 

*solation of the neutral

conductor 

!or"ed e#ample of cable calculation

LV switchgear: functions and selection

Oeroltage !rotection

,nergy ,fficiency in electrical distribution

Power .actor Correction

Power harmonics management

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lculation_of_minimum_levels_of_short-circuit_currenthttp://www.electrical-installation.org/enwiki/Verification_of_the_withstand_capabilities_of_cables_under_short-circuit_conditionshttp://www.electrical-installation.org/enwiki/Verification_of_the_withstand_capabilities_of_cables_under_short-circuit_conditionshttp://www.electrical-installation.org/enwiki/Verification_of_the_withstand_capabilities_of_cables_under_short-circuit_conditionshttp://www.electrical-installation.org/enwiki/Protective_earthing_conductor_(PE)http://www.electrical-installation.org/enwiki/Connection_and_choice_for_protective_earthing_conductorhttp://www.electrical-installation.org/enwiki/Connection_and_choice_for_protective_earthing_conductorhttp://www.electrical-installation.org/enwiki/Sizing_of_protective_earthing_conductorhttp://www.electrical-installation.org/enwiki/Sizing_of_protective_earthing_conductorhttp://www.electrical-installation.org/enwiki/Protective_conductor_between_MV/LV_transformer_and_the_main_general_distribution_board_(MGDB)http://www.electrical-installation.org/enwiki/Protective_conductor_between_MV/LV_transformer_and_the_main_general_distribution_board_(MGDB)http://www.electrical-installation.org/enwiki/Protective_conductor_between_MV/LV_transformer_and_the_main_general_distribution_board_(MGDB)http://www.electrical-installation.org/enwiki/Equipotential_conductorhttp://www.electrical-installation.org/enwiki/The_neutral_conductorhttp://www.electrical-installation.org/enwiki/Sizing_the_neutral_conductorhttp://www.electrical-installation.org/enwiki/Protection_of_the_neutral_conductorhttp://www.electrical-installation.org/enwiki/Protection_of_the_neutral_conductorhttp://www.electrical-installation.org/enwiki/Breaking_of_the_neutral_conductorhttp://www.electrical-installation.org/enwiki/Breaking_of_the_neutral_conductorhttp://www.electrical-installation.org/enwiki/Isolation_of_the_neutral_conductorhttp://www.electrical-installation.org/enwiki/Isolation_of_the_neutral_conductorhttp://www.electrical-installation.org/enwiki/Worked_example_of_cable_calculationhttp://www.electrical-installation.org/enwiki/LV_switchgear:_functions_and_selectionhttp://www.electrical-installation.org/enwiki/Overvoltage_protectionhttp://www.electrical-installation.org/enwiki/Energy_Efficiency_in_electrical_distributionhttp://www.electrical-installation.org/enwiki/Power_Factor_Correctionhttp://www.electrical-installation.org/enwiki/Power_harmonics_management

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Characteristics of !articular sources and

loads

PhotoVoltaic $PV% installation

"esidential and other s!ecial locations

,lectroMagnetic Com!atibility $,MC%

Contents

 [hide]

1 - Use of

formulae

2 - Simplified

table

3 - Examples

Use of formulae

Figure G27 below gives formulae commonl used to calculate voltage drop in a given circuit per

!ilometre of length "copper cable with #$%E insulation&'

(f)

(*) +he full load current in amps

$) $ength of the cable in !ilometres

,) ,esistance of the cable conductor in .!m

  for copper 

  for aluminium

/ote) , is negligible above a c's'a' of 0 mm2

http://www.electrical-installation.org/enwiki/Characteristics_of_particular_sources_and_loadshttp://www.electrical-installation.org/enwiki/Characteristics_of_particular_sources_and_loadshttp://www.electrical-installation.org/enwiki/PhotoVoltaic_(PV)_installationhttp://www.electrical-installation.org/enwiki/Residential_and_other_special_locationshttp://www.electrical-installation.org/enwiki/ElectroMagnetic_Compatibility_(EMC)http://www.electrical-installation.org/enwiki/Calculation_of_voltage_drop_in_steady_load_conditionshttp://www.electrical-installation.org/enwiki/Calculation_of_voltage_drop_in_steady_load_conditions#Use_of_formulaehttp://www.electrical-installation.org/enwiki/Calculation_of_voltage_drop_in_steady_load_conditions#Use_of_formulaehttp://www.electrical-installation.org/enwiki/Calculation_of_voltage_drop_in_steady_load_conditions#Simplified_tablehttp://www.electrical-installation.org/enwiki/Calculation_of_voltage_drop_in_steady_load_conditions#Simplified_tablehttp://www.electrical-installation.org/enwiki/Calculation_of_voltage_drop_in_steady_load_conditions#Exampleshttp://www.electrical-installation.org/enwiki/Characteristics_of_particular_sources_and_loadshttp://www.electrical-installation.org/enwiki/Characteristics_of_particular_sources_and_loadshttp://www.electrical-installation.org/enwiki/PhotoVoltaic_(PV)_installationhttp://www.electrical-installation.org/enwiki/Residential_and_other_special_locationshttp://www.electrical-installation.org/enwiki/ElectroMagnetic_Compatibility_(EMC)http://www.electrical-installation.org/enwiki/Calculation_of_voltage_drop_in_steady_load_conditionshttp://www.electrical-installation.org/enwiki/Calculation_of_voltage_drop_in_steady_load_conditions#Use_of_formulaehttp://www.electrical-installation.org/enwiki/Calculation_of_voltage_drop_in_steady_load_conditions#Use_of_formulaehttp://www.electrical-installation.org/enwiki/Calculation_of_voltage_drop_in_steady_load_conditions#Simplified_tablehttp://www.electrical-installation.org/enwiki/Calculation_of_voltage_drop_in_steady_load_conditions#Simplified_tablehttp://www.electrical-installation.org/enwiki/Calculation_of_voltage_drop_in_steady_load_conditions#Examples

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#) inductive reactance of a conductor in .!m

/ote) # is negligible for conductors of c's'a' less than 0 mm2' (n the absence of an other

information ta!e # as being eual to '4 .!m'

) phase angle between voltage and current in the circuit considered generall)ϕ

(ncandescent lighting) cos5 6 1

$ed lighting) cos 7 '8ϕ

9luorescent with electronic ballast) cos 7 '8ϕ

:otor power)

 ;t start-up) cos5 6 '30

(n normal service) cos5 6 '4

Un) phase-to-phase voltage

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*alanced 3-phase) 3 phases "with or without neutral&

Fig. G27: Voltage-drop formulae

Simplified table

=alculations ma be avoided b using Figure G2 which gives with an adeuate approximation

the phase-to-phase voltage drop per !m of cable per ampere in terms of)

>inds of circuit use) motor circuits with cos5close to '4 or lighting with a cos5close to 1'

+pe of circuit? single-phase or 3-phase

x (* x $

> is given b the table

(* is the full-load current in amps

$ is the length of cable in !m'

+he column motor power @cos5 6 '30A of Figure G2 ma be used to compute the voltage drop

occurring during the start-up period of a motor "see example no' 1 after the Figure G2&'

c!s!a! in mm2 Single"p#ase circuit $alanced t#ree"p#ase circuit

otor po&er 'ig#ting otor po&er

ormal service Start"up ormal service Start"up

Cu * cos + , -! cos + , -!./ cos + , 0 cos + , -! cos + , -!./

1'0 2B 1'C 3 2 8'B

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2'0 1B'B C'B 14 12 0'D

B 8'1 B'1 11'2 4 3'C

C 1 C'1 2'8 D'0 0'3 2'0

1 1C 3'D 1'D B'0 3'2 1'0

1C 20 2'3C 1'10 2'4 2'0 1

20 30 1'0 'D0 1'4 1'3 'C0

30 0 1'10 'C 1'28 1 '02

0 D '4C 'BD '80 'D0 'B1

D 12 'CB '3D 'CB '0C '32

80 10 'B4 '3 'BD 'B2 '2C

12 140 '38 '2C '3D '3B '23

10 2B '33 '2B '3 '28 '21

140 3 '28 '22 '2B '20 '18

2B B '2B '2 '18 '21 '1D

3 0 '21 '18 '10 '14 '1C

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Fig. G29: Example 1

1ample 2 "see Fig! G.-&

 ; 3-phase B-wire copper line of D mm2 c's'a' and a length of 0 m passes a current of 10 ;' +he

line supplies among other loads 3 single-phase lighting circuits each of 2'0 mm2 c's'a' copper 2 m

long and each passing 2 ;'

(t is assumed that the currents in the D mm2 line are balanced and that the three lighting circuits are

all connected to it at the same point'

hat is the voltage drop at the end of the lighting circuitsF

Solution)

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Figure G2 shows '00