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ETAP Cable Calculated Impedance 2

Nina~

Student
Joined
Jul 15, 2025
Messages
2
Hello Sir. Is there a reason why when I set protective conductor in 4/C cable, the impedance calculation cannot be perform ? It only work when i set it to neutral.

Also the No.of Conductor of the neutral is only one condutor. When I try to use 4*1/C cable and increase the No. of conductor of the neutral up to 4 conductor, the impedance cannot be calculate. I am using IEC standard. Does IEC standard only consider one neutral conductor as a return path ?

Thank you.
 

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I am not a ETAP user but, if it is to follow IEC standard -let's say, for instance, IEC 60364-1- and you consider TN-S earthing system, the fourth conductor is for earthing and then the impedance of neutral it is actually the phase-to-earthing impedance. If it is only for neutral used and it is earthed only one end-usually the supply end-that means you have another earthing conveying way, not through this cable. However, you may use, in a way, for both neutral and earth as per TN-C-S system.
If you have an outside means for earthing it is not cable theory the address.
By the way, it will be easier if your cable presents 5 conductors-3 for lives 1 for neutral and 1 for earthing.
 
I am not a ETAP user but, if it is to follow IEC standard -let's say, for instance, IEC 60364-1- and you consider TN-S earthing system, the fourth conductor is for earthing and then the impedance of neutral it is actually the phase-to-earthing impedance. If it is only for neutral used and it is earthed only one end-usually the supply end-that means you have another earthing conveying way, not through this cable. However, you may use, in a way, for both neutral and earth as per TN-C-S system.
If you have an outside means for earthing it is not cable theory the address.
By the way, it will be easier if your cable presents 5 conductors-3 for lives 1 for neutral and 1 for earthing.
Hello, thanks for replying. At trafo element editor i set the earthing type to TN-S. My confusion with this is :

A). When i want to use 4*1C cable (12 Phase+4 Aux Neutral+ 4 Protective) from trafo to Main D.B. It shows that the cable pos and zero sequence impedance cannot be calculated using this configuration. But when i change the cable configuration to 12 Phase + 1 Aux Neutral + 1 Aux Protective, only then ETAP will show the result.

B.) Same issue occurs when i use 4C cable (3P+1PE) connect from MCC to the motor. The pos and zero seq impedance can only be calculated when i change the configuration (for this 4C cable) to 3P+1N.

The confusion that i still have based on those two point is :
A. Why if i set the number of neutral condutor more than 1, the impedance calculation cannot be perfom ?
B. Why for 4C cable (mcc to motor), the impedance can only be calculated when using 3P+1N, not 3P+1 PE ?

ETAP states that this impedance calculation is based on IEC 60909-3 and IEC 60287-1-1. This is just for study purposes, so I was curious whether it has something to do with those two IEC standards or not ?

Thanks
 
IEC 60909-3 [Part 3]:
Currents during two separate simultaneous
line-to-earth short circuits and partial short-circuit
currents flowing through earth
I have the 2003 Edition
However, that means the short-circuit current return it is not through the PE conductor but through ground: there are two points -two different phase-earthed [See fig.3]
The line it is an OVHL [it is not a cable] and instead of PE conductor
there is an Earth wire on the poles.
On the other hand, IEC 60287-1-1 does not present any cable impedance calculation but only how to calculate current carrying capacity of a cable:
IEC 60287 Electric cables.
Calculation of the current rating.
Part 1-1:
Current rating equations (100 % load factor)
and calculation of losses.
General
IEC 60909-3 Fig.3.jpg
 

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