C-value

[Toros]

hi
I am calculating short circuit at various equipments supplied by various conductores .
one more time, where do I get the list of values for c-value and also Z-value
tanx

 

[Tony S]

I take it you require them for the adiabatic equation?

I would get them from tables and constants in BS7671 which aren’t applicable to you unfortunately.

If they’re not in the codes I would say look on line. I’ve had a quick scan of 2014 and can’t see the constants.

 

[Julius Right]

For cable Z you may take from NEC 2014 Table 9 Alternating-Current Resistance and Reactance for 600-Volt Cables, 3-Phase, 60 Hz, 75°C (167°F) — Three Single Conductors in Conduit
However, in my opinion, you need the total Z circuit-let’s say from the transformer ,feeder and branch –if any-in order to calculate the short-circuit current.
In order to calculate the allowable conductor cross-section area withstanding the short-circuit current NEC Art.240.4 Protection of Conductors. Informational Note: recommends ICEA P-32-382-2007.
See :
http://www.generalcable.com/NR/rdonlyres/D60F2C04-B580-4C2C-A4DC-07B638A1DA02/0/SpecF125.pdf

 

[Bugman1400]

For the cable, you can get those values from the cable manufacturer. For the source, you can get those values from the utility or use an infinite bus.