PFC Three-phase supplies

[Sly]

Can someone tell me how to correct measure Prospective fault current and external earth fault loop impedance (Ze) for a domestic property in Three-phase supplies!
I use Fluke 1653
Thanks in advance

 

[Guest123]

Hey.

Ze - same as you would for single phase, only do it 3 times and record the highest.

PFC - (3 lead instrument) measure betwenn L,N+E and multiply by 2, as the highest fault current is usually between phases.

 

[Sly]

Thanks a lot

 

[DanBrown]

So basically, you put test leads on
L1 - N - E = ?? then X by 2
L2 - N - E = ?? then X by 2
L3 - N - E = ?? then X by 2

The highest reading out of these 3 test, you record...
Is that correct??

 

[Guest123]

For a 3 wire instrument, correctamundo.

For a 2 wire, test L+N and L+E multiply whichever is highest by 2 and het presto.

 

[BristolSpark]

Do you not have to disconnect the earth first also.

 

[trebor]

No the earthing conductor stays connected for pfc to include parallel earth paths when measuring pefc, yoo only disconnect for Ze, you can of course with most instruments take a pefc at the same time as Ze but it may not be a true highest reading