domestic radial

[karmannmann]

I want to measure PFC and Ze on a radial cuircut can someone explain how to?



cheers

 

[telectrix]

do you mean Zs? Ze is measured at source, nothing to do with a circuit as regards measuring Ze.

 

[pushrod]

Ze is done at the origin of the installation with either a 2 lead or 3 lead test using an earth fault loop impedance tester with the installation turned off and the earth disconnected to eliminate parallel paths. PFC is similar (meter on different setting) but with all potential parallel paths in place (ie earth reconnected).

 

[RWJ]

You don't have to measure PFC (PSSC) on a radial circuit (unless it's a distribution circuit).

Not sure why you need to measure Ze on a radial (unless as above), but you could do a loop test to find out Zs then do a continuity test find out (R1 + R2)
Then
Ze = Zs - (R1+R2)

 

[wade88]

Disconnect the main earthing conductor at the MET and using an earth fault loop impedence tester connect to the line supply side and to your disconnected main earth and carry out your Ze test.

For PFC you need to test PEFC (prospective earth fault current) and PSCC (prospective short circuit current). To test PEFC you must connect line/earth supply side, to test for PSCC you connect line/neutral. Record your highest result.

 

[wade88]

If its a TNCS system you can also calculate the PFC as the neutral of the supply is used as a protective earth and neutral (PEN). When you have obtained your EFLI, you can convert it to PSCC by using the following equation:

PSCC = V/Ze = I

for example if your Ze is measured at 0.37: 230/0.37 = 621.6 amps

 

[telectrix]

you don't use " no trip" for Ze.

 

[karmannmann]

Its a solar installation and the radial is in fact a back feed from the inverter im using a standard installation cert it asks for pfc and external loop impedance Ze

 

[Modular1]

Ze is the earth loop impedance at the mains source. Eg the meter. Nowhere else. The e stands for external (ie outside the building). You can't measure it on the end of a circuit.

 

[wade88]

you don't use " no trip" for Ze.

Who said that?

 

[telectrix]

you did

For PFC you need to test PEFC (prospective earth fault current) and PSCC (prospective short circuit current). To test PEFC you must connect line/earth, set tester to "no trip" if RCD is present, to test for PSCC you connect line/neutral, again, "no trip" if RCD is present. Record your highest result.

 

[wade88]

Just re-read my Kitcher book...stand well corrected. apologies. shall edit that post right away

 

[telectrix]

don't worry. the man who never made a mistake , never made anything. i nce fittede 12 halogen floods on a driveway of a posh house, then lamped them up with 110v lamps. was like chinese crackers.

 

[wade88]

complimentary firework show? Im just installing a 1kw quartz heater and just fixed the bracket upside down... :\ must be one those mornings.

 

[ian.settle1]

don't worry. the man who never made a mistake , never made anything. i nce fittede 12 halogen floods on a driveway of a posh house, then lamped them up with 110v lamps. was like chinese crackers.

Loved to have seen that, client must have thought someone was taking pot shots at them