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# r1 r2 and pfc

Discuss r1 r2 and pfc in the Periodic Inspection Reporting & Certification area at ElectriciansForums.net

D

#### davino

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couple of questions...in regards to r1 r2, when testing what is the lowest reading thats accepted on say a 1.5 t&e, to a 10.0 t&e I got a reading of 0.39 on a 10mm t&e and I got a right -------in for puttin it on the sheet..

and is this the right calculation for pfc? voltage divided by Ze? so if my voltage is 230v and the Ze is 0.12 the answer is 1966 which is around 1.9Ka ???
someone please tell me this is right am gettin a right grilling from my boss ...

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A

Hi,

Firstly your calculation for PFC works out at 1.9KA which seems like a reasonable reading in my experience. With regards your r1+r2 - it obviously depends on the length of the cable. The most important things to be considering with regards limits, is the voltage drop at the end of the cable and the measured Zs. Make sure youre nulling your test leads first!

#### ian.settle1

##### -
Mentor
Arms
couple of questions...in regards to r1 r2, when testing what is the lowest reading thats accepted on say a 1.5 t&e, to a 10.0 t&e I got a reading of 0.39 on a 10mm t&e and I got a right -------in for puttin it on the sheet..

and is this the right calculation for pfc? voltage divided by Ze? so if my voltage is 230v and the Ze is 0.12 the answer is 1966 which is around 1.9Ka ???
someone please tell me this is right am gettin a right grilling from my boss ...

In the back of the OSG you will find a table for reisistance of cables per metre so if you know the approx length then you can check against it,

B

#### Bright-spark

PFC is the highest of Pscc and Pefc.

Pscc (prospective short circuit current) is the short circuit current between 'Live' conductors ie in single phase between Line & Neutral and in three phase between Line conductors.

Pefc (prospective earth fault current) is the the short circuit current between line and earth. So Pefc is Uo/Ze.

For three phase Pscc is taken as 2x line neutral fault current.

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