Help with PSC at origin of supply.


Postby remelad » Wed Oct 10, 2007 10:33 pm

Looking for some help with a psc reading i am getting,i'm useing a Fluke 1653 multi test meter. I am connecting the earth lead to the earth block in the c/u and connecting to the phase and neutral at the main switch on the live tails,switch turned off. The reading i am obtaning is Z=0.42 ohms ( which is in tollerance as this is a T N S supply) and a PSC of 577 amps. When i do the math this works out correct 0.42x577= 242Volts. I was under the impression that the PSC reading should be much higer because on the electrical installation form they are looking for a reading in the kiloamp range. Could someone please point me in the right direction to what if anything i'm doing wrong. Not sure if i'm useing meter corretly. Many thanx in advance Remelad.
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Postby sparx » Thu Oct 11, 2007 8:22 pm

Hi Remelad, no worries, with a Ze 0.42ohms, you won't get into kA region. just line through the 'k'.
Test sheets are set up for in town, close by sub station readings!!
Here in 'the sticks' it's rare to get kA readings, also some meters do 2 readings at once, they read PSCC at highest of either L-N or L-E and Ze @ L-E so maths don't always add up, in fact only TN-C-S systems work out as N&E effectively the same thing.
Glad to see you're still out there, not seen you for a while , Best Wishes SPARX
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Postby jackhawk » Thu Oct 11, 2007 8:27 pm

[quote="remelad"]Looking for some help with a psc reading i am getting,i'm useing a Fluke 1653 multi test meter. I am connecting the earth lead to the earth block in the c/u and connecting to the phase and neutral at the main switch on the live tails,switch turned off. The reading i am obtaning is Z=0.42 ohms ( which is in tollerance as this is a T N S supply) and a PSC of 577 amps. When i do the math this works out correct 0.42x577= 242Volts. I was under the impression that the PSC reading should be much higer because on the electrical installation form they are looking for a reading in the kiloamp range. Could someone please point me in the right direction to what if anything i'm doing wrong. Not sure if i'm useing meter corretly. Many thanx in advance Remelad.[/quote]

I would read instructions very carefully. As for connecting the earth lead to the earth block in the CU that is not recomended. To measure Ze you need to disconnect earth conductor from CU and connect earth lead to that for your reading. Connecting the earth lead first, then N, then L. Ensure earth conductor is re fitted after testing!!!
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Postby remelad » Thu Oct 11, 2007 10:38 pm

Hi Sparx/jackhawk, thanxs for your replies do i take it that on the test form where it asks for the P S C i would write down .577KA. Jackhawk thanxs for your concern when measuring the Ze, i did remove the main earth cable it was replaced for the P S C measurement. Sparx have been around just not asking to many silly questions,not really in your leauge to give out sound advice like the others and yourself.Look after yourself young man. Thanxs to the 2 of you. Remelad
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