Odd psc

[micky j.c.]

Hi Guys,

I have ben changing a C/U for a client and whilst performing my Ze/PFC/PSC tests I obtained the following results using my Fluke 1652 multitester

The installation is a TT I have just installed a new spike and did not test the old one before I removed it so I have no reference

Ze L - Pe = 4.7ohms @ 56A PFC

Ze L-N = 25.6ohms @ 51A PSC

Should I be worried by these results

Thanks

Mike

 

[revjames]

I would have expected L-N to be significantly lower than L-E especially in a TT are youn sure those readings are the right way round?

 

[revjames]

sorry just re read and seen PFC and PSC even though I reckon L-N should be a lower path than L-E

 

[micky j.c.]

Exactly why i am asking the forum for info as usually PSC would be better than PFC on a TT system

 

[Lurch]

Duff neutral connection somewhere between the transformer and you?

 

[electrician Fife]

Contact the supply authority is my recommendation .

 

[Andy™]

Hi Guys,I have ben changing a C/U for a client and whilst performing my Ze/PFC/PSC tests I obtained the following results using my Fluke 1652 multitester

The installation is a TT I have just installed a new spike and did not test the old one before I removed it so I have no reference

Ze L - Pe = 4.7ohms @ 56A PFC

Ze L-N = 25.6ohms @ 51A PSC

Should I be worried by these results

Thanks

Mike

something seriously wrong with L-N loop. how exactly did you measure it?

 

[PC Electrics]

Assuming there's nothing wrong with your meter or methods, you should get on the phone to the DNO toute de suite, 25ohm is way too high for the loop impedance of L to N.

 

[Andy™]

tbh, if L-N loop really is 25 ohms, i think it would have been noticed by now with things not working as they should etc

 

[PBC_1966]

[quote name='Andy

 

[revjames]

I have a feeling its a measurement error.

 

[batty]

I have a feeling its a measurement error.

My thoughts too can we run a book on it?

 

[Bez]

Even Money, dodgy meter

2/1 User error

33/1 Supply fault

 

[binky]

It would be nice to know what the rod resistance was.

 

[Doc Hudson]

Even Money, dodgy meter2/1 User error

33/1 Supply fault

Can I put

 

[Bez]

Can I put

 

[Andy™]

put

 

[micky j.c.]

Hi guys

and the answer is........... the rod!

I dont know why but its the only answer i can give. My Dad was performin the test and he Knows what he is doing, properly calibrated Fluke 1652.

I called E-on they came out next day measured just L-N as its a TT system and got 0.12ohms @ 10 KA whilst he was there anyway I asked him nicely to supply an earth so he installed a Sheath (TN-S) earth for free but wouldn't hook up my new tails to the meter and get rid of the old earth leakage trip:O saying not wanting to be a jobsworth but thats ur electric suppliers department n left me too it.

So with a nice new sheath earth I am obtaining brilliant results ( L-PE 0.21omhs @ 1.2KA - L-N 0.01ohms @ 10KA). I may use that one in the future if i cant get a good spike on a TT system again thus avoiding paying for a PME( i know a sheath ain quite as good but its loads better than a spike)

I did test the Ze of the spike again out of curiousity just L-PE this time it was 41ohms @ 7Amps.

 

[batty]

Hi guysand the answer is........... the rod!

I dont know why but its the only answer i can give. My Dad was performin the test and he Knows what he is doing, properly calibrated Fluke 1652.

I called E-on they came out next day measured just L-N as its a TT system and got 0.12ohms @ 10 KA whilst he was there anyway I asked him nicely to supply an earth so he installed a Sheath (TN-S) earth for free but wouldn't hook up my new tails to the meter and get rid of the old earth leakage trip:O saying not wanting to be a jobsworth but thats ur electric suppliers department n left me too it.

So with a nice new sheath earth I am obtaining brilliant results ( L-PE 0.21omhs @ 1.2KA - L-N 0.01ohms @ 10KA). I may use that one in the future if i cant get a good spike on a TT system again thus avoiding paying for a PME( i know a sheath ain quite as good but its loads better than a spike)

I did test the Ze of the spike again out of curiousity just L-PE this time it was 41ohms @ 7Amps.

Out of interest how do they connect the earth wire to the sheath.

 

[ianmacd]

I may use that one in the future if i cant get a good spike on a TT system again thus avoiding paying for a PME( i know a sheath ain quite as good but its loads better than a spike)

Why do you say this? IMHO rod is safest of all as any faults on DNO's network will not cause you to loose your Earth unlike on TN systems.

Also when you say 'paying for PME' does that mean you pay the DNO to convert their network (or at least the part you are using) to PME and are then able to present you with a TN-C-S earth?