Problem with PSSC on three phase supply

[sparksburnout]

I have a domestic premises (it was once a shop) that has a three phase supply, although only one is being used now. I am using a di-log 9083P tester, and when doing a Ze test am getting 23KA as the reading for PSC, with 0.01 ohms as the loop resistance. I am getting a Ze of 0.35 ohms and a PFC of 565A. The values for PSC and L-N loop impedance seem unbelievably low to me? I am not sure where the local transformer is but it is not next door, I think it is about 400yds away. System is TNS. I have looked at the thread in the I&T forum, and used the method of inserting an impedance in the earth lead of the tester, but I am still getting the same readings, which as far as I can see you would, as it is for low Ze not low PSC. I have used the tester on about 3 other installations, and it is giving expected results. Could it be possible that these values are correct? In which case the main switch and breakers are well underrated!!

 

[GLENNSPARK]

just check your readings again will you on Zpn....caus 23KA ffs....

 

[sparksburnout]

just check your readings again will you on Zpn....caus 23KA ffs....

I know! I just tried it again over the road at my mates house, and it's giving very similar readings now - the previous ones I mentioned were Zs. This meter is quite new, I suppose it could be faulty, or is it that these meters are just not capable of working properly at low Ze's? It is still giving a P-N loop res of 0.01 ohm that can't be right even if the transformer was next door???

 

[tom79bmth]

I know! I just tried it again over the road at my mates house, and it's giving very similar readings now - the previous ones I mentioned were Zs. This meter is quite new, I suppose it could be faulty, or is it that these meters are just not capable of working properly at low Ze's? It is still giving a P-N loop res of 0.01 ohm that can't be right even if the transformer was next door???

Hi if I leave my megger in the van over night when it's cold I get strange pfc and loop readings I leave it inside in the warm for a hour works fine it has been calibrated a few times now with out any problems,had me scratching my head at first

 

[pepparz]

I know! I just tried it again over the road at my mates house, and it's giving very similar readings now - the previous ones I mentioned were Zs. This meter is quite new, I suppose it could be faulty, or is it that these meters are just not capable of working properly at low Ze's? It is still giving a P-N loop res of 0.01 ohm that can't be right even if the transformer was next door???

it can be 0.01, thats what it is at the factory i work at

 

[Bobster]

It can be lower than that still, although you start needing specialised gear to test that low.

 

[Engineer54]

it can be 0.01, thats what it is at the factory i work at

Only close to the Factories distribution Transformer(s)...

 

[Engineer54]

It can be lower than that still, although you start needing specialised gear to test that low.

Not outside of a large commercial/industrial environment...

 

[Bobster]

Not outside of a large commercial/industrial environment...

I was just making the point.

 

[Engineer54]

I was just making the point.

So was i. ...lol!!

 

[pepparz]

Only close to the Factories distribution Transformer(s)...[/QUOTE
where else would u test Ze

 

[pepparz]

eng u dont need to write what everone already knows

 

[Engineer54]

Errr, Who know's if you even had your own Distribution TX??

 

[pepparz]

by the low reading durrr

 

[Geordie Spark]

eng u dont need to write what everone already knows

I didn't know.

But I know my way around a Regin Regu 35 Manometer AND I have two Neon Screwdrivers!!