Ze at origin tns

[Electricalserv]

0.01ohms? Does this comply? Tns system. Unsure because, usually given as 0.8ohms, previous test cert gives 0.08 ohms. Not sure if previous spark rang supplier or just put 0.08 anyway. Is this value ok anyhow?

 

[IQ Electrical]

Its quite possible to have a pfc that high especially if the transformer is nearby.

It is theoretically possible to approach values above 16KA but in practice, it's almost unheard of.

Since becoming aware of the scenario that I described in post 11, any conventional Ze measurement that we find below 0.10 Ohms is re-measured with an adjusting impedance added to lift the meter into it's acceptable range (normally above 0.30 Ohms).

The difference always makes this a worthwhile 10 minute exercise and shows how poor our meters are at values below 0.30 Ohms.

 

[Electricalserv]

Found substation around 20m from house....why so low? Anybody?

 

[IQ Electrical]

Found substation around 20m from house....why so low? Anybody?

Lol, I've explained it twice!

 

[Chr!s]

It is theoretically possible to approach values above 16KA but in practice, it's almost unheard of.

Well if you have a 1000kva transformer, using a transformer impedance of 4.75% you would get 30.5ka at the terminals, so if your close to the transformer a high PFC is possible.

 

[IQ Electrical]

Well if you have a 1000kva transformer, using a transformer impedance of 4.75% you would get 30.5ka at the terminals, so if your close to the transformer a high PFC is possible.

Absolutely right but from my point of view as a serial measurer of Ze, I have yet to actually measure a value of Ze low enough to give a PFC higher than 16kA

 

[Electricalserv]

Well here you have it. Nulled leads etc. Remeasured 0.02 ohms 11.5ka 20m from substation. This is the house my bro has just bought. Previous test result was 0.08 ohms so very low aswell.....

 

[gamblor6]

It is theoretically possible to approach values above 16KA but in practice, it's almost unheard of.

Since becoming aware of the scenario that I described in post 11, any conventional Ze measurement that we find below 0.10 Ohms is re-measured with an adjusting impedance added to lift the meter into it's acceptable range (normally above 0.30 Ohms).

The difference always makes this a worthwhile 10 minute exercise and shows how poor our meters are at values below 0.30 Ohms.

i regularly find high pfc readings iq, had one recently.01 ze off the scale ipf. what would be your course of action in that situation?

 

[gamblor6]

Well here you have it. Nulled leads etc. Remeasured 0.02 ohms 11.5ka 20m from substation. This is the house my bro has just bought. Previous test result was 0.08 ohms so very low aswell.....

how did you null the leads? for a pfc test?

 

[IQ Electrical]

i regularly find high pfc readings iq, had one recently.01 ze off the scale ipf. what would be your course of action in that situation?

No, your meter displayed a reading of 0.01 Ohms, read back through the thread, the bit regarding 2nd digit tolerance, it makes a massive difference to PFC as you can imagine when a Ze reading can be between 0.01 and 0.09 Ohms.

The only way to increase accuracy at those levels is to use a known resistance in series to lift the meter into it's 'sweet spot' accuracy area.

I wrote a piece on how and why to add the resistance, I'll find it following my house move and get it posted up.

If you do a lot of testing, it's well worth doing this 10 minute procedure.

Out of interest, check your meter's quoted accuracy range-a Megger 1553 is >0.30 Ohms!

 

[gamblor6]

will do iq. i think any ze above .12 is high tho lol. city centre edinburgh. please pm me with your piece on how and why to add resistance.

 

[IQ Electrical]

will do iq. i think any ze above .12 is high tho lol. city centre edinburgh. please pm me with your piece on how and why to add resistance.

Will do.

 

[Electricalserv]

how did you null the leads? for a pfc test?

Meter has auto null and measures pfc when Ze is taken.

 

[Engineer54]

You can always calculate the Ze at origin, like we used to have to do, before Loop Testers were around!! Get an accurate volt meter and a load of around 40 to 50A. Measure the voltage at no-load, and then with the connected load, there will be a voltage drop. Whatever the voltage drop difference measured, divide by the current you applied, ...that's your value!!! You can then go onto find the PSC by dividing the no-load voltage, by the figure you attained above....

At the very least it will give a good indication if your meters measured value, is anywhere near accurate. Your only problem being, ...is providing a known current load to measure the volt drop. We used to have home made load banks, that we made as part of our training. But any steady load can be used of sufficient current to cause a volt drop at the origin of your supply.