Loop impedance

[buttonmoon]

I was doing a Ze test today with my 1651 fluke and it was reading >2000 ohms.

The main switch was isolated and the earth disconnected. I had the green probe crocked onto the TN-S clamp on the incoming main, the blue on the neutral bar and the red on the supply side of the main switch.

Assuming there was a problem with the supply company's earthing I was about to call them when I thought I'll just do a Zs test on a socket outlet to be sure and I got a reading 0.8 ohms or something like that.

Would anyone mind telling me what is going on here? My tester just got back from being calibrated so I can only assume there is something I am doing wrong

I ended up calculating Ze from Zs-(R1+R2) as 0.1 ohm.

thank you for any ideas.

 

[Spudnik]

Did you disconnect all bonds etc before testing Ze?

Did you reconnect when you performed Zs?

If yes to both, then i expect the reading were assisted by parallel paths.

Also, i would be jumping down the fone at the DNO for them to sort it out.

However, in the meantime, you should bang a rod in as a temporary earth.

 

[buttonmoon]

So what you're saying is that despite getting a reading for Zs at in fact several socket outlets in the end, the result is being caused by parallel paths within the installation and my external earth is still non existent.

Earth spike might be difficult due to no garden (central London property).

If that is the case should I double check main bonding use the gas and water services as a temp spike install an RCD or just call the DNO now?

I would rather not get someone from EDF or whoever to come down and tell me I got it wrong and make me look like a complete idiot

 

[Des 56]

I dont have your particu;ar meter,so I cant comment on its use
What5 I did notice from your post was that you had the main switch isolated, probe on neutral bar

If you are using a 3 lead tester,then I take it that you should have a functioning neutral to do this test
An isolated neutral may be giving you these readings

Do the test again with the main switch on and rcds and mcbs off,or alternatively, probe into the incoming neutral not after the isolated main switch

Or use a 2 lead probe for your meter

 

[SirKit Breaker]

I was doing a Ze test today with my 1651 fluke and it was reading >2000 ohms.

The main switch was isolated and the earth disconnected. I had the green probe crocked onto the TN-S clamp on the incoming main, the blue on the neutral bar and the red on the supply side of the main switch.

Assuming there was a problem with the supply company's earthing I was about to call them when I thought I'll just do a Zs test on a socket outlet to be sure and I got a reading 0.8 ohms or something like that.

Would anyone mind telling me what is going on here? My tester just got back from being calibrated so I can only assume there is something I am doing wrong

I ended up calculating Ze from Zs-(R1+R2) as 0.1 ohm.

thank you for any ideas.

Are the fuses Ok in the probes? are the probes OK? I assume you did socket Zs with the plug lead not the probes.

 

[pjb1]

Agree with Des56
I use a 3 lead tester a Fluke 1653, to test Ze with earth conductor disconnected connect the flukes green test probe/croc to this. and the red and blue test probes go to the live side of the consumer unit main switch. Which it self will be off.

Hope that helps