I have completed Part P and C%26amp;G 2381 as I have to notify alterations to existing circuits when I install boilers to fuse spurs etc. I understand Zs=Ze + (r1+r2) and Zs can be calculated. Best practice tells me to measure Zs to add to my Minor Works. I would like to know how to measure Zs, I know it is done live but unsure where I place my test probes from my Megger 1552, is it two leads or three? If anyone can give me honest advice I would really appreciate it. I think I connect one lead to the MET earth and the other lead to the supply side of the main switch, with the switch in the off 'open' position. Any help really appreciated, ie a link to a site, or pictures please. Thankyou.
Hi. Can any time served electricians help me understand how to test earth fault loop impedance (Zs) please?
Zs is at the accessory, Ze is at the CU, on the load side, with ALL CIRCUITS TURNED OFF, and bonding disconnected.
It's a three-lead test.
For Zs Double up N%26amp;CPC probes on the earth if no neutral is present at the accessory.
Honest advice is:
If you really don't know how to test then you shouldn't be doing it.
Pauline
Reply:For Zs you have to test from the furthest socket outlet, or light fitting on that circuit. The test is done using phase and earth.
The on site guide and guidence note 3 give you further info on how to do this.
From what you discribe, you want to know what the Ze is. This is done from the consumer unit, and again, consult the on site guide or guidence note 3
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