Two and Three Wire Testing ???

[j.capes]

Hi all,

Im in the early stages of learning testing and was wanting to know if any of you could help me understand two lead / three lead testing.

Why do you need a third lead for some tests, when other makes of meter can do the exact same test but with two leads??

I understand that the meter needs to be powered from the circuit under test with some meters but with tests like Ipsc and Ipfc I would like more explanation.

Hope you can help me understand this better.

Thanks

 

[white armour]

Hi j.capes, think it all depends on the make & model of the meter. Mine requires 3 leads for loop testing RCD protected circuits even with the trip lock facility enabled, know that there are meters on the market that can do this using only 2 leads.

With Ze/PSCC/PEFC think most types of meter employ the 2 lead method.

Regards wa

 

[j.capes]

Thanks for your reply. Was confused because seen people testing pfc at the consumer unit with three probes connected to line, neutral and MET (fluke meter). Does this test both Short circuit current and earth fault current at the same time and give you the reading in KA for the highest of the two to put down as your PFC reading on the form? Would have though these would have been two separate tests? One between line and earth (two leads) and one between line and neutral ??

 

[needasparks]

Think you will find the three wire meters use the neutral to power the meter on the test whereby the two wire combine it in the test.