Testing

[Wilson12]

Hi whilst doing the split method insulation resistance test.
After opening the mid point socket,whilst putting 500v through one of the legs are you supposed to leave the other end in the mcb and if not do u terminate it?

 

[Darkwood]

Depends on how you have acheived safe isolation, been an mcb the IR test will not damage it but the issue is that it is turned on making open ends live, if you are trying to split the 2 halfs of the ring at the fuseboard to the midpoint then they need disconnecting from the mcb and N bar anyway and ends making safe for the testing. (leaving the N connected globally could see false readings from other circuits or a dead S/C between E/N if main switch is still on due to the supply TX where you may have only disconnected at the mcb.

 

[Wilson12]

So when testing from one end the other end is terminated

 

[Darkwood]

You effectively need to turn the ring into 2 seperate radials and then test each one to find which half the fault is on, you split the cores in the CU and also split them at the midpoint or as near to as possible, as you cannot be at both ends during the test then just pop the ends seperately into some connectors to ensure no-one will get a zap from your insulation tester.