short circuit on socket outlets while doing insulation resistance test

[faretra 1]

I have 2 questions on an exam paper I need help with they are -

1.When carrying out an insulation test between live conductors of a radial socket outlet circuit a short circuit is discovered, describe how you would perform a test to determine the location of the short circuit within the damaged cable.

2. Describe the action to be taken to rectify the problem above.

any help most appreciated...

 

[M107]

1. Dissconnect legs between sockets & retest at each dissconnection untill you get a failure reading (assuming you know the half way point of the circuit break here & test either side, this will shorten the fault finding process....divide & conquer)
   
2. Replace damaged length of cable beween two points/sockets
   

 

[Evans Electric]

What he said !! Divide and divide again until you find it.

 

[NozSpark]

Technically it's called the half split method....

and you replace the faulty cable/accessory

 

[PC Electrics]

No need to spend time dismantling, not initially anyway. Remember this is a radial circuit.

Lets assume the testing has been carried out at the origin of the circuit and the insulation tester has returned a 0.00Mohm reading.

Now switch to low ohms range and take a reading between the affected conductors.

(at this stage if this is a dead short you will get a very low reading which will represent the resistance of the cable between the point of test and the fault. You could use the R1+R2 tables to estimate the length of cable between the test point and the fault if this info is likely to prove helpful)

using your tester and a suitable adaptor, now measure the low ohms between the affected conductors at each socket in turn. the fault should be between the two sockets with the lowest readings. Remove these socket fronts and disconnect. test all the cables to confirm which has the fault.

If one of the readings was virtually zero, then it is probably a short within the socket or just behind it. In this case examine all the cables closely as you dissassemble. test the socket on its own too.

How you fix depends on the fault you find. If its broken conductors behind a socket, cut back and crimp on some extra length. If it's nicked insulation apply heatshrink tubing. If it's the socket, replace it. If it's the cable leg between two sockets it'll probably need to be replaced unless you can accurately find the fault and cut and crimp back together.

 

[faretra 1]

Thanks for all your the replies...it is most appreciated, a great help !!!

 

[spinlondon]

The OSG has a Table giving R1+R2 per meter.

For instance, 2 X 2.5mm

 

[bengie]

pc electrics has it!

 

[faretra 1]

Just noticed in the exam question, they want us to do a diagram for the test to determine the location of the short circuit within the damaged cable. anyone have an idea of a simple way of showing the test to find the short....

 

[faretra 1]

the exam question also asks for a labelled diagram... anyone know how to show a simple labelled diagram showing how you would test to find the short circuit the socket outlets circuit, is there a certain way of showing this or do they mean just an illustration showing sockets and tester etc ??? is a bit confusing this one but it is part of the exam question....