meger mft testing

[james king]

hi all

at collage we use the megger mft 1553!

now on a ring cct say 10m long we get a reading of 0.45ohms on sockets 1,2,3,4 but on socket no 5 the reading states 0.00ohms can any one give me some examples of what the metre will show upon faults?

 

[ukpablo]

i guess that the cables are twisted together in the back of skt 5, therefore the ring is still complete, however they are not connected in the bak of the skt plate, so u would remove skt plate to investigate! this is why u are prob getting no reading.

also did u swop the probes into neutral to check that it is not wired up in wrong terminals too?!

i take it u are testing R1+R2?

 

[telectrix]

you don't say what you are testing. R1+R2? L/N? what?

 

[telectrix]

i guess that the cables are twisted together in the back, therefore the ring is still complete, however they are not connected in the bak of the skt plate, so u would remove skt plate to investigate!

he's getting 0.00 not O/C, and cables should not be twisted

 

[james king]

sorry testing R1+R2

 

[james king]

O/C?????

 

[telectrix]

doesn't make sense. if reading 0.00, that's a dead short. remove socket no.5 and check connections. O/C = open circuit. btw.

 

[IQ Electrical]

O/C?????

Think about it jiga, if it was open circuit, how would you have zero resistance?

 

[ukpablo]

what readings did r1 rn and r2 show?

 

[james king]

i thought a dead short would give a reading?? only on IR would it show 0.00.

open cct would be >99 ohms

 

[ukpablo]

if u reset the megger to 0.00 on and plug in than it will show 0.00 if no cct is made, therefore like i said earlier they are not connected in bak of skt.

does the little black gate on the screen of the megger show open or lclosed when u plug it into skt 5?

 

[james king]

ahh ok ! just need to get use to the metre!

what are the 3 little circle at the top left with l-n l-e n-e or somw thing like that can remember of the top of my head?

 

[ukpablo]

he's getting 0.00 not O/C, and cables should not be twisted

i know that they should not be twisted, however most test beds at colleges do this to introduce faults like this one.

 

[ukpablo]

jiga, go onto youtube and look for megger 1552-3 tutorials, this will give u some pointers.

 

[telectrix]

i thought a dead short would give a reading?? only on IR would it show 0.00.

open cct would be >99 ohms

i agrre open crcuit should show >99Ω