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

 

[IQ Electrical]

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?

Register on the Megger site and download the manual here:

Megger

 

[telectrix]

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?

they indsicate supply voltage and polarity. only come on when plugged into energised circiut. as said, look at megger tutorials on utube and practice with your tester till you can do it blindfold.

 

[ukpablo]

i dont think it is an open cct, like i said if the skt plate is not connected, the cct is still being made, but the terminals are not connected into the cct in skt 5, therefore the tester will still show 0.00 because it is not measuring anything!......do u not agree?!

 

[james king]

so im still confuzuled???

open cct mean >99ohms

closed cct would give u a reading

IR

open circuit will give u >299

close cct (dead short) will give 0.00Mohms

can the megger tell you if the N is in L terminal and so on

 

[ukpablo]

sorry mate, too hard to explain on here, u need to be shown in real time. ask ur tutor to do it for u, if u pm me i have a dvd i can burn for u on megger testing and will send to u in post if thats any good to u?