New so be easy on me. I work in a AC factory and we hipot all cables and wires and I understand what is going on with this. Now I have a buyer that wants his unit megger. These cable are control cables no more then 10 feet long and are 120v . Now if I have hipoted them what advange is there to megging? These are new cables. And if there is what kind of reading should I be looking for on the megger? I have a Biddle megger 359 hand crank.
Megger and Hi pot asap
- Thread starter toddross
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zog
Senior Member
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- Charlotte, NC
Huh? Someone wants his unit meggered? You work in a factory that makes AC? (We usually call those power plants).
Are you doing an AC or DC hipot test on these cables?
brian john
Senior Member
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- Leesburg, VA
Chances are you have terms mixed up.
What voltage are you testing at? Then we can sort out the answers.
What voltage are you testing at? Then we can sort out the answers.
brian john
Senior Member
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- Leesburg, VA
What is your hipot and what is the duration of the test, is your hipot test AC or DC.
SORRY I should have asked these questions last time.
Don't know why they want to megger a control circuit but a rough rule is; any reading below a meg is a problem. Read this for a more specific answer;
http://www.biddlemegger.com/biddle/A Stitch In Time.pdf
http://www.biddlemegger.com/biddle/A Stitch In Time.pdf
SG-1
Senior Member
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- Ware Shoals, South Carolina
The advantage to the megger reading is that everyone has a megger. Few people have an AC dielectric test set, due to cost & the test is destructive.
You will be supplying the customer with a base reading that he will compare with the readings that he will take when doing future preventive maintance. Some of our network protector customers request this.
You will be supplying the customer with a base reading that he will compare with the readings that he will take when doing future preventive maintance. Some of our network protector customers request this.
brian john
Senior Member
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- Leesburg, VA
While Biddle publishes that one meg rule, THAT IS NOT A GOOD VALUE, check NETA Standards.
zog
Senior Member
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- Charlotte, NC
Let's keep the rules of thumb to the DIY forums. Minumum insulation resistance requirements will vary based on the equipment type and voltage rating, are you looking for something specific?
richxtlc
Senior Member
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- Tampa Florida
A hipot and a megger test for different characteristics of the insulation under test. A megger tests for the quality of the insulation, its leakage. A hipot tests for its dielectric withstand capability. A cable can pass a hipot test and fail a megger test. There is usually no specification for hipoting a cable other than level and time. If the milliamps stay constant or decrease the cable passes the test. On the other hand a megger test, the cable must be above a minimum value in order to pass.
When doing a hipot test, the first test is to perform a megger for one minute, then, if ok, perform the hipot. At the completion of the hipot, re megger the cable to insure that it did not damage the insulation.
When doing a hipot test, the first test is to perform a megger for one minute, then, if ok, perform the hipot. At the completion of the hipot, re megger the cable to insure that it did not damage the insulation.
megger
megger
Yes, makes sense but I see nothing wrong with a rough rule of thumb to indicate a problem may exist. If their is any question at all I would certainly investigate farther. So what is the answer to Todds meggering question? Naturally you want to know the wire size and voltage. Do you also want him to measure the lenth of the wire, describe the enclosure type, components and termination? It seens to me he's just looking for a reasonable reading to determine if the insulation is compromized. Realisticly I would say anything over 2meg is probably fine. I have not heard any other numbers. Or are we ridgid on having all the exact details?
megger
Yes, makes sense but I see nothing wrong with a rough rule of thumb to indicate a problem may exist. If their is any question at all I would certainly investigate farther. So what is the answer to Todds meggering question? Naturally you want to know the wire size and voltage. Do you also want him to measure the lenth of the wire, describe the enclosure type, components and termination? It seens to me he's just looking for a reasonable reading to determine if the insulation is compromized. Realisticly I would say anything over 2meg is probably fine. I have not heard any other numbers. Or are we ridgid on having all the exact details?
zog
Senior Member
- Location
- Charlotte, NC
Well Brian already gave the NETA reference but these are headed to a nuclear plant in Japan so likely they will have a different standard to adhere to. Nuclear plants don't use rules of thumb, they have very strict standards. Here in the US most nuclear plants will follow EPRI recomendations, not sure about Japan.
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