IEEE/IEC std for isolating electronics when equipment is meggered 2

[edison123]

Does anyone know what is the IEEE/IEC standard that states that all the control & instrumentation electronics should be isolated before the connected power equipment is meggered ?

I would appreciate if a copy of the extract of the relevant section (not the entire standard) can be posted here by anyone as an attachment to his post.

 

[edison123]

In one of the earlier threads, someone had posted a good article by AVO on principles of meggering. Does anyone remember that thread ?

 

[Zogzog]

http://www.electricalstoreonline.com/avo-common-viewproduct.php?Refer=&Product=121

 

[Zogzog]

oops, hit the post button too quick, that is a link to the AVo publication "A stich in time" which I think is what you are asking for, however, it is not a recognized standard, but a good guide to insulation testing that is based on current standards.

You dont need a standard for this, if you dont disconnect the electronic compoents your readings will be invalid and there is a good chance you will fry some expensive stuff.

 

[edison123]

"you will fry some expensive stuff."

That's exactly what my stupid client did and is now refusing to accept the blame stating that there is no standard that states it. Did I say he is stupid ?

Thanks for the link. Is there anyway get a pdf format since that is in paper form ?

 

[Zogzog]

Hmmm, not sure where to find that in a standard, any qualified testing company/tech should be aware of this, the standards dont say all of the dumb things NOT to do, that list could be endless, I will see if I can dig something up. What was the equipment he was testing?

 

[edison123]

The client was meggering plant equipment and in the process have caused damage to control equipment, namely ET200 control modules analogue and Digital I/O modules. We are certain that during the process of meggering pump motors (in one case) and meggering Excitation system (in another case), the client did not remove control cables. He was using 1000 volts megger.

I am 2000 miles away from the site and so have not personally seen the damages he caused. But I will be there next week and want to be prepared to answer his silly questions.

 

[DanDel]

NETA Acceptance Test spec for insulation resistance testing (meggering) of switchboard control wiring (7.1.2.4) states:

"Perform insulation-resistance tests on control wiring with respect to ground. Applied potential
shall be 500 volts dc for 300-volt rated cable and 1000 volts dc for 600-volt rated cable. Test
duration shall be one minute. For units with solid-state components or control devices that can
not tolerate the applied voltage, follow the manufacturer’s recommendation."

 

[edison123]

Thank you DanDel.

"For units with solid-state components or control devices that can not tolerate the applied voltage, follow the manufacturer's recommendation."

That is exactly the same advice I got AVO people. (Thank you zogzog. I put this question to them thru' their website and got an answer as Dandel's within 15 minutes. I was pleasantly surpised.)