Electrical Testing Question for Metal Clad Switchgear

[nightfox1925]

We have a NEW Metal Clad switchgear rated for 13.8kV.


We have made several eletrical tests and we have a concern on two specific tests.

Is a AC Hi-Pot and Insulation Power Factor tests a mandatory installation test requirement for the switchgear and associated power circuit breakers. Is an insulation resistance test taking both D.A.R. and P.I. enough?

NETA specifies Insulation Power Factor as an optional requirement.

I would like to know your experience for me to know when to decide to go for these tests. Thank you.

I'm a fan of this forum as well.

 

[Zogzog]

NETA is an ANSI standard, if that is what you are required to follow then the Overpotential test is mandatory and the PF test is optional, but what is required depends on what spec you are required to follow (If any).

I was a NETA level IV tech, did NETA testing for 10 years and rarly did Pf tests on MV switchgear, only if the customer required it or if the hipot test results were questionable. A Pf test is a better test than AC hipot, more of a condition assesment measurment, so it might be good to have some baseline data for future reference.

 

[nightfox1925]

Thanks for the insights Zogzog.

 

[DanDel]

A PF test is not necessary on MV switchgear, and not recommended on MV vacuum C/Bs (I'll assume you have vacuum C/Bs since you say the gear is new). Applying an AC test voltage across open vacuum-bottle contacts can create dangerous X-ray radiation.

The Overpotential (Hipot) test along with a preliminary Insulation Resistance (Megger) test (DAR and a 10-min test for PI is not necessary), and bus connection resistance tests, are recommended for the switchboard bus.

 

[nightfox1925]

Thanks dandel.

What about a dielectric test on the vacuum bottles, is this going to be part of the standard test?

 

[Zogzog]

Yes it should be, it is called a vacuum bottle integrity test and can, be done by applying a voltage across the open contacts and making sure they dont flash over, be sure to use only the test voltages in the OEM's maintenence manual.

 

[nightfox1925]

Ok, thank you very much!

 

[DanDel]

The vacuum bottle integrity test is performed as the main component of the overpotential test (Hipot), typically at about 37kV for a 15kV C/B. Check the manufacturer's recommendation for voltage.