Question on the LRM-ST type voltage indicators installed in 33kV switcghear

[Powerykh]

Hello all,
I am a user of this product: LRM-ST type voltage indicators.

We have this voltage indicators installed on our 33kV switchgear cable side, to indicate whether the cable is energizing or not.

Just would like to know better on the following:

During we carried out VLF (very low frequency ), test at 58kV peak in 0.1 Hz, do we need to remove this ST type voltage indicators?
Because recently we carried out the VLF test on one of the cable feeder, this voltage indicators is not remove, and the voltage indicator also without any damage after the test (The VLF test last for 1 hour, 58kV peak, 0.1 Hz)
I am quite surprise on this and the person in charge of the VLF test explained to me that:
1. For VLF test , we no need to remove the voltage indicator
2. For DC pressure test or AC pressure test on the same voltage level, then we need to remove the voltage indicator.

I cannot figure out what is the theory behind. Because as what I think, the VLF test also produce the high voltage, same as AC or DC test, except different in the frequency generated.
Do anybody have any idea on this?

 

[unclebob]

Just to be on the safe side, and to VLF the cable and nothing else, I would remove these indicators as if I was doing a Megger test.

 

[Powerykh]

Thanks unclebob.