Urban Legend of Exploding Meters???

[ndcctrucks]

Hi All:

I am an industrial electrician (steel mill) who just started working as a hydro plant electrician. As such, I don't have a lot of training on high voltage yet.

I was sent to a remote site which has a full 3-phase (not open-delta), 480 volt service; the call was no power in the building.

My Fluke 87 meter showed 160 volts A-B, 140 volts A-C, and 54 volts B-C. When I went from ground to any phase, I got an audible arc noise and my meter showed "OL", which is either open circuit or out of range.

Carefully approaching a phase lug showed the meter indicating 800 volts and higher.

We stopped the job and contacted the utility. We also found on the way back that two of the pole-mounted primary fuses had blown, so one phase was feeding the bank, but was an open circuit.

Later I was told that touching a meter probe to a secondary can cause the service meter to explode out of the socket. If that had happened, I would have gotten my hardhat blown off.

I ain't skeered, but I do like to be aware of real hazards.

Any info?? Is it true that a service meter can blow out of its socket when the primaries are not right? Is it normal for high voltage to be present in this situation?

Thanks

-Ken

[Engineer]

I have seen this situation on more than one occasion. If you have a delta- delta power bank and 2 out of 3 primary fuses are blown the bank won't be energized but there will still be a live connection to the primary winding (from un blown fuse). There is capacitve coupling from the primary to the secondary winding causing voltage to be present. In one case on a 4800/8320 system (2 out of 3 fuses blown) we measured 1600 volts to ground . This can also happen if a medium voltage Ct secondary is not properly grounded. Be careful.

[ndcctrucks]

Thanks very much Engineer.

I wonder if this situation is discussed in any apprenticeships?