Maintenance on station class surge arrestors.
Maintenance on station class surge arrestors.
(OP)
Has anyone heard replacement of 115kV arrestors (MOV type) is required on a periodical basis?
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Maintenance on station class surge arrestors.
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RE: Maintenance on station class surge arrestors.
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: Maintenance on station class surge arrestors.
1. Washing/cleaning periodically(9 month to 1 year) to avoid dust accumulation
2. Earth resistance measurement(2years)
3. Track of Earth leakage current & surge counter readings(monthly).
There might be earth leakage current indicator close to earthing point of Surge arrester, check if it has crossed the safe limit. Contact vendor for max leakage earth current.
RE: Maintenance on station class surge arrestors.
SA are replaced based on following criteria in most networks:
1. When the Continuous / Steady State Leakage current as measured in the leakage current meter is 4/6/8/10 times the value at commissioning instant
2. More than twice the number of discharges in any specific period, as per the adopted maintenence period / practice, in comparison with another identical unit's activity within or in a nearby similar installation
3. Pre and Post monsoon readings of the counter exceeding expected values based on isokeraunic level of the installation.
Periodic replacement without regard to any one or all the above could be expensive.
Regards
RE: Maintenance on station class surge arrestors.
RE: Maintenance on station class surge arrestors.
RE: Maintenance on station class surge arrestors.
This current leakage would occur internally, and the units are supposed to be environmentally sealed (though there have been some problems with sealing) so I suspect that internal current leakage (failure to electrically seal) would not only be a coastal problem.
Thank You.
RE: Maintenance on station class surge arrestors.
I heard an engineer who designed surge arresters say that it was a very simple product - no moving parts. And if it ever has any moving parts, you'd better get out of the way!
RE: Maintenance on station class surge arrestors.
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: Maintenance on station class surge arrestors.
Do some arresters come with operation counters? I hadn't heard of that.
Doble testing is a good test for lightning arresters. Of course you've got to pay attention to the resutls. We had a lightning arrester fail. Went back and look at the trends... sure enough power factor had been trending up for several readings in a row.
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RE: Maintenance on station class surge arrestors.
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RE: Maintenance on station class surge arrestors.
I am designing the gnd system for a 67kV Substation where there is two lightning arrestors (one just before the high side of the step-down XFMR and the other on the main incoming post).
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I am sizing the earth connection for the MOVs and I was curious on how this is done. So I did a search. Interestly I read that the earth connection is suppose to be insulated and isolated from the XFMR tank. Why?
If I size a #4/0 AWG stranded bare copper run from the GND point of the MOVs down the side of the XFMR's tank to a gnd rod, will this be a problem?
RE: Maintenance on station class surge arrestors.
We did have operation counters installed on a CT around the ground lead from the arrestors. These were valuable in determining whether the failed arrestor had extra duty.
The ground lead from the arrestor might be insulated for a couple of reasons:
it could help with testing the arrestor (though that could also be disconnected at the top during testing)
In the event of an arrestor discharge, large current flow will dissipate thru this conductor and it would be best to direct that to the ground grid and not thru the transformer tank. The failed arrestor in original question had burn marks across the small isolators at the foot of the arrestor (special devices for mounting) and I would imagine this would be worse if a bare 4/0 were leaning against the tank.
These are simply observations that might be confirmed if you speak to a transformer manufacturer.
RE: Maintenance on station class surge arrestors.
RE: Maintenance on station class surge arrestors.
RE: Maintenance on station class surge arrestors.