Message Board Thread - "Electric Utility-Distribution Class MOV Arrestors"

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Electric Utility-Distribution Class MOV Arrestors George 8/12/2004
Looking for anyone who has established an upper threshold temperature rise on MOV arrestors. We have been finding numerous MOV's with a 20 to 30 degrees rise over reference temperature. Responses will be greatly appreciated.
Re:Electric Utility-Distribution Class MOV Arrestors Doctir bob 8/16/2004
Richard Strmiska of Sumter Electric Cooperative published a very nice paper called "Lightning arresters' effect on power line reliability" in the InfraMation Conference 2003 Proceedings available on fully searchable CD ROM from the ITC. They found water ingress was lowering the resistance of some problem arresters beyond acceptable limits.

Bottom line is there should be no temperature rise on lightning arresters due to leakage current through the MOVs. The warm areas indicate where the arrester is still resistive, as the cooler area must be very conductive as the same leakage current is flowing through both parts of the arrester.
Re:Electric Utility-Distribution Class MOV Arrestors Manuel 8/17/2004

do you have any image with this arrestors that can share with us? ..

it will be appreciate.

thanks ..

Re:Electric Utility-Distribution Class MOV Arrestors George 8/20/2004
Manuel, here is a picture of one of the MOV type arresters we have been noticing have a temperature rise.
Re:Electric Utility-Distribution Class MOV Arrestors TDLIR 8/27/2004
Here is a dmaged arrestor from a 132KV sub-station.

Re:Electric Utility-Distribution Class MOV Arrestors chip 9/1/2004
I can't offer any experience with utility applications of MOVs and haven't established threshold temperatures for same, but this is an area about which I have some considerable interest.
In our industrial and commercial TVSS applications, MOVs are typically used for surge suppression, as I assume they are also used for utility installations. Typical of solid state components, MOVs do not tolerate heat very well and with repeated voltage spikes, they will degrade to the point where they become more of a circuit load than protector. Eventually they will fail; often catastrphically.
Is the temperature rise that you are speaking about the increase that I would expect to see as an MOV starts to break down and it's protection level starts to approach that of it's nominally applied voltage?
Re:Electric Utility-Distribution Class MOV Arrestors George 9/7/2004

We haven't determined the temperature at which these MOV's are failing as of yet. The normal temperature on the units we have examined showing ne increase in temperature is approximately 36 degrees "C". The units we have shot are showing temperatures anywhere from 10 degrees rise up to 24 degree rise "C".

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