MOVs begin to OVERHEAT due to SUSTAINED conditions
Most Common Cause of TVSS Failure:
Some products attempt to contain heat inside a sand packed enclosure.This doesn’t always work as heat radiates outward.
Caused by distribution system problems: - Open neutral - Loss of phase - Transformer failure, etc. MOVs draw low,
sustained currents while trying to clamp a sustained overvoltage.This severely overheats the MOVs.(Overcurrent protection doesn’t see this as a problem;
I.e, 30A breaker
won’t trip for 25A.)