Super Heavy Duty Surge Suppressor

Old 10-05-14, 04:29 PM
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Super Heavy Duty Surge Suppressor

Can a surge suppressor be constructed to withstand a prolonged multi-thousand volt overvoltage?

Every once in awhile we hear of a house whose wiring is fried from the inside out. This can happen if a primary line, typically about 7000 volts to ground, falls on a secondary (120/240 volt) line.

What I am thinking of is two metal plates with a thin gap in between, connected to hot and neutral of the house service. (A second unit would be connected to the other side of the 120/240 volt service.) This would require that the main breaker be upstream of the first breaker panel with the surge suppressor(s) in between.

Should a medium-high voltage surge occur, we expect that the current will arc between the suppressor plates before it arcs through the insulation of the house wiring. Should the surge last long enough and the suppressor plates melt, the plates would be large enough and thick enough to come to a fairly low temperature despite the resulting dead short circuit.
Old 10-05-14, 04:38 PM
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Usually a whole house surge arrestor is tied to a two pole breaker like a 2P20A.
You're talking about having it trip the main. That would have to be pretty big device with big wiring.

Two metal plates with a gap between them is called a spark gap. It would be difficult to make something like that... that would be safe and accurate enough to use reliably in a house. Normally MOV's (metal oxide varistors) are stacked up to increase protection but that would become extremely costly.
Old 10-06-14, 03:54 PM
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At the bottom of some AM broadcast towers, you might find a couple of large metal balls. One is grounded and the other is bonded to the tower. If lightning hits, the current conducts between the balls. You have to get the spacing correct, so they are close enough to start an arc if exposed to 7kV and up, and yet clear the arc at normal voltages. Air at atmospheric pressure is not the best for clearing arcs. Magnetic fields, compressed air, vacuum, CO2, and SF6 are all used to quench arcs, including inside very large circuit breakers (500kV, 4kA etc).

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