Lightning protection AND putting a receptacle on UPS

[Ignoramus16420]

but they have a lot of inertia to overcome. My baldor starts relatively slowly.

i

[w_tom]

Typically destructive common mode transient is lightning. Typically occurs about once every 8 years - a number that varies even within a town due to factors like geology, exposure, manmade objects like nearby pipelines, and frequency of thunderstorms. A location that has high number of CG strikes per thunderstorm is WV. Another common mode transient can be generated by AC power switching by the utility.

Items frequently blamed for destructive transients such as washing machine or refrigerator, instead, create noise. Noise that is easily made irrelevant even by circuits in dimmer switches, GFCIs, and electronic power supplies. If appliances created destructive surges, then we all would be trooping weekly to hardware stores to replace dimmer switches, GFCIs, ... and those appliances.

CG lightning is a connection from the cloud to earthborne charges. Lightning forms a plasma wire that connects cloud charges, via lightning bolt and earth, to earthborne charges that may even be kilometers away from that 'at risk' household. Transistors are damaged when that electrical circuit passes through transistors which explains why one appliance might be damaged and an adjacent appliance remains unaffected.

BTW, > Tom, can you describe the scenario for a common mode transient.

[w_tom]

[Ignoramus16420]

OK. What do you mean by common mode: the occurrence of high voltage between the hot legs and electrical circuit ground? I do not think that it would be referred to as common mode in electronics.

Or do you mean occurrence of high voltage between the ground in the circuit as well as hots and neutral, vs. true earth ground?

The above does not explain what common mode transient is, it just says how often it occurs and when.

What I want is some clear understanding of what it is electrically. Just what voltages (potentials) become high in relation to what references.

A lightning striking outside cannot meaningfully raise potential of circuit neutral (which is tied to local ground at the panel, and that's where electricity comes from outside), it can only raise potential of the hots.

If so, I am not sure if that would be properly called a common mode transient, for devices that feed from the difference between potentials of hots and neutral, like consumer electronics.

Am I missing something?

i

[w_tom]

Common mode, from a building's perspective, is a current that seeks earth ground. Common mode, from appliance perspective is a current incoming (same direction) on any one or all wires of that port or cable, then outgoing on any one or all wires of another port.

From an appliance perspective, common mode means current on multiple wires moving in the same direction whereas normal mode is current incoming on one wire and outgoing on its mate. Common mode means current seeks earth - the common ground. Normal mode does not care whether earth is or is not of that path.

Current can change potential of a neutral wire where that end of wire is not connected to earth ground. Again, impedance. Assume a wall receptacle maybe 50 feet from the breaker box. That wire may have less than 0.2 ohms resistance, but may have as much as 120 ohms impedance. At the wall receptacle, a trivial 100 amp surge would put a wall receptacle at something less than 12,000 volts in relation to the wire's other earthed end. (Actual voltage would be far lower for other reasons.) Even if far end of a neutral wire is earthed, the receptacle end of that same neutral wire can carry a transient incoming to the appliance, as demonstrated by a previous example using the adjacent plug-in protector.

How often a transient occurs is part of an answer to another questi> Or do you mean occurrence of high voltage between the ground in the