On 10/23/2015 4:27 PM, westom wrote:
On Friday, October 23, 2015 at 12:24:48 PM UTC-4, Muggles wrote:
You sure know a lot about this subject. Are you an electrician?

We did this stuff in facilities that must suffer direct lightning strikes without damage. In some cases, damage could mean major explosions.

Concepts such as low impedance are not taught to electricians. Electricians know what must connect to what for human safety. Code is only about human safety - not about transistor safety. Sometimes we had to teach electricians how to wire to also exceed code requirements.

A good electrician is great to have. He can show what is necessary to pass inspection. And show how code requires things to be wired; resulting in a 'damn good idea' revelation.

But protection of equipment (ie appliances and transistors) involves aspects not require by code. An earth ground required by code is best upgraded to both meet code and exceed code requirements to also provide surge protection. Concepts such as equipotential and conductivity apply. In at least one case, a nuclear hardened communication facility needed its earth ground upgraded to stop damage from direct lightning strikes. Concepts that apply (such as longitudinal and transverse currents) would be understood by engineers; and not by electricians or technicians.

Basic concept of surge protection was demonstrated by Franklin in 1752. How to make that principle work better for semiconductors is even discussed in papers in 1950s Bell System Technical Journals when telephone COs were converting from frame relays to semiconductor switching. They discovered that techniques used to protect mechanical relays for decades (with some exceptions) were also sufficient to protect transistors. And still, so many do not understand why 'whole house' protection is so critically important. Transistors arriving in 1970 homes made that protection necessary there.

Only summarized is how protection is done. 'Art' of protection is single point earth ground. What a homeowner should / can do to have or upgrade protection (even for HVAC equipment) has not yet been discussed since nobody has asked. Earthing is the 'art' of surge protection.


Thanks for the explanation. You mentioned a nuclear hardened
communication facility. What exactly is that? Were you like an engineer?

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Maggie