Hi guys, new guy here so I ask for your patience as I learn the site. My question is about isolation transformers for lightning protection. I repair Auto Transfer Switches 200 - 1000 amp. They are installed on farms and see a lot of lightning in some areas. The Electronic Controllers (PCB) receive lightning damage many times in some areas. They cost 1000 to 3000 dollars. Would an isolation transformer help prevent this at all? Another concern is...the controller monitors the voltage level and sends an engine start signal if the voltage drops or rises above the parameters set. Is there any or much difference in the primary and secondary voltages. Thanks in advance.

 

You have hijacked someone else's thread which is a rude thing to do.
You now have your own thread.

 

You have a valid question and you will get better at forum etiquette alone the way.

Lightning protection is very tough to deal with because lightning does not play by our rules. Adding an isolation transformer will only add protection in some cases. There are people who make lightning protection their career.

I suggest you Google "lightning protection" and read about what protects circuits and what doesn't. Take some time and gain your own understanding on the subject. You being there on site is more effective than a bunch of engineers making comments on a forum.

Mark

 

Primary and secondary voltages can be near equal.

Yes, you will get some protection.

Movs on the output of a small isolation transformer will be less likely to self destruct. As will other connected circuitry, as less fault current is available. Pick the smallest transformer that will power the electronics.

 

If the isolation transformer windings arc over from the high voltage of the lightning strike then it won't provide much protection.

 

You have to take a comprehensive view when deciding how to protect a piece of equipment from lightning. It is not simply spikes on the AC line that you have to protect against. During a lightning strike massive current is induced on conductors, chassis, frames, conduits, anything conductive between the strike point(s) and ground will have current running through it.

Do not design your equipment to be able to survive a lightning strike, design it so it out of the path of a lightning strike. This is the main purpose of lightning rods, they are to steer the energy away from the equipment you are trying to protect.

Mark

 

Do not design your equipment to be able to survive a lightning strike, design it so it out of the path of a lightning strike.

Exactly, it won't.

During a lightning strike massive current is induced on conductors, chassis, frames, conduits, anything conductive between the strike point(s) and ground will have current running through it.

Actually it's worse than this.

(Earth) ground is normally at a fixed safe potential.
But the effect of feeding kilo to mega amps into it for the short duration of the strike is to raise local ground potential hugely, ie a huge voltage spike is injected into your equipment earth.
So the

 

Exactly, it won't.



Actually it's worse than this.

(Earth) ground is normally at a fixed safe potential.
But the effect of feeding kilo to mega amps into it for the short duration of the strike is to raise local ground potential hugely, ie a huge voltage spike is injected into your equipment earth.
So the

I have seen a differential pressure transducer, fully enclosed in explosion proof metal housing and bolted to a 16" main in a vault 8' underground at a water tank get blown up by lightning that struck the tank.

At the current of a strike the voltages across milliohms is still large. In security electronics the floating systems fare better than ones grounded per UL.


Lightning does what it wants, we just Hang on for the ride. ;0