I'm new within the power industry and was introduced to a scenario I had a question about. So, while discussing the need for surge arresters came up, we began talking about lightning. I know that lightning is produced by a voltage difference (between the clouds and ground/earth) which causes a strike. So, if this lightning strikes equipment within the power/substation grid, this would cause a huge surge in current right? Well, when discussing the surge arresters, they are rated and were being discussed in terms of voltage. So I was reading that lightning causes voltage surges. Can someone explain how this happens outside of equations. I get V=I/R, so by the equation, if you increase the current you get a larger voltage. But can someone explain this in terms of like physics/real world, how does the potential difference inside the station increase due to an influx of current. Sorry if this is a dumb question, I can really only conceptualize voltage in terms of like batteries, and I can't seem to make sense of this through that anology.

  • \$\begingroup\$ The current in lightning is one way which means it increases the charge imbalance to a system which changes the potential. Think...static electricity or even charging a capacitor. \$\endgroup\$
    – DKNguyen
    Sep 15, 2022 at 15:10
  • 2
    \$\begingroup\$ Lightning doesn't cause a huge surge in current; it is a huge current. So, 50,000 amps hitting a live conductor that has an impedance of maybe 0.1 ohms, raises the voltage by 500 volts. \$\endgroup\$
    – Andy aka
    Sep 15, 2022 at 15:20
  • \$\begingroup\$ I would suspect the emp from the lightning bolt induces a voltage in the line \$\endgroup\$
    – Bryan
    Sep 15, 2022 at 15:44
  • \$\begingroup\$ Lightning causes a surge current when it touches the line. It cause also a surge in voltage when the wave generated touches (after propagation) the substation. This is the reason why the impedance of a added short transmission line (+/- 500 m), just before the substation, is enough "long" and of very low impedance to make a voltage reflection coefficient = -1. So the overvoltage on substation equipment is the "lowest" possible. \$\endgroup\$
    – Antonio51
    Sep 16, 2022 at 5:04

2 Answers 2


Here is a simulation ... of what "happens" in the electrical "system" when lightning strikes a line but not to the very nearest of the substation ...
It is only an example. It is up to you to use the exact parameters of the whole system.
One can see the "drastic" reduction of "overvoltage" at the substation, in some cases.

enter image description here

Other case

enter image description here

Long line is open

enter image description here


I know that lightning is produced by a voltage difference (between the clouds and ground/earth) which causes a strike.

That's more or less true, up to a point. It's probably better however to look for how the voltage difference is caused.

The thunderstorm moves electrical charge about. Some clouds or parts of the cloud end up with more positive charge on them, others with more negative charge. I don't recall which way the ground/cloud charge difference tends to happen, and that's not important right now.

The clouds have relatively low capacitance with respect to each other and to earth, so that charge separation creates a very high potential difference.

Now we come back to your quote. The high potential gradients close to the charged parts ionise the air creating a conducting channel, and allows the charge to move along the channel. When the channel has grown to bridge two clouds, or the cloud and ground, the charge can flow rapidly along the ionised channel, causing a very high current (current = charge/time). This is the lightning stroke, transporting charge from one place to another.

In the context of a power station, what a lightning stroke does is dump a large quantity of charge into the conductor that it hit. The capacitance with respect to ground of the part struck may be fairly low, so again this creates a high potential difference. That difference may be much smaller than the cloud to ground difference that caused the lighting stroke, but it may be much larger than the difference the power station was designed to withstand. The insulators in the power station could flash-over and fail, allowing large currents to flow and cause damage to themselves and what they're connected to.

Surge arresters, and more importantly the equipment that surge arresters form part of, channel this current, this movement of charge, safely around rather than through vulnerable parts of the power station.

The charge in batteries is the same basic stuff as the charge on thunderclouds, electrons, charged ions, it's only the magnitudes and the precise charging mechanisms that are different. Chemical batteries use chemical energy to move charges around. Thunderstorms use mechanical energy in something similar to a natural Van de Graff generator to move charges.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.