Lightning Question

quique

This is not a solar or renewable energy topic per se but please bare with me.

We just had the first thunderstorm of the season and a lightning struck somewhere nearby.

I think the chronology was:

1). Milliseconds before the lightning, power dipped.
2). Lightning lit up the sky
3). Thunder was heard and by that time power was back to normal.

The dpi I refer to was the lights dimming and the AC slowing down.

My question is, what causes those dips in power?

I understand lightning strike on a tower or cables can cause voltage spikes. But why dips?

BB.

Re: Lightning Question

My first guess--Lightning is a DC current... Hit a power line and you create a DC current in the power system. AC transmission transformers are usually designed to limit current by saturating the core (limits maximum current). Throw a DC current into an AC transformer, they will generally saturate and limit their output current (short brownout).

If the system does not "shunt" the power or open a breaker (they can be computer controlled and will try to reconnect after a trip a couple of times). That can also cause your quick power failures.

Anyway, my first guesses.

-Bill

BB.

Re: Lightning Question

I should add another possible reason for a brown out--High voltage from the lightning creates a plasma from lightning strike line to ground (across an insulator, through insulation, etc.)--That plasma could have low enough resistance to short out one phase of an AC line (tripping breakers, browning out a phase, etc.).

-Bill

niel

Re: Lightning Question

first explanation sounds better bill.

brboyer

Re: Lightning Question

Lightning strike on/near distribution line. The emergency breakers trip (and automatically re-close a couple seconds later) on the affected circuit. Customers on that circuit see it as a momentary outage, customers on other circuits may see a voltage sag due to the increased demands on the remainder of the system and the perhaps because of the 'increased distance' the power has to now flow.

niel

Re: Lightning Question

that sounds plausible too.

quique

Re: Lightning Question

Just so y'all know, I learned tons just from thinking and reading about the subject!

Found this:http://www.academia.edu/5738413/Electric_Power_Syatem_Basics_by_Steven_W.Blume

Thx guys!

Just wish there was an easier way to distinguish between transformers (all subtypes), breakers, reclosers, regulators etc.

They all share any common features.

techntrek

Re: Lightning Question

From that document: "Suppose a lightning strike hits a distribution feeder’s “B” phase near the substation and causes a B-phase-to-ground fault. The ground overcurrent relay would sense the increase in ground current and instantaneously send a trip signal to that feeder’s breaker."

So, that tends to sound like the plasma argument above is correct since the strike is temporarily grounding the phase.