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Lightning and power surges..

Old 05-20-2013, 08:31 PM
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Default Lightning and power surges..

It has been storming heavily here this evening. Nearly 6" of rain since 2:30 and lots of lightning. Very close to the house too. You see a flash and hear the crack at the same time.

So what causes the lights to dim when lightning strikes nearby?
Old 05-20-2013, 08:41 PM
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Originally Posted by ScarabChris View Post
It has been storming heavily here this evening. Nearly 6" of rain since 2:30 and lots of lightning. Very close to the house too. You see a flash and hear the crack at the same time.

So what causes the lights to dim when lightning strikes nearby?
When the base of a light bulb constricts the flow of electricity is restricted.

Happens to me, too.
Old 05-20-2013, 10:15 PM
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Originally Posted by ImNotiFly View Post
When the base of a light bulb constricts the flow of electricity is restricted.

Happens to me, too.
lol. My base constricts when there's nearby lightning as well.


Changes in the voltage of the electricity coming into your home during thunderstorms are behind the flickering lights. Normally, a 7,000 volt differential exists between the power lines that carry electricity and the ground over which they pass, says Carl Segneri, Operations Vice President of ComEd. But, that 7,000 volt spread drops when the energy from a lightning strike travels into the ground, temporarily raising the voltage there and, in so doing, decreasing the voltage entering your home. The effect is comparable to that of a dimmer switch, says Segneri, and your home lights dim for an instant. When a power line takes a direct hit, lights can flicker as a lightning protection system built into the power grid activates. Like a surge protector, voltage is temporarily reduced and the lights dim.

Last edited by round2it; 05-20-2013 at 10:17 PM. Reason: info
Old 05-20-2013, 10:23 PM
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I don't know but I wish FP&L would figure it out.

Powers been out for over an hour up here in West Palm
Old 05-20-2013, 10:47 PM
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Originally Posted by round2it View Post
...My base constricts when there's nearby lightning as well.

Changes in the voltage of the electricity coming into your home during thunderstorms are behind the flickering lights. Normally, a 7,000 volt differential exists between the power lines that carry electricity and the ground over which they pass, says Carl Segneri, Operations Vice President of ComEd. But, that 7,000 volt spread drops when the energy from a lightning strike travels into the ground, temporarily raising the voltage there and, in so doing, decreasing the voltage entering your home. The effect is comparable to that of a dimmer switch, says Segneri, and your home lights dim for an instant. When a power line takes a direct hit, lights can flicker as a lightning protection system built into the power grid activates. Like a surge protector, voltage is temporarily reduced and the lights dim.
Until this past year, I did not have this reaction to lightning. But, my last encounter had me sucking saltwater through my drain plug.

That is an interesting reference from ComEd. The grounding effect of lightning is (I think) a good place to focus.
Old 05-21-2013, 06:31 AM
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Originally Posted by round2it View Post
lol. My base constricts when there's nearby lightning as well.


Changes in the voltage of the electricity coming into your home during thunderstorms are behind the flickering lights. Normally, a 7,000 volt differential exists between the power lines that carry electricity and the ground over which they pass, says Carl Segneri, Operations Vice President of ComEd. But, that 7,000 volt spread drops when the energy from a lightning strike travels into the ground, temporarily raising the voltage there and, in so doing, decreasing the voltage entering your home. The effect is comparable to that of a dimmer switch, says Segneri, and your home lights dim for an instant. When a power line takes a direct hit, lights can flicker as a lightning protection system built into the power grid activates. Like a surge protector, voltage is temporarily reduced and the lights dim.

That makes sense, thanks. But I don't know what that other dude was talking about with the light bulb base. LOL.
Old 05-21-2013, 06:37 AM
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Originally Posted by ScarabChris View Post
That makes sense, thanks. But I don't know what that other dude was talking about with the light bulb base. LOL.
Maybe it depends upon where the light bulb is. ;?
Old 05-21-2013, 06:50 AM
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This happens when lightning hits energized conductors or equipment. The sequence of events and how the customer perceives it is dependent on many factors. Not all utilities use the same protecting design and therefore do not experience the same surge/dimming.

Assuming the voltage is 7.2K per phase, the lightning arrestors will be a higher voltage so no "spill" occurs when the voltage varies (normal load)... so the protection voltage spill will probably be around 8.5K. When lightning hits the distribution power line the circut breaker in the substation opens momentarily and then re-closes (milliseconds) During that sequence of events a customer will/may observe the light bulb getting brighter then dim and possibly go off then come back on if everything works and nothing fails.

Lots of variations can be observed with lightning.
Old 05-21-2013, 06:56 AM
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Lightning doesn't have to hit the conductors. The energy of a nearby lightning strike can induce a potential in power lines, resulting in a voltage fluctuation.
Old 05-21-2013, 07:07 AM
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Originally Posted by airbrush View Post
Lightning doesn't have to hit the conductors. The energy of a nearby lightning strike can induce a potential in power lines, resulting in a voltage fluctuation.
... hence the reason I said conductors and equipment.

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