Harford County Power Surge Part 1

The Harford County Power Surge Incident,
August 23, 1988 Started at 10:35AM
Moores Mill Road, Bel Air, Maryland
(Video clips from an original copy)

A Power surge was created when Aspen Tree service dropped a tree branch on to 33,000 volt line. Then the 33,000 volt line fell onto a 13,000 volt line, and it dumped 20,000 extra volts into the electric lines and houses. The safety system failed to shut off the electric! This tape is used for different electric, and fireman training classes.

Category:

Science & Technology

Tags:

• harford
• county
• power
• surge
• moores
• mill
• road
• Bel
• Air
• Maryland
• August
• 23
• 1988
• BGE
• 10-15kV
• 34-13Kv
• arc
• fire
• flash
• Part1

[Dockshund]

Our records indicate you used 5 Billion dollars worth of electricity last month. Please remit.

[torontomapleleafer]

Jesus, look at that eaves trough on the house just  light up from all the extra electricity, I never seen anything like that in my life, I didn't know it was possible.

[fl0r1svdk]

in Belgium we don't ever have problems. the onely time power goes out it is to change somthing on the wireing

[bloodfox0]

What caused the surge?

[GeneralPurposeVehicl]

Son: Ma, why is the gutters sparking?

Mother: What are you talking about?

Son: Look!

Mother: Holy...

[jchambers2586]

I would shut the main breaker off to prevent any more damage.

[ApolloWasReal]

@c0rrupts3ct0r555 The theory behind single-point grounding is NOT to keep the lightning surge out of your house; it's to ensure that when lightning strikes, everything in your house rises and falls together. Only voltage *differences* are bad; that's why birds can sit on power lines unharmed. If all three pins in your wall outlet plus the water pipe, phone and cable line all go to exactly 5,384 kV and back to 0V in 534 microseconds , then there's much less likelihood of damage or injury.

[ApolloWasReal]

@c0rrupts3ct0r555 There are no guarantees with lightning, but you can greatly reduce your risk with proper single-point grounding. If you have cable, code requires a grounding block where it enters the house; the block must be bonded to the ground/neutral point in your main electrical panel. If you have a phone line (including DSL), the phone company must install a similarly grounded protector block. The main panel ground should be bonded to a copper water pipe (NEVER gas!) and a ground rod.

[c0rrupts3ct0r555]

@ApolloWasReal then explain why every pc that gets hit by lightning ( outside pole ) has internal damage like in the Ethernet port, or in the power supply? they had surge supressors, and the electronics still died, massive internal damage.

[ApolloWasReal]

@c0rrupts3ct0r555 A lot depends on the details. With modern "single point grounding" methods plugged-in equipment can often withstand nearby lightning strikes that lift all the voltages on internal house grounds, outlet pins, etc equally. Although this fault probably lifted each house to some kilovolts, appliance damage was probably from the line/neutral voltage going to 33/13 = 2.5x the normal 120V; a good surge protector plus fuse might well have worked.

[ApolloWasReal]

@shawnkquinn Everybody blames the tree trimmers but I don't. At least not that much. Power line accidents do happen. If that tree hadn't come down while being trimmed, it could have come down in a storm. It or the line could have been struck by lightning. Ice and snow can weigh down trees and wires. Cars can hit poles. Hardware can work loose and let wires fall for no apparent reason. The utility is supposed to take precautions to limit the resulting damage.

[ApolloWasReal]

@penguin848 Do you know of any reports on this incident? I'm still trying to figure out how those gutters arced like that. The fault must have somehow lifted the neutral to the house well above ground potential, but the electrical distribution system has many redundant grounds intended precisely to keep that from happening. Each house bonds the neutral to a cold water pipe and/or ground rod, and I think each pole with a transformer also has a ground rod. That fault current must be huge.