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denisbii
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Join Date: Apr 2016
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High Voltage Snaps and Touches LV Line

04/29/2016 12:17 AM

I saw an incident where a overhead 11 kV line snapped and came in contact with a 415 V line. What happened was tragic since one of the consumers connected to the 415 V was electrocuted when he tried to switch off one of his appliances. The other consumers had their electronics e.g. TVs, fridges and any other connected appliances destroyed. The PMEs in several installations were also destroyed. Does anybody has a technical explanation to this?
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Pathfinder Tags: electrocution overhead lines safety clearances
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lyn
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#1

Re: High Voltage snaps and touches LV line

04/29/2016 12:21 AM

It should be obvious.
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IdeaSmith
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#2

Re: High Voltage snaps and touches LV line

04/29/2016 2:25 AM

That is 11000 Volt in a system with isolation rated for 415 V.

The isolation failed on Over-Voltage rendering the switch unsafe to use.

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denisbii
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#6
In reply to #2

Re: High Voltage snaps and touches LV line

04/29/2016 3:00 PM

Thank you for your response, I can then conclude that the 11kV came in contact with both the live and neutral of the LV since the PME was destroyed and the switches were also energized.
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PWSlack
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#12
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Re: High Voltage snaps and touches LV line

05/03/2016 5:50 AM

It didn't need to contact both of them, because they are both connected via the secondary windings of the local LV distribution transformer; one would have been sufficient.

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PWSlack
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#3

Re: High Voltage snaps and touches LV line

04/29/2016 2:56 AM

Yes. Equipment that is rated for 415V to earth became energised at 11kV to earth. So the outcome was as a result of an overvoltage fault. The cause was <...overhead 11 kV line snapped and came in contact with a 415 V line...>. Does that explain it or is further explanation required?

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SolarEagle
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#4

Re: High Voltage Snaps and Touches LV Line

04/29/2016 10:01 AM
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dkwarner
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#8
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Re: High Voltage Snaps and Touches LV Line

04/30/2016 12:28 AM

Wow! that's the biggest Jacob's Ladder I've ever seen, and it doesn't even have a ladder!

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Mikerho
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#5

Re: High Voltage Snaps and Touches LV Line

04/29/2016 12:03 PM

Where did this happen?

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denisbii
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#7
In reply to #5

Re: High Voltage Snaps and Touches LV Line

04/29/2016 3:13 PM

It happened in Nairobi, Kenya
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BertHickman
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#9
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Re: High Voltage Snaps and Touches LV Line

04/30/2016 9:59 AM

The flaming arc above occurred at the 500 kV Eldorado Substation near Boulder City, Nevada. It was caused by a failure of one of the SF6 switches (half of a pair in series). The defective SF6 switch failed to open, and when the remaining good switch tried to open, it flashed over. This caused the rotary air disconnector to open with one phase still energized. BTW, the arcing disconnector was not actually breaking a true load. It's only carrying about 100A of reactive current instead of its normal 2 kA load. Details can be found on our web site:

http://www.capturedlightning.com/frames/longarc.htm#500_kV_Switch

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Mikerho
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#10
In reply to #9

Re: High Voltage Snaps and Touches LV Line

05/01/2016 2:31 AM

Why did the SF6 (sulfur hexafluoride - at least I know that much!) switch fail? Was there leakage? I am very curious. I have not gone to the site you provided yet, so maybe the answer will be there. Going there now.

Thank you for this information!

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adreasler
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#11
In reply to #9

Re: High Voltage Snaps and Touches LV Line

05/02/2016 10:22 AM

Oh, only a hundred amps, well in that case, not a big dea- WHAAAAAAT!

That's still enough juice to make someone instantly a corpse, if not render them into fine pink mist.

It's events like this that 'encourage' the electrical codes at substations to require PLENTY of insulating space between the voltage levels. Codes that might not be up to date in places like Kenya.

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adreasler (1); BertHickman (1); denisbii (2); dkwarner (1); IdeaSmith (1); lyn (1); Mikerho (2); PWSlack (2); SolarEagle (1)

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