High voltage arc gap design

Tom Bruhns wrote:


Feh. Examine the remains of three 20 kV lightning arrests mistakenly connected across a 66 kV transmission line.
The fireball looked pretty cool too. But not to the lineman who was standing practically underneath them closing the switch.
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On Fri, 30 May 2008 21:33:50 -0700, "Paul Hovnanian P.E."

Ouch! That close, did that person live through that/et seq.?
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| Feh. Examine the remains of three 20 kV lightning arrests mistakenly | connected across a 66 kV transmission line. | | The fireball looked pretty cool too. But not to the lineman who was | standing practically underneath them closing the switch.
Wish you had videos/pictures.
Which kind of mistake was make? Wrong type of protectors? Wired the wrong way?
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snipped-for-privacy@ipal.net wrote:

It was a portable substation, mounted on a semi trailer, used when it was necessary to de-energize a fixed station for maintenance.
The portable unit has a high side switch, lightning arresters, high side fuses, a transformer and low side breakers. The transformer has primary and secondary windings with taps so that it can be reconfigured for multiple uses. The substation maintenance group's responsibility is to reconfigure it as we specified and then our crews connect and energize it.
The substation group took a unit that had previously been used for a 12 kV to 4 kV step-down and rewired it for 66 kV to 12 kV. They did a turns ratio test to verify the work and then shipped it.
Unfortunately, the lightning arresters consist of three 20 kV units per phase, stacked in series. When this station had been used with a 12 kV input, the bottom two sections of each phase were jumpered to ground. Nobody noticed this (there's a whole story behind the problems at this utility that lead up to this f*k-up worthy of another post.
When the unit was delivered, due to its construction, nobody could see the jumpers. Our crew hooked it up and, Blam!
To answer Joseph's question, nobody was hurt. The handle of the high side switch was accessible by swinging a panel up. Our (tall) lineman bitched about this, having to bend over to operate the switch. But the end result was that he was standing underneath a steel roof.
The portable substation was well grounded, so nobody got shocked.
It was quite an event. I was standing about 100 feet away. After the initial fault, the system breaker (about 20 miles away) de-energized the entire line. We stood there for a few seconds and, just as a few people were thinking about walking up to it, someone shouted, "Wait for the reclose!" Sure enough, the system operators had neglected to disable the reclose operation. About 15 seconds later, another fireball.
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On Sun, 01 Jun 2008 12:26:34 -0700, "Paul Hovnanian P.E."

Wow. Only one reclose? Or was some system monitor person really on the ball?
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| Unfortunately, the lightning arresters consist of three 20 kV units per | phase, stacked in series. When this station had been used with a 12 kV | input, the bottom two sections of each phase were jumpered to ground. | Nobody noticed this (there's a whole story behind the problems at this | utility that lead up to this f*k-up worthy of another post.
Technically, configured wrong. That and inadequate checklist/testing.
I'll look forward to the "another post" some day.
| It was quite an event. I was standing about 100 feet away. After the | initial fault, the system breaker (about 20 miles away) de-energized the | entire line. We stood there for a few seconds and, just as a few people | were thinking about walking up to it, someone shouted, "Wait for the | reclose!" Sure enough, the system operators had neglected to disable the | reclose operation. About 15 seconds later, another fireball.
How long did it take to make the repairs and reschedule the substation maintenance?
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snipped-for-privacy@ipal.net wrote:

[snip]
Only a couple of days. All that was seriously damaged were the lightning arresters.
I'm sure they had to re-paint the scorched spots when the portable unit was taken off line.

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snipped-for-privacy@ipal.net wrote:

They had an a*hole for division superintendent. When we, the supervisors, took turns being on call to dispatch crews for after hours emergencies, he had a habit of trying to persuade us to skip things like sending them out to work along roadways with proper traffic control, flaggers, etc.
One day, when I was on duty, I had to call a crew to repair a pole along a busy highway. It was a nice Saturday afternoon. When I had trouble locating a couple of people to do the flagging, I got a call from the superintendent "suggesting" that I send them out as is. I told him that I wasn't going to take responsibility for doing so and I would continue to try and find the proper personnel.
A few days later, my boss informed me that I had made a "career limiting" move.
Meanwhile, word had gotten back to the linemen. They nearly had a wildcat strike over that event. But I always got along with them, since they figured I'd stand up for them.
About 6 months later, a similar situation arose. The guy on duty caved in to pressure and sent the crew out without flaggers. A drunk ran his pickup truck into the back of our line truck, killing two and crippling one of our employees.
What had been my eventual termination (when a convenient excuse arose) was immediately converted into a very well funded retirement. They didn't want me around when the state Dept. of Labor and Industries came around to do an investigation. Financially, I've never needed to work another day in my life.
I did get a chance to tell my story to a state inspector after all. They aren't so stupid that they forget to look up past employees. As a result of the investigation, the utility's state insurance rates were jacked up so high, they effectively became unable to field their own maintenance and construction crews. Its all contracted out now. Thanks to that (and some other screw-ups), they have been bleeding money for years. They are now being taken over by a private investment group. They have been promised by the investors that their management will remain in place.
By a strange coincidence, having come into a large sum of money years ago, I have invested in numerous private funds. My contacts at one of my funds inform me that there will be quite a butt-reaming once ownership changes hands.
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