Damage from large fault

[citcapp]

System:
A 69 kv line feeding a privately owned substation with a ABB switch which feeds a 8MV 69kv to 12470 KV transformer that steps the power down to 15 kv which feeds three single phase voltage regulators which then connect to a 15kv overhead bus duct which then connects to a 15 kv breaker/switch which feeds a 15KV line up which feeds 6-15kv to 480/277 volt transformers

The problem: The 15 KV overhead inclosed bus duct shorted out and the up stream ABB breakers batteries were dead so it did on sense the fault. The power companies rirst up stream substation fuse did not sense the fault, the second upstream substation did sense the fault and shut the overhead line off.

The Damage: The 8 MV transformer was distroyed and the bus duct was distroyed along with the incomming section of the 15kv switch. We replaced the 8 mv transformer all of the cables and the 15kv bus duct, the incomming section of the 15 kv switch/breaker and had all items tested. Had the batteries and charger replaced on ath ABB switch and the settings confirmed and tested. Tested all of the cables to the 15 kv lineup and they were fine.
Tested all of the downstream transformers and they were fine. turned everything on and everything was fine. At the time it was noted by the Eaton testing person that the highes fault was on the A phase recorded at the 15 kv switch (logged in the memorly. This all happened in December of last year.

Current issue: We got called out by the same customer due to a feeder short on one 4000 amp MDS switchboard #1 which also feeds a motor control center phase A in one of the 11 feeders on the switchboard went to ground to phase C, the same thing happened on the 1200 amp mcc. Seems odd to me. Is there any way that the high fault current recorded on the 15 kv switch worked its way downstream. Any thoughts\

Thanks in advance

 

[Pierre C Belarge]

System:
A 69 kv line feeding a privately owned substation with a ABB switch which feeds a 8MV 69kv to 12470 KV transformer that steps the power down to 15 kv which feeds three single phase voltage regulators which then connect to a 15kv overhead bus duct which then connects to a 15 kv breaker/switch which feeds a 15KV line up which feeds 6-15kv to 480/277 volt transformers

The problem: The 15 KV overhead inclosed bus duct shorted out and the up stream ABB breakers batteries were dead so it did on sense the fault. The power companies rirst up stream substation fuse did not sense the fault, the second upstream substation did sense the fault and shut the overhead line off.

The Damage: The 8 MV transformer was distroyed and the bus duct was distroyed along with the incomming section of the 15kv switch. We replaced the 8 mv transformer all of the cables and the 15kv bus duct, the incomming section of the 15 kv switch/breaker and had all items tested. Had the batteries and charger replaced on ath ABB switch and the settings confirmed and tested. Tested all of the cables to the 15 kv lineup and they were fine.
Tested all of the downstream transformers and they were fine. turned everything on and everything was fine. At the time it was noted by the Eaton testing person that the highes fault was on the A phase recorded at the 15 kv switch (logged in the memorly. This all happened in December of last year.

Current issue: We got called out by the same customer due to a feeder short on one 4000 amp MDS switchboard #1 which also feeds a motor control center phase A in one of the 11 feeders on the switchboard went to ground to phase C, the same thing happened on the 1200 amp mcc. Seems odd to me. Is there any way that the high fault current recorded on the 15 kv switch worked its way downstream. Any thoughts\

Thanks in advance

I am sorry, I cannot help here much.

But...do you have any pictures of the event(s)?
Sounds like some heavy duty pictures.

 

[zog]

I am sorry, I cannot help here much.

But...do you have any pictures of the event(s)?
Sounds like some heavy duty pictures.

Sounds like a typical week to me

 

[zog]

Current issue: We got called out by the same customer due to a feeder short on one 4000 amp MDS switchboard #1 which also feeds a motor control center phase A in one of the 11 feeders on the switchboard went to ground to phase C, the same thing happened on the 1200 amp mcc. Seems odd to me. Is there any way that the high fault current recorded on the 15 kv switch worked its way downstream. Any thoughts\

Thanks in advance

I doubt the 2 events are related. What is apparant is that this facility has no PM program and that is why they are having failures.

 

[zbang]

which feeds a 8MV 69kv to 12470 KV transformer

You might want to rewrite the description. I doubt that it's an 8 megavolt transformer or a 12470 kilovolt line. That all makes it kinda hard to read.

 

[wireguru]

I think pictures are in order here. There should be a rule: you post a thread like this, it must come with photos.

 

[mxslick]

I think pictures are in order here. There should be a rule: you post a thread like this, it must come with photos.

You mean like as in THIS THREAD?

<snip>Is there any way that the high fault current recorded on the 15 kv switch worked its way downstream. Any thoughts\

Considering that electricity can and will take all available paths, it is possible in theory that the events are related.

Before I get flamed for making that statement, remember that fault current can be contributed by motors and that transformers will work in reverse.

 

[charlietuna]

Many electrical fault's causes are very hard to pinpoint--like "What came first, the chicken or the egg" . You might have had a weak, or near failure device(from manufacturing(?) or overload(?)) that the original 1200 amp fault triggered the upstream explosion to occur? Of course the insurance companies start their investigation and want to point fingers to whats best suited for their policy. An example might be where a major switchboard explodes under warentee and the insurance company is blaming it on the manufacturer and the manufacturer automatically finds roddent hair in the burnt gear?? We had a multi million dollar switchgear fire in a high rise office building and during the investigation nothing could be pinpointed as the cause. Something(??) caused a short circuit on the line side of a 4000 amp-480 volt main breaker and it burnt all the bus duct up all the way back into the power company's vault. There wasn't too much left in the exxplosion to determine any cause. The insurance investigators never ask the opinion of the repairing contractor for some reason? But months later - we were readying for the switchgear swap out which had to be done "on site" and "in place" and found that the switchgear had the standard lifting eyes in each corner and of course the eyes were removed during the install. But the manufacturer had 6 inch plate steel with a 1/2 inch threaded hole for these lifting eyes to screw into. These plates were not welded,nor fastened to the switchgear and were supposed to be removed upon installation. They were held in place only by paint. One of them was missing???? The missing one's location was directly above the open bus bars on the line side of the 4000 amp switch.

I discussed our findings with our customer -- and at this point they did not want to open up the insurance company's investigation since everything had been submitted qand agreed to. Maybe the installing electrician only removed that one plate ?? i doubt it, but that was ten years ago? I'm sure the manufacturer's installation instruction booklet, the one we NEVER read was laying on the switchroom floor as the gear was set in place!!!

 

[zbang]

These plates were not welded,nor fastened to the switchgear and were supposed to be removed upon installation. They were held in place only by paint.

Does that scream poor construction practice to anyone else? IMHO everything inside the box should be welded, bolted, or somehow mechanically tied in place on the inside. (At least everything heavy and metallic..) Even if they're supposed to be removed. Fail safe and all that.

Some robots I installed a while ago had a special panel inside a door to store all the shipping restraints, with little outlines for each one. And all the restraints were painted bright orange. And a big sign was taped to the main channel showing the location of all of them.

 

[wireguru]

ive seen gear sitting in place with lifting hooks on top. Maybe these particular ones werent supposed to be removed.

 

[weressl]

System:
A 69 kv line feeding a privately owned substation with a ABB switch which feeds a 8MV 69kv to 12470 KV transformer that steps the power down to 15 kv which feeds three single phase voltage regulators which then connect to a 15kv overhead bus duct which then connects to a 15 kv breaker/switch which feeds a 15KV line up which feeds 6-15kv to 480/277 volt transformers

The problem: The 15 KV overhead inclosed bus duct shorted out and the up stream ABB breakers batteries were dead so it did on sense the fault. The power companies rirst up stream substation fuse did not sense the fault, the second upstream substation did sense the fault and shut the overhead line off.

The Damage: The 8 MV transformer was distroyed and the bus duct was distroyed along with the incomming section of the 15kv switch. We replaced the 8 mv transformer all of the cables and the 15kv bus duct, the incomming section of the 15 kv switch/breaker and had all items tested. Had the batteries and charger replaced on ath ABB switch and the settings confirmed and tested. Tested all of the cables to the 15 kv lineup and they were fine.
Tested all of the downstream transformers and they were fine. turned everything on and everything was fine. At the time it was noted by the Eaton testing person that the highes fault was on the A phase recorded at the 15 kv switch (logged in the memorly. This all happened in December of last year.

Current issue: We got called out by the same customer due to a feeder short on one 4000 amp MDS switchboard #1 which also feeds a motor control center phase A in one of the 11 feeders on the switchboard went to ground to phase C, the same thing happened on the 1200 amp mcc. Seems odd to me. Is there any way that the high fault current recorded on the 15 kv switch worked its way downstream. Any thoughts\

Thanks in advance

The high faullt current on the primary side and the switching surges associated with it can induce high voltage excursions on the secondary sdie which in turn would stress the equipment weaken the insualtion. If you have surge protection installed it should protect you to a degree. Absolute and total proptection is not practical.

Seems like somebody forgot to design a control power supply monitoring and alarm that would have detected the loss of DC.

We had a major issue with some 15kV breakers where the trip could would not de-energize after trip as the aux contact failed to open the power to it. The coil consequently burned up and was unavailable when the relay, responding to a fault, tried to open it the next time. The upstream protection worked as designed, but the shutdown was more extensive than necessary.

As it runed out there was some minor modification made on the breaker mechanical parts, the actuator had too much slop in it and that caused the failure. All of our MV breakers - manufactured after a certain date - had to be retrofitted.

The manufacturer eat the cost, but not our time and losses associated with switching around and making the breakers available. Our cost exceeded the manufacturers cost by x15 or so.

 

[charlietuna]

The lifting eyes on this gear had to be removed just due to the tight quarters that the bus duct (secondaries) and vault stubbs ran. I have seen switchgear with temporary threaded plates and also perminent threaded into it's frame work. But, since then, i have noticed those with the temporary show arrows identifying the plates to be removed upon installation. And at the same time i could see an electrician unscrewing the lifting eyes without checking whats inside-temporary or fixed mounts!

 

[citcapp]

Thanks for all of the input. At this point I am going to have the damaged cable tested to see if that helps shed a little more light on the subject. The customer has now consented to have us test and evaluate his electrical systems each year. This should help put and end to this. We have installed an alarm system on batteries and will be installing current cts on both the line and load side of the 8 mv transformer for further protection.

 

[HCC]

I'm not sure, but I think that I am your answer.
I build custom bus. I build replacement bus duct and custom bus systems. I also have a 69KV / 12470 transformer for sale.
I am new to the forum world. Can you contact me directlly?
Tony Humbert
Humbert Copper Connect


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