Catastrophic failure SF6 Circuit Breaker

In summary, a SF6 circuit breaker failed catastrophically, leading to the destruction of switchgear in a substation. The failure was caused by a synchronising problem, as well as a failure to maintain the circuit breaker.
  • #1
BIGEYE
20
0
We have had a catastrophic failure of an SF6 circuit breaker. This breaker
was used as a synchronising breaker for a CHP on our 11kV system.
Does anyone have or can point me to articles on failures (causes & effects)
of SF6 circuit breakers.

TIA
 
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  • #2
BIGEYE said:
We have had a catastrophic failure of an SF6 circuit breaker. This breaker
was used as a synchronising breaker for a CHP on our 11kV system.
Does anyone have or can point me to articles on failures (causes & effects)
of SF6 circuit breakers.

TIA
I tried to do a little internet searching but all I could really find pointed to installation problems being the cause of most failures. In paticular; connectors and connections.

I'm sure there are others here that might be able to help.
 
  • #3
Not an installation problem, circuit breaker has been in operation for a few years. We are focusing on the following as the cause:
  1. Synchronising problem
  2. Excessive number of operations, 2439 ops.
  3. Loss of SF6 gas.
The extent of destruction of the CB has taken everyone by surprise, including manufacturers and insurance investigators, so one of thr questions is why did the switchgear fail so destructively. The CB was used well within its rating. Had anyone been in the sub station at time, it may well have been a fatality. If I get time later today, I will post some photos.
 
  • #4
Try sending a PM to m.s.j -- most of his posts here in the EE forum are puzzles about failure of high voltage power distribution systems. He seems pretty knowledgeable about these kinds of questions.
 
  • #5
When I was reading about these, there were a couple mentions about maintenance programs where they checked the SF6 gas and contacts. Do you have a maintenance program for your breakers? I'm thinking any documentation might come in handy during insurance investigations etc.
 
  • #6
We do have a maintenance program and the CB was maintained recently onsite, which is basically a service of external components. However, there is a recommendation (that we didn't know about as it is not stated in the O&M manual), that the CB is serviced at factory after 2000 ops. This had not been done because we didn't know about it. This was a verbal recommendation given by the manufacturer when he carried out the site service.
 
  • #7
Image links:
http://tinyurl.com/9yvsw3"
http://tinyurl.com/7ou8pa"
http://tinyurl.com/8vqxkj"
http://tinyurl.com/7k85ze"
http://tinyurl.com/7wrvjk"
http://tinyurl.com/7s4v9p"
http://tinyurl.com/7vtvhl"
http://tinyurl.com/7z3yhq"
http://tinyurl.com/7r6g6a"
http://tinyurl.com/8ofrr3"
http://tinyurl.com/84y37h"
http://tinyurl.com/8tewxl"
http://tinyurl.com/92jcwu"
http://tinyurl.com/8ysw6t"
http://tinyurl.com/9aochw"
http://tinyurl.com/7tll6k"
http://tinyurl.com/8tufz4"
http://tinyurl.com/6v3be7"
http://tinyurl.com/7a8zxt"
http://tinyurl.com/92glox"
http://tinyurl.com/9scqhc"
http://tinyurl.com/85xmv6"

Larger pics are available.
 
Last edited by a moderator:
  • #8
Wow. Thanks for sharing BIGEYE. Glad I wasn't in there when it blew. Looks like there was a fairly large fireball involved.

Let us know if you ever determine what exactly happened.

Regards
 
  • #9
BIGEYE said:
We have had a catastrophic failure of an SF6 circuit breaker. This breaker
was used as a synchronising breaker for a CHP on our 11kV system.
Does anyone have or can point me to articles on failures (causes & effects)
of SF6 circuit breakers.

TIA

Hope you have now found the problem But your installation has many safety issues. Gen pirpose breakers used for sync duty are rated only at 25% Isc for out of phase switching. What is the ratio of actual FLC and breaker rating. Is your switchgear ventilated. Are you familiar with the hazards of handling decomposed SF6 arc products. Is yours a definite purpose gen breaker? You should be doing mtce, contact res, gas analysis more frequently. Your switchgear should be arc resistant type C or BC to IEEE C 37.20.7. Was this a failure to interrupt fault/load current or a failure to synchronize(close ) A vacuum MV CB will be more robust , ie. higher mechanical life , for this duty but it must have adequate open gap 60hz withstand and have an adequate O-o-P SC interrupting rating
Hope this helps avoid future problems
 

Related to Catastrophic failure SF6 Circuit Breaker

1. What causes a catastrophic failure in SF6 circuit breakers?

A catastrophic failure in SF6 circuit breakers can be caused by a variety of factors, including insulation breakdown, overheating, mechanical stress, or external factors such as lightning strikes or power surges. These failures can result in a high energy arc fault, leading to damage or destruction of the circuit breaker.

2. How can catastrophic failures in SF6 circuit breakers be prevented?

Proper maintenance and monitoring is key to preventing catastrophic failures in SF6 circuit breakers. Regular inspections and testing can identify potential issues before they escalate into failures. Additionally, following manufacturer guidelines for installation and operation can help prevent stress on the circuit breaker and minimize the risk of failure.

3. What are the consequences of a catastrophic failure in an SF6 circuit breaker?

The consequences of a catastrophic failure in an SF6 circuit breaker can be serious and costly. It can result in power outages, damage to equipment, and even pose a safety hazard to personnel. In extreme cases, it can also lead to environmental damage due to the release of SF6 gas, which is a potent greenhouse gas.

4. How does SF6 gas contribute to catastrophic failures in circuit breakers?

SF6 gas is used as an insulating medium in circuit breakers due to its high dielectric strength and thermal stability. However, if there is a leak or a fault in the circuit breaker, the SF6 gas can rapidly decompose into by-products, such as sulfur dioxide and sulfur hexafluoride, which can cause insulation breakdown and lead to a catastrophic failure.

5. Are there any alternatives to SF6 gas in circuit breakers?

Yes, there are alternatives to SF6 gas in circuit breakers, such as vacuum and air circuit breakers. These alternatives do not have the same environmental impact as SF6 and can also have a longer lifespan. However, they may not have the same level of insulation and arc quenching capabilities as SF6, so careful consideration must be given when choosing an alternative.

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