Explosion of surge arresters

[terra]

Can someone please advise the possible cause of explosion of mediunm voltage surge arresters in the line?

 

[NormGA]

It's most likely an active gap arrester you're talking about, and not an mov. Over time some of the series spark gaps fail, and at some point the entire spark gap assembly passes enough current to rapidly heat the silicon carbide blocks. The result is quite often an explosive failure. If this is a common problem on your system, and it's a line class arrester, you might benefit from changing to an intermediate class arrester. Next up would be a station class.

 

[gordonl]

Arrestors can also fail if they are misapplied, on an ungrounded system the arrestors must have a voltage rating equal to or greater than the line to line voltage and not the line to ground voltage. During a ground fault the L-G voltage would rise to the L-L voltage, so the arrestor would need to stop conducting for this higher voltage.

 

[wbd]

Depending on the type, if moisture gets into the arrester thru a bad seal, this could cause a failure.

Is this a one-time event or have you been experiencing numerous failures? If numerous, is it all the same type and vintage?

wbd

 

[PowerSaudi1]

I would not discuss the causes. I want to discuss the maintenance. In our utility, we have two years program to make Preventive Maintenance. One of the tests is to measure the power factor (pf). If there is any increase of pf reading, then there is a seriuous problem.

 

[electricpete]

Good comments by all. I know the older Silicon-carbide gapped surge arresters were susceptible to failure and the newer metal-oxide are more reliable.

 

[terra]

Thank for all advice. As PowerSaudi1 told about the preventive maintanance program. I would like to know the detail of program and why we should check the power factor and how to do.

 

[wbd]

The best way I know to test for pf is using a Doble test set. I know in the USA, Doble leases test sets or you could probably hire a test company.
The Doble test checks for insulating qualities which might be affected by moisture, dirt or corrosion. The good thing about Doble is that they have test data on lots of Surge Arresters, so that you have a large population to compare your surge arresters against.
Check out their website at

http://www.doble.com

wbd

 

[jbartos]

Suggestion: Visit

http://www.sepw.com.cn/prod1e.htm

http://www.jensenab.se/surge_arrester.html

http://www.mtlsurgetechnologies.com/

http://www.ev.siemens.de/uk/arrester/

etc. for more info

 

[hy]

Hi
Failure noormaly are due to moisture inside the arresters, because of seal failures.

Preventive maintenance.
- visual inspection of external part, may be a cuasi-failure with a superficial track and seals condition.
- PF measure with Doble equipment
- LCM leakage current meter, that are test equipment for measuring the resistive leakage current. For MOA Arresters
is one of the most accurate way for detecting problems.
There are CIGRE 2000 works presented. ABB sells LCMs that are from Transinor a maker from Norway.
Are only for MOA arresters.

http://www.transinor.no