Frequent Failure of Lightning Arrester

Why not deal with the dust instead? If it's affecting the lightning arrestor, then imagine what it may be doing to people's lungs!

I would consider ther OP's handle and expect that the dust they are referring to is from the (natural) environment.

try to get enclosed type of arresters or use longer ones than the ones you are using now and also use insulated leads.

thanks

Have you contacted the manufacturer? The last thing you should be doing is coating or modifying the sheds.

UK power companies use a high pressure water mist to clean live equipment. You're local power company may be able to do this.

Go for LA with a higher creepage perhaps!

Find the engineers who decided to put the substation down wind of the cooling towers while being in a dusty location and make them go and clean the LA off once a week wearing a full body HV suit.

It may not fix your problem exactly but I guarantee that from now on the engineers will pay much closer attention to the local wind,atmospheric conditions, and primary systems placements in everything they design for today on!

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The other option is to replace your lead line going to the LA with a section of insulated underground type power line lead then insulate and seal the connection point as well so that the HV has much further to travel before arcing over.

The arrestor is weakening? How are you testing this? Do you mean the lightning air terminal?

All in all, I would refer to NFPA 780-2011 for assistance in choosing the proper materials for the job. Stacks (your cooling tower) are directly addressed in the publication.

Do you mean electrical failure or structural? is the dust insulating the cable or is the dust overloading it?

If there is a chimney upwind, you may have acid forming on the cable. Follow cuba pete's advice, above.

Never mind the local community's lung damage, then?

I would consider ther OP's handle and expect that the dust they are referring to is from the (natural) environment.

The cooling tower mist is the problem, cooling water chemistry is for the water to coat a surface, the lightening arrestor when new the water will bead on the surface. Sometimes this problem only occurs during some months of the year when the prevailing winds change.

Consider relocating the cooling tower or the substation, there is no other solution. I have seen substation(s) try all kinds of "solutions" to no avail.

Hi Sir, You may need to change the brand of surge arresrors because there are various brands. You can look at the Ka rating (increase the lightning withstand fault level from 10ka and move up to 40ka). There are different brands available that have better moisture ingress capabilities and withstand. You could move away from porcelain outer bodies to silicon insulated bodies. Some manufacturers provide a insulated cap that fits onto the surge arrestor. However, surge arrestors all have a lifespan and are subjected to replacement. They are exposed to surges and lightning and are expendable after a given number of years and Live Line Technology are surge arrestors with a replaceable function. These "drop out surge arrestors" are replaceable via a link stick, have live line capabilities and they have decent moisture ingress withstand. This version of surge arrestor is of a great quality and is adaptable to all the brands available on the market. In South Africa, these have been used for years and work very effectively across networks that are largely rural. Eskom, SEC, BPC and Namibian networks all employ them. These drop out surge arrestors cater for frequent surge arrestor replacement for places such as the Congo where there is high lightning densities and intensity. Most surge arrestors in this environment need frequent replacement. There are two versions of the drop out surge arrestor. One unit is placed in a "Firewall" bracket for protection of the overhead line and ancillary equipment such as auto-recloser etc. The "Transformer Combi unit" is a Combination of the (LA) surge arrestor and MV fuse for transformer protection. The units are available from 3,3kv-33kv. All this information is available on the Internet.

Silicone rubber insulators prevent flashovers under dusty/humid environments. 'Silgard' is the silicone coating that can be applied on already existing porcelain insulators.

You didn't identify the type of surge arrester or the failure mechanism but the best type of arrester to use in a heavily contaminated environment is polymer-housed, gapless metal oxide. Gapped silicon-carbide surge arresters will have some type of internal grading circuit across the gaps to more uniformly grade the line to ground voltage across the gap structure. External leakage currents, due to lightly wetted surface contamination, can upset the internal grading circuit, and cause failure of the silicon carbide blocks. If the external leakage current exceeds about 100 mA, the housing may flashover externally. Check the power frequency withstand of the housing and consider a polymer-housed, gapless MOV surge arrester with the appropriate external leakage distance and withstand.

There is a cover manufactured for the L/A you are talking about. Go back to the manufacturer and they will give you the information for it.