Energize Inbox, August 2018

Our winning letter

re: Gas insulated power transformers: a growing technology

Dear Editor

I really enjoyed reading Mike Rycroft’s article “Gas insulated power transformers: a growing technology” (Energize, June 2018), since I am a retired, ex-senior electro/mechanical designer of power transformers up to and including 700 MVA, 400 kV, most of which were for Eskom. I was responsible for the installation of the new 132 kV GIS substation at Springs in the 1980s.

The gas insulated system is not totally new to me as although I have never been involved with type of transformer.

The preparation work is very important, particularly the civils but with a good level floor as a start, the work becomes easier as the flanged joints need to be perfectly done to prevent leaks. I am sure this works for both switchgear and transformer assemblies.

I am aware of the cost implications for this type of installation but I am convinced that with space savings, no oil leaks and hardly any maintenance of the outer structure, to name a few, over a long period, the system is more cost effective.

The last paragraph of the article refers to vandalism on distribution transformers, i.e. oil theft for frying. Of course, once the oil-less transformer fails, the scrapped unit can be purchased cheaply. If the windings are of copper they can be sold a good scrap price. Obviously should the windings be made of aluminium, the scrap price will be quite low.

I can personally confirm that this is happening as I travelled into sub-Saharan Africa for four years doing technical presentations on distribution and power transformers and have actually seen the results of vandalism. Even CO2 filled transformers will fail once the tank is punctured and the gas has escaped.

The answer in my opinion, is a dry type, cast resin or filament wound transformer built into a sealed corrugated tank. I have actually made and successfully tested
100 kVA, 200 kVA and 11 kV units with great success. The corrugated tanks provided very good cooling due to the increased surface area.

The principal advantage, of course, being that vandals can puncture the tank with no ill effect to the operation of the transformer.

Jean Tanzino


re: Gas insulated power transformers: a growing technology

Mike Rycroft’s article “Gas insulated power transformers: a growing technology” (Energize,
June 2018) was an interesting read, but unfortunately I felt that by the end of the article there is actually no real replacement for SF6 gas which has a global warming potential of 22 000 times worse than CO2. The only possible replacement, C4F8, has a global warming potential of 10 000 times worse than CO2 – hardly something anyone these days would like to invest in. “GITs have been in use since 1960s but has been restricted due to higher costs and other reasons” – if the author had mentioned those GWP reasons in the opening paragraph I think it would have painted the picture a bit more clearly.

Michael de Klerk

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Source: EE plublishers

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