What kind of oil is used in large electrical transformers?

[Nick]

ISTR reading yonks ago that this must be a vegetable oil. Reason for asking: I'm shipping a biggish transformer to warmer climes. Shipper specifies that all fluids must be drained. Buyer not happy about this but it's a fact of life. On arrival they can likely fill it with palm oil. Contains about 460L. I'm wondering if this would be suitable as a finish for wood. Probably hardwood and probably indoors. Have drained a few litres off today. Very clean. Nice light golden colour, quite thin, slight aroma but not unpleasant. Have tried some on a lump of untreated ash. Immediate result quite favourable. I suppose I'm trying to find out if it is safe to use as a finish. Thanks, Nick.

[Tim Watts]

It's usually a mineral oil.

Not sure that coating wood with it would have been my first thought!

[gareth]

Some of the older pole pigs contain the carcogenic PCB - I'm no chemist but ISTR polychlorinatedbiphenyls.

[Davey]

Well, Google is your easy-to-use friend:

Simple. It looks as though it might be expensive.

[Kevin]

A quick look at wikipedia suggests that if it's an old transformer, it could even still have PCBs as its "oil", which seem fairly unpleasant to have around. Later ones are more likely to have mineral oil - plenty of MSDSs to check typical constituents. Vegetable oil does not seem to be favoured. Get some well-written terms in your contract!

And don't fry chips in what you drain out of it without testing.

[ARW]

The 270kV transformer at Ferrybridge power station buzzes a bit.

I would call that a large transformer. Dunno what it is filled with though.

[Andrew Gabriel]

If the transformer is older than 1980, the fill could be PCB rather than oil, and this is highly toxic. Even if it's been refilled with oil since then, the residual PCB contamination is still toxic and classed as a hazardous waste. It's almost certainly illegal to ship such a transformer anywhere as it will be impossible to get all the PCB out.

Otherwise, I think it's a thin high temperature oil. Can't think why vegetable oil - I would have expected mineral oil.

[John]

Midel 7131 used to be my favourite when I used to deal with distribution transformers, because I wasn't allergic to it - the same couldn't be said for SSE's 'reclaimed' oil.

[newshound]

As Kevin and others say, it is most unlikely to be vegetable oil and

*if* it is old, maybe 30 years or more, might well contain PCBs which were the "villains" in the Seveso accident. You do not want to be handling these, and it might expensive to dispose of legally.

If you would like to give me some more details of the age, type, source of the transformer (off group if necessary) I will look up some documentation and see if I can provide more advice.

[e-mail]

[newshound]

My brain has gone addled, can't tell my PCB from my TCDD. Nevertheless, as Andrew's link shows you do not want to be messing with PCBs either.

[Graham.]

I drove past an outdoor substation this morning Plenty of "Danger of Death", signs, and, ironically, an electric fence on top of the railings.

You may have noticed that Asda stores often surround their loading docks with electric fences. No doubt an idea imported from their opperation in Arkansas.

[tony sayer]

Are the makers in existence still worth giving them a call perhaps?.

Sure someone her on the group still does or used to work in the leccy distribution industry...

[tabbypurr]

Veg oil gums up. Some oil filled transformers used some very toxic oil, some don't.

NT

[Martin Brown]

Depends a lot on what it is. As others have said old transformers used PCBs as a stable high temperature oil. It isn't at all good for you.

PCBs and Dioxins impurities in them were the cause of eggs and chickens disappearing off Belgian supermarket shelves in 1999 (but not before all the contaminated stuff had been mostly sold into Germany).

The analyst who finally broke the story to the press when the corrupt Belgian government failed to act for over three months was fired!

And so were the corrupt politicians (eventually).

We were lucky enough to have our own chickens at home.

[Steve B]

I spent a while flash testing 11kV and 13kV switchgear in the early eighties. IIRC correctly the oil used was derived from coconut palms. It was known to be toxic and one had to be careful when handling it, so the PCB association is very probable. Flash testing was at 33kV. I did hear that one of these oil filled units had exploded on site. When I left, the company was developing gas filled switches - Sulphur Hexafluoride.

Steve

[Dave Liquorice]

Hum, I wonder when mains power arrived here and what is in the gently rusting pole transformer. Looked at pole but the capping for one of the ground connections is bang slap over the carved information that ought to give the age of the pole. I suspect power arrived in the mid to late 70's.

Could this be (one of) the reasons ENW are reluctant to do anything with our supply? Even though when ever an engineer looks at it there is a sucking of teeth and "it shouldn't be like that"...

[gareth]

35 years ago I was working on a SCADA system for the National Grid.

When those HF6 breakers went off in the substation compound a klaxon was sounded so that all could take cover.

[Vir Campestris]

Electric fences usually just give a tickle - they put out a short spike of HV, with no real power behind it.

Of course there _are_ ones with real power, but they're not likely to be on top of Asda's loading bay.

Andy

[damduck-egg]

Would you be passing an adjoining pole sometime? Carved date might not be obscured on them all. There has been an ongoing programme to raise line heights for some years now as Agricultural machinery has got larger and clearances got compromised ,your remoteness probably means you line may be well down the list but when it happens the old Transformer will probably go. A lot of old ,ancient ,rusty but interesting looking transformers some going back to the thirties and forties have disappeared in recent times. It may be an optical illusion caused by the higher poles but many of the modern replacement Transformers appear to be mounted lower with some almost touchable from the window of a closely parked lorry cab.

G.Harman

[Adam Aglionby]

Big transformers can go with a bit of a bang, Parsons Peebles 1999 trafo on test let go: