40,000A Current Supply 2

[bigmantony]

I require to design a current tranformer for use with a primary current of 40,000A (forty thousand)

Problem: getting a supply to test the bugger!

Does anyone know of a test house or supply (preferably UK) that can generate 40,000A for me?

Looping a primary conductor many times around the CT is not an ideal solution for the test.

HELP????

 

[cuky2000]

It is 40 kA current expected to be measured during continuous or momentarily conditions such as short circuit or lightning strike ?

 

[jtkirb]

The only thing capable to doing this (that you can rent) is a low voltage circuit (480V) breaker test set. Most are set up to plug the breaker on to and inject quite a bit of current at very low voltage to test the instant trip funcitons.

Multi-amp used to make them. Not sure who in the UK.

JTK

 

[ScottyUK]

The British Short-circuit Testing Station at Hebburn on Tyneside could probably help if they are still in business:

Victoria Road West, Hebburn, NE31 1UB. Tel 0191 483 2135.

Out of interest, what is wrong with using multiple turns? You could reasonably rent a LV mobile diesel generator and (for example) a 11/0.415 kV distribution transformer. Connect the generator to the HV winding. The LV winding of a 1.5MVA transformer will give you up to about 2000A at 15V. You're then looking at about 20 turns. Aggreko carry this sort of equipment for rental. You could even do this from a standard industrial 3-phase supply if your source is of a reasonable capacity.

Why do you want to do a full rating test? A mag curve for saturation is normally done from the secondary side (because it is not especially practical to source 40kA!) and the turns ratio can be done at far more reasonable current levels.


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I don't suffer from insanity. I enjoy it...

 

[scottf]

Without knowing exactly what bigmantony is doing, I suspect that looping the primary is unacceptable because for a continuous current rating of 40 kA, local saturation is a big concern. Often special winding design and shielding is required to guard against this.

Sure you can prove the protection class accuracy from excitation testing from the secondary side, but the standards also require a ratio test at rated current.

 

[ScottyUK]

Hi ScottF:

Your post makes a lot of sense - thanks for the input. As your company makes these things, how do you arrange the test source for testing, say, a CT with a 40kA rated current? If it isn't proprietary or commercially sensitive, I'm interested how you go about arranging a source of that capacity, largely because we have CTs rated 18kA primary current on our steam turbine generator's bushings. I like to know how to test the things which I'm responsible for maintaining. Send it to XYZ is an entirely valid answer!

Tony,

Another possible company to discuss testing with is KEMA in the Netherlands - I think they have a very high current test facility there IIRC.


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I don't suffer from insanity. I enjoy it...

 

[scottf]

ScottyUK-

The National Reasearch Council in Canada is equiped to do such measurements.

To be honest, I'm not exactly sure how we generate that much current. I don't believe we're able to get up to 40 kA continuous. We aren't that big of a player in generator CTs in the US...more so in Europe, but I'm not familiar with the test set-up's there.

I'm pretty sure our current step up transformers are built in-house in Europe.

 

[ScottyUK]

Wonders out loud:

Where do the aluminium (check out the spelling, North America!) smelting plants buy their transformers? I seem to recall five-digit DC currents being commonplace in that industry. The one smelter I have visited had busbars with greater cross section than my waist: I'm sure that it wasn't that size purely because it impressed visitors (But it surely did!)


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I don't suffer from insanity. I enjoy it...

 

[Skogsgurra]

Scotty,

I remember being asked to visit an aluminium (EU spelling) smelting work in Sweden to check the rectifiers. There was a problem with the "trimmer rectifier" (the one that was used to sdjust the last few percents of current in the process. It had a rated current of 20 000 amps. The main rectifiers were a lot bigger. I think around 300 000 amps. So you can easily change the five digits into six digits.

And, no. They didn't tell where they got their transformers from.

Gunnar Englund

http://www.gke.org

 

[amorrison]

If you drop a wrench(spanner) across a 12 volt automotive lead acid battery you are supposed to get 1000 amps for several seconds.

Forty batteries in parallel if 12 Volts - 20 if six volts.

Safety considerations ?

I am told that a automotive starting motor will draw 300 amps at engine temperature of -30F (-34C) - a common situation in cold climates so 1000 Amps really isn't all that wild especially if the battery is warm(72F or 22C).

If rail gun tests the cheapest way to get the required millions of amps was to go to an automotive battery supplier.

Check with the battery engineers - not the battery salesmen.

Another option - check with electroplating plant engineers - probably to them 40000 Amps is nothing.

 

[itsmoked]

Drop one across my batteries and you'l' get more than that.. The starter draws 1,600A. It's a diesel.

 

[Skogsgurra]

Is it a DC transformer that bigmantony is designing? Or do you know any good way getting AC out of a battery? I mean 40 kA AC.

Gunnar Englund

http://www.gke.org

 

[waross]

We're the concept group.
The concept is good.
If you want a sin wave, you will have to contact the details group.

 

[Skogsgurra]

It is good to see a short and snappy answer, waross!

Gunnar Englund

http://www.gke.org

 

[itsmoked]

Flip the battery connections. Rapidly.

 

[Skogsgurra]

Same comment, smoked!

Gunnar Englund

http://www.gke.org

 

[bigmantony]

Thank you all for your kind responses. We shall review them just now.

Its an AC transformer, it will have screen windings, and require to meet BSEN/IEC6044-1.

We require a continuous supply as we have to show that it meets the ratio error limits.

ScottyUK - BSTS is a skeleton of its former self and would not be able to supply. The generator advise is something that we have carried out before but as I say, it the ratio errors that we have to prove.

 

[djs]

Hello;
Have you looked into a spot welding transformer? Some of the larger units can go aboce 40KA. You will have to supply the measuring instruments.

 

[bigmantony]

Hi DJS, these spot welding transformers are good for quick bursts of current but alas we require something more continuous. Cheers anyway.

For those interested in this thread, we came up with the idea of putting evenly spaced Taps throughout the winding and testing section at a time at lower primary current.

This will tell me that the turns are correct. we are still not able to test at rated current to ensure that the unit meets the classification.

Also, the application is for a generator. (a big one.)
"I think the Chinese want to drill to the Earths core."

 

[randyman]

Bigmantony -

Your approach with taps seems sound as I have also used that concept with high-turnage coils. We have made several high current ratio CTs ourselves and resorted to multiple primary turns for RCF/PA readings. But even with that scheme it is still difficult to get up to 40kA-turns. And you know the performance of this CT will be constant from 2% to 100% rated current with the readings differing by less than the certainty limits of test.

I know working with Chinese OEMs and their "technical councils", they are sticklers for detail and will hold you to the standards you are working to. Be greatful these are not gapped-core (class TPY) designs!!!