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Unelec ACB details

Hello,

I'm designing for an upgrade of some very old electrical distribution boxes. These are fed by 1000A Unelec ACBs. I'd like to find out if these have been set to a different trip current, as they are connected to PILC cables of perhaps 185-240mm2. It looks as if these cables can't handle anywhere near 1000A.

From the engraved plate on the side of the breaker, the two types of breakers in use are:

- DVAS UR 7 IN

- PVRT UR 7 IN.

Nothing appears on google for these. Much of the field equipment dates back to the 1960s and 70s, so I'm assuming the breakers are from that era too.

Does anyone know anything about these kinds of breakers, or would know who to talk to? I have emailed Unelec as well, but given their website has not been updated since 2007 I'm not sure what to expect.

Thanks

0 Weeser Tan over 7 years ago

Hi Manish,

Unelec is pretty much the ACB from the past. I worked in a power station in Singapore, which was built in 1997, and we had similar ACBs. And they are quite a nightmare.

I suggest you to do a secondary injection test and ensure that the trip coils are still in order. If not, might as well upgrade ACBs together. There is a big possibility that contacts/ coils may not be functioning properly after years of being inactive.

Thanks and regards

Weeser
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0 Manish Makwana over 7 years ago

Thanks Weeser! That is a great point about the trip coils/contacts perhaps not functioning. I will definitely look into that - we're already talking about putting on a power quality meter to measure the downstream load, to size a replacement breaker and cable. But at that point we're looking at an entire switchboard replacement - this project began as just overhauling some field distribution panels!

Also, because who doesn't love pics of old switchgear:
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0 Weeser Tan over 7 years ago

Hi Manish,

Most welcomed. Safety has the highest priority. When it comes to protection, electrical people are extra sensitive.

Power quality meter is interesting. May I know what is the reason for this? I suppose you want to monitor harmonics, and maybe some current/voltage disturbance? What kind of load do you have?

Thanks and regards

Weeser
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0 Manish Makwana over 7 years ago

The idea with using a PQM is to identify the size of the downstream loads. Many are protected by fuses, and while I can see the maximum size of fuse that can go in the fuse holder, I don't know the size of the installed fuse. Also, the paper insulated lead covered cables that supply the field distribution boxes seem to be oversized for the downstream loads. Yet the 1000A breakers at the switchboard appear to be massively oversized for the cables. So basically there is a mess of outdated and mismatched equipment with no site records!

I'm not interested in harmonics as there aren't any VSD loads, I just want the average and peak size of the loads.
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0 Weeser Tan over 7 years ago

I see. Thanks for the explaination.

Interesting work.

Best wishes.
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0 Manish Makwana over 7 years ago

Just an update for anyone interested, I heard back from the manufacturer. Our particular Unelec ACB became obsolete in the early to mid 1970s. No spare parts, drawings or specs are available. So it looks like we'll be doing a full switchboard replacement down the track.
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0 Weeser Tan over 7 years ago

Thanks for the info Manish.

Good luck then.
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Unelec ACB details

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