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Topic Title: 415V switch fuse unit arc flash
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Created On: 14 November 2017 04:46 AM
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 14 November 2017 04:46 AM
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vijaymail86

Posts: 3
Joined: 14 November 2017

Hello electrical engineers,

In one of our 415V motor feeder, there was an arc flash. Attached are the photos. Relay in incomer saw the fault current as 12kA in all 3 phases for 100ms and fault current disappeared before the relay can trip. We see the cable from main bus connector to SFU got damaged but the cable from SFU to main contactor is OK. Fuse of R, Y phase got damaged severely. SFU is found OK when we opened it. Motor outgoing cable, motor IR tests were OK. SFU IR test is also OK.

We are confused what could have caused the accident.
My doubts are,
In SFU incoming, Y phase lug is still in SFU and connected tight but the cable got disconnected. So when it got disconnected it might have caused an arc which turned into 3 phase fault?

Requesting your valuable suggestions/opinions. Thanks in advance!

Thanks,
Vijay

Note: by the way how do I attach photos.
 14 November 2017 09:43 AM
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broadgage

Posts: 2435
Joined: 07 August 2007

New members cant normally attach photos straight away, unfortunately.
 14 November 2017 09:44 AM
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vijaymail86

Posts: 3
Joined: 14 November 2017

then how do I send photos for engineers to answer my question.
 14 November 2017 11:04 AM
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AJJewsbury

Posts: 16007
Joined: 13 August 2003

Note: by the way how do I attach photos.

You can't upload photos directly to this site,but if you put them publicly accessible elsewhere on the internet you can then include a link to them in a message here. New member's links aren't displayed (that's just a precaution against spammers) but established members can re-post your links for you if they're obviously legitimate.

- Andy.
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