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Need help in solving my problem

Need help in solving my problem

Need help in solving my problem

(OP)
Hello Every one

I am working in a petrochemical company. We have got number of substations in our company. Recently couple of months back we faced some unusual problem.. Our main feeder breaker (VCB) 13.8kV is feeding to 4 VCB in different substations its like a loop these are connected with Bus Tie Bus A & Bus B. If any unabnormal in the main feeder the down stream feeders get switched to Bus B. That day sudden switching was taken place but unfortunately Main feeder breaker showed any sign of abnormality all protective relays were safe Differential relay, U/V,OC..etc but in the downstream in one of the substation UV relay flag was set and only that VCB did not switched to Bus B automatically.Other substations VCB were switched to Bus B and also no sign of any abnormality in any relays in remaining S/S. After troubleshooting in one of our flag S/S we found the loose connection at the back of the VCB which it was not transfered to Bus B. But still why this switching took place still we are unable to find out. No ground fault relay, no signs of any relays alram. Today again we faced the same problem but in different S/S this time same UV flag was set and transfered stop automatic. Could anyone help us any giving the right solutions what exactly is happening in our Main feeder. We assume main feeder VCB needs to calibrate as it was recently calibrated along with others.Help me Enginners.

RE: Need help in solving my problem

I cannot quite understand what happened and much less why it happened. Usually, a detailed study of recordings of voltages and currents involved will point to the root cause of the switching.

Such recordings plus a diagram over the plant and all the relay settings would make an analysis a lot easier and safer.

Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

RE: Need help in solving my problem

If I understand correctly, you have a system which is meant to change over from Bus A to Bus B when there is an undervoltage condition on Bus A, but the system is not behaving as envisaged. There are many possible reasons for this and you are not going to get an instant answer over the internet. You need a commissioning engineer on site to do some investigation and testing, which would include simulating the undervoltage event and observing the results. Testing on a high voltage system is a specialist activity requiring a great deal of knowledge and experience to carry out safely, and reduce the risk to production.,
Regards
Marmite

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