Ring Main Substation Protection

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roykav Commentator Join Date: Dec 2011 Posts: 96 Good Answers: 2	Ring Main Substation Protection 07/20/2015 2:59 AM
	please advice, why there is only solkor protection in ring main substations. it protects ony the cable from end to end. ex. in a 4panel swbd. there is 2incoming feeders and 2transformer o/g feeders. incoming feeders having solkor relay only whee o/g feeders having current protections, 50,51. my question is why there is no protection provided for busbars/switchboard. sokor relay sense the diff. current in restricted zone only. thanks.
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IdeaSmith Guru Join Date: Mar 2012 Location: Out of your mind! Not in sight! Posts: 4424 Good Answers: 108	#1 Re: ring main substation protection 07/20/2015 3:55 AM
	Just a guess. The busbar has a higher rating and only the cable needs protection? __________________ Common Sense Dictates
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roykav Commentator Join Date: Dec 2011 Posts: 96 Good Answers: 2	#2 In reply to #1 Re: ring main substation protection 07/20/2015 4:56 AM
	no, normally incomer having current protections as standard, solkor is using where underground cables having more length. bcos it may damage due to any excavation etc.. i seen the case in ring main substations only, i dont know y. ie if there is a short circuit in the busbar there is no any protection.
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PeterT Guru Join Date: May 2010 Location: Liverpool, NY Posts: 961 Good Answers: 131	#3 Re: Ring Main Substation Protection 07/20/2015 8:09 AM
	You misunderstand the concept of how your system operates and what the relays are protecting. The transformer feeders are only sourced from your bus. Therefore only overcurrent relays are needed to detect and trip for fault current (unless you want to add differential protection on the transformers themselves for more sensitive detection of internal faults). The incoming feeder cables can be fed from both ends in the event of a cable fault - both from the utility source end and from your switchboard bus (from the other source feeder). Normally current flow will only be from the external source into your switchboard. If there is a fault in the cable, it will draw from both ends and your differential relay (Solkor) will trip. Differential relays usually also have a high instantaneous overcurrent function, so that a fault in your switchboard will cause the relay to trip for an internal fault on your bus. Take a course in protective relaying and it will help you understand. Also, study this free resource: GE - Art & Science of Protective Relaying __________________ To get the right answers, first you need to ask the right questions.
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roykav Commentator Join Date: Dec 2011 Posts: 96 Good Answers: 2	#4 In reply to #3 Re: Ring Main Substation Protection 07/21/2015 12:54 PM
	dear peter thanks for ur reference
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IdeaSmith (1); PeterT (1); roykav (2)

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