Generator Tripping Problem

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neeuor Participant Join Date: Feb 2011 Posts: 1	Generator Tripping Problem 02/13/2011 2:14 AM
	Hi All, We have a 30MVA, 11kV generator installed at our complex. The generator neutral is grounded through NGR with current being limited to 400A. The protection scheme of generator have Hitachi make Earthfault Overcurrent relay installed for protecting 90% of the winding. This relay has tripping time of the tune of 10ms for earth fault current of the order of 300A. When ever any earth fault occurs on any of the outgoing feeders of 11kV Bus, Generator gets tripped instead of outgoing feeder. Please help me finding some solution for this problem with out compromising the generator 90% winding protection. Outgoing feeder have MICOM P127 relay installed for earth fault overcurrent scheme. This MICOM relay have minimum tripping time of 35ms. Please help.
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nguyenkhoadung98 Active Contributor Join Date: Aug 2010 Posts: 22	#1 Re: Generator Tripping Problem 02/13/2011 10:48 PM
	My understand is: 1. Earthfault protection from incoming feeder from generator is intantanneous protection (50N) 2. The same schematic for outgoing feeder (50N also) If so, there are no codination betweent incoming and out going feeder. the solution is just remove the intantanneous function at incoming feeder as per IEEE std 242-2001 pages 622, item m. they recommended, do not use the intantanneous function at incoming feeder because of Maloperate.
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1boybk1 Member Join Date: Jul 2012 Location: Hanoi, Vietnam Posts: 7	#7 In reply to #1 Re: Generator Tripping Problem 03/01/2014 3:54 AM
	Dear Mr.Dung! Can u please shared to me IEEE std 242-2001 file. I'm looking for this std on internet long time but difficulty to get it. Now i'm working in Mong duong II power plant project, in-charge protection relay system. So i need this file for studying. If you're possible, please send to me via email address: dinhbka51@gmail.com Thanks a lot!
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Joshua Gabriel SAADA Active Contributor Join Date: Jan 2010 Posts: 10	#2 Re: Generator Tripping Problem 02/13/2011 10:57 PM
	Hi! You need an Electrical analysis of the all system, load and Generator – Medium ///large generators ought to be tested from time to time and not to focus only to one tripping device. It's also recommended to check the protective relay & calibrate your protective system.! Generators have to operate at maximum balanced load with a minimum current on the neutral. Your system suspect of Harmonics generation . You need to test the THD I & V parameters! You need to check the PF of your system running. Best regards Joshua Saada Joshua Gabriel InterAmerica Energy Project corp. @ :saadaj@netvision.net.il @:Joshua@aps-microgen.com Israel Tel: 972(0) 88652424- 972(0) 774100494 Cell: 972(0) 546566191 Tel/fax on demand: 972(0) 88652424 U.S. FL.: 1- 3058488196 Electrical Test Engineer: License Nr: 085195 Senior Electrical license Nr: 007922
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mountk2 Power-User Join Date: Jun 2010 Posts: 348 Good Answers: 10	#3 Re: Generator Tripping Problem 02/13/2011 11:10 PM
	There is an IDMT function that means the protection relay tripping time can be directly proportional to the quantum of fault current. Check out the relay manufacturer's IDMT curves and properly grade the earth fault relays for resolution of the problem. __________________ Knowledge sharing is a WIN-WIN situation
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Anonymous Poster	#4 Re: Generator Tripping Problem 02/14/2011 5:30 AM
	Hello friend, I would like to suggest two solutions for the problem: 1. Enable the 50N(instantaneous earth fault protection) for your outgoing feeder and let the generator operate on 51N(IDMT earth fault protection) with minimum current and time settings. 2. Go for bus bar protection so that you need not change the settings of generator.
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Priyadarshan Associate Join Date: May 2010 Posts: 46 Good Answers: 1	#5 Re: Generator Tripping Problem 02/14/2011 6:27 AM
	As already suggested by one of the friends, you must have a faster acting relay for the outgoing feeder. It could be an instantaneous relay without any time delay so that the out going feeder trips off and the generator will not trip off. Still better solution could be, if the outgoing feeder has sub feeders, then the sub feeders most prone to earth faults should have separate earth fault relays so that only the faulty sub feeder would be isolated and the healthy part remains on load. What is important is proper coordination of relay current settings and the tripping times so that the most critical equipments are protected and also, only the defective circuits are discriminated for isolation. In your case the supplier of the protection systems could be the best advisors. Priyadarshan
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Anonymous Poster	#6 Re: Generator Tripping Problem 02/16/2011 1:22 AM
	connect a 400A ct on the earth of the generator and connect the leads to the earth fault current input
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1boybk1 (1); Anonymous Poster (2); Joshua Gabriel SAADA (1); mountk2 (1); nguyenkhoadung98 (1); Priyadarshan (1)

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