Fault Locating Feature with SEL Distance Protection Relays

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Richard Matsiko Associate Join Date: Jun 2015 Posts: 49	Fault Locating Feature with SEL Distance Protection Relays 05/21/2017 8:14 AM
	I have tried to set/configure the fault locator embedded in distance relays type SEL 421...with little or no success, much as the parameters used for configuring the locator appear straight forward. The fault locators always point farther than actual fault location. In the latest incident, the actual fault was located about 3km but the locator pointed to 24km! I am now wondering how much influence, if any, the infeed into the fault from the remote end of the relay/locator has on the fault location measurements. For instance, if a fault were to be fed only from one end where I have the locator, rather than feed it from both local(where locator/relay is) and remote ends of a transmission line, would the accuracy improve?
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PWSlack Guru Join Date: Jan 2007 Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain. Kettle's on. Posts: 32175 Good Answers: 839	#1 Re: Fault Locating Feature with SEL Distance Protection Relays 05/21/2017 2:40 PM
	Naturally. __________________ "Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
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jack of all trades Guru Join Date: Sep 2006 Location: Auckland, New Zealand Posts: 8777 Good Answers: 376	#2 Re: Fault Locating Feature with SEL Distance Protection Relays 05/21/2017 4:08 PM
	It cannot calculate the fault distance with any accuracy if part of the fault current comes from another source not being measured by the SEL relay. Have you read through the manual and application guides for further guidance? Link __________________ jack of all trades
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Jpfalt Guru Join Date: May 2016 Posts: 1746 Good Answers: 87	#3 Re: Fault Locating Feature with SEL Distance Protection Relays 05/23/2017 11:29 AM
	When doing heat mat diagnosis, we use a time domain reflectometer that sends a pulse down the line and looks for a reflected pulse from where the impedance on the line changes. Major setup consideration is the velocity of propagation, which is the rate that the pulse travels down the wire and is expressed as a percentage of the speed of light. For our wires and layouts, VOP is usually around 62%. Is your sensor based on TDR type operation and do you have access to such a parameter in your sensing equipment?
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Richard Matsiko Associate Join Date: Jun 2015 Posts: 49	#4 In reply to #3 Re: Fault Locating Feature with SEL Distance Protection Relays 05/23/2017 12:31 PM
	I do not have such testing apparatus. I rely on the relay which uses measured impedance during fault to determine the distance to fault.
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