11kV Line Insulator Sparking

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ahmadtouqir Participant Join Date: Feb 2016 Location: Pakistan Posts: 4	11kV Line Insulator Sparking 03/17/2016 2:28 PM
	Due to the fierce rain storm, the 11kV line pole insulators had a sparkling, but there was no tripping. Later, the insulator started giving vibrating/buzzing noise. I will get those insulators replaced, but I wanted to know the reasons behind the phenomenon. Thanks __________________ Work until your idols become your rivals
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	Pathfinder Tags: 11kV flash over insulator

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#2 "Re: 11kV line Insulator Sparking" by SolarEagle on 03/17/2016 3:35 PM (score 2)

Tornado Guru Join Date: May 2009 Location: Richland, WA, USA Posts: 21017 Good Answers: 795	#1 Re: 11kV line Insulator Sparking 03/17/2016 3:15 PM
	Interesting question. I'm marking this OT as it is mostly speculation. As can be observed, the "stack of inverted funnels" that makes up an insulator is designed to shed water at multiple places, which tends to prevent a film of water from building up over the length of the insulator. High cross-winds could compromise that feature, leading to sporadic arcing, which seems to have occurred. In turn, the arcing could have "cooked" the insulator, degrading its effectiveness later on. __________________ In vino veritas; in cervisia carmen; in aqua E. coli.
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Rixter Guru Join Date: Apr 2010 Location: About 4000 miles from the center of the earth (+/-100 mi) Posts: 9913 Good Answers: 1141	#3 In reply to #1 Re: 11kV line Insulator Sparking 03/17/2016 3:42 PM
	Doesn't look like OT to me.
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Tornado Guru Join Date: May 2009 Location: Richland, WA, USA Posts: 21017 Good Answers: 795	#4 In reply to #3 Re: 11kV line Insulator Sparking 03/17/2016 4:01 PM
	Too bad you inherited my self-marked OT. (Gotta watch those.) This isn't my field of experience, but just an attempt to think along engineering lines. Maybe RAM Consult, MSamad, et al., will weigh in. __________________ In vino veritas; in cervisia carmen; in aqua E. coli.
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SolarEagle Guru Join Date: Mar 2007 Location: by the beach in Florida Posts: 33392 Good Answers: 1817	#2 Re: 11kV line Insulator Sparking 03/17/2016 3:35 PM
	This could be caused by several different problems... Cracking of Insulator... ...The porcelain insulator mainly consists of three different materials. The main porcelain body, steel fitting arrangement and cement to fix the steel part with porcelain. Due to changing climate conditions, these different materials in the insulator expand and contract in different rate. These unequal expansion and contraction of porcelain, steel and cement are the chief cause of cracking of insulator. Defective Insulation Material... ...If the insulation material used for insulator is defective anywhere, the insulator may have a high chance of having failure... Porosity in The Insulation Materials... ...If the porcelain insulator is manufactured at low temperatures, it will make it porous, and due to this reason it will absorb moisture from air thus its insulation will decrease and leakage current will start to flow through the insulator which will lead to insulator failure. Improper Glazing on Insulator Surface... ...If the surface of porcelain insulator is not properly glazed, moisture can stick over it. This moisture along with deposited dust on the insulator surface, produces a conducting path. As a result the flash over distance of the insulator is reduced. As the flash over distance is reduced, the chance of failure of insulator due to flash over becomes more. Flash Over Across Insulator... ...If flash over occurs, the insulator may be over heated which may ultimately result in failure... Mechanical Stresses on Insulator... ...If an insulator has any weak portion due to manufacturing defect, it may break from that weak portion when mechanical stress is applied on it by its conductor... ...additionally... http://www.uesystems.com/wp-content/uploads/2012/07/high-voltage-electric-equipment-failure-diagnosis.pdf __________________ All living things seek to control their own destiny....this is the purpose of life
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RAMConsult Guru Join Date: May 2007 Location: NYC metropolitan area. Posts: 3230 Good Answers: 444	#5 Re: 11kV line Insulator Sparking 03/17/2016 7:56 PM
	It's nothing more than what's known as "tracking" across the insulator "skirts", and is usually caused by a buildup of pollutants/dirt/dust on the insulator surfaces. The "fierce" rain got driven across the underside of the skirts, stuck to the gunk, and provided a semiconductive path from the line to earth. The "noise" is the sound of the current cooking that gunk and boiling off the moisture, the residual noise is the arcing through the paths that remain. __________________ “Tell me and I forget. Teach me and I remember. Involve me and I learn.” Ben Franklin.
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WAWAUS Guru Join Date: Aug 2010 Location: Melbourne, Australia Posts: 740 Good Answers: 24	#6 Re: 11kV line Insulator Sparking 03/17/2016 10:32 PM
	This sounds like a very common phenomena. The insulators build up a coating of contamination during dry weather and when there is a rain storm the contamination forms a solution which is partially conductive and a corona discharge occurs. This sounds like a loud buzzing. Further rain will eventually clean the insulator and the buzzing will subside or a return to dry weather will allow the insulator to dry off and the buzzing will subside. If the buzzing does not subside it may be an indicator of a more serious issue which should be investigated.
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Khinzawmyint Member Join Date: Aug 2015 Posts: 9	#7 Re: 11kV line Insulator Sparking 03/18/2016 1:39 AM
	Hi 11kv Insulator has specific characteristics to defense against Failure such as dry flash over and wet flash over , impulse lightning withstand voltage and so on to sustain insulstion of insulator. But during thunder rain some thunders may strike insulator causing small cracked lines in its porcelain layer.As you know a fraction of an inch of Porcelain can withstand tens of kilo volts.Cracked insulator has a leak path. So voltage pressure forced to break insulation at any time causing magnetic instabilities.Such a phenomena of sufficient Energy may cause flash to trip circuit breaker. Some corona effects can't have enough energy to trip but can burn Cross Arm as a fire hazard though breaker can't be tripped. In my days of wilderness 11 kv lines along the jungle Trees touching their leaves and of branches causing many sparks flickering likely to be seen on Festival but don't trip circuit breaker ,that lines need Vegetation so they have not enough energy to trip. I found that a 33 kv termination has a buzzing sound and corona rays ever that I know it is dangerous but that withstood for many years. Thank you for recalling My memories of Old experiences. KZM, Myanmar.
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James Stewart Guru Join Date: Mar 2011 Location: Lubbock, Texas Posts: 14331 Good Answers: 162	#8 Re: 11kV Line Insulator Sparking 04/07/2016 2:35 PM
	That something about the "fierce" rain storm allowed the 11kV insulators to have corona discharge (but not arcing?) indicates not a failure of the insulators but a "dirty" location. If you are near the sea, but still mostly arid due to infrequent rains (monsoons), salt air may allow salty dust deposits to accumulation on and under the insulating "bells" or "aprons" depending on the jargon for these parts. Upon moistening, a highly conductive path results, just enough so that the corona discharge initiation gap is introduced. Later on, rain has either washed away the salty deposits or not, and the crackling sound is a continued low current discharge that is apparently the result of "burn tracks" on the surface of the insulator. If the problem does not subside, periodic replacement may be the preferred answer. __________________ If it ain't broke, don't fix it. Just build a better one.
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#2 "Re: 11kV line Insulator Sparking" by SolarEagle on 03/17/2016 3:35 PM (score 2)

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Users who posted comments:

James Stewart (1); Khinzawmyint (1); RAMConsult (1); Rixter (1); SolarEagle (1); Tornado (2); WAWAUS (1)

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