manitoba hydro tests surge arresters at delivery
DESCRIPTION
Testing Prevents Surge in Arrester FailuresTRANSCRIPT
11/12/2015 Manitoba Hydro Tests Surge Arresters at Delivery
http://tdworld.com/substations/testingpreventssurgearresterfailures 1/4
Dec 1, 2009
Tweet COMMENTS 1
Testing Prevents Surge in Arrester FailuresFor more than 30 years, Manitoba Hydro has been testing surge arresters ondelivery, at installation and during operation.
Reg Gamblin, Manitoba Hydro, and Keith Hill, Doble Engineering Co. | T&D World Magazine
SURGE ARRESTERS ARE OFTEN OVERLOOKED WHEN PERFORMINGPOWER FACTOR TESTS on transformers, breakers and other apparatus in asubstation. Oftentimes, the testers are aware of how a transformer or a breaker functionsbut unaware of the intended purpose of the surge arresters. Because there are no movingparts to maintain or an oil sample to pull, it is often policy not to perform any arrestertesting.
Manitoba Hydro (MH; Manitoba, Canada) has been following a surge arrester testingprogram for more than 30 years. Under the program, typically 30 to 40 arresters areidentified each year as requiring replacement. This can be due to an increase in 10kV,60Hz wattslosses; a decreased voltage to produce 1 mA and 2 mA of resistive current; areduced sparkover withstand voltage; or an increased sparkover operating voltage. MH'sarrester testing program has been especially successful in identifying moisture ingressconcerns because of design inadequacies specifically related to the newer generation ofpolymerhoused metaloxide arresters.
MH purchases an average of several hundred surge arresters per year. These are mainlydistribution and station class but also include some specialty units for installation atgeneration and converter stations. The arrester test program requires that arresters beacceptance tested prior to the supplier being paid. MH's acceptance test includes theDoble (Boston, Massachusetts, U.S.) wattsloss test, a partialdischarge test and acharacterization of the voltagecurrent (VI) response of each unit. The maintenance testsare limited to the Doble wattsloss test and, when practical, the VI characterization orsparkover test. When reviewing test results, limits are applied as specified in standardsIEC 60099 and IEEE C62. Also, the methodology for the qualification of test resultsrequires that results for similar models and sister units be comparable.
ACCEPTANCE TEST PROGRAM
All new station class and specialty arresters are acceptance tested by MH upon delivery.Typically, on new orders of both the station and distribution classes of arresters, MHexperiences failure rates below 0.1%, although problem orders have been discovered attimes. An example of this was for an order of 54 polymerhoused stationclass arrestersfor installation at system voltages of 115 kV, 138 kV and 230 kV. The arresters originallypassed acceptance tests, but several of them failed the Doble wattsloss test onsite priorto energization. The problem was revealed to be moisture ingress due to a vulnerableweather seal. The manufacturer replaced the entire order with porcelainhoused unitsand addressed the cause of the vulnerability.
In another instance, an unusual number of polymerhoused distribution class arresterswere failing acceptance tests. These suspect units showed increased wattslosses, lowvoltages at the 1mA resistive current and excessive partial discharge. The entire orderwas returned to the manufacturer, which identified the cause of the failures as havingbeen related to the assembly of the units.
MAINTENANCE TEST PROGRAM
All serviceaged arresters are field tested by MH staff either on an 8 or 10year cycle,depending on the arrester's make and history. The 10kV, 60Hz wattsloss test is
DEC 10, 2015
DEC 10, 2015
DEC 10, 2015
DEC 10, 2015
DEC 10, 2015
DEC 10, 2015
DEC 10, 2015
DEC 2, 2015
Connect
Latest News
VIDEO
Restored CustomerConnection
NEWS
Toronto Hydro toLaunch World's FirstUnderwater EnergyStorage System
NEWS
TVA Seeks Commenton ProposedTransmission Project
NEWS
National GridAwarded £23 Millionfor Three MajorInnovation Projects
Latest on T&D How™
VIDEO
Restored CustomerConnection
VIDEO
How to Host a TailgateSession
VIDEO
Cable Replacement atMeritex Caves Part 5
VIDEO
Cable Replacement atMeritex Caves Part 4
HOME > SUBSTATIONS > TESTING PREVENTS SURGE IN ARRESTER FAILURES
SHARE 1Recommend
Subscribe About Us Magazine Issues Advertise Shop Electrical Jobs Today Newsletters
Energy Times Overhead Distribution Overhead Transmission Underground T&D Substations Smart Grid Smart Consumer
Renewables
TDWorldREGISTER LOG IN
11/12/2015 Manitoba Hydro Tests Surge Arresters at Delivery
http://tdworld.com/substations/testingpreventssurgearresterfailures 2/4
performed and, when practicable, either the VI response is characterized or a sparkovertest is performed. The VI characterization is performed on metaloxide arresters, whilesparkover tests are performed on gapped arresters. The VI and sparkover tests confirman arrester's protective characteristics are at acceptable values. It is important to note thatgapped arresters more than 25 years old are generally recommended for replacementbecause of their age. Also, all arresters undergo an infrared scan biannually. Arresterswith temperature variations between adjacent units above 5°C (41°F) are investigated.
All arresters kept in stock for unplanned replacement purposes are tested every five years,while salvaged station class arresters are reacceptance tested and returned to stock.
RELIABILITY IMPROVEMENT
Through this arrester test philosophy, MH has found many units that either have haddesign vulnerabilities or suffered from the effects of deterioration. Both of these situationsgenerally lead to unintentional arrester operation, which, because of the proximity of thearrester, can cause damage to important equipment. This test program has the addedbenefit of improving MH's electrical systems reliability as well as reducing the costsassociated with forced outages. Additionally, the acceptance test program has enabledMH to extend the time between outages for maintenance tests on arresters. Thisacceptance test program also has the added benefit of fostering the development of inhouse expertise by making available the necessary test equipment to thoroughlyinvestigate problem arresters.
Reg J. Gamblin ([email protected]) is a technical officer in the InsulationEngineering & Testing department of Manitoba Hydro, where he is responsible for thecondition assessment of generators, transformers, insulating oil, surge arresters, bushingsand instrument transformers. In 1998, he earned a diploma in electrical engineeringtechnology from Red River College. He has authored and coauthored several papers forindustry conferences on condition assessment and highvoltage testing.
Keith Hill ([email protected]) has been employed at Doble Engineering since 2001 andcurrently works as a principal engineer in the Client Service department. He is secretaryof the Doble Client Committee on Arresters, Capacitors, Cables and Accessories. Prior tojoining Doble, Hill had over 25 years of testing experience, with the last 18 years as theelectrical supervisor of engineering services at LyondellCITGO Refining (formerlyARCO). At ARCO, Hill started the testing group that was responsible for the plant powerdistribution system, electrical testing, power quality, plantwide electrical reliability andinfrared. Hill received his bachelor's degree, with a major in power, from the University ofHouston. Hill is a member of IEEE, a Level I and II thermographer, and a former NETAcertified technician.
please send additional review pdf to Liisa Colby [email protected]
Surge Arresters
Surge arresters help prevent damage to apparatus due to transient overvoltages. Thearrester provides a lowimpedance path to ground for the current from a lightning strikeor switching overvoltage and then restores to a normal operating condition. A surgearrester may be compared to a relief valve on a boiler or hot water heater. It releases highpressure until a normal operating condition is reached. When the pressure is returned tonormal, the safety valve is ready for the next operation. When a high voltage (greaterthan the normal line voltage) exists on the line, the arrester immediately furnishes a pathto ground and thus limits and drains off the excess voltage. The arrester must provide thisrelief and then prevent any further flow of current to ground. The arrester has twofunctions: it must provide a point in the circuit at which an overvoltage pulse can pass toground, and it must prevent any followup current from flowing to ground.
The technology of surge arresters has undergone major changes in the last 100 years. Inthe early 1900s, spark gaps were used to suppress overvoltages. In the 1930s, siliconcarbide arresters replaced the spark gaps. In the mid1970s, zincoxide gapless arresters,which possessed superior protection characteristics, replaced siliconcarbide arresters.
SILICONCARBIDE ARRESTERS
Siliconcarbide arresters are currently less popular than the metaloxide varistor (MOV),yet a great number of them are still in service.
In the October 1996 issue of IEEE Transactions on Power Delivery, Dr. M. Darveniza
White Papers
White Paper: The Energy Revolution
The Importance of Weather Readiness forUtilities
MORE WHITE PAPERS
T&DW Learning Center
Handbook of Energy EngineeringCalculationsSOLVE ENERGY PROBLEMSQUICKLY AND ACCURATELY
American Electrician's HandbookSixteenth Edition
For a century, the American Electricians'Handbook has served as the definitiveindustry reference for...
Temporary Grounding forLineworker Protection
This essential safety reference showshow to install grounds...
VIEW CATALOG VIEW SHOPPING CART
Featured Jobs
LeidosOrlando, Florida
Engineer (Substation Design) (I – IV)TriState Generation & TransmissionWestminster, Colorado
Senior Protection & Control EngineerLeidosHouston,
Featured Video3M ACCR Corrosion Performance Hawaii FieldTest
SHARE
Sponsored By:
MORE T&D TV VIDEO
11/12/2015 Manitoba Hydro Tests Surge Arresters at Delivery
http://tdworld.com/substations/testingpreventssurgearresterfailures 3/4
recommended all siliconcarbide arresters that have been in service for more than 13 yearsbe replaced because of moisture ingress. His tests revealed that degradation was evidentin 75% of arresters tested.
To determine if a siliconcarbide arrester warrants replacement, field testing must beperformed. The ideal method is to determine the protective level of the arrester; this is notpractical since an impulse generator is required. An effective and morepractical methodis to determine the wattsloss of the arrester and compare to like arresters.
MOV ARRESTERS
The MOV arrester is the arrester usually installed today. Doble (Boston, Massachusetts,U.S.) documentation reveals that MOVtype arresters entered the market in the UnitedStates around 1976. The metaloxide arresters are without gaps, unlike siliconcarbidearresters. This gapless design eliminates the high heat associated with the arcingdischarges. The MOV arrester has two voltage ratings — duty cycle and maximumcontinuous operating voltage — unlike the siliconcarbide arrester, which just has thedutycycle rating. A metaloxide surge arrester using zincoxide blocks provides the bestperformance, as surge voltage conduction starts and stops promptly at a precise voltagelevel, thereby improving system protection. Failure is reduced, as there is no air gapcontamination possibility; however, there is always a small value of leakage currentpresent at the operating frequency.
It is important for the test personnel to be aware that when a metaloxide arrester isdisconnected from an energized line, a small amount of static charge can be retained bythe arrester. As a safety precaution, the tester should install a temporary ground todischarge any stored energy.
POLYMER/PORCELAIN ARRESTERS
Polymer arresters are gaining in popularity over the porcelain arresters. When a recloseoperation occurs and the fault has not cleared, the arrester is subjected to a second faultcurrent. This second operation can lead to arrester explosion, if the porcelain had alreadybeen weakened by the first fault. If the pressurerelief rating of the arrester is exceeded,the arrester may fail violently, since it cannot controllably vent the excess gasses. This typeof failure can lead to other equipment being damaged or injury to personnel who may bein the vicinity of the failure. Because of the ability of the polymer station arrester to ventout the side, the housing is not weakened when exposed to the fault current. Therefore, apolymer arrester can be reclosed on multiple times without risking a violent failure. Thepolymer arresters are less expensive than porcelain arresters and appear to avoid some ofthe inservice problems, such as moisture ingress, often occurring in porcelain arresters.One manufacturer reports that moisture ingress is the direct cause of failure in 86% of allfailures.
TESTING SURGE ARRESTERS
Two of the most common tests to perform in the field on surge arresters are the Doblepower factor test and infrared analysis. Some manufacturers state that no single test willindicate the complete operating characteristics of an arrester. Reference service advisoriesfrom some manufacturers recommend power factor testing and infrared as methods todetect possible problems caused by moisture ingress. Field testing of arresters by powerfactor, infrared or other methods is used as a reference.
Different models and makes of arresters will have different wattsloss readings. The testeris attempting to identify a variance in the past wattsloss readings. Power factor is notcalculated because the current is so small. The arrester should have a visual inspection todetect cracks in the porcelain, abnormal rust staining and any abnormal physicalcondition of the arrester that is observed. Incorrect factory installation of arrester gasketshas been detected by visual inspection upon receipt of the arresters.
HANDLING SUSPECT ARRESTERS
A damaged sealgapped arrester should be handled with care. Because of increasedpressure caused by the destruction of internal elements, a defective arrester could be anexplosive hazard. If the decision is made to perform an internal inspection of a failedarrester, ensure the arrester has vented properly. Likewise, do not throw away a defectivearrester; the arrester should be properly vented before disposing.
More Jobs >>
Houston,
Construction EngineerU.S. Department of State,
COUNTRY*
EMAIL*
Signup to receive our free newsletters
Energizing (Weekly) View Sample
The Smarter Grid: Initiatives, Insights, Innovations (BiWeekly) View Sample
Test, Monitor & Control (BiWeekly) View Sample
Projects in Progress (Monthly) ViewSample
Etrain (BiWeekly) View Sample
Grid Optimization (Weekly) ViewSample
Vegetation Management Insights (Monthly) View Sample
Product Insider (Monthly) ViewSample
Experience Station Newsletter (Monthly) View Sample
Daily Energy Fix (Daily) View Sample
IEEE PES Show Update (Show Daily)View Sample
The Energy Times (Weekly) ViewSample
Lineman's Rodeo News (Weekly)View Sample
United StatesEnter your email above to receive messages aboutofferings by Penton, its brands, affiliates and/or thirdparty partners, consistent with Penton’s Privacy Policy.
Bet You Haven't SeenThis
Jury Finds Utilities toBlame in Las ConchasFireA jury decided lastmonth that two utilitycompanies hold most of
the liability in one of the largest wildfires in NewMexico’s recorded history....
More
11/12/2015 Manitoba Hydro Tests Surge Arresters at Delivery
http://tdworld.com/substations/testingpreventssurgearresterfailures 4/4
Site FeaturesMedia Center
Subscribe
Newsletters
RSS
Sitemap
View Mobile Site
Penton CorporateAbout Us
Advertise
Terms of Service
Privacy Policy
Follow Us
Search TDWorld.com
EC&M Electrical Wholesaling Electrical Marketing TD Compare Lineman's Rodeo
Copyright © 2015 Penton
TDWorld.com
Overhead Distribution Overhead Transmission Underground T&D Substations Smart Grid Business Smart Energy Consumer
Renewables
Related Penton Sites
PRINT REPRINTS FAVORITE EMAIL
Tweet
NAME: Anonymous
Sign In or register to use your TDWorld ID
EMAIL:
YOUR COMMENT: *
Discuss this Article 1
SUBMIT COMMENT
Related Articles
Laser Scanning is Substation Bound
ABB Wins Power Order in Canada
HV Surge Arrester Retrofit Service Provides Lightning Protection for Outdoor Substations
MegaMonitoring Initiative
Canada: ALSTOM Wins HVDC Transformer Contract
SHARE 1Recommend
vipin mehta (not verified) on Dec 9, 2013
reply Log In or Register to post comments
Please provide supporting document to establish that the porcelain surge arresters are prone tomoisture ingress.