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Surge Arresters

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Surge ArrestersSurge Arresters

Gaps and gaplessGaps and gapless Silicon Carbide and Metal OxideSilicon Carbide and Metal Oxide ClassClass Tests and RatingsTests and Ratings InstallationInstallation Field testing and FailuresField testing and Failures

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Silicon Carbide ArrestersSilicon Carbide Arresters Blocks cannot conduct continuouslyBlocks cannot conduct continuously Series gapsSeries gaps Fast transients cause the series gaps to short over and insert the Fast transients cause the series gaps to short over and insert the

silicon carbide blocks silicon carbide blocks Gaps must reseal after the arrester operates (grading circuitry)Gaps must reseal after the arrester operates (grading circuitry) Duty cycle ratingDuty cycle rating is the maximum 60hz voltage where the gaps is the maximum 60hz voltage where the gaps

can still re-seal against power follow currentcan still re-seal against power follow current Subject to external contamination Subject to external contamination Doble study shows that 50% of silicon carbide arresters tested Doble study shows that 50% of silicon carbide arresters tested

cannot meet original protection characteristicscannot meet original protection characteristics Problem with moisture contamination and gaps changing Problem with moisture contamination and gaps changing

characteristicscharacteristics Oldest SiC arresters do not have a pressure relief ratingOldest SiC arresters do not have a pressure relief rating

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Metal Oxide arrestersMetal Oxide arresters

Station Class Metal Oxide arresters were first Station Class Metal Oxide arresters were first introduced around 1980 for transmission introduced around 1980 for transmission applicationsapplications

Originally three varieties:Originally three varieties:– Gapless – Westinghouse 4” discsGapless – Westinghouse 4” discs– Shunt gap – General Electric 3” discsShunt gap – General Electric 3” discs– Series gap – Ohio Brass 3” discsSeries gap – Ohio Brass 3” discs

Today all station class arresters are gaplessToday all station class arresters are gapless Intermediate and distribution ratings introduced in Intermediate and distribution ratings introduced in

mid 80s (gapless)mid 80s (gapless) Polymer housings introduced in 90s Polymer housings introduced in 90s

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Arrester base left on structure Arrester base left on structure after failure.after failure.

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Typical 46 kV MOV ArresterTypical 46 kV MOV Arrester

Polymer Housing

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Failed Polymer ArresterFailed Polymer Arrester

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