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For Insulators, Bigger Is Not Necessarily Better
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2019-01-12
How to choose insulators, one constraint was the service environment, characterized by severe coastal pollution. For example Insulators at Encina are exposed to “heavy marine layer”, caused whenever cool air blowing in from the ocean meets a relatively warm land mass. In the past, this phenomenon required the substation to be live washed as often as once every several weeks, a practice regarded as costly and also risky in terms of inadvertently triggering flashovers from overspray.
Several years ago they made the decision to stop all washing at the site. This was achieved by replacing all ceramic suspension insulators with polymeric types and also applying RTV coatings to susceptible key components such as disconnect switch supports and breaker bushings.
Indeed, because of Encina’s location near the ocean, selecting suitable insulation for the project became a critical consideration. In this respect, past design philosophy in such cases usually relied on over-insulation, with specification of the highest BIL levels possible. However, this did not always succeed in preventing flashovers.
For example, that a 1050kV BIL insulator flashed over on a disconnector at the 230 kV switchyard of another power plant and took out the entire bus in the process. This incident that when it comes to insulators, bigger is not necessarily better. It's not size but rather type of insulator that determines this.
Several years ago they made the decision to stop all washing at the site. This was achieved by replacing all ceramic suspension insulators with polymeric types and also applying RTV coatings to susceptible key components such as disconnect switch supports and breaker bushings.
Indeed, because of Encina’s location near the ocean, selecting suitable insulation for the project became a critical consideration. In this respect, past design philosophy in such cases usually relied on over-insulation, with specification of the highest BIL levels possible. However, this did not always succeed in preventing flashovers.
For example, that a 1050kV BIL insulator flashed over on a disconnector at the 230 kV switchyard of another power plant and took out the entire bus in the process. This incident that when it comes to insulators, bigger is not necessarily better. It's not size but rather type of insulator that determines this.
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