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Monday, October 4, 2010

Emergency Shutdown of Power Circuit Breaker (Arcing due to Insulator Cleaner)

I. Background of the Problem:

115kV Power Circuit Breakers were scheduled for maintenance on September 29, 2010. The breakers were maintained one at a time. The testing for Breaker 1 started at 0601H and ended at 1024H. The testing for Breaker 2 started at 1026H and ended at 1152H. Initial results of the tests were satisfactory for both breakers.
Before testing of equipment, the pakyaw group who were assigned to clean the porcelain insulators mopped off the dusts on insulators and after testing, they applied insulator cleaner solution and buffed them until they looked glossy and shiny. The solution was one part Insulator cleaner to two parts water as per label instruction. Upon normalization of the breakers, no abnormalities were observed or noticed by the SS engineer on-duty as well as the Test groups. Around 1810H in the evening, Substation Engineer-on-duty conducted patrolling and reading of gauges at Switchyard. He heard a loud buzzing sound coming from the Breaker 2. He informed another SS Engineer and they both inspected where the buzzing sound comes from. They noticed that the sound originated from the arcs formed in between the base of Phase C pole (lower stack) to the porcelain insulator. The arcs were visible and noticeable. They informed the Chief Engineer of Substation about the abnormality found. Chief Supervisor advised them to isolate the breaker since no outage of the line will be involved. SS Engineer-on-duty coordinated to Area Control Center. At 1850H, 115kV Breaker 2 was SCADA tripped.



II. ACTIONS TAKEN



The scheduled shutdown of 50 MVA Transformer on September 30, 2010 still included the 115kV Breaker 2. So the Test Group conducted insulation test on Phase C of Breaker 2 breaker together with its current transformers and the result was already failing compared to yesterday’s result. To determine which part of the group of equipment had failed the test, they isolated the CTs on both sides of the breakers. Then, they conducted insulation resistance test to individual CTs, upper and lower stacks of Phase C of  breaker 2. The results showed that the lower stack of the breaker failed the test. While the results showed that the other parts were within the limits, the results were poorer compared to the yesterday's results. Other equipments that were applied with insulator cleaner were tested again, and the results were not that satisfactory. It was decided that the cleaner had caused the poor result as well as the arcing of Phase C breaker 2. So, all the equipments that were previously applied with insulator cleaner were washed with detergent and water. Then, the test group tested again the equipment after washing and the results were all satisfactory.



III. ROOT CAUSE OF THE PROBLEM



The root cause of the problem is the improper use of Insulator cleaner. As per experience of another Substation, the cleaner had removed the heavy dirt and stains on their Transformer bushing, which had improved the testing result on the said equipment. Since the porcelain insulators at the substation are not excessively dirty and stained, tap water is enough to clean the insulators.



IV. RECOMMENDED ACTION PLAN



A. Cleaning of insulators must be conducted first before testing of high voltage equipment so that when improper cleaning is done, the test result will show that the insulation is not good and other remedies can still be implemented.

B. Insulator cleaner must be applied only to porcelain insulators with heavy dirt and stains. To be certain that the cleaner does not affect the insulation of the equipment, the porcelain insulators must be washed again with water.

C. Pakyaw group in charge of insulator cleaning must be properly supervised and instructed so that they will do their work correctly.

8 comments:

  1. Sir ano ung ginamit nung insulator cleaner??? arnox b? kc nangyari din sa ss namin yan..maingay nung i-energized na namin...

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  2. hello

    yes, we used arnox insulator cleaner. this cleaner need to be diluted first with water, right? anyways, our Head's recommendation is to used this cleaner to heavily soiled insulators or those petticoat insulators, since it is really effective in removing dirt, and we had already purchased six containers of this cleaner. but make sure to wash it again with water.

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  3. Thanks for info sir...hindi namin hinalo sa tubig kaya halos masunog sa init mga kamay at kuko namain...hehehe...sa Labrador SS ako sir..

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  4. thanks for reading my blog bro. just keep it posted for new updates. you can also share some of your substation concerns so that we can work it out together with other readers.

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  5. Power circuits experience shutdown when the insulator is not clean.

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  6. @serviced offices: yes, insulators that are not clean can cause flashovers that can result to tripping of affected line/equipment. In our case, we did an emergency shutdown to abate tripping of our transformer since the power circuit breaker involved is a transformer breaker. since only one breaker was tripped, the transformer remained energized because of the breaker-and-a-half scheme. thanks for sharing.

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  7. na try niyo na ba sir linisin ng distilled water using pressure washer habang naka energize ang power transformer?

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