by Lisa Meiman
Transmission facilities endure a lot from nature—dust, fog and animal deposits—increasing risk for outages without the drama of a storm. Good maintenance requires removing contaminants that whittle away at equipment’s conductivity and create escape routes for electricity outside controlled paths. What is a flashover?
A flashover is a damaging and dangerous event where electricity is unintentionally discharged. Flashovers can cause explosions, a bright arc between two pieces of equipment, showers of sparks and loud bangs and buzzing sounds. The heat generated by a flashover can reach 35,000 degrees Fahrenheit, four times hotter than the surface of the sun.
The week of Sept. 15, Sierra Nevada gave Tracy Substation east of Sacramento, California, a good wash down to wipe away contaminants that could cause flashovers or other issues in this critical substation.
“Because our equipment is not immune from the naturally occurring wind, dust, and fog endemic to the Tracy area, our field crews regularly wash insulators to ensure they remain free of any foreign materials,” said Senior Vice President and Sierra Nevada Regional Manager Subhash Paluru.
The Central Valley Project is particularly susceptible for contaminants as it provides water for more than half of the top-10 agricultural counties in the state. “Tracy and other Central Valley Project substations are often located near agricultural land and are subject to blowing dust and other contaminants on the insulators,” said SN Power System Dispatcher Charles “Van” Stickels. “Another interesting byproduct of the agriculture is a plentiful source of food for birds. The birds like to camp out on the 500-kilovolt series compensation platforms; this causes a different contamination that causes flashovers of the capacitors.”
Sierra Nevada began its wash program for Tracy Substation in the 1980s. After experiencing a series of outages caused by contamination in the 1990s, the Tracy 500-kilovolt and Maxwell 500-kilovolt series compensation station was added to the program. During the wash, the equipment is de-energized and washed with high-pressure water. “Some years the contamination on the 500-kilovolt series compensation platforms is so bad that putty knives and shovels are required before the washing can start,” said Stickels. Maintenance crews wash Tracy Substation
One year for one week
SN successfully completed the wash without a single California resident experiencing an outage. Coordinating the downtime for two critical links in both Path 66 and Path 15, which provide reliable electricity for northern and central California, took a year of concentrated planning and collaboration within and outside Western.
“We plan the outages to not subject customers to outages. Operations and Maintenance folks get together to discuss the wash logistics and the outages required to accomplish the wash safely,” said Stickels. SN staff also met with the California Independent System Operator, Peak Reliability Coordinator, Sacramento Municipal Utility District and Pacific Gas and Electric to ensure adequate transmission capacity was in place to cover for the facilities out for the wash.
“The process of scheduling outages may appear to be simple and straightforward, but it involves a significant amount of coordination and communication and the dedicated effort of our outage coordinator as he tries to balance reliability against the internal and external staffing and service requirements,” said Paluru.
Maintenance and operations staff worked 14- to 16-hour days to complete the wash in a week. In five days, 24 switching programs were completed for the crew to wash the equipment. “The 2014 wash went well. The crews completed the week-long wash with no injuries and no switching errors, and we were able to identify areas of improvement,” said Stickels.