The performance of automated systems designed to protect infrastructure from damage during severe system conditions must be addressed to limit the scope and severity of bulk power system disturbances in North America, the North American Electric Reliability Corp. (NERC) told stakeholders in a letter last week.
Known as “system protection,” these systems were a causal factor in nearly 45% of category two and higher system disturbances in 2007 and have contributed to every major system disturbance since 1965, the quasi-public agency said.
In the letter (PDF), NERC announced a new initiative designed to align a number of ongoing efforts to better address this reliability issue. The initiative prioritizes efforts of most concern, focusing on relay loadability, protection system redundancy, protection system coordination, generator frequency and voltage protective relay coordination, transmission and generation protection system misoperations, and protection system maintenance.
“Widespread outages on the power system are rarely the result of a single factor,” said Rick Sergel, NERC president and CEO. “Grid operators are faced with many unavoidable reliability risks on a daily basis—from severe weather to unexpected, simultaneous equipment failure. It is therefore critical that we reduce those risks under our control.”
Sergel said that system protection performance is one such area, along with vegetation management, operator training, and visualization tools—all of which contributed to the August 14, 2003 blackout. “The electric industry has made significant strides in each of these areas over the past five years,” he added. “Today’s initiative seeks to continue those efforts to ensure reliability in the months and years to come.”
Protection system relays are installed on nearly every element of power system infrastructure—from substations to transmission lines to generation plants. Like the circuit breakers or fuses in a home, protection system relays are designed to detect problems and open breakers to isolate system components from service during faults (short circuits) and other system conditions to avoid physical damage to the equipment.
When they misoperate, these controls can isolate equipment from service unexpectedly or may not isolate equipment when they should. Such misoperations can cause or significantly worsen system disturbances, NERC said.