The PJM Interconnection recently tested its ability to temporarily reduce voltage in order to practice and validate an emergency procedure used to ease system conditions under extreme circumstances.
Kevin Hatch, PJM Senior Manager, Dispatch, said PJM conducted the test of its Voltage Reduction Action on Aug. 14 and Aug. 15.
The procedure involves PJM ordering voltage reductions on the distribution system in order to reduce the strain on the transmission system during times of heavy electricity usage, which reduces the distribution voltage and the amount of power being used. The effects are not noticeable to most people and equipment, the grid operator noted.
PJM has not implemented a Voltage Reduction Action in response to real-time conditions since the Polar Vortex of January 2014. The purpose of the August test was to verify the level at which this procedure can reduce system load while also exercising transmission owners’ ability to implement it.
The Voltage Reduction Action test was one of many recommendations stemming from PJM’s review of system performance during Winter Storm Elliott. During that stretch of swift and abnormal freezing temperatures in December 2022, PJM issued a Voltage Reduction Warning in response to as many as 40 GW of generators abruptly tripping offline.
Overall, the tests allowed PJM and its transmission owners to benefit from increased communication and understanding about the time to implement the voltage reduction test, coordination with field personnel, and evaluating the impact on the overall system. The test also provided an opportunity to validate the operation of transmission and distribution equipment and verify equipment operating characteristics and parameters. Transmission owners emphasized the value of performing this test and the opportunity it provided field personnel to practice the critical procedure, enabling them to be prepared if needed.
PJM coordinated with member transmission owners and neighboring independent system operators for the 30-minute tests.
An Aug. 14 test in the Mid-Atlantic region of PJM yielded an estimated 280 MW load reduction, or 0.7% of the region’s load that afternoon. The second test conducted on Aug. 15 in PJM South and West regions netted about 360 MW of load reduction, or about 0.85% of those regions’ load.
There were no reported impacts to customers.
These results were short of the approximately 1.5% reduction in system-wide load that PJM expects in a Voltage Reduction Action, Hatch said. The tests also demonstrated a drop in generators’ reactive-power capability during the voltage reduction, emphasizing the importance of increasing reactive-power reserves availability to enhance transfer capability across the PJM system and to other regions. The inaugural test will be followed by regular tests that will include both summer and winter. The August test represents an initial set of data; subsequent tests will help PJM and its members to better assess transmission owners’ individual voltage reduction capabilities and refine estimates of expected load relief to be achieved with Voltage Reduction Actions.
