In the wake of recent major electrical service interruptions in the St. Thomas – St. John district, engineers at WAPA have determined the cause, and have taken steps to minimize reoccurrences in the future. The findings came out of a series of investigations and meetings held within the past week, which included WAPA personnel and contractors — APR Energy and General Electric.
Executive Director Lawrence Kupfer said Thursday that following several major service interruptions, which resulted in losing all of the Randolph Harley Power Plant’s generating capacity, it was prudent for engineers at WAPA and the company from which the authority rents generating units to determine the cause of the service interruptions.
“We were seeing a pattern of complete power plant failure when our units were dispatched along with APR-owned units and any of those units tripped. Once a WAPA unit (Unit 14 or 15) tripped, the APR units (25, 26 or 27) were not holding load and recovering from the loss of generation as they should have. Instead the units were tripping as well,” Kupfer said.
Initially, the discussions included WAPA and APR Energy, but engineers from General Electric (GE) were added to the discussion. GE is the manufacturer of units operated by both WAPA and APR Energy.
“Our joint investigation identified several changes to the electrical, fuel, water and control systems of the generating units that would increase reliability and ensure the seamless transfer process that is required when any of the generating units are interrupted unexpectedly,” Kupfer said.
He explained that during normal operation, the Randolph Harley Power Plant operates a combination of WAPA gas turbines and APR TM2500 generating units. The plant is designed for instant transfer of load when any of the dispatched units are interrupted.
“This has not been the case of late. In fact, the district-wide service interruptions stemmed from the fact that once a unit trips, the entire power plant was losing all generation capacity simultaneously.”
Kupfer said that several of the system changes have already been instituted. “However, to implement and test the remaining reliability improvements, short, scheduled service interruptions will be required. I am advising our customers that these interruptions will be scheduled in the very near future.
Over the next few days we will finalize our implementation and testing schedule and advise the public when this will occur. The testing will be done during off-peak times in an effort to minimize inconvenience to our customers.”
Once the process has been completed, the public will be updated on the results of the final implementation and testing.