Loss Of Communication Between Components In W.A.P.A.’s Largest Generating Unit Cause Of Thursday’s District-Wide Power Outage

ST. THOMAS — A loss of communication between key systems in W.A.P.A. generating unit 23 was responsible for the unit’s tripping off line, the loss of another generating unit and subsequently the failure of all electrical feeders in the district, W.A.P.A. said on Thursday via press release. Unit 23 is W.A.P.A.’s largest generating unit, often times referred to as the authority’s workhorse.

W.A.P.A. Interim Chief Executive Officer Julio A. Rhymer, Sr. said Thursday that an investigation by plant personnel revealed that unit 23’s exciter tripped “due to a loss of communication with the unit’s exciter control modules. This loss in turn activated the generator’s protection scheme resulting in the unit tripping off line. The loss of Unit 23 had a domino effect on the other generator on line at the time, Unit 25.”

The loss of the units occurred at 12:57 a.m. and in the ensuing hours, plant personnel, Line Department and System Planning engineers began to troubleshoot the cause and effect of the electrical service interruption. Due to the unique nature of unit 23’s failure, plant personnel were required to spend considerable time in ensuring that the root cause of the unit’s tripping had been identified prior to attempting its restoration. Thereafter, three smaller generating units: 14, 18 and 25 were brought on line and restoration of service was begun at 4:40 a.m. “The plant also brought a fourth unit, Unit 15, on line in the event additional generation capacity was needed,” Mr. Rhymer explained.

With the restoration complete, plant personnel rebooted various components within Unit 23’s control modules and the unit was restored to service at around 10 a.m. W.A.P.A. has already reached out to the unit’s original equipment manufacturer to provide additional technical assistance in improving the unit’s reliability until a scheduled major overhaul takes place in September, according to the release. The unit must undergo a major overhaul before it is converted to burn tri-fuel: propane, natural gas and oil.

Mr. Rhymer apologized to W.A.P.A.’s customers for the inconvenience caused by the service interruption and thanked the authority’s employees who responded to the power plant in the early morning hours of Thursday to assist in the restoration of service to residents of the district.