Princeton reports generator failure, 43‑minute outage; repairs could take months

City generation staff told the Princeton City Council that a failure at the municipal generation plant on Sept. 4 removed a primary engine from service and caused a 43‑minute outage that cut the town’s tie to the regional power line.

Jeff (city generation staff) said the unit — identified in the meeting as engine 8 — “came apart” around 10:30 a.m. on Sept. 4 after about 60 hours of run time since an overhaul. When engine 8 failed, the other online units could not absorb the lost output, and the town experienced a temporary blackout. Staff said all customers were restored within about 43 minutes after crews restarted other units.

Why it matters: engine 8 is one of the largest units in Princeton’s municipal fleet and contributes materially to local generation capacity and to the city’s capacity credits. The city said the insurance‑backed contractor is assessing whether the engine can be repaired; estimates provided in the meeting ranged from 6–9 months for a repair to more than a year for a replacement.

Key details provided at the council meeting

- Scale and timing: The city’s total generation capacity with all units online is about 38 megawatts; staff identified engine 8 as approximately 8.8 megawatts. The failure occurred about 10:30 a.m. on Sept. 4, and power was restored in about 43 minutes.

- Repair timeline and insurance: The contractor that warranties the engine inspected the damage and told staff to proceed with teardown and assessment. City staff said they are “hopeful” the unit can be repaired; contractors estimate 6–9 months for a repair and more than a year for replacement if a new engine is needed.

- Financial consequences: Staff said the city receives capacity credits tied to operating the engines; city testimony included two numbers during the discussion. One remark said the missing capacity credit equates to about $30,000 (monthly basis) that the city will not collect until the engine is back in service. Later in the discussion staff referenced capacity credits on the generation fleet that “tune to about $1,500,000 a year.” The transcript therefore contains inconsistent figures on the exact annual/monthly credit; staff said they will continue to clarify with insurance and the city’s financial officers.

- Additional unplanned work: Separately, engine 1 — the smallest and oldest unit — returned a lubricating oil sample with metals, indicating internal wear. Staff said prisoned components were found and the city plans a scheduled outage beginning Oct. 1 with a hoped‑for return to service by Jan. 1; staff estimated that repair will cost in the “300,000–500,000” range and is an unbudgeted expense.

Council questions and operational context

Council members asked how many trailer‑mounted backup generators would be required to replace engine 8’s output; staff said roughly five large semi‑trailer generators (~2,000 kW each) would be needed to make up the difference. Staff also reported that Princeton’s recent peak city load was about 25.5–26.4 megawatts, so the city retains enough generation to serve municipal load at present but loses the benefits of surplus capacity and the related revenue/credits when an engine is offline.

Next steps

- The city’s insurance contractor has been asked to assess whether the engine is repairable and whether the contractor will perform the work. The insurance company and the contractor are engaged in the teardown and damage assessment.

- Staff will continue to update the council on repair progress, insurance coverage and the budget impact of the engine outages.

Ending

City staff said generation saved the community during a larger regional outage earlier in the week and thanked crews for restoring power quickly. Officials said they will return to the council with a fuller cost and timing estimate after the contractor completes its teardown and assessment.