Utilities update: hydro units, substation planning and solar safety consume staff time

City utility staff reported extensive operations and maintenance work on Mount Pleasant’s electric system, including repairs to multiple hydro generators, planning for a new substation, and concerns about solar interconnections and aging fleet equipment during the work session.

Public-works and utility staff said they are working on Unit 1, Unit 3 and Unit 4 at the hydro plant, including a generator rewind and vibration testing; Unit 1 was described as an older hydro (staff referenced “1939”) with complex high-voltage components that may require major rewiring. Staff said a failed exciter and related components contributed to recent generator issues and that a brushless exciter design is under consideration to reduce future failures. The utility is also pursuing a recloser replacement at a local substation using a spare on hand and is evaluating property for a planned Substation 3 where a new transmission line is expected to land.

Staff reported tree-trimming work reduced outages by about 45 percent, but recent outages stemmed from regional Rocky Mountain transmission issues beyond local control. The utility is tracking supply and cost pressures for transformers and cautioned that procurement lead times are long; staff said transformer orders can have multi-year waits and that city budgeting will need to account for that timeline.

Workforce and fleet issues were raised: the city’s bucket truck is a 1999 model and the manufacturer Altec will stop inspecting trucks older than Feb. 2001, potentially creating compliance and service concerns. Staff said a new line truck is expected next year and recommended establishing a vehicle-replacement reserve in the budget.

Staff also described time-consuming problems tied to distributed solar systems and net metering. They said when a rooftop system’s inverter does not isolate properly it can backfeed the grid and complicate outage crews’ safety. Staff described one recent intertie problem where a customer’s solar system energizing the line during an outage caused an unexpected electric load at a residence; the city said the solar company corrected that system’s inverter. Staff asked the council to consider whether reimbursement policies for staff time spent troubleshooting customer-owned solar should be revisited; staff noted recent troubleshooting is time-intensive and currently not charged at a level that reflects staff effort.

Staff said they are reviewing meter contracts, have a spare recloser to install, and are considering a new substation transformer purchase because lead times and costs are increasing. No formal action or vote on procurement was taken during the work session; staff said they will return with budget proposals and further reports.

Notes: The update included technical descriptions of generator and exciter failures, staffing and procurement concerns, and solar interconnection safety issues; no formal procurement decisions were approved in the session.