Pursuant to
10 CFR 21.21(d)(3)(i), this is a non-emergency notification by Energy Northwest concerning a defect on a control power transformer (
CPT) resulting in a failed starter coil while in service at Columbia Generating Station. The defect was associated with a
CPT provided by Spectrum Technologies (model Micron B150-2957-1).
On June 14, 2019, a failure analysis was completed that determined that the failure of the coil occurred because the starter coil was exposed to chronic elevated temperatures. These elevated temperatures were caused by the associated control power transformer (CPT) secondary voltage being maintained outside the coil's rated voltage range. Previously on June 10, 2019, it was determined that the CPT installed in the Spectrum Technologies motor starter assembly did not meet procurement specifications resulting in a turns ratio that produced higher voltages on the motor starter coil than its rated voltage. This led to overheating and breakdown of the coil insulation that created a short between two windings.
On August 5, 2019, Energy Northwest completed a Part 21 evaluation in accordance with 10 CFR 21.21(a)(1) and determined that this deviation could create a substantial safety hazard as defined in 10 CFR 21.3.
The NRC Resident Inspector has been notified.
The licensee has 14 Spectrum transformers that are continuously energized that could be affected. The one transformer that experienced the failure was out of service for maintenance at the
time of discovery. Four other coils were inspected for extent of condition and no more failures were found.