Early last week, Wrangell Municipal Light & Power repaired an issue involving one of its newer diesel generators. Light & Power Director Rod Rhoades said a computer controlling the generator's output was refusing to detect the generator in question. It was a difficult problem for them to figure out, he said, but was relatively easy to fix with just a simple wire replacement.
Rhoades said all of the city's generators are expected to work together, matching their voltage and frequency to meet power demand. This is controlled through a computer, he said, which receives inputs from the machines and makes appropriate adjustments. The system was working for most of the utility's generators, but was proving to be an issue with one unit.
Wrangell normally gets its power from the Southeast Alaska Power Agency's hydroelectric capacity, but relies on diesel generators for backup. The city received two generators from the city of Nome back in September 2019 to add to Wrangell's backup power output. However, Rhoades said, the computer that kept all the generators working together was refusing to detect one of the Nome generators.
The generator's power supply is up and available, he said, and it runs flawlessly. However, whenever Wrangell separated from SEAPA power, the power to the generator's control systems would disappear and the computer would try to detect five generators but only find four.
To make matters more complicated, the issue would disappear when Wrangell reattached to SEAPA power, creating a "ghost" problem.
Rhoades said they are still unclear as to some of the "whys" of this issue, but they got it fixed. The problem, he said, was when a substation breaker would open, separating Wrangell from SEAPA power, control voltage to the generator would drop. They discovered a missing 24-volt power supply wire in the generator. It was mistakenly removed during its relocation from Nome to Wrangell, Rhoades said. Once it was replaced, the computer was able to detect the Nome generator without any issue.
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