A utility opened a new 110 kV switchyard and needed its revenue metering point commissioned to utility-accuracy before the first billing period. NAHU supplied the instrument transformers and our field engineers supervised the installation and accuracy verification on site.
The challenge
The switchyard mixed two feeder bays and one transformer bay, each needing its own metering and protection cores. Accuracy had to hold to 0.2S on the metering cores from 1% to 120% of rated current, and the whole point had to pass utility acceptance before energisation.
Our solution
We supplied dual-core current transformers (0.2S / 10P10) and class 0.2 voltage transformers with 100/√3 V secondaries, matched to the bay ratings. Our engineers then ran the full site test sequence: insulation resistance, ratio verification by primary injection, polarity checks and secondary wiring continuity end-to-end.
Products supplied
Indoor cast-resin current transformers and voltage transformers for the two feeder bays, dual-ratio outdoor current transformers for the transformer bay, plus terminal blocks, shorting links and documentation packs per bay.
Outcome
The metering point passed utility acceptance on the first attempt. Meter readings matched the reference instrument within the 0.2S band across the full load range, and the switchyard was energised and billed without rework.