Metering 2 Feeders with a Single Power Quality Meter


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I was asked to check the output of a power quality meter. My station has two step up transformers 13.8-115 kV and 18-115 kV. A single PQM is used to meter the combined output of both lines. Of course, prints are never available for something like this, so I was required to trace and map the circuits.

I assumed that the PQM would have individual CT inputs from each feeder but instead found the CT leads from each feed paralleled at a terminal strip. Each phase is then routed through another set of CT's and then finally terminated on the PQM.

Could someone explain how the PQM does the summing of the CT feeds with the leads in parallel, and not terminated individually?