A grid company in the north of Sweden had a customer complaint where the customer’s carport trigged for over-voltages. An electrician went to the customer and measured the voltage using a voltage meter. The result was that the voltage was ok. Additionally, a power quality measurement was done where it was noticed that there were some existing harmonics. A larger measurement was done using two Unilyzer 900 in the closest transformer station. One instrument was installed per outgoing feeder, on one of the feeders the load was only private houses and on the other there was a water plant for cleaning of water.
Diagnostics
After a period of measuring data, it was clear that the 17th, 19th and 21st order harmonics failed according to the Swedish power quality grid code, EIFS.
When it was clear that high harmonics existed in the voltage, two different analyses were done to estimate the direction of the harmonics. First, the current was plotted along with the failing harmonics on the measurement which was measuring on the feeder with the water plant, the load somehow corresponds to the rise of harmonic levels in the voltage.
Secondly, the power harmonics were compared between the two outgoing feeders.
