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On a request from the water sewage plant Gryaab in Gothenburg a power quality survey wasperformed. The voltages and currents have continuously been sampled in the incoming 10 kVsubstation HSP01 from April-August 2008. Power quality measurements were also performedin Gryaabs other 10 kV substation HSP04 fed from HSP01 and at the terminals of theinduction motor IN_PU4040 of 1.3 MW which controls one of the four large inflow pumps tothe plant. The reason for the latter measurement was due to registered negative transients eachtime the motor was connected to the grid. The cause of the transients could be explained by thecoupling in the substation, the ageing of the motor which could result in damage of thebearings or resonance in the motor circuit which amplifies high frequency harmonics. Duringthe survey 58 transients was registered, of which 56 was caused from the coupling ofIN_PU4040 in HSP01. The additional two transients could not be explained by any event atGryaab. Two transients occurred during the measurements in HSP04. A comparison betweenthe breaker actions in the substation HSP01 showed that these transients were caused by thebreakers on the outgoing lines to the induction motor IN_PU2040 and IN_PU3040respectively. Due to the fact that these two breaker actions never caused transients in HSP01,there are reasons to believe that the transients caused by the breaker actions are amplified inthe substation HSP04. Twenty-one voltage dips occurred during the measurements, of whichfour had a retained voltage between 60 % - 75 % and a duration of 100 ms to 200 ms. Thesedips tripped the frequency converters, motors and active filters on the low voltage side ofHSP04. A comparison between the measurement data at Gryaab and Gothenburg Energy?smeasurement data at the feeding 10 kV station in Repesäll, shows that all of the dips below 90% at Gryaab are caused by faults on higher voltage levels than 10kV. According to GothenburgEnergy mostly of the dips are caused by faults at 130 kV and upwards. In order to mitigate theeffects of the voltage dips on the frequency converters, motors and filter at the low voltage sideof HSP04 a dynamic voltage stabiliser (DVR) can be installed. But at this moment this cannotbe recommended because of the low cost effectiveness. The DVR can compensate voltagesags, swells, voltage unbalance, phase angle jumps. All of the measured data from individualharmonics, THD, frequency variations and voltage unbalance fulfils the requirements set bythe European EMC standard EN61000-2-12 with a large marginal. The prominent individualharmonics measured in HSP01 and HSP04 are equally distributed, these are the 5th, 7th, 11thand the 13th harmonic.