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Master Thesis
Department of Electrical
Engineering
HV Wound-Rotor Induction
Machines – Harmonic Field
Effects and Power Quality
Issues
By Torstein Kastet
Supervisor: Trond Toftevaag
Background
The wound rotors used in the motors at the
pump station are likely to play a part in creating
the disturbance.
Line diagram of hydro pump station with three
asynchronous motors and accompanying
capacitor banks.
A few years back, some low voltage end consumers in Trøndelag complained about very poor
lighting quality. The problem was described as slow, but distinct flicker, easily noticeable
by the human eye. Extensive measurements revealed that the problem was caused by
asynchronous machines operating in parallel with capacitor banks at a hydro pump station
nearby.
Fifth and seventh harmonics that resonate with the capacitor banks is assumed to cause
the flicker. However, exactly what cause the harmonics and how they interact with the
asynchronous machines in the hydro pump station to create this specific distortion, is still
not clarified. The objective of the thesis is to process data from the measurements, to extract
more information from them. Also, experiments in the laboratory will be performed and the
results will be used to evaluate the latest theory for the cause of the flicker.
For the laboratory exercise, one of NTNU’s asynchronous machines with wound rotor will be
used. To control the input signal and create similar conditions to those at the pump station, a
frequency converter will be used. Also, FEM simulation using COMSOL software is planned.