Harmonic propagation in transmission system with multiple capacitor installations

The South West Interconnected System (SWIS)-the main transmission system of Western Australia, experienced rapid development in response to the growing load demand. New capacitor banks are progressively being installed around the system to support the voltage profile and compensate for the load reactive power. On the other hand, the increased size of capacitor banks and their multiple installations created potential risk of high harmonic voltages and currents, adversely affecting the utility and customer equipment. This paper presents the results of harmonic distortion investigations and studies performed for the Western Power transmission system in response to the growing number of reported capacitor bank tripping and failures at some terminal and zone substations. The measurements performed in the 132 kV transmission system identified the locations with excessive levels of 5^th harmonic voltage and current. However, only computer harmonic simulation allowed the source of the resonance conditions causing overloading of the capacitor banks to be identified. The paper describes the harmonic measurement and simulation results and demonstrates a solution for avoiding harmful harmonic resonances in the existing capacitor banks