HARMONIC MEASUREMENTS MADE ON THE UPGRADED NEW-ZEALAND INTER-ISLAND HVDC TRANSMISSION-SYSTEM

This paper introduces the recent upgrade to the New Zealand inter-isla nd HVdc transmission system. It then details the procedure of one of s everal tests conducted to measure harmonic levels created by the upgra ded transmission system. Harmonic levels were measured using the CHART (Continuous Harmonic Analysis in Real-Time) harmonic monitoring instr umentation. The connection of CHART to the high voltage network and it s configuration during the test is discussed. A sample of results gath ered while monitoring are presented, including characteristic harmonic s of the converter, and maximum voltage and current levels up to the 5 0th harmonic for each of the three a.c. phases. During the tests one o f the two a.c. harmonic filters was switched out to observe its effect on harmonic levels. It was found that with both a.c. harmonic filters operating, most harmonic levels were lower than with only one filter operating. However some harmonic levels, namely the 4th harmonic, were larger with both filters operating. The paper is concluded with a dis cussion of the results and of the difficulties encountered in measurin g harmonics of very low level.