Planning levels and harmonic measurements on Hydro-Quebec's transmission system

A power quality survey has been conducted at 28 stations on Hydro-Quebec's 69 to 315 kV transmission system, between 1993 and 1996. This paper provides results for the harmonic voltage components and compares the results with the indicative planning levels proposed in IEC 1000-3-6. It is shown that planning levels may be exceeded for some harmonic voltage components at a few locations. The harmonics that are of most concern are the fifth, the eleventh, and higher order harmonics like the twenty-third, twenty-fifth, thirty-fifth and thirty-seventh. In most cases, these excess levels are caused by the harmonics produced by large disturbing loads with possible amplification due to resonance. On the other hand, planning levels proposed in IEC 1000-3-6 are very low for some high order harmonics (0.2% for multiples of 3 and even order harmonics) and it is difficult to see any reason for limiting these harmonic voltages to such low values. Finally, results indicate that there is no correlation between the level of distortion and the short-circuit impedance of the network at different sites.