Audible noise evaluation for six‐phase overhead lines transformed from existing three‐phase double circuit infrastructures with uprated voltages

Abstract

The drive to reduce carbon emissions and meet climate change targets set by governments worldwide has led to the growth of renewable energy sources and electric vehicles in recent years. Resulting intermittent generation and centralised demand require increased transmission capacities when operating associated power systems. Existing transmission lines are not capable of meeting planned needs. In many countries, obtaining a new right of way to build an overhead line (OHL) is increasingly difficult. There is therefore an urgent need to study techniques for transmission line uprating. Simply increasing voltages is not feasible because elevated surface potential gradient at conductor surfaces increases audible noise (AN) levels unacceptably. The feasibility of high phase order, especially six-phase, transmission techniques has been previously demonstrated, and it has been proved to be an effective way to uprate existing three-phase double circuit OHLs with increased voltages. This study analyses two typical overhead line structures, whose conductor surface potential gradient and AN level are calculated. The average and maximum surface potential gradient of the six-phase OHL are 18.5% and 18.6% lower than that of the three-phase ones. The AN of the six-phase single circuit OHL is predicted to be 6.33 and 6.45 dBA lower than that of the three-phase double circuit OHL after the voltage is increased by 45% and 50% for the lines considered. It is shown that six-phase OHLs can increase capacity by allowing elevating phase voltages without increasing acoustic noise levels.