In order to gain a better understanding of the DC discharge performance of a string of ice-covered insulators with icicles, discharges were performed with three shapes of artificial icicles under DC voltages in a cold chamber. The DC flashover voltage is shown to increase with a decrease in temperature because of the simultaneous increase of the resistance of the icicle. This increase in resistance occurs as the thickness of the water film on the icicle surface decreases exponentially with the decrease in temperature. The melted weight W/sub m/ of the icicles was greater for negative polarity than for positive polarity when melting occurred by corona discharge. These differences in W/sub m/ may confirm reports that negative flashover voltage for ice-accreted insulators is lower than positive flashover voltage. There was a hot region on the icicle surface of the rod type near the boundary between the electrode in the ice and the ice. >

DC discharge performance at the tip of an icicle

This paper reviews the concepts behind HVDC systems and the advantages of their integration with AC power systems. Available modelling and analysis techniques for HVDC-AC systems are presented for load flow, and steady state and transient stability studies.

F. A. Qureshy

Papers

HVDC — A review of applications and systems analysis methods