Experimental Investigation of the Effect of Conductor Temperature on Corona Performance in Overhead Transmission Lines

Abstract

The maximum conductor temperature regulates the maximum amount of power that overhead lines can transmit. Excessive line sag and accelerated conductor ageing may occur if this maximum temperature is exceeded. This is particularly true for the most popular steel-reinforced conductors or aluminium anneals, in which high temperatures can cause grease, which is used to prevent corrosion from seeping. High-temperature low-sag conductors have been developed to increase current carrying capacity. In addition to the temperature constraint, overhead transmission lines largely depend on the corona discharge performance. This paper presents experimental results on the investigation of corona performance due to conductor temperature. An experimental configuration that uses a 10 kVA power transformer in cascade with a 10 kVA high current low voltage transformer both connected to the conductor in the corona cage was successfully developed. This configuration allows for heating the conductor while connected to the high voltage and allows for measuring corona current using the screened electrode method of corona cage. The results indicate an increase in corona current with rising conductor temperature, accompanied by a 25% to 32% decrease in inception voltage. The primary factors contributing to these trends were identified as relative air density and the Townsend coefficient. A temperature model incorporating the ionization region was developed to calculate the relative air density accurately. Additionally, To account for the effect of conductor temperature, the well-known surface inception field strength formula proposed by Peek was refined through optimization. Comparisons between the refined Peek’s formula and the measured results demonstrated successful alignment. This research enhances our understanding of corona performance with conductor temperature, providing valuable insights for optimizing transmission line design and operation.

Keywords

• Conductor temperature
• corona discharge
• inception voltage
• ionization radius