Power loss due to Corona on High Voltage Transmission Lines

Abstract

The effect of corona on high-voltage transmission lines is one of the causes power loss and this is uneconomical and undesirable. The study of corona and factors responsible for the loss is investigated through sample calculation based on Peek's formula and the results are then simulated through matlab program. This paper presents the relations between power loss due to corona to corona parameters through matlab programs When in an insulation system, the voltage gradient (voltage stress) exceeds a critical voltage, the air molecules surrounding the high voltage transmission line conductors become ionized (transient gaseous ionization) resulting in partial discharges. Corona loss occurs if the line to line voltage exceeds the corona threshold. The conductive region is not high enough to cause electrical breakdown or arcing to any nearby objects (1). Corona can occur within voids of an insulator, at the conductor or at the insulator interface. Rough surfaces are more liable to corona because the unevenness of the surface decreases the value of the breakdown voltage. It can be detected due to its visible light in form of purple glow consisting of micro arcs and its sound can be heard through its hissing and cracking sound (2). The smelling of the presence of ozone production is noticed during corona activity (3). The effects of corona are cumulative and permanent and the failure can occur without warning. In insulation system, corona discharges result in voltage transients. The effects of corona associated with the operation of high voltage transmission lines include radio interference, audible noise, gaseous effluents (Ozone and Nitrogen oxide) and shock potential. Conductor voltage, diameter and shape, dusts, water drops, and surface irregularities such as scratches are factors that affect the performance and conductor's electrical surface gradients. The energy loss due to corona is transformed into sound, radio noise, chemical reactions of the air components and heat (4). Corona reduces the reliability of insulation system thereby degrading insulation and causes system failure due to dielectric breakdown. The study becomes necessary because of the prevailing negative effect of corona parameters on the power loss of high voltage transmission lines. The power loss under fair weather conditions and under stormy weather conditions when investigated, analyzed and simulated using matlab programs gives the results which help us to take necessary measures to minimize the power loss under fair and stormy weather conditions. High quality insulated and good service design underground high transmission cables can help to eliminate the loss due corona effect The advantage of corona is that the sound generated during corona activity can be used to build high accuracy audio speakers and also it has no mass to be moved to create the sound so that transient response is improved. The controlled corona discharge can be used for filtrations and printing.