Risk assessment of desert pollution on composite high voltage insulators

Abstract

Transmission lines located in the desert are subjected to desert climate, one of whose features is sandstorms. With long accumulation of sand and with the advent of moisture from rain, ambient humidity and dew, a conductive layer forms and the subsequent leakage current may lead to surface discharge, which may shorten the insulator life or lead to flashover thus interrupting the power supply. Strategically erected power lines in the Egyptian Sinai desert are typically subject to such a risk, where sandstorms are known to be common especially in the spring. In view of the very high cost of insulator cleaning operation, composite (silicon rubber) insulators are nominated to replace ceramic insulators on transmission lines in Sinai. This paper examines the flow of leakage current on sand-polluted composite insulators, which in turn enables a risk assessment of insulator failure. The study uses realistic data compiled and reported in an earlier research project about Sinai, which primarily included grain sizes of polluting sand as well as their salinity content. The paper also uses as a case study an ABB-designed composite insulator. A three-dimensional finite element technique is used to simulate the insulator and seek the potential and electric field distribution as well as the resulting leakage current flow on its polluted surface. A novel method is used to derive the probabilistic features of the insulator’s leakage current, which in turn enables a risk assessment of insulator failure. This study is expected to help in critically assessing – and thus justifying – the use of this type of insulators in Sinai and similar critical areas.

Potential and Electric Field Characteristics of Broken Porcelain Insulator

“…Figure 10 shows the electric field distribution in string with 10 unit of insulator. It is observed that the present of the broken shed in the insulator has decreased the average electric field distribution in string; this findings is agreed by Shahat [18]. Figure 11 shows the electric field distribution of 10 units of porcelain insulator in a string.…”

Risk Assessment of Polluted Glass Insulator Using Leakage Current Index Under Different Operating Conditions

“…Three parameters Weibull distribution function has been utilized for the statistical model of the flashover occurrence and can be represented as [36] (22) U 0 , U AV , U C , R hio , and R hi(av) are withstand voltage (probability flashover =0), average flashover voltage, continuous operating voltage. LC index value when flashover probability is zero and the average value of LC index obtained at each pollution level, k, α, and γ are constant and n is the constant equal to 2 [35].…”

Optimised performance of cap and pin insulator under wet pollution conditions using a mono-objective genetic algorithm

“…Failures in high voltage insulators is frequently initiated with the leakage current flow [39], and this important factor is considered in this investigation. Figure 16 shows the leakage conduction current density distribution along the insulator profile for Scenarios 1 to 4.…”