TECHNOLOGY pH Based Smart Sensor for Condition Monitoring of Overhead Insulators

Abstract In this paper a real time monitoring system is presented for predicting flashover voltage of overhead insulator, it uses pH level as the pollution severity indicator and a smart sensor is used for measurement of pH level. The performance of insulator is examined under artificially polluted conditions with different contaminants. The contaminants chosen for artificial pollution test is on the basis of the presence of different types of salts in natural polluted conditions. Flashover voltages (FOV) of the insulator for different pH value have been recorded to relate FOV with pH of the contaminants and designed a pH based condition monitoring system for predicting flashover voltage of the contaminated insulator. Keywords : Flashover voltages (FOV), Pollution, Insulator, pH, Virtual Instrumentation, Labview Introduction For economical and reliable use of power generated interconnection of multiple available power sources is required. Interconnecting the power system network improves overall reliability. However, this increase in reliability comes at a price of increased risk associated with the possibility of a minor disturbance propagating and resulting in complete shutdown of the whole system. In the last 10-15 years an increasing number of large-scale black-outs have been witnessed, throughout the world. The main reason for these blackouts is concurrent malfunctioning of a large number of transmission lines and power generators, often triggered by the initial failure of a single component of the grid e.g. the breakdown of a power line. Therefore efforts are going on to minimize the probability of such terrible blackouts by developing advanced techniques for monitoring of transmission lines [1]. The insulation used on the transmission line is one of the critical areas prone to failure, as this insulation is exposed to the effects of pollution which accumulate on its surface and an electrolyte layer forms on it under the influence of environment and weather conditions such as moisture and rainfall [2, 3]. This layer extends over time and in some cases, such as in the case of inappropriate insulation designing, leads to flashover and system outage. Thus, identification of the factors causing insulation surface contaminated, pollution severity measurement, and tackling its unfavourable effects has an important role in increasing the network reliability, about 70% of high voltage transmission lines errors result from the inappropriate performance of insulation. Thus, it is the need of hour to develop a reliable system for monitoring the performance of the insulator with the help of smart sensors [4, 5] by sensing some pollution severity parameter to minimize the possibility of the system outage. With the ever increasing demand for power, there has been a steady growth in high voltage transmission line required for optimum and economic transfer of large blocks of power over long distances. As the level of transmission voltage is increased, switching and dynamic over voltage and withstand ability of the insulator under polluted conditions are important factors which determine the insulation level of the system. The reliability of the system mainly depends on the environmental and weather condition which causes flash over on polluted insulator leading to system outage. It is generally recognised that the main events leading to flash over of polluted insulators under service voltage are: a) The formation of a conductive layer on the insulator surface. b) Leakage current surging with associated dry band formation and partial arc development along the insulator surface eventually spanning the whole insulator [14].