THEORETICAL AND ANALYTICAL INVESTIGATION OF LIGHTNING OVER-VOLTAGES AND ARRESTER OPERATION

One of the main problems in high voltage networks is over voltages due to lightning. These over voltages, which are not possible to prevent, create problems where the insulating level of the equipment is not enough. Selecting a high insulating level will increase the costs and volume of the equipment. For the sake of decreasing insulating levels and their costs, it is necessary to control over voltages and lead them to earth by equipment like arresters. In this paper, over voltages, mostly due to lightning and its dangers to power networks, have been studied for: 1- The effect of arrester earthing resistance, 2- Tower footing resistance, 3- Capacitive voltage transformer and 4- Tower structure. An EMPT program has been used for simulation of a line and a substation of 230kv/123kv (Ahwaz-Omidieh) as a case study.