LIMITATION/ REDUCTION OF SWITCHING OVER VOLTAGES IN HIGH VOLTAGE TRANSMISSION LINES IN POWER SYSTEM
International Journal of Engineering Science Invention Research & Development
This paper presents limitation / reduction of switching over voltages in a transmission line which are generated due to the energization of the transmission line when the circuit breaker is closed. Controlled switching of circuit breaker, pre insertion of resister, surge arresters, shunt reactors are used as protective devices to mitigate energization as well as reduce over voltages. This paper will study / present some practical rules for switching surge transacts which will be applied for
... be applied for reduction of switching over voltages generated due to energization of transmission line / lightening strokes on sub stations. I INTRODUCTION With the increase in transmission voltages up to 800 and above ;the over voltages generated inside the system reached the same order of magnitude as that of lightening over voltages last for longer durations and therefore are dangerous for the system. The long transmission energization can cause high over voltage stresses along the transmission line also in the supply network. Switching over voltages of transmission line are calculated at different spots of the line. Maximum switching over voltage is compared with protection level of the transmission line if the maximum over voltage exceeds protection level then it has to be reduced Pre insertion resistors were installed in parallel with the transmission line circuit breakers but this method is not no more in use now. Another method for reducing over voltages is switching with switch synch relays. And another method to reduce switching over voltages is installation of surge arresters in one or two suitable locations along the transmission line. Each for switching at two locations of the line. Shunt reactors are used to limit the over voltages due to Ferranti effect. Shunt reactors cannot drain the trapped charge but will give rise to capacitance of the system.