Transient Overvoltages Protection for Series Capacitors in Compensated Transmission Lines

The enhancement and improvement of existing electric power transfer systems to increase their electric power transfer capability is necessary, due to the growing demand on electric power. This enhancement can be done by inserting capacitors in series with transmission lines, which are called, in this case, series-compensated lines. The benefit of series capacitors are reducing transfer reactance of transmission lines and giving greater electric power transfer capability. Because the cost of series capacitors are high, and they are subject to high electric fault conditions in power transfer systems, it is highly desirable to protect them against fault overvoltage that exceeds their voltage rate. This overvoltage protection is achieved using protection system connected in parallel with these series capacitors. The protection system normally contains elements such as metal oxide varistor (MOV), trigger gap, bypass switch, and damped device, the purpose of protection system is to dissipate the generated energy due to the high fault current. In this paper, a series-compensated transmission system with its overvoltage protection are developed and simulated in MATLAB/SIMULINK. This model is used to study behavior and performance of the overvoltage protection system. The performance is evaluated under different types of AC faults. The overvoltage protection system is found to satisfy the needed objectives.