Parametric study of varistor energy requirements for 500 kV series capacitors

Results are presented that show the energy absorption of a series capacitor protective varistor as a function of the most important parameters that affect energy: series capacitor impedance, power system short-circuit impedance, and varistor protective level. These results were developed from computer simulations of a simple 500 kV network model for a realistic range of parameters. Graphs of energy as a function of the three parameters provide an approximate method of determining varistor energy requirements. Two examples are given that demonstrate how to use the curves. The examples also show that the energy curves are a valid way to approximate varistor energy requirements without the use of digital simulation. The results are general because many specific series capacitor installations in actual networks can be reduced to the simple model used here