Design Considerations for High Voltage DC Components

Two high voltage engineers from a large multinational company were overheard talking at a conference. One said to the other, What are you doing these days? which produced the reply Designing high voltage DC accessories with the response, Gee, I hope you're retiring soon! Anyone who has designed DC high voltage systems will understand the exchange, but the reasons may not be obvious to those who have not. As the late Prof. A. Pedersen of the Danish Technical University liked to point out, DC is an abstraction which exists only at infinite time. In the real world, all systems exist in a state somewhere between capacitively graded and resistively graded. Power system components designed for an AC system are designed to be graded capacitively, as most such components rarely, if ever, are subjected to a sustained DC voltage. Designing capacitively graded components is relatively simple, as in this context, the dielectric constant is truly constant, i.e., the dielectric constant of the dielectric materials with which we design AC systems is a very weak function of both temperature and electric field, so that capacitive grading tends to be very stable with changes in temperature, voltage, and frequency. © 2012 IEEE.