A Novel Pole-to-Ground Fault Current Calculation Method

This paper proposes a simplified fault current calculation and evaluation method for pole-to-ground fault in symmetrical monopole DC system. According to the theory that the DC grid in fault can be divided into healthy circuit and faulty circuit, the whole equivalent impedance of the fault circuit is obtained in the first step. And then, by decomposing the obtained impedance into single equivalent resistance and inductance component, the complex DC grid is transferred into a simple two-order circuit. Through the two-order circuit, the fault current expression is deduced and is further simplified by Taylor expansion. Nevertheless, the practical index to evaluate different DC grid fault current level is also proposed. The simulations based on six-terminal DC grid verify the above analysis.