PROTECTION CONTROL DEVICE AND PROTECTION CONTROL METHOD FOR DC TRANSMISSION SYSTEM

A protection control device and a protection control method for a DC transmission system (102) are capable of, using only local information, distinguishing between and detecting a line accident and a bus accident (601) and identifying an accident line when the line accident occurs. The DC transmission system having a symmetrical unipolar configuration includes a self-excited converter (106) that converts AC to DC, a DC bus (107) connected to a DC terminal of the self-excited converter, a plurality of DC breakers (109Xp, 109Xn, 109Yp, 109Yn) that connects the DC bus and a plurality of DC lines (103Xp, 103Xn, 103Yp, 103Yn), and an AC breaker (105) that connects AC terminals of the self-excited converter and an AC system. In the protection control device, when a bus accident at a positive or negative terminal of the DC bus is detected based on a sum of currents flowing into the positive or negative terminal of the DC bus, the plurality of DC breakers and the AC breaker are opened, and when a line accident of the DC lines is detected based on ground potentials at positive or negative terminals of the DC lines, the DC breaker of a DC line where the accident is detected is opened.Fig. 1