With rapid developments in different areas, there emerges new status of power grid, for example, the AC-DC hybrid networks appear; the grid-connected capacity of clean energy continues to grow; and more and more power electronic appar. With rapid developments in different areas, there emerges new status of power grid, for example, the AC-DC hybrid networks appear; the grid-connected capacity of clean energy continues to grow; and more and more power electronic apparatus are adopted. For the power generation, the application of distributed energy on the power side has effectively. In recent years, more and more new kinds of loads begin to appear, such as electric vehicles. In contrast to AC loads, DC loads appear. DC load is the general term of the power load supplied by DC, such as electric vehicles, variable frequency air con-ditioners and mobile phones, etc. Also, the controllable load is proposed under the circumstance o. Relay protection device is an integral part of power system. When a fault or disturbance occurs in a part of the power system due to natural, man-made or equipment failure, relay protection devices should quickly isolate the fault part to ensure the stability of the power system, to maximize the non-fault part of the power grid, and to continue rel. The coordination of power system relay protection setting values should comprehen-sively consider the working range and performance of protection components, the volt-age level of the system, the sensitivity and selectivity of protection actions, and the cooperation between different protection components. And the setting plan will change with syst. Online checking for the relay protection setting system is used to verify the perfor-mance of the relay protection setting value during operation. To determine whether the protection value meets the requirements of selectivity and sensitivity under the current operating state, it is necessary to consider the topology structure, operating state fact.
