PURPOSE: To prevent the destruction due to erroneous operation by eliminating a changeover switch for each device and performing the centralized management of states of power systems by an SVP to realize the convenience for operation and that for maintenance together.

CONSTITUTION: Power sources 2a to 2i and cooling systems 31a to 31i of a cooling device 3 are provided with two operation modes, namely, the normal mode and the maintenance mode, and operation mode switching and operation/ stop switching are performed by the indication of an SVP 4 in every mode, and power sources 2a to 2i and cooling device 3 send the abnormality report signals to the SVP 4 in the normal mode and suppress this sending in the maintenance mode.