Power system and protection device

Abstract

To suppress circulation of ground current between a plurality of appliances in a ground structure of a multipoint ground system.SOLUTION: A power system in an embodiment includes a first appliance, a second appliance, a plurality of ground lines, a detection unit, a storage unit, a switch unit, and a control unit. The second appliance is connected to the first appliance through a cable. The plurality of ground lines are connected to a middle point between the first appliance and the second appliance. The detection unit detects ground current of at least one ground line among the plurality of ground lines. The storage unit stores an allowance value of the ground current about each of the plurality of ground lines. The switch unit switches between ON and OFF of a conduction state of a predetermined ground line among the plurality of ground lines. When the ground current detected by the detection unit becomes larger than the allowance value corresponding to the ground line where the ground current flows, the control unit controls the switch unit so that the conduction state of the predetermined ground line becomes OFF.SELECTED DRAWING: Figure 1