PURPOSE: To allow the controller to cope with emergency or the like quickly by providing a data transmission calculation device sending system data or tentative data to the controller.

CONSTITUTION: A data transmission calculation device 6 monitors whether or not system data are sent from a power system 1 via a data transmitter 2, a sequence number is added to the system data and the result is sent and when no system data are sent, a sequence number is added to tentative data and the result is sent. Then, a job execution calculation device 7 discriminates whether or not the order of data is correct based on the sequence number added to the system data or the tentative data and, when the data whose sequence is correctly sent are the system data, a prescribed job processing is implemented based on the system data and, when the data sequence is not correct and the system data or the tentative data are not sent even lapse of a prescribed time, the retransmission of the system data or tentative data is requested to the data transmission calculation device 6.