To shorten transfer time from a workstation 12 preparing dummy failure waveform data to an oscillator OSi transforming the data to an analog signal, in a dummy transfer device 11 which inputs the dummy failure waveform in place of the secondary output or a transformer to protective relays RYi which perform mutually cooperative action that are installed in a substation and mutually perform cooperative action by being connected by transmission and distribution lines, a failure state to inspect the cooperative action.

The dummy failure waveform data prepared at the workstation 12 is transmitted from a transceiver TX1 to a transceiver RXi via the Ethernet 15. An interface IFi extracts corresponding data from the adress of GPIB bus Bi added on received data, and outputs them to the oscillators OSi. Therefore, the dummy waveform data are simultaneously transmitted to each oscillator OSi in a short time and whether desired performance is obtained by this verification work can be verified in a short time.