The PWF series digital relay testing system is designed for IEC61850 complied relay test applications. The unique three fiber optical ports configuration enables it to receive GOOSE messages from three relays separately. This feature is especially important when testing IEC61850 based differential relays, where three separate GOOSE messages from the differential relay should be sent to the separate GOOSE ports of the relay testing system. The Ethernet port also enables the remote control of the test process via Internet.