Application of Digital Radio for Distribution Pilot Protection and Other Applications

This paper describes basic digital radio technology and shows some possible applications of digital radio for distribution protection. As with any other pieces of the protection system, it is important to understand the reliability and performance of digital radio. The test results documented in this paper show that digital radio successfully sends an IEC 61850 GOOSE message within 10 to 15 ms 99% of the time. In no case during the test was a message not received. Therefore digital radio is reliable enough to use as part the distribution protection system. The 10 to 15 ms channel latency is more than acceptable for distribution protection, is interoperable, and requires no special adaptation of standard pilot protection schemes. The channel latency compares quite favorably to that of analog tone over an analog microwave, or a digital channel through a modem, meaning that digital radio is appropriate for pilot protection communication on sub-transmission lines. Advantages of digital radio in being able to establishes an Ethernet network was presented. Additionally, digital radios support any standard protocol over Ethernet, including Modbus, DNP 3.0, and IEC 61850. At a minimum, this allows digital radio to send the binary signals necessary for pilot protection, such as permissive and blocking signals. In addition, digital radio, like any other Ethernet network, allows simultaneous traffic. Therefore digital radio can support communications for pilot protection, SCADA communications, and metering communications simultaneously without any degradation in performance.