Interrelationship of protection and communication to improve power system reliability

Dependencies of protection schemes on communications have been acknowledged and discussed in various papers. This paper expands this topic by examining field experiences that required protection engineers to deepen their understanding of communication technologies to interpret protection scheme behavior and perform event analysis. A deployed power system line protection application utilizing segregated phase comparison protection scheme with distance protection as a backup is described. Communication channels including interfaces, technologies and equipment are covered. Event analysis and investigations are presented. Root cause analysis and evaluation of risk mitigation options are discussed. Explanations of factors that affect protective relay behavior (including communications) and how communications can be used to improve security are provided. A broader discussion of communication parameters known to affect protection performance are considered, such as bit error rate, latency, time synchronization accuracy, specifics of communication protocols, equipment, and implementations. Field examples are used to explain these details. The paper aims at deepening communications awareness and expertise among protection engineers and showing how communication and protection can work together to improve power system´s reliability.