Performance Analysis of Overcurrent Protection in a Digital Substation with Process Bus

Abstract

The digitization of electrical substations brings great challenges for the commissioning of electrical protections, and interoperability tests must be performed with different equipment. Therefore, this work evaluates the response time of an electrical protection relay operating with sampled values in a digital substation with a process bus. A test scheme is proposed to emulate the process bus based on analyzing the main components in a digital substation with multi-vendor device interoperability. In addition, the delay times of the protection relay with the process bus are measured, considering interoperable infrastructure as a fundamental factor in the system performance. The results are compared with the response times of a conventional relay that operates with analog signals to identify the impact of the digitalization of signals in electrical substations with a process bus. Each relay has an instantaneous overcurrent function adjusted to operate with the same pickup currents at different fault current levels. The results show that tripping times are admissible for the operation of the protection relays, considering three-time measuring points in the test scheme. The time delays found are related to high data traffic in the communication network and the traffic saturation according to the time measuring point. Other delays related to processing SVs in an MU do not represent a risk for the protection scheme. For the industry, the methods presented in the research are useful for configuring and testing electrical substations with different equipment and topologies. In addition, the results presented here seek to generate confidence in companies and engineering teams when migrating to systems with digital substations.