Electrical Switchgear Protection and Control Scheme Design Techniques to Improve Security and Dependability

Protection and control circuit design plays a critical role in the correct, desired operation of circuit breakers. Redundancies in protection and control circuit design are implemented to improve system reliability (security and dependability). This paper presents protection and control circuit designs of increasing redundancy and complexity and their impact on the reliability of power system operations. The paper focuses on voting schemes using multiple relays. In addition, the paper discusses some considerations and recommendations for designing a more reliable scheme, including various hardware redundancies, such as battery or direct current source redundancy, breaker trip coil circuit redundancy, and redundancy in the inputs to the relay. Many of the schemes presented in this paper have been implemented in switchgear, tested, and are in service. The schemes presented in this paper are explained with figures of the protection and control circuits that illustrate their applications.