Reliability design approach for protection and control equipment for MV distribution networks

Reliability is a main requirement for MV distribution networks. One of the key components is the protection and control equipment. Both functions have traditionally been implemented separately. However, the latest generation of numerical devices available in the market offers a high degree of integration of protection and control functions. Reliability data of conventional protection relays has been based on historical information and experience. As numerical devices are based on computer technology their design has to take into account system architecture, communication network, structure of the algorithms etc., and their reliability has to be evaluated with rigorous techniques. This paper describes the methodology used by the authors´ company to monitor reliability and maintainability during specification, design, validation and useful life of equipment