Simplifying and improving protection of temporary and unusual bus configurations with microprocessor-based relays

Breaker substitution, stub bus, and station bypass are temporary substation configurations used to facilitate the maintenance of primary equipment while keeping assets in service and supplying loads. These configurations provide considerable operational advantages but create challenges for protection systems. Traditional solutions to temporary bus configurations required for electromechanical relays utilize test and bypass switches to ensure the affected relays are provided with the appropriate currents and voltages and the trip signals are routed to the appropriate breakers. In some cases, spare relays, settings changes, and the rerouting of pilot signals and communications have been required. All these manual operations increase the danger of misoperation when making changes, during temporary configurations, or when restoring to the normal configuration. As a result, temporary bus configurations have been carefully considered and often avoided, resulting in underutilization of the network assets. This paper shows how modern microprocessor-based relays can simplify applications under temporary bus configurations, eliminate the need for any manual reconfiguration, and improve the performance of protection. These benefits stem from the ability to connect multiple current and voltage inputs, the ability to trip multiple breakers, communication between relays, and programmable logic, allowing automatic detection and dynamic response to temporary bus configurations.