Evolution of numerical generator protection for application to a Powerformer

This paper discusses a protection relay under development which provides all the fundamental functionality required for the protection and monitoring of generating plant. In addition, it provides advanced protection necessary for the Powerformer, including:compensated generator differential protection which compensates for the standing capacitive charging current resulting from the stator winding cables, phase selective 100% stator earth fault protection, suitable for a high impedance earthed or a solidly earthed network, without the need for voltage measurement at the neutral. breaker failure protection with single pole stuck detection and overvoltage protection for parallel machines connected directly to the busbar.