Phase comparison protection using adaptive carrier modulation

The flexibility of numerical relays brings a fresh perspective to the traditional approach to phase comparison protection and power line carrier communication (PLCC). This paper describes an adaptive modulation of the carrier based on pre-fault load and earth fault sensitivity to provide coverage for high resistance earth faults. Phase comparison protection traditionally had limited application over long lines but charging current and propagation delay compensations allow the protection to be applied over long lines without an exaggerated stability angle setting.