Protection in Expanded Power System with Fault Current Limiter and PLL

In this book, a new method is proposed that can be used to discriminate faults from switching transients. The method is mainly intended for use in systems where fast fault recognition and rapid fault clearing before the first peak of the fault current are required. An industrial system, in which high short-circuit power is most wanted but in which high short-circuit currents cannot be tolerated is an example of such a system. A phase-locked loop (PLL) is used to perform the discrimination. Computer simulations have been performed and it has been demonstrated that the output of the PLL is completely dissimilar for a fault compared to a switching transient. This difference can be used for discrimination between a fault and a switching transient.