ABSTRACT
This chapter presents the step-up transformer secondary or relay ohms for the backup impedance and out-of-step relay functions. The transformer per-unit base impedance at 555 MVA needs to be converted to the generator base of 578.6 and corrected for voltage differences on the generator side of the transformer and tap differences on the high voltage side of the transformer. There are a number of concerns the protection of generating station high voltage switchyards. The main concerns are the clearing of electrical system faults before the unit goes out-of-step and backup protection. Many of the electrical protection functions in a generator package are applied to protect the prime mover or turbine and not just the generator. The chapter shows an offset mho impedance circle for generator backup applications. It provides suggested settings for generator sync-check relays. Some of the newer digital sync-check relay functions also include slow breaker protection.
