Introduction
This chapter outlines a program for testing and commissioning of protective and overcurrent relays and instrument transformers used in switchgear and/ or standalone applications. The frequency of testing of these devices may be dependent upon many factors; however, an annual schedule of inspection and maintenance is recommended for electromechanical and induction relays; and inspection and testing of solid-state and microprocessor relays when trouble is indicated or upon unanticipated operation of these relays. Before a successful maintenance and inspection program can be imple- mented, it is essential that the personnel performing or evaluating inspec- tion and maintenance should be thoroughly familiar with the types of protective relays, devices, and auxiliary equipment. Therefore, in this section a brief overview of protective and overcurrent relays, and instrument trans- formers is given for the reader to become familiar with the system equip- ment. The maintenance and testing of electromechanical and induction relays involves inspection, mechanical adjustment, and electrical tests. Similarly, the maintenance and testing of solid-state and microprocessor relays involves inspection and self-diagnostics and tests. Since the protective equipment plays such an important role for the safety of personnel and property, they should be given special attention. Moreover, since these devices operate during abnormal conditions on the power system, the only way to assure correct operation is by a comprehensive inspection, mainte- nance, and testing program.