Coordination of surge arresters with medium voltage current limiting fuses

Current limiting fuses are commonly used for unit substation primary protection. Simultaneously surge arresters are also provided on the primary side of the transformers, more so for the dry type transformers. The arc voltages generated by current limiting fuses will store energy in the inductive elements of a distribution system. This stored energy divides between the current limiting fuse and surge arrester and the surge arrester may operate. The paper outlines a procedure to calculate the energy diverted to the surge arresters, and shows that in some cases surge arresters may fail on operation of the current limiting fuses. Guidelines are developed for selection and application of the surge arresters at 13.8 kV, 4.16 kV and 2.4 kV voltage levels.