Improved Fault Protection for Rural Distribution Systems

The use of automatic oil circuit reclosers on rural distribution lines has re-sulted in improved continuity of service as well as reduced maintenance cost. How-ever, automatic circuit reclosers now in use are limited in application because of their inability to co-ordinate properly with fuses on the load side of the reclosers. An improved oil circuit recloser has been de-signed to incorporate the advantages of minimum time-delay opening on the first and second operations to clear all transient faults on the protected section, and greater time-delay opening on the third and fourth operations to allow the blowing of a sec-tionalizing or transformer fuse to isolate a permanent fault without causing a lockout of the recloser. A description is given of the design, operation, and advantages of this recloser which permits clearing of all transient line faults and isolates permanent faults by properly co-ordinating with sec-tionalizing fuses.