Network 21C-an update [overhead system protection]

Three distinct stages of overhead power system operation have evolved in East Midland Electricity. Experience has shown that the majority of faults affecting the overhead system were transient, nondamage, and that the best performance, in terms of the lowest `customer-hours lost´ was achieved with minimum numbers of strategically positioned fuses, coupled with automatic reclosing 11 kV switches. This replaced the initial, heavily fused, system design. The third, and current, stage is still that of a minimum `fused´ system but with optimum use of source and pole mounted automatic reclosers, new electronic sectionalisers (which can replace fuses), fault passage indicators and automatic pole mounted isolators