It uses the same basic components as in the primary loop. Each transformer can have supply from two sources (see Fig. 1.3c). High voltage automatic switching is provided ahead of the consumer's transformer. In the event of loss offeeder, transfer to the second feeder is automatic and the interruption duration can be limited to two or three seconds. Each service now represents a potential two feeder outage if the open switch fails, but under normal contingencies, service restoration is rapid and there is no need to locate the fault, as with the loop switching system, reliability
is high. It also offers little advantage to sensitive load-like computer problems caused by temporary faults. This scheme is normally used for
large, essential or continuous process industrial consumers.