Abridgment of an A-C. low-voltage network without network protectors

The object of this paper is to present a description of the underground network system in Spokane, Washington, and to describe the “operating experience and problems resulting from the installation of ring primary feeders and a four-wire 120/208-volt secondary network supplying universal service. Reasons for the choice of the system described are presented with particular reference to the use of a fuse in the secondary circuits instead of the “Network Protector” device. The general design of the primary feeders, secondary network, pilot-wire relays and fuse protection, and transformer vaults is discussed. Descriptions of all apparatus and equipment are given. A report is included covering tests made under fault conditions. The tests, which simulated actual operating conditions, indicate that the system will operate as designed. The paper concludes with a statement that no difficulties have been encountered on the system and that its operation to date has been perfect.