An A-C. Low-Voltage Network Without Network Protectors

The object of this paper is to present a description of the Spokane, Washington, underground network system, and to describe briefly the operating experience and problems which have resulted from the installation of ring primary feeders and a four-wire, 120/208 volt secondary network supplying a universal service. Reasons for the choice of the system described are presented with particular reference made to the use of a fuse in the secondary circuits instead of the device commonly known as the ``Network Protector.´´ The general design of the primary feeders, secondary network, pilot wire relays and fuse protection, and transformer vaults is discussed. Descriptions are given of all apparatus and equipment used. A report is included covering tests made on the system under fault conditions. The report shows that the tests which simula ed actual operating conditions indicate the system will operate as designed. The voltage regulation of the network having been recently investigated, gated, is covered in detail. The procedure in the change-over from d-c. to a-c. service is discussed and the problem of customer consideration analyzed. The paper is concluded with a statement that no difficulties have been encountered on the system and that its operation up to this time has been perfect.