City distribution by solid low-voltage networks

Abstract

A few years ago, the most economical form of distribution system for use in cities was considered to be obtained by the use of duplicate high-voltage transformer-feeders in combination with radial low-voltage distribution. Since that time the solid low-voltage network has been widely adopted in other countries, particularly in America. With this arrangement the supply route to any consumer is at least duplicated all the way, which results, it is claimed, in improved voltage regulation and reliability of service. On the other hand the parallel operation of the transformers introduces unfamiliar problems such as increased fault duty in the l.v. network and the reverse flow of power from the l.v. network into transformer or h.v. cable faults. This latter has hitherto been dealt with by sensitive reverse-power protection on the transformers, but it now appears that all the requirements can be met merely by fuse protection. With this modification the scheme is worthy of serious consideration for application in this country, and it is thought that with certain precautions as to fault duty in areas of dense loading many existing city distribution systems could advantageously be converted to solid working. The scheme is, however, most attractive where a rather light section of l.v. cable is laid and is proving inadequate with orthodox methods.