Abstract :
The main principles governing the design of a city distribution system and their detailed application in the amalgamation of several undertakings are described. It is suggested that rationalization into larger units will extend, and therefore the problems of standardization are of particular interest at the present time. The standard system described utilizes a low-voltage grid with injections from a primary high-voltage network by means of decentralized transformers in accordance with load demand. The h.v. network is operated on a ¿radial¿ basis, and the l.v. network is ¿solidly¿ connected up to 3 000 kVA and further interconnected through fuses into 12 000-kVA units. The mode of operation permits of growth in loading without exceeding the initial rupturing duty on the switchgear, which is thereby allowed to serve its full life. Simple well-tried forms of protective gear are used and reliance is placed on ¿burning off¿ for clearing l.v. faults. Attention is drawn to the question of fault kVA in l.v. networks, and high-rupturing-capacity fuses are used in service cutouts and recommended for more general use. Improvements effected by the adoption of the system are mentioned, and in particular a comparison is made between adjacent districts developed on different systems. Each district had similar loads but the distribution cost for the one developed on the standard system was less, although the load had to be delivered over a greater area. It is claimed that the system which has been standardized is the one best suited for densely loaded areas; it has been applied to distribution in a large city over a number of years with successful results.
