Some problems encountered on a distribution system, with special reference to Shanghai

The paper describes several distribution-system problems and discusses the experiences encountered in dealing with them in Shanghai. Starting with an outline of automatic protective equipment, its characteristics and operating problems, the necessity for co-ordinating all units of protection on the system is illustrated. Specific cases involving low-voltage power fuses and high-voltage ¿drop-out¿ fuses are described, and in the latter case the performance of the fuse under various fault conditions is discussed. The next problem is the testing of insulating material by the time/voltage method and its application as a means of estimating the condition of the insulation of a large number of units of equipment. Test results are given to illustrate the procedure adopted. The economical loading of power transformers is reviewed and operating data are given to support the conclusions reached. Following this, a chimney-type ventilator is described and an empirical formula, based on test results, is given. The paper concludes with a few remarks on the maintenance of equipment.