This article describes the present in power plants and large enterprises common distribution systems equipment and select the option of, and distribution systems in various areas of protection. In the distribution system, a reasonable choice of distribution systems equipment is related to the complete equipment of the normal operation and to enterprises by electricity flowing ； for the distribution system of protection is even more significant relationship, if the design of protection of inadequate distribution, are unable to the required period of time to cut down and damaged wire circuits, and even the expansion of the accident, or result in a selective and expand the scope.
From the distribution system design specifications, the distribution system design in distribution systems equipment chosen and distribution systems relay protection. the system of distribution system and design requirements and attention. and the classroom with practical problems theoretical analysis on the text of the distribution system of protection and the choice.
Keywords ： distribution systems;relay protection ;equipment chosen.；Transformer；DSB High-voltage fuse
