本指南涵盖了一次电压为601 V至38 kV时，在112.5 kVA或更大范围内降压操作的三相单元变电站。 本指南不包括以下安装: a） 在IEEE标准C57中，变压器部分被描述和定义为“网络”、“地铁”、“保险库”或“地下”的变电站。12.24和IEEE标准C57。12.40. b） 在ANSI C57中，变压器部分被描述并定义为“垫装”的变电站。12.22和IEEE标准C57。12.27. c） IEEE标准C37中描述的气体绝缘变电站。122 d） 整流式变电站。 e） 移动单元变电站。 f） 船舶、船艇、铁路车辆、飞机或汽车上的装置。 g） 矿山设施。 h） 专用于机车车辆运行的发电、变电、输电或配电的铁路装置，或专用于信号和铁路通信的装置。 i） 由通信设施独家控制的通信设备的安装，位于户外或专门用于此类安装的建筑空间内。 j） 由电力公司独家控制的用于通信或计量的装置；或用于发电、控制、转换、传输和分配位于公用事业专门用于此类目的的建筑物内的电能，或位于公用事业拥有或租赁的财产或公共公路、街道、道路等户外的电能；或者通过私有财产的既定权利进行户外活动。

This guide covers three-phase unit substations for step-down operation in the range of 112.5 kVA or greater at primary voltages of 601 V through 38 kV. This guide does not cover the following installations: a) Substations in which the transformer section is described and defined as "network," "subway," "vault," or "underground" in IEEE Std C57.12.24 and IEEE Std C57.12.40. b) Substations in which the transformer section is described and defined as "pad-mounted" in ANSI C57.12.22 and IEEE Std C57.12.27. c) Gas-insulated substations as described in IEEE Std C37.122. d) Rectifier-type substations. e) Mobile unit substations. f) Installations in ships, watercraft, railway rolling stock, aircraft, or automotive vehicles. g) Installations for mines. h) Installations of railways for generation, transformation, transmission, or distribution of power used exclusively for operation of rolling stock, or for installations used exclusively for signaling and railway communication purposes. i) Installations of communication equipment that is under the exclusive control of communication utilities, located outdoors or in building spaces used exclusively for such installations. j) Installations under the exclusive control of electric utilities for the purpose of communication, or metering; or for the generation, control, transformation, transmission, and distribution of electric energy located in buildings used exclusively by utilities for such purposes or located outdoors on property owned or leased by the utility or on public highways, streets, roads, etc; or outdoors by established rights on private property.