TABLE OF CONTENTS Switchgear is a general term covering switching devices and their combination with associated control, measuring, protective and regulating equipment. The term covers assemblies of such devices and equipment with associated interconnections, accessories, enclosures and supporting structures intended for use in connection with transmission and distribution networks. The different types of air, oil, vacuum and SF 6 switchgear together with the theory of arc interruption are already well-covered in standard reference books. [1 4 ] This chapter therefore concentrates on the description of various switching phenomena under different practical circuit conditions and then relates these basic principles to the different switchgear designs currently available on the market. In particular this chapter is intended to assist the reader in specifying switchgear for particular applications.
The descriptions of different types of switchgear, intended for different duties, are listed in Table 13.1. It is important not to be too lax with the terminology. For example, the use of the term isolator to describe a switch will not on its own sufficiently describe the required capability of the device.
| Terminology | Description |
|---|---|
| Circuit breaker | A mechanical switching device, capable of making, carrying and breaking currents under normal circuit conditions and also making, carrying for a specified time and breaking currents under specified abnormal circuit conditions such as those of short circuit. |
| Contactor | A mechanical switching device having only one position of rest, operated otherwise... |
