AC Circuits and Power Systems in Practice

14Operational Aspects of Power Engineering

In this chapter we examine some of the operational issues that practising engineers encounter every day, with a view to providing the new engineer with an introduction to some of the more important items. The material presented includes a discussion of the different bus arrangements and switchgear used in AC networks, electrical safety from the point of view of both electric shock and arc flash injury, limits of approach as well as isolation and switching procedures. Familiarity with these will assist in a more rapid integration into the profession. We begin with a discussion of device numbers and a description of the one line diagram.

14.1 Device Numbers

In chapter 12 symbols were used in some illustrations to identify protection relays. In addition to these symbols (defined in IEC 60617‐ Part 7), device numbers and acronyms are also defined in IEEE Standard C37.2 where they provide a shorthand notation for the function of devices installed in electrical installations. While most relate to electrical functions, some mechanical functions such as flow and pressure switches are also included.

Historically each device number represented an individual item of equipment, such as protection relays. Today they also apply to particular protection functions generated by the hardware or software contained in a multi‐function relay. Device numbers are often preceded by a numerical prefix which may indicate a particular unit in a multiple unit ...