Electrical power is a commodity in the modern world, bought and sold on the open market like any other. Thus, it is important to be able to measure and control electricity, not only for reasons of efficiency but also for sale, taxation, safety, equipment protection, and reliability of service.
As with any other quantity we wish to measure and control, the systems designed for these purposes may be divided into three general categories: sensors to measure, final control elements to exert influence, and controllers to make the necessary control decisions automatically. This chapter will discuss all three of these categories as they relate to measurement and protection subsystems found in modern electrical power grids.
This chapter cannot in any way do justice to the scope and complexity of electrical power grids. What it aims to do, however, is focus on the monitoring and protective functions subsystems essential to any functional power grid – the instrumentation within an electrical power grid, as it were – touching on the function of various pieces of electrical equipment as necessary to understand the purpose and application of those monitoring and protective subsystems.