Switching in Electrical Transmission and Distribution Systems

1 Switching in Power Systems

1.1 Introduction

As electricity comes out of AC outlets every day, and has done so for more than 100 years, it is nowadays considered a commodity. It is a versatile and clean source of energy; it is rather cheap and ‘always available’.

The purpose of a power system is to transport and distribute the electric energy generated in the power plants to the consumers in a safe and reliable way. Generators take care of the conversion of mechanical energy into electric energy, aluminium and copper conductors are used to carry the current, and transformers bring the electric energy to the appropriate voltage level. Society's dependence on this commodity has become extremely large and the social impact of a failing power system is unacceptable. The electrical power system is the backbone of modern society.

Switching operations in power systems are very common and must not jeopardize the system's reliability and safety. Switching in power systems is necessary for the following reasons and duties:

• Taking into or out of service some sections of the system, certain loads, or consumers. A typical example is the switching of shunt capacitor banks or shunt reactors, de-energization of overhead lines, transformers, and so on. In industrial systems, this type of switching is by far the most common of all the switching operations.
• Transferring the flow of energy from one circuit to another. Such operations occur when load current needs to be transferred without interruption ...