2.1 Introduction

Most wind power capacity is connected to electricity supply networks, and this is likely to continue for the foreseeable future. The advantages of connection to a grid include:

• the ability to locate wind farms where the wind resource is plentiful, irrespective of demand;

• the ability of an interconnected grid to absorb variations in wind generation unrelated to overall demand variation;

• provision of excitation, enabling simple induction machines to be used as generators.

These advantages are qualified by various limitations of the power supply system, and Chapters 4 and 5 will consider how the resulting problems can be overcome. However, the fact remains that grid connection has provided a major impetus to the growth of wind energy. Hence it is important to understand the fundamentals of electrical power engineering presented in this chapter.

The chapter will start with the basic principles of electrical engineering. The discussion will lead naturally to the transformer, found in all wind farms as well as throughout power supply systems. We then consider alternating current (AC) systems, with particular emphasis on active and reactive power and the use of phasors. Power supply systems are then considered. The chapter will close with an introduction to AC power transmission.

2.2 Basic Principles