Power systems dynamics-What are they? What are the options?

The majority of power today is supplied as three phase AC generated by directly coupled rotating generators, the majority of which (on developed networks) are the large synchronous type. This ensures that the electricity supply is locked into a coherent form bringing the benefits of a constant voltage and frequency supply. Unfortunately the picture is not as simple as has been indicated. Generators are electromechanical devices with spinning inertia, loads vary with time of day (and year) and the interconnecting network can be subject to interference-usually by the weather. All lead to situations where for short periods of time (hundreds of milliseconds to minutes) the power system can be induced into an operational mode that varies significantly from that of the steady state. All generation sources which are connected to the network, operate on the principle of protect yourself to prevent damage to the generator leading to loss of generating capacity and in a short space of time, eventual system collapse. Hence rapid mitigation of this dynamic condition is required if the system is to maintain its ability to supply electricity. The author discusses why power systems are never raised to their full capacity, the impact of privatisation on system dynamic conditions, and approaches to mitigating the dynamic conditions.