Use of Computers and Microprocessors – The first methos for solving various power system problems were AC and DC network analysers developed in early 1930s. AC analysers were used for load flow and stability studies whereas DC were preferred for short-circuit studies.
Analogue computers were developed in 1940s and were used in conjunction with AC network analyser to solve various problems for off-line studies. In 1950s many analogue devices were developed to control the on-line functions such as generation control, frequency and tie-line control.
The 1950s also saw the advent of digital computers which were first used to solve a load flow problem in 1956. Power system studies by computers gave greater flexibility, accuracy, speed and economy. Till 1970s, there was a widespread use of computers in system analysis. With the entry of microprocessors in the arena, now, besides main frame computers, mini, micro and personal computers are all increasingly being used to carry out various power system studies and solve power system problems for off-line and on-line applications.
Off-line applications include research, routine evaluation of system performance and data assimilation and retrieval. It is mainly used for planning and analysing some new aspects of the system. On-line and real time applications include data-logging and the monitoring of the system state.
A large central computer is used in central load despatch centres for economic and secure control of large integrated systems. Microprocessors and computers installed in generating stations control various local processes such as starting up of a generator from the cold state, etc. Table 1.2 depicts the time scale of various hierarchical control problems to be solved by computers/ microprocessors. Some of these problems are tackled in this book.