INTERACTIVE TRANSIENT ANALYSIS OF POWER SYSTEM NETWORKS

Zein El-Abidin A. BABA

With increasing complexity in power networks, a complete knowledge of transients and their effects assumes greater importance for safe, reliable and economic operation of the system.

Overvoltages are caused mainly by lightning, maloperation of the system and switching operations. One technique which can simulate the disturbances in power systems is by developing computer programs. Nowadays, most of the researchers effort is directed towards software developments and the emphasis has shifted to devising and producing friendly programs on personal computers and from this, interactive methods have been developed.

Initially, the computer used the batch file as the method of entering the necessary data to run a program. At the beginning of the 1970’s, computer architecture began to change and computer systems were designed to be capable of supporting large numbers of interactive terminals and other methods of presenting input data were developed.

Nowadays, the advent of personal computers, or desk top computers, has dramatically changed work in many fields. One of the reasons is that the ‘computer power’ of a personal computer compares well with the capacity of minicomputers of a decade ago, while the price is considerably lower.

Three basic stages can be distinguished in a computer program: input data, the solution algorithms and the resulting output. The intercommunication between user and machine can be utilised during both the input of data and the output of results and can be improved using interactive methods which may permit graphical input-output facilities. A graph is probably the best way of presenting information in power system transients studies, and a microcomputer as an information processing device, is able to present results in this form, either on a graphic display or as a hardcopy. Charts and graphs help point out trends and sudden changes that might go unnoticed while scanning over a table of numbers.

This thesis is concerned with the calculation of transient voltages and current in power system networks.An interactive general-purpose program developed on an IBM AT Personal Computer is presented. This program is based on the combined Kutta-Lattice method. It is capable of representing both the distributed parameter and the lumped parameter elements with a high versatility of network configuration. The program is capable of simulating various circuit-breaker operations, lightning surges, fault studies and line attenuation and distortion.

Using the developed program, the transient overvoltages in transformer-feeders, due to energisation, have been investigated. The multiple prestrike phenomenon associated with the energisation of a cable-motor system has also been investigated. Further, the effects of variation in the system and the circuit-breaker parameters on the system overvoltages have been discussed.