Computer aided design of substation switching schemes

Abstract

Every switching operation in a power substation must be executed after proper evaluation of its consequence. Often, switching actions for various operating conditions and contingencies are pre determined by using the control engineer's knowledge and previous experience. When the need arises, either a computer or an operator carries out these actions. However, it is difficult for an operator to know all the operating conditions and contingencies in advance. An on line decision making tool can provide an operator with the most appropriate switching decisions for the present system configuration and system state so the continuity and quality of power supply can be maintained by implementing those switching decisions. Since the circuit configuration varies from one substation to another, such decision-making tools developed for one substation may not be applicable to another substation. This thesis presents a technique to design digital computer based substation switching schemes. The technique is applicable to all practical substations. The rules of interlocking and sequence switching used by the schemes are generalized and are not based upon a particular substation configuration. While being applicable to all substations, these schemes also ensure the most appropriate switching operations with minimum operator intervention. The switching schemes ensure the safety of the system before making any switching action. They assist human operators in the evaluation of abnormal circumstances and are easy to integrate with other monitoring, control and protection systems. A software application for developing switching schemes for substations called SSP was developed by using the techniques presented in this thesis. Switching schemes were developed for eight substations by using the semi-automated design tools provided with SSP. The switching schemes were then tested for their correct operation. Results of the tests showed that the technique developed by the work presented in this thesis can provide appropriate switching scheme for a substation of any practical configuration.