Model for security of service costing in electric transmission systems

The security cost of a transmission system is investigated in the paper by means of an indirect method. The theory of a basic system, which only provides transport service with an almost zero security level, is developed. Different concepts are defined for the relationships of contingency effects with branches, nodes and system. An expected load reduction in this system is obtained as a weighted average of the calculated values for different contingencies and operating conditions. Customer reliability worth is used to obtain interruption costs, which are interpreted as the costs that would be incurred if the complete power system did not not have security elements. The model is tested on the 24 bus-IEEE system. With results of system and nodal interruption cost and security indices. It is proved for the sample system that the security cost calculated with this model is a significant part of the transmission annual investment costs. Nodal security costs vary with location, though a group of them present common values