Determining rational redundancy of 500-kV reactors in transmission systems using a probability-based economic analysis approach: BCTC´s practice

This paper presents a methodology to determine a rational redundancy level of power system equipment based on a coordination among the electric energy market information, the total transfer capability (TTC) in the transmission system and the estimation of random equipment failures. The proposed approach includes the models of unavailability due to both repairable and aging failures of equipment, the calculation method of two discrete statistical distributions representing energy prices and export powers, and a probabilistic benefit/cost analysis technique. An actual example of 500-kV reactors at British Columbia Transmission Corporation (BCTC) has been given to demonstrate the procedure of the application. The results indicate that the redundancy level determined using this approach not only enables the utility to avoid possible losses in the income from energy sales and improves the profile of system TTC but also guarantees a high benefit/cost ratio in a financial justification of redundant equipment addition.