Reliability assessment of line protection based on reliability graphs and Monte Carlo simulation

A reliability assessment methodology for transmission line protection systems is presented, which is based on a probabilistic modeling of the protection system´s successful operation, and considering both the availabilities of the line protection hardware and the failure function of the current differential protection caused by communication delay. The system successful operation is described by reliability graphs, and solutions are obtained from Monte Carlo simulation. The developed methodology is applied to three protection schemes to show its effectiveness.