Sensitivity of voltage sags to network failure rate improvement

In this paper, a stochastic approach for predicting voltage sags is applied. The methodology, developed by the authors, allows to characterize network sites by time series of voltage sags, described by amplitude, duration and type. A responsibility sharing curve is used to establish an adequate voltage sag index. The developed methodology is based on Monte Carlo simulation and considers the stochastic nature of power system faults, as well as the probabilistic nature of successful operation of transmission line and busbar primary protection systems. An application example is presented, considering the IEEE Reliability Test System. The sensitivity of the voltage sag index with regard to the transmission lines failure rate is assessed. Results allow to establish a linear dependence, which is used for site characterization, showing that the methodology is an important tool for network planning, design, operation and maintenance. It allows to quantify the benefits obtained, at each network site, from reducing the transmission lines failure rate.