Reliability assessment of multiple-voltage regional transmission and distribution system considering substation interior failure

Abstract

With the increase of load density and the high request of supply reliability, voltage level of urban power grids is continuously rising. 220 kV has been popular in cities and even 500 kV substations have been directly located in urban area. Multiple voltage levels coexist in a rather small area, forming a meshed transmission and distribution network in urban region. So traditional distribution system reliability evaluation approaches can barely satisfy the requirements of reliability evaluation in urban power grid planning and operation. A reliability assessment approach for multiple-voltage regional systems based on reliability equivalent law of series system is proposed. An equivalent model of substation bus system has been introduced, considering simultaneous outage of multiple feeders and common mode failure (CMF) inside substations, which incorporates the effect of substation failures on the reliability of the network. This method has been applied on a typical urban grid in China with medium- and high-voltage distribution network. Simulation results have proven the effectiveness and advantages of this method, which can act as an aid in decision making for urban grid planning and design.