Impact of Coupling Breakers in a Power Plant Fault Analysis

Over the last decades, the private sector power plants are integrated into the power system with growing number and size. Since these power plants are large, their impacts on the grid are strong as well. The steady state and transient analyses required for plant connection to the grid, mostly play a role in the selection of the equipment and determination of the protection settings. Installation and commissioning of power plants based on accurate analyses are of great importance in raising the reliability of the system. The number of generating units in a power plant can be increased for capacity expansion. The coupling breakers (bus tie breakers) are used in plant substations configured in double bus scheme. Each generator are connected to the grid through these buses having the coupling breaker in a closed/opened position. This study investigates the impact of these breakers in terms of short circuit faults by using a real data obtained from the natural gas power plant connected to the 154 kV grid through overhead transmission line. Fault currents are computed based on IEC 60909 and compared for different status of coupling breakers.