Transmission voltage recovery following a fault event in the Metro Atlanta area

This paper describes a multiple contingency fault and breaker failure event at two Metro Atlanta 230 kV substations. After the fault activity, the transmission system in the Metro Atlanta area experienced a voltage depression lasting around 15 seconds, followed by a voltage overshoot. Over 1900 MWs of load was lost. Evidence suggests that the majority of the load was dropped due to the operation of induction motor protection removing the motors from the extended low voltages. Dynamic simulations using aggregate load models that included the effect of induction motors and distribution system impedances were used to recreate the response of the transmission system. Real world data, including a plot from a data fault recorder, is presented and compared to the dynamic simulations. This paper describes the event, and the study techniques required to simulate the observed transmission system behavior. The effectiveness of new bus arrangements, enhanced relaying, and dynamic and static MVAr support toward mitigating the voltage depression is also discussed.