On-Line Fast Load Shedding to Maintain System Stability and Operation for Isolated Oil Field Power System

This paper demonstrates the design and implementation of smart on-line fast load shedding to maintain system stability and operation when a major generating unit is suddenly tripped. The design stage included load flow and transient stability study cases to determine system stability limits, transient frequency variation curves and transient voltage profiles. Numerous outage scenarios that cover all possible operating conditions are simulated and key system stability parameters are identified. A fast load shedding priority list has been provided by system operations and has been included as needed into transient stability simulation cases to maintain system stability and generation/load balance. Fast load shedding logic diagrams are developed with triggering parameters including generating unit breaker status and on-line frequency measurements. On-line measurements of system generation, tie line flow and loads are continuously monitored and fed into a PLC system that processes information and issues load shedding trip signals to maintain balanced generation/load and stability. This fast load shedding scheme has been tested in real time outages several times, and proved to be accurate and in agreement with transient stability simulation results. Since its implementation, this load shedding scheme has successfully saved the oil field power system from total shutdown and maintained system operation after sudden tripping of major generating units