Impact of Compressor Protection System on Rundown Characteristics

Knowledge of compressor system behaviour during trip is essential to obtain reliable operation. Experience at Troll Kollsnes gas treatment plant has shown that the compressor can suffer from surge and rotating stall in situations with voltage drops in the electricity grid. The electric motor driven compressor and the protection valves and piping has been modelled and dynamic simulations has been done to reveal the transient response. An elaborate plant model has been created with the dynamic simulation tool OTISS by AspenTech and tuned to represent the plant. The paper focuses on the impact of different compressor discharge volumes, dimensions of the recycle piping as well as the sizing, characteristics and trip signal delay of the recycle protection valve(s). Sensitivity analyses for the actual plant reveal the response and protection during compressor driver trip.