Validation of Compressor Transient Behaviour

Major challenges are related to compressor and driver integration during run down. In order to understand these challenges, the pipeline compressor facility at Troll Kollsnes gas treatment plant, Norway, has been subjected to detailed trip testing and dynamic simulation analysis. The plant includes five pipeline compressors and is utilised as a pilot for analysing the transient response of a 40 MW compressor driven by a variable speed electric motor. The compressor control and protection system include an anti-surge and a hot gas bypass system. Vibration records have shown that under power outage the compressors were exposed to violent vibrations. Further investigation revealed that during a short power outage, the compressor enters the surge- and rotating stall area under certain operating scenarios. The rotating stall response resulted in reduced operating range and flexibility for the pipeline compressors. Specific precautions had to be taken to prevent the compressor from running into the low flow operating area of the performance envelope. Dynamic simulations cover important aspects related to the transient scenario analyses performed to reveal the root cause of the compressor problems. The simulation system enables sophisticated plant models to be configured from high quality standard model algorithm building blocks. Verification of the model blocks have been performed against plant records in order to validate the transient predictions. The paper reports experience from testing and verification of compressor and driver integration with reference to transient behaviour during run down. This includes the validation of the dynamic models, which apply both to the design and commissioning phase where actual plant trip tests should be used to verify the design and stability margins.