Compressor Transient Behaviour

An important issue related to compressor and driver integration is the behaviour during driver trip. Field tests at Troll Kollsnes gas treatment plant have shown that under a short power outage and within certain operating scenarios, the compressor enters the surge- and rotating stall area. These problems lead to a reduced flexibility in the operation of the pipeline compressors. The 40 MW variable speed electric motor driven compressors have therefore been subjected to dynamic simulation analyses to reveal the transient response. Dynamic simulations based on earlier trip tests have been performed so as to understand what parameters affect the severity and duration of a surge under power outage. An elaborate plant model has been created with the dynamic simulation tool OTISS™ by AspenTech and tuned to represent the plant. The model is validated against actual plant tests and operating data. The paper reports experience from analyses of the compressor and driver behaviour during run down. It is based on earlier tests and dynamic simulations performed for the Troll Kollsnes gas treatment plant. The main objective has been to study the compressor system sensitivity related to variation in polar inertia, driver power decay and trip signal delay on the transient rundown behaviour.