Thermal stress limiter for 13K215 steam turbine retrofit in Połaniec Power Plant, Poland

Abstract

This paper studies the functioning of a thermal stress limiter for a 13K215 steam turbine in Połaniec Power Plant, whichis a typical example of a 200 MW steam turbine retrofit. The share of renewable energy sources in the energy market isgrowing, leading to an increased demand for flexibility in conventional units, i.e., fast loading, fast unloading and fast startup etc. Thermal stress in steam turbine thick-walled elements, the steam turbine rotor in particular, is a major limit on theflexible operation of steam turbines. Therefore, steam turbine are usually controlled and protected by on-line stress control,i.e., a thermal stress limiter. In steam turbine retrofits in Połaniec Power Plant, each steam turbine was delivered by Alstomtogether with a thermal stress limiter implemented on a stand-alone PLC (Programmable Logic Controller). The thermal stresslimiter for 13K215 steam turbine retrofits protects HP and IP rotors as well as HP and IP valve chests. The thermal stresslimiter ensures safe operation of the steam turbine for the operating period required by the steam turbine owner. The thermalstress limiter also ensures the shortest possible steam turbine start up time for a guaranteed number of startups.