4.3 MODELLING OF STEAM TURBINE

The dynamic response of a steam turbine is largely influenced by two factors:

1. Entrained steam between the inlet steam valve and the first stage of the turbine,
2. The storage action in the re-heater, which causes the outlet of the low pressure stage to lag behind that of the high pressure stage

The dynamic response of a steam turbine can be related in terms of changes in steam valve opening ΔyT. The following figure shows the transfer function model of re-heat steam turbine

Fig 4.4 Block diagram representation of a steam turbine

The typical value of the turbine time constant T₁ lies in the range ot 0.2 to 2.5 seconds.