Abstract
In this paper are specified causes of ambiguities and difficulties in determining an efficient operation standard for land and marine turbine power plants. Two of them, namely: lowering values of working media inlet parameters and changes in configuration of connections between component devices of thermal cycles, have been analyzed. As a remedy for resulting difficulties a thermal cycle computational model of modular structure has been proposed. As showed, the tuning of the computational model with respect to correct measurements by elaborating individual corrections for calculation coefficients of computational methods used for particular devices ensures good accuracy of determination of unserviceability symptoms in these conditions. Introduction to the modular computational model - of control modules making use of valve opening indicators in DCS system ensures good accuracy also in the case of changes in structure of complex power object.