This paper describes the possibilities of applying object-oriented analysis, design and programming methods to the modeling of individual segments of the power system, and proposes an object-oriented model of the operation of a power subsystem with a predominant share of hydroelectric power plants for the purposes of short-term simulation of operation. It also provides an overview of the possibility of using such a model for analyses that are related to short-term simulation, such as short-term optimization of operation, medium-term and long-term simulation and optimization, hydro-thermal coordination and optimization, etc.