Impact of operating modes of industrial thermal power plant on steady-state stability of turbogenerators when isolated from power system

Abstract

The main trend of the electric power industry is the expansion of its own power supply sources of the industrial enterprises. At the same time, isolated operation mode remains the mode that may cause emergency conditions. The relevance of the conducted studies is confirmed by experience. Thermal power plants (TPP) are continuously reconstructed, the power of the generators is increasing, and they are transferred to operate in generator – transformer units. The generating equipment is constantly changing because of repairing, maintenance, and emergency conditions. Therefore, part of the machines operates in electrical mode, the other part operates in thermal mode. In case of isolated operation, some machines are unable to control frequency of the unit. Then, a danger of loss of static stability may occur under conditions of reactive power deficiency. In this regard, the research to define the reasons of the loss of static stability of industrial STG, to conduct computational experiments and to develop activities to reduce emergency situations is relevant. Calculation of the operating modes of industrial thermal power plant has been carried out using the KATRAN software package. A consistent weighting method is used to analyze the static stability of the power plant. The consistent equivalent method is applied to calculate the steady-state modes in case of isolated and parallel operation with the power system. An algorithm has been developed that differs from the existing ones as it considers the impact of the thermal load on the static stability factor of turbogenerators of industrial thermal power plants. Also, it allows you to choose turbine–generator unit that will maintain constant pressure in the steam pipeline. The modes of isolated operation have been studied in terms of static stability of the power plant when all speed control units are operating and in case that one of the turbine-generator unit operates to maintain constant pressure in the steam pipeline. The results have shown that during maintenance operation of one of the machines of thermal load can lead to loss of static stability. Recommendations to improve stability are presented. The obtained algorithm allows us to develop activities to increase static sustainability in case of isolated operation with the power system. The suggested key activity is to redistribute between the turbines the function to keep the steam pressure in the steam pipeline. The computational experiment conducted using the example of the industrial thermal power plant has proved its effectiveness.