Abstract
Modern gas-turbine units (GTUs) and gas-reciprocating units (GRUs) have found a wide use at power plants, including distributed generation facilities, running on gaseous fuel. The design features of these generating units have a considerable effect on the nature and parameters of transient processes due to emergency disturbances in the adjacent network. The study shows that single-shaft gas-turbine and gas-reciprocating units do not allow even short-term considerable frequency drops. These schemes and operating conditions arise due to emergency active power shortages when the connection between the power plant and the power system weakens due to repair conditions or islanded operation. The paper presents the results of transient process calculations for operating power plants (distributed generation facilities), which make it possible to identify the unfavorable properties of GTUs and GRUs. The results show that two-shaft (three-shaft) GTUs and GRUs can switch to out-of-step conditions even when short-circuits in the adjacent network are cleared with high-speed relay protection devices. The features of out-of-step conditions and the admissibility of their short-term duration for the spontaneous restoration of generators’ synchronization are considered. The findings suggest that considering the fundamental design features of generating units provides informed technical decisions on equipping power plants (distributed generation (DG) facilities) and the adjacent network with efficient emergency control systems.
Highlights
Steam turbine units (STU) have been used at thermal power plants (TPPs).Unit capacities of steam turbine units (STU) steadily rose, which made it possible to commission new TPPs with power units with a capacity of 300, 500, and 800 MW
The initial network scheme is under repair
As a result of a three-phase short-circuit, all generators of the cycle gas turbine plants (CCGTPs) switch to the out-of-step operation, the attempt to synchronize them with one another and with the power system fails, and the out-of-step condition continues
Summary
Steam turbine units (STU) have been used at thermal power plants (TPPs). The new construction and modernization of TPPs have involved a wide use of gas-turbine units (GTUs) and gas-reciprocating units (GRUs), which increase fuel heat utilization factor and efficiency. Of surplus electricity to the grid; Fast direct starts of large electric motors; Normal operation of electrical loads in the event of a sudden shutdown of a generating unit or a distributed generation facility. The development of projects for the construction of new power plants, including DG facilities, should focus on a set of tasks. These are the tasks associated with an increase in short-circuit currents, which may require replacement of high-voltage circuit breakers, if their breaking capacity is insufficient, or the installation of current-limiting devices (isolation transformers) [12]. This study focuses on the influence of design features of the gas-turbine and gasreciprocating units on the nature and parameters of transient processes due to emergency disturbances in the adjacent network and shows how this influence should be taken into account when designing the emergency control systems
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