COMPUTATION OF AN EXPEDIENT AMOUNT OF DEMAND THE UNDER FREQUENCY LOAD SHEDDING AND ITS PLACEMENT IN THE POWER SYSTEM WITH DISTRIBUTED SOURCES OF ELECTRICAL ENERGY
Under Frequency Load Shedding (UFLS) is one of the main tools widely used in power systems to prevent frequency dropping too much. The UFLS is able to disconnect some consumers in milliseconds, and in seconds to stop the frequency drop in areas of the power system, which were formed as a result of a cascade accident to disconnect lines and generators.
To support a temporary balance of active power in emergency in power system must be provided an amount of Demand for discon-nection. Therefore, the National Transmission System Operators (TSO) or the Network of Transmission System Operators for Electricity establish the so-called Total Load Shed (TLS). Most often in the standards and policy of power systems, this indicator is calculated for total peak demand and recommended to place in the power system evenly geographically. This mode of placing TLS does not take into account the structure of power system, daily and seasonal changes in generation capacity and consumption, despite the fact that standards and policy the TSO require it to be taken into account. A mathematical model and a method are propposed determining total load shedding (TLS) the Under Frequency Load Shedding (UFLS) Power System and its placement. TLS is determined taking into account distributed (at consumer nodes) renewable energy sources, possible options for emergency separation of the power system, requirements of international standards and policy the functioning of Power Systems. The model is an integer (binary) linear programming problem. Ooptimal relays are selected for UFLS based on the categorization criterion located in predetermined nodes of the Power System whose operation ensures the power balance in emergency separation areas. The electrical parameters of the normal modes, as well as the efficiency of the optimal amout of Demand load shedding and distribution its in the network are determined and verified (detected) in a series of a priori and a posteriori calculations on exact mathematical models of the software products of the electric power industry recognized in the world practice. The distribution of the amout of Demand load shedding in case of an emergency situation increases the likelihood of balancing a larger number of emergency areas of the power system. Ref. 9, tabl. 3, fig. 2.
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