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COOPERATION OF DISSIPATED ENERGY SOURCES WITH POWER SYSTEM Michał Zeńczak Faculty of Electrical Engineering West Pomeranian University of Technology, Szczecin (former Szczecin University of Technology) ul. Sikorskiego 37 70-313 Szczecin Many incompatible classifications of distributed generation (DG) are used. For example: • small DG (5 kW < P < 5 MW), • medium DG (5 MW < P < 50 MW), • big DG (50 MW < P < 150 MW). www.keine.zut.edu.pl CONNECTION • Electric power companies have their own rules about technical requirements OF DG TO for the units connected to power system, POWER SYSTEM • The question is essential if the DG is adopted to isolated operation (islanding). • DC or AC? • Cable line or overhead line. • The choice of method of working of neutral points. www.keine.zut.edu.pl CONNECTION OF DG TO POWER SYSTEM www.keine.zut.edu.pl DG AND LEVEL • New sources of electrical energy in power system change the reactive power OF VOLTAGE flows and value of voltage in nodes, • Often the levels of voltages would be too high, if the regulation of voltage were not be done, • The important limit is allowable range of operation of generator, which should not be exceeded, • Possibility of effects of generator on the level of voltage depends on its location in power system and their parameters. www.keine.zut.edu.pl DG AND LEVEL For cable lines for the power 200 kW the LV OF VOLTAGE is sufficient. For the power at 5 MW the MV is sufficient. For 515 MW the MV or HV are sufficient. Over 15 MW the HV is necessary. Still's formula makes it possible to calculate approximately the proper value of voltage level for overhead line: l U 5.5 0.01P 1.609 www.keine.zut.edu.pl PD DG AND CURRENTCARRYING CAPACITY ~ PF P’AB A C B P”AB PB When then When then www.keine.zut.edu.pl PC P"AB PG PB PC PABcc DG AND • DG have rather not high power, therefore the changes of short-circuits SHORTconditions are not high. CIRCUIT CONDITIONS • DG appears very often on the areas, where the distribution network is not developed, the short-circuits capacities of elements selected for low shortcircuits currents. • The highest value of power of WPF Sn should fulfill the relationship: S 20S n " K www.keine.zut.edu.pl DG AND • Principles of protection of big DG units are the same like units in common POWER electric power station. SYSTEM PROTECTION • In case of medium and small DG there are special requirements for the protection of the connection of DG to power system, apart from the autonomous protection of DG units. www.keine.zut.edu.pl DG AND POWER SYSTEM PROTECTION PROTECTION OF DG AND POWER SYSTEM HAVE THE FOLLOWING FUNCTIONS: • disconnection of generator from power system, when the parallel cooperation with grid is impossible, • protection of power system against disturbances in DG units, • protection of DG units against disturbances in power system. www.keine.zut.edu.pl DG AND POWER SYSTEM PROTECTION Influence of DG on existing protections in Power System: • Changes in current flows, changes of resultant impedances cause the necessity of analyzing setting of protection equipment. • Correction of setting values in distance protection. • Frequency protection of DG and automatic load shedding in PCC. • Cooperation of Autoreclosing with distance protection. www.keine.zut.edu.pl DG AND • Local (static) stability is determined by the immunity from little disturbances in STABILITY power system. • Global (dynamic) stability is determined by the immunity from big disturbances comparable with nominal power of units (for example short-circuit). www.keine.zut.edu.pl DG AND STABILITY Behavior of DG units during short-circuits RFT - Ride Fault Through. www.keine.zut.edu.pl OTHER PROBLEMS • Harmonics, • Flicker, • Electric and magnetic fields of 50 Hz related to dissipated generation and their effect on natural environment, www.keine.zut.edu.pl www.keine.zut.edu.pl Dissipated Generation (DG) creates many technicals problems in Power System Team for grid analysis and unconventional power stations deals with these problems: Ryszard Pałka, Prof. D.Sc. Ph.D. Eng. Michał Zeńczak, D.Sc. Ph.D. Eng. Olgierd Małyszko, Ph.D. Eng. Sebastian Szkolny, Ph.D. Eng. www.keine.zut.edu.pl RESEARCH PROPOSAL • The research proposal is related to the above mentioned problems • The study should be done for the micro, small, medium and big DG units connected to the isolated power system (islanding) or to real power system • The problems may be very interesting for connection of power systems of two countries www.keine.zut.edu.pl Thank You for Your Attention www.keine.zut.edu.pl