Short circuits, Electricity, Electricity, and Short circuits
The transmission network expansion may cause a power system at risk of high short-circuit current level. This thesis presents transmission network reconfiguration algorithm by bus splitting to limit short-circuit current to less than the interrupting capacity of the circuit breakers. Standard rules of bus splitting are developed with regard to the feasibility in practice. The proposed algorithm determines suitable pattern of the bus splitting while minimizing the number of buses to be split. Then, the impact on voltage stability of the system will be evaluated through PQ voltage stability index (PQVSI). The proposed solution has been tested on the actual transmission system in Thailand, considering the short-circuit currents only at the 21 high voltage stations in the metropolitan area. When comparing to other techniques proposed earlier, the test results show that the proposed method gives less impact on the system security with respect to the computed PQVSI.
Buildings -- Energy consumption, Electricity, Electric power, Buildings -- Energy consumption, Electric power, and Electricity
Combined Cooling Heating and Power (CCHP) can be applied to energy management system in buildings to increase the efficiency of primary energy consumption, as well as to reduce the carbon dioxide emission. This thesis proposes an algorithm to determine optimal hourly scheduling of the CCHP system for building load. Heat storage tank and photovoltaic system are also incorporated into energy management system. The objective function is to minimize total operating costs with the constrains of equipment operating limits and energy balance conditions. The formulated problem is solved by the Linear Programming. The determined operating conditions are displayed on the Graphic User Interface (GUI) to assist the operator to operate such system. Performance verification of the proposed building energy management has been done using power demand of one shopping complex. The results show that the total cost of electrical and cooling energy decreases by 12% per year, and increase to 40% when additional income from selling the surplus cooling water is considered.
Solar cells, Electricity, Short circuits, Electric circuit-breakers, Electric relays, Electric power systems -- Protection, Electric circuit-breakers, Electric power systems -- Protection, Electric relays, Electricity, Short circuits, and Solar cells
This thesis proposes the anti-islanding method for distribution systems with Photovoltaic Generation System (PVGS) by using voltage and frequency relays. This thesis derives Non Detection Zone (NDZ) of Over/Under voltage and Over/Under frequency ranges by using load quality factor in order to increase the accuracy for islanding prevention. In addition, another method to prevent islanding situation is derived by using Newton-Raphson's power flow. The islanding prevention is considered necessary for the currently increasing Photovoltaic Generation Systems. In addition, the thesis proposes the protective device placement for system reliability improvement by using Genetic Algorithm (GA) optimization. The optimization also takes the account of islanding prevention as a constraint. The proposed method is brought to apply with RBTS Bus 2 distribution system, and a modified system of the Provincial Electricity Authority (modified Banlen system).
Electricity, Electric currents, Power resources, Electric currents, Direct -- Power supply, Electric currents, Alternating -- Power supply, and High voltages
This thesis presents the prototype of AC voltage supply which can be controlled the frequency in the range of 10 - 500 Hz from DC power supply. This uses to supply the power for high voltage electrical equipment with high capacity load such as underground high voltage cable or GIS etc. Using the AC output voltage through the resonance transformer for increasing the voltage up to 5 kV. Typically, the test system of electrical equipment on-site with 50 Hz is large, the transportation of the testing device is quiet difficult. This test system can be adjusted the frequency of AC output voltage to fit with resonance frequency with the test equipment. This reduces its primary current and size. The results from the test system can be used with the capacitor between 600pF and 48.2nF at testing voltage of 5kV. It is given the resonance frequency at 333 Hz and 45.5 Hz and provide the minimum currents from AC power supply at 637.7 mA and 3.1743 A, respectively.
Electricity, Genetic algorithms, Electricity, and Genetic algorithms
Transmission Expansion Planning (TEP) is a process of selection of transmission construction plans to meet growing demand in the future. The selected construction plan must have the lowest total cost while maintaining the ability of the transmission system to securely transfer power. Mathematically, TEP is classified as a Mixed Integer Nonlinear Programming problem (MINLP). This problem combines difficulties of both nonlinear programming and integer programming together. Considering planning period, TEP can also be divided into 2 problems, i.e. single stage planning which does not consider change of demand and multi stage planning where demand growth is taken into account. Genetic Algorithm (GA) is one of the techniques to solve the optimization problem which is suitable for handling the MINLP. In this thesis, the GA is used to solve multi stage transmission expansion problems. The TEP considering in this thesis comprises construction of transmission lines, and installation of shunt reactive compensators. In addition, system voltage stability constraint is also considered through the PQ-Voltage Stability Index (PQVSI). All the TEPs in this thesis are formulated using AC models. The proposed method has been tested with the modified-Garver 6-bus and the IEEE-RTS79 test systems. Satisfactory results were obtained.