General Structure of Electrical Power System

General Structure of Electrical Power SystemIntroduction to Power timesThe superior voltage electric infection is the pile depute of galvanising zip, from generating power plants to substations. This is from the local wiring between high voltage substations and customers are referred to as electricity distribution. Transmission railroad lines, when interconnected with each some other, become high voltage transmission networks. Transmission lines mostly use three phase alternate menses (AC), although single phase AC is sometimes used in railway electrification systems. High-voltage direct legitimate (HVDC) technology is used only for very long distances undersea cables. Electricity is transmitted at high voltages to sl ratiocinationerise the energy lost in long distance transmission. Power is usually transmitted through everywherehead power lines. Underground power transmission has a very high cost and greater operational limitations. The main problem in the Power distri bution is that electrical energy squeeze outnot be stored so it is generated base on the necessity. A control system is required to ensure electric power generations match the involve. Power generating plant low voltage is produced. The reference oddment voltage is then stepped up by the power station transformer to a higher voltage for transmission over long distances.Power Losses infection electricity at high voltage reduces the fraction of energy lost due to resistance. For a given amount of power, a higher voltage reduces the current and thus the resistive losses in the conductor. At extremely high voltages, conductor and ground, corona discharge losses are so large that they can offset the disappoint resistance loss in the line conductors. Transmission and distribution losses are generally below 10%. In general, losses are estimated from the discrepancy between energy produce and energy sold to end customers the difference between what is produced and what is consumed c onstitute transmission and distribution losses. In an alternating current circuit, the inductance and content of the phase conductors can be significant. The currents that flow in these components of the circuit impedance constitute reactive power, which transmits no energy to the load. activated current causes extra losses in the transmission circuit. The ratio of real power (transmitted to the load) to apparent power is the power factor. As reactive current increases, the reactive power increases and the power factor decreases. For systems with low power factors, losses are higher than for systems with high power factors. At the substations, transformers reduce the voltage to a lower level for distribution to commercial and residential users. This distribution is accomplished with a combination of sub-transmission (33 kV to 132 kV) and distribution (3.3 to 25 kV). Finally, at the point of use, the energy is alter to a low voltage.Power Load balancingThe transmission system pro vides for base load and treetop load capability, with safety and fault tolerance margins. The peak load times vary by region largely due to the industry. Power requirements vary by the season and the time of day. Distribution system designs eer take the base load and the peak load into consideration. The transmission system usually does not have a large buffering capability to match the wads with the generation. Thus generation has to be kept matched to the load that prevents cloging failures of the generation equipment. Multiple sources and loads can be connected to the transmission system and they must be controlled to provide orderly transfer of power. In centralized power generation local control of generation involves synchronization of the generation units to prevent large transients and overload conditions.In distributed power generation the generators are geographically distributed and the process to bring them online and offline must be carefully controlled. The load co ntrol signals can either be sent on separate lines or on the power lines. To load balance the voltage and frequency can be used as a signaling mechanism. In voltage signaling, the variation of voltage is used to increase generation. The power added by any system increases as the line voltage decreases. voltage based regulation is complex to use in mesh networks, since the individual components and set points would need to be reconfigured every time a new generator is added to the mesh. In frequency signaling, the generating units match the frequency of the power transmission system. In droop speed control, if the frequency decreases, the power is increased. Wind turbines and other distributed storage and generation systems can be connected to the power grid, and interact with it to improve system operation.5.2 Power generation and distribution through overhead lines with single line diagramElectrical power system deals with the technology of generation, transmission and distributi on of electrical energy. An electric power system consists of different subsystem are explained as followsI. Generation subsystemThe innovation from one source to electrical energy through the process of electromagnetic conversion. This system consists of group of generation systems. Power system comes into existence with the growing demand of electrical energy. Power generations are classified as Hydraulic, nuclear power, fossil fuel and non-conventional power, solar power.II. Transmission subsystemThe overhead transmission network transfers electrical energy from generating stations located at long distance to the distribution system. The Transformer and transmission line subsystems are designed in such way to transmit bulk power for consumption at the load line. The step-up transformers are used in various range of step-up voltage based on the requirements. A transmission voltage varies between 66 kV to 440KV in India.III. Sub-transmission systemThe sub-transmission network is t he portion of transmission system connected to the high voltage substations using transformers.IV. Distribution subsystemBy this process energy is connected to different distribution subsystem to a place a main transmission subsystem. A distribution subsystem consists of over headlines and underground cables. The distribution of power system is generally in two levels feeder or primary voltage at 11kV and secondary/consumer voltage at 415 Volt for three-phase and 230 Volt for single phase supply for house hold application. Each individual customer is connected to the secondary circuit through religious service leads and a meter. Distribution system is classified as Radial distribution system, loop distribution system and network distribution system. From the main switch electrical energy is distributed to the various points using distribution board system and tree system.V. Control subsystemThis subsystem is formed by relays, switch and other control elements to protect other subs ystems to protect faults and overloads to ensure efficient, reliable and economic operation of electric power system.Figure 6.1 Block diagram of single line power system intensify and step down Transformers are used in all subsystems. At the sending end from generator step up Transformers are used and the receiving end step-down Transformers are used. Power and distribution Transformers are used in power line system depending upon the power handling capacity.EarthingThe earthling of electrical installation is undertaken for the following reasons.To avoid shocks to a living body.To ensure the potential with respect to the earth of any current carrying conductor does not rise in a higher place its designed level.To provide safety to operating personalTo avoid fire hazard due to leakage current.Representation of the transmission lineA transmission line has series resistance, series inductive reactance, shunt capacitance and leakage resistance which are distributed evenly along its len gth. Except for long lines, the total resistance, inductance, capacitance and leakage resistance of the line can be concentrated to give a lumped-constant circuit which simplifies calculation. The particular lumped-constant circuit used depends on the length of the line and the required accuracy of the calculations. For the purpose of this introduction to power system calculations, we will consider a representation which is accurate for short transmission lines up to about 80 km in length. For this length of line, the shunt capacitance and leakage resistance can be ignored. It should be noted that this assumption is not validated for unloaded lines when the shunt capacitance dominates.Power system analysis is required for a large number of different purposesSystem design and control to exert consumer voltage at statuary levels as affected by conductor sizing and transformer tap charger position.Fault calculations to ensure that the maximum fault current can be interrupted by circ uit breakers or fuses and that large fault currents cause the minimum of damage to the power system.Design of security measure systems to ensure faulty circuits are switched off rapidly (