General Structure of Electrical Power System

General Structure of Electrical Power System Introduction to Power generation The high voltage electric transmission is the bulk transfer of electrical energy, 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 lines, when interconnected with each other, become high voltage transmission networks. Transmission lines mostly use three phase alternating current (AC), although single phase AC is sometimes used in railway electrification systems. High-voltage direct current (HVDC) technology is used only for very long distances; undersea cables. Electricity is transmitted at high voltages to reduce the energy lost in long distance transmission. Power is usually transmitted through overhead power lines. Underground power transmission has a very high cost and greater operational limitations. The main problem in the Power distribution is that electrical energy cannot be stored so it is generated based on the necessity. A control system is req uired to ensure electric power generations match the demand. Power generating plant low voltage is produced. The generator terminal voltage is then stepped up by the power station transformer to a higher voltage for transmission over long distances. Power Losses Transmitting 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 lower 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 constitute transmission and distribution losses. In an alternating current circuit, the inductance and capacitance 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. Reactive 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 transformed to a low voltage. Power Load balancing The transmission system provides for base load and peak 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 always take the base load and the peak load into consideration. The transmission system usually does not have a large buffering capability to match the loads with the generation. Thus generation has to be kept matched to the load that prevents overloading 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 control 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 diagram Electrical power system deals with the technology of generation, transmission and distribution of electrical energy. An electric power system consists of different subsystem are explained as follows I. Generation subsystem The conversion 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 subsystem The 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 system The sub-transmission network is the portion of transmission system connected to the high voltage substations using transformers. IV. Distribution subsystem By 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 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 subsystem This subsystem is formed by relays, switch and other control elements to protect other subsystems 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 Step-up 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. Earthing The 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 above its designed level. To provide safety to operating personal To avoid fire hazard due to leakage current. Representation of the transmission line A transmission line has series resistance, series inductive reactance, shunt capacitance and leakage resistance which are distributed evenly along its length. 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 valid for unloaded lines when the shunt capacitance dominates. Power system analysis is required for a large number of different purposes System design and control to maintain 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 circuit breakers or fuses and that large fault currents cause the minimum of damage to the power system. Design of protection systems to ensure faulty circuits are switched off rapidly (

Essays --

Page 1 James Earl Carter Jr. was a unique president not because of everything he has done as a president, but because of things he has done after his presidency. He has emerged as a champion of human rights and worked for charitable causes. Carter worked with Habitat for Humanity International, an organization that works worldwide to provide housing for underprivileged people. Carter has served as a freelance ambassador for a variety of international missions, including soothing disputes between countries, observing elections in nations with histories of fraudulent voting processes, and advising presidents on Middle East issues. These are things that have set Jimmy Carter apart from all the presidents that the United States has had. During Carters presidency he also faced something that we were not easy for him. Carter could point to a number of achievements in domestic affairs. He dealt with the energy shortage by establishing a national energy policy and by decontrolling domestic petroleum prices to stimulate production. He prompted Government efficiency through civil s...

Mcdonald’s and Kfc: Recipes for Success in China

McDonald’s and KFC: Recipes for Success in China 1. Assess KFC’s strategy in China? What should KFC do next? KFC’s strategy in China firstly aimed to be the first leader in foreign quick –service restaurant. KFC differentiated itself from other local Chinese fast food restaurants by not only providing normal standard KFC foods but also offering customers with high quality service with different concept and ambiance. Moreover, KFC adapted itself in the foods variety to match with customer needs. Its menu localization brings the concept of â€Å"American brand with Chinese characteristics.People are significant resource for KFC. Thus, KFC started talent development since the first day it started by offering training and providing career growth within the company. This talent development program, later on, greatly supported the expansion of KFC in China successfully. During crisis, KFC created opportunities for itself by expanding aggressively in China. Neve rtheless, KFC developed its own logistics system with STAR system. The own logistics system helps KFC to lower the costs, control the quality and deliver products and services to customers faster.With all these strategic plans, KFC succeeds in China greatly. To compete with other foreign fast foods which are coming to China in the near future, KFC should consider backward integration. KFC may set up its own farm to raise its own chickens and other major ingredients in order to control the quality and safety of the materials. This farm will be the only supplier for all the franchised KFC stores in China in order to control the quality and standards of foods. KFC should also set up training center.All the employees should be trained here and hence, to control the quality of the services in different stores. Nevertheless, in order to gain customers trust and loyalty, KFC should also focus on CSR (Corporate Social Responsibility) to show its concern of brining the best quality foods to customers while protecting environment and society. KFC should maintain its core competency of its products while keep developing its food innovations to reach its changing customers preferences and cultures. 2. Assess McDonald’s strategy in China?What should McDonald’s do next? McDonald strategy in China was to maintain the first world standards as a global brand. It focused to keep its quality of food consistency and food preparation process. It first kept the food menu instead of adaptations to local preference. With this strategy, McDonald did not gain great success at the beginning as KFC did. However, it gradually learned to adapt to local preferences by offering different menu to match with customer needs. It also expands in China through joint venture or sole proprietor instead of franchising.It also took a strategic move to link with China’s SinoPec and build drive-through outlets. It offers convenience to customers by offering 24-hour service. Though, it didn’t use aggressive expansion, gradual expansion of McDonald helps it learn and develop itself steadily in the long term. In order to compete with other fast foods business in China, McDonald should keep its core competence of high quality standards. However, it should also start its R&D center in China in order to understand Chinese market and hence, to offer the right products to match with customer needs.This may be done through more variety of foods. To maintain high quality of products, McDonald had fewer suppliers who could meet its standard. This might bring higher costs to McDonald. In order to compete in the long run, McDonald should find lower-cost source of materials. Similarly to KFC, it should consider backward integration to have its own farm to be its source of major raw materials and ingredients. This will not only result in lower costs but also in higher quality of the raw materials.Moreover, with the concept of 24-hour service, McDonald should consi der to have more variety of foods such as night meal which may include warm milk or smaller-size burger, more variety of salads instead of only heavy big meal. It should also try to differentiate itself from other restaurants by offering different services such as delivery service, fast-process-time-guarantee service (this is to ensure its fast service), and nice ambiance (as it also opens at night, instead of providing normal counter seats, McDonald may offer the sofa seats so that customers can come and relax, work or have a small meeting here).With this concept, customers may not only perceive McDonald as a fast food restaurant but more like a cafe or nice informal meeting point with their friends and colleagues during both rush hour and non-rush hour. This may help McDonald to capture more customer groups and hence generate more revenues.

The Deregulation Of The Electricity Market - 1556 Words

What deregulation means The term liberalization or deregulation generally refers to the â€Å"abolition of rights of monopolies, creating a competitive market that guarantees fair prices for the consumers and efficient economic cost of supplying electricity. Three economic conditions are a â€Å"prerequisite† to a competitive market in order to achieve a successful transformation from a highly regulated monopolistic to a transparent and deregulated market: - Free consumer choice: consumers must be able to freely choose their electric energy supplier after having compared prices and services of competing electricity supply companies), - Third party access (TPA): free and competitive market has to guarantee unimpeded access to transmission and distribution networks for companies which do not own them. Otherwise, competition in the electricity market would not be possible due to the physical characteristics and the natural monopolistic market design within the sector - Unbundling: transmission and distribution networks have to be separated from the generation and retail business of vertically integrated utilities Description of the electricity market First of all, it is to mention that the electricity sector is a comparatively complex one. 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