File Name: electrical power system generation transmission and distribution .zip
Premium Membership. Learn from experienced power engineers. The purpose of the electric transmission system is the interconnection of the electric energy producing power plants or generating stations with the loads.
Transmission & Distribution
An electric power system or electric grid is known as a large network of power generating plants which connected to the consumer loads. Electrical energy is a form of energy where we transfer this energy in the form of flow of electron. So, electrical energy is obtained by converting various other forms of energy.
Historically, we have done it from chemical energy using cells or batteries. However, as the invention of generator had occurred, it became the technique to first convert some form of energy into mechanical form of energy and then converting it into electrical form of energy using generator. Generators produce two type of power AC and DC. Electrical energy has grown immensely over two centuries because the flexibility it provides for its use.
The variety of use has led its demand to increase monotonously. However, as the load or demand has increased practically one requirement is consistent. That is, we must generate the amount required by the load at that very instant because this large amount cannot be stored for delivering this high amount of demand.
Therefore, the generation of electrical energy is happening simultaneously as we use it. In addition, our demand is always varying. Therefore, the generation is also varying with it. Apart from varying demand, the type of current we consume also varies.
These variations put many constraints and conditions. This is the reason of the complex and big control rooms across the whole power system. The lines network between Generating Station Power Station and consumer of electric power can be divided into two parts. We can explore these systems in more categories such as primary transmission and s econdary transmission as well as primary distribution and secondary distribution.
This is shown in the fig 1 below one line or single line diagram of typical AC power systems scheme. It is not necessary that the entire steps which are sown in the blow fig 1 must be included in the other power schemes.
There may be difference. The main objective of an electric power system is to obtain electrical energy and make it reachable safely to the load point where it is being used in usable form. This is done in five stages namely. The following parts of a typical power supply scheme are shown in figure 1. After these five levels, the energy must be available as the stated form in terms of voltage magnitudes, frequency and consistency.
Generation means the conversion of a form of energy into electrical energy. Transmission implies the transport of this energy to very long distance with very high amount of voltage magnitude. Moreover, distribution is fulfilling the demand of the consumers at certified voltage level and it is done in terms of feeders. Feeders are the small-small chunks of load distributed at different places, physically. The ordinary power plant capacity and generating voltage may be 11kV , But economically, it is good to step up the produced voltage from 11kV, Generation is the part of power system where we convert some form of energy into electrical energy.
This is the source of energy in the power system. It keeps running all the time. It generates power at different voltage and power levels depending upon the type of station and the generators used. The maximum number of generators generate the power at voltage level around 11kVkV. The increased voltage level leads to greater size of generator required and hence the cost involved.
Presently the generating stations we employ mainly over the world are following We generate electric energy through these power plants at different voltage levels and at different locations depending upon the type of the plant. They are used for different purposes viz. Accordingly, the plant is made to handle the load.
This categorization is important for the quality of power is being developed. It is also important for the fact that the power must be generated at the same instant when the load is taking up the power.
So, as we know the type of load and approximate amount of load at the station, different type of generating station is chosen. For example; Thermal plant, Hydel plant, Nuclear plant, Solar plant, Wind plant and Tidal plant are chosen to handle the base load on the system whereas Gas plants, Diesel plants are used to handle peak load demand.
This is mainly governed by the nature of the time they take in the process of starting the delivery of power. Base load plants take more time in delivering the power whereas peak load plants must start very fast to supply the demand.
The electric supply in kV , kV , kV or greater is transmitted to load center by three phase three wire 3 Phase — 3 Wires also known as Delta connection overhead transmission system. As the voltage level which is generated is around kV and the demand is at various levels of voltage and at very far away places from the generating station. For example, the generating station can be generating voltage at 11kv, but the load center is km apart and at the level of V.
Therefore, for the delivery of electrical energy at such a long distance, an arrangement must be there to make it possible. Hence, the transmission system is essential for the delivery of electrical energy.
This is made possible by using the transmission lines of different length. These are overhead transmission lines in almost every cases. Some exceptions occur when it is needed to cross an ocean. Then there is a compulsion to use underground cables. But, as the system grew and load demand increased, the challenge in this process has become very complex.
At low voltage level, the amount of current flowing through the line for high load demand is more and hence the voltage drop due to the resistance and reactance of the transmission line is very significant. This leads to more losses in the transmission lines and the decrease in the voltage at the load end.
This affects the cost of the system and the working of the equipment the consumers use. So, transformer is used to increase the voltage level at certain values ranging from kV to kV. This makes the current value lesser for the same load that would be having higher values of current at certain load. The current value can be calculated using formula This system connects multiple generating stations generating voltage at different levels being connected together as a combined system.
This makes the system to reach out to various load centers and this provides a great system of having higher reliability. Presently, this system has grown to size of a country. One more system is being used now a days is the use of HVDC.
HVDC is used for greater distances and sometimes used to connect two grids of different voltage or frequency levels. HVDC also provides lower corona losses, lower communication interferences, elimination of inductive effect and elimination of frequency of operation.
Transmission lines vary in sizes. This size determines its characteristics and its behavior in the system. For example, in long transmission lines the voltage at the consumer end becomes higher than its rated value during light load condition due to the dominating capacitive nature of the transmission lines.
Area far from the city outskirts which have connected with receiving stations by lines is called secondary transmission. At a sub station, the level of secondary transmission voltage kV, 66 or 33 kV reduced to 11kV by step down transforms. Generally, electric supply is provided to those heavy load consumer commercial power supply for inductries where the demands is 11 kV, from the lines which caries 11kV in three phase three wire overhead system and they make a separate sub station to control and utilize the heavy power in industries and factories.
In other cases for heavier load consumers at large scale , the demand is upto kV or 33 kV. So electric supply provided them directly by secondary transmission or primary distribution in kV, 66kV or 33kV and then step down the level of voltage by step-down transformers in their own sub station for utilization i. When the transmission lines get closer to the demand centers, the voltage level is reduced to make it practical to distribute at different places of load. Therefore, power is taken from the grid and stepped down to kV , depending upon the places where it is being delivered.
This is then transmitted to substations. For example, the system voltage at substation level in India is 33KV. Many control mechanisms are provided in the substations to make the power delivery a controlled and continuous process without much disturbance.
These feeders are in towns, cities, or villages or it may be some group of industries, which takes the power from the substation, and convert its voltage level according to its own use. For domestic use , the voltage is further reduced at VV phase to ground to be used by the individuals at different power factor.
The combined amount of demand is the load on the entire system and that must be generated at that instant. Depending upon the scheme of the distribution system, it is categorized as radial or ring mains. It gives different degree of reliability and stability to the system. All these systems are protected using various protection schemes comprising of circuit breakers, relays, lightening arresters , ground wires etc.
Electric power is transferred by from primary distribution line i. These transformers called Distribution transformers , three phase four wire system 3 Phase — 4 Wires also known as Star connection. Residential load i. Fans, Lights, and TV etc may be connected between any one phase and neutral wires, while three phase load may be connected directly to the three phase lines. In short, secondary power distribution may be divided in three sections such as , feeders, distributors and service lines details below.
The entire structure of the power system is consisting of the source Generating station , transfer Transmission and Distribution and the load Consumer. The objectives are These all objectives are met by using different sets of generating stations, transmission systems, distribution systems and the enhanced quality of safety equipment.
At any instant, our load varies in different magnitudes. Therefore, for following the demand, the generation must change and catch up the demand. For this purpose, there are many control mechanisms like governing valve in thermal plants, control rods in nuclear plants, which changes the amount of power, which is being generated.
Electric Power Systems Research
Electric power distribution is the final stage in the delivery of electric power ; it carries electricity from the transmission system to individual consumers. Distribution transformers again lower the voltage to the utilization voltage used by lighting, industrial equipment and household appliances. Often several customers are supplied from one transformer through secondary distribution lines. Commercial and residential customers are connected to the secondary distribution lines through service drops. Customers demanding a much larger amount of power may be connected directly to the primary distribution level or the subtransmission level. The transition from transmission to distribution happens in a power substation , which has the following functions: .
An electrical grid , electric grid or power grid , is an interconnected network for delivering electricity from producers to consumers. It consists of: . Electrical grids vary in size from covering a single building through national grids which cover whole countries to transnational grids which can cross continents. Power stations connected to grids are often located near energy resources such as a source of fuel or to take advantage of renewable energy resources, and away from heavily-populated areas. A bulk-power transmission network is therefore used to move the power long distances, sometimes across international boundaries, until it reaches its wholesale customer usually the organisation that owns the local electric power distribution network.
Emphasis is given to create a clear mental picture of a power system to a beginner of the course Electrical Technology. As consumers, we use electricity for various.
Transmission & Distribution
There are three stages of electric power supply; generation, transmission and distribution. Each of these stages involves distinct production processes, work activities and hazards. Most electricity is generated at 13, to 24, volts. The hazards of the electrical power generation process include explosions and burns resulting from unexpected equipment failure. These procedures are in place to control energy sources.
Electricity generation and transmission concept
Not a MyNAP member yet? Register for a free account to start saving and receiving special member only perks. Growing loads and aging equipment are stressing the system and increasing the risk of widespread blackouts. Modern society depends on reliable and economic delivery of electricity. Moreover, effective and significant utilization of intermittent renewable generation located away from major load centers cannot be accomplished without significant additions to the transmission system. In addition, distribution systems often are incompatible with demand-side options that might otherwise be economical.
На самом деле я его не продала, - сказала Росио. - Хотела это сделать, но она совсем еще ребенок, да и денег у нее не. Вот я его и отдала. Но если бы знала, сколько вы мне за него предложите, то сохранила бы это кольцо для. - Почему вы ушли из парка? - спросил Беккер. - Умер человек.
Расстояние между ним и Беккером быстро сокращалось. Он нащупал в кармане пиджака пистолет. До сих пор Дэвиду Беккеру необыкновенно везло, и не следует и дальше искушать судьбу. Пиджак защитного цвета от него отделяли теперь уже только десять человек. Беккер шел, низко опустив голову. Халохот прокручивал в голове дальнейшие события. Все было очень просто: подойдя к жертве вплотную, нужно низко держать револьвер, чтобы никто не заметил, сделать два выстрела в спину, Беккер начнет падать, Халохот подхватит его и оттащит к скамье, как друга, которому вдруг стало плохо.
ГЛАВА 115 В голове Дэвида Беккера была бесконечная пустота. Я умер. Но я слышу какие-то звуки.
- Когда мистер Беккер найдет ключ, он будет вознагражден сполна. ГЛАВА 22 Дэвид Беккер быстро подошел к койке и посмотрел на спящего старика. Правое запястье в гипсе.
Не может быть? - повторил он, сохраняя ледяной тон. - Может, пройдем, чтобы я смог вам это доказать. - Не стану вас затруднять, - ухмыльнулась она, - благодарю за предложение.
Вызвать доктора. Беккер поднял глаза на усыпанное родинками старческое лицо. - No, gracias. Estoy bien. Человек смерил его сердитым взглядом: - Pues sientate.