Power supply to mining plant
- Added: 29.07.2014
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I. Electrical section
1.1. Brief description of electromechanical plant and electric power receivers
1.2. Classification by degree of uninterrupted power supply and characteristics of workshop environment
1.3. Determination of design or consumption capacity of an industrial enterprise for all components
1.4. Voltage selection of supply and distribution networks
1.5. Selection of number and power of GPP transformers
1.6. Load Mapping and Electrical Load Center Definition
1.7. Selection of quantity and location of shop substations, their type, quantity and power of TC transformers
II.Preparation of power supply diagrams (3 variants)
2.1. Selecting the Section of Supply and Distribution Networks
2.2. Technical and economic calculation and selection of power supply scheme
List of used literature
A power supply system is called a set of devices for the production, transmission and distribution of electricity. Power supply systems of industrial enterprises are created to provide power to industrial receivers, which include electric motors of various machines and mechanisms, electric furnaces, electrolysis plants, devices and machines for electric welding, lighting plants and other mechanisms.
The task of power supply to industrial enterprises arose simultaneously with the widespread introduction of an electric drive as the driving force of various machines, mechanisms and the construction of power plants. The need for power generation at factory power plants is due to the following reasons:
a) the need for heat for technological purposes, heating and the efficiency of associated electricity production;
b) the need for backup power supply for essential consumers;
c) the need to use secondary resources;
d) the great distance of some enterprises from the power system.
All machines and mechanisms of enterprises are currently operated by electric motors. For their normal operation, electricity is accepted as the most flexible and convenient form of energy that ensures the operation of production mechanisms. At the same time, electricity should have the appropriate quality, namely frequency and voltage stability.
Modern production is subject to high requirements in the training of specialist engineers in the field of industrial electricity supply; at the same time, there is a growing demand for engineers with knowledge in the field of automation and computer technology.
I. Electrical section
1.1. Brief description of industrial
enterprises and electric power receivers
Today, the main activity of the mining plant is the development and manufacture of equipment for the mining industry.
At the mining plant, the main receivers are steel, woodworking, iron foundry, blacksmith and mechanical repair shops. In the mechanical repair shop, the main receivers of electricity are metal cutting machines. Metal cutting machines are designed for machining metal products with the help of cutting tools. Depending on the process that determines the method of processing, the shape of the surface formed, the nature of movement, the type of tool and the workpiece, metal cutting machines are divided into groups, the main of which are turning, strict, milling, drilling, grinding.
By the nature of the organization of the production process, machine tools are distinguished: universal, on which various operations are performed, for example, turning, thread cutting and others in the processing of products of many names: wide-ranging, on which certain operations are performed, for example, drilling, building and others.
Heavy machines usually operate in a long-term mode with variable load, and light and medium machines in a re-short-term mode.
The group of lathes includes simple and universal screw-cutting and turret, special, as well as frontal and carousel. On lathes process external, internal and face surfaces and also make undercutting, to a piece, slotting, drilling of openings and cutting of a carving. Face surfaces are machined on frontal machines.
The group of strict (woodworking) machines includes cross-strict, longitudinal-strict and long-term machines. A characteristic feature of strict machines is the reciprocal movement of a cutter or part with a construction mode at direct stroke and the implementation of intermittent transverse feeding after each single or double stroke of the cutter or part.
Distribution line voltages
The voltage selection of the distribution network is closely related to the solution of power supply issues of the enterprise. The final decision is made as a result of a technical and economic comparison of options that take into account the difference in the combination of voltages of individual links of the system.
A voltage of 35 kV is used to power medium-capacity enterprises and to distribute electricity to the first stage of electricity supply of such enterprises using deep inputs. At high-power enterprises, the voltage of 35kV is not rational to use as the main one. It can be used to power electricity consumers with a nominal voltage of 35 kV, and to power remote electric receivers.
The advantage of a 20 kV voltage over a 35 kV voltage is a simpler network arrangement and cheaper switching devices.
Compared to 10 kV voltage at 20 kV voltage, power losses in the components of the power supply system and short-circuit currents in the networks are reduced. However, a voltage of 20 kV, like a voltage of 35 kV and 10 kV, is not advisable to use as the main voltage.
10 and 6 kV voltage is widely used in medium-capacity industrial enterprises - for supply and distribution networks, in large enterprises - in the second and subsequent stages.
A voltage of 10 kV is the most economical compared to a voltage of 6 kV. 6 kV voltage is allowed only if the plant is dominated by a load with a voltage of 6 kV or when a significant part of the load is supplied from the factory CHP, where 6 kV generators are located.
a) If the percentage of high-voltage load with a voltage of 6 kV to 30%, then the voltage of 10 kV distribution lines, we accept 10/6 lowering transformers.
b) If the percentage of high-voltage load is greater than 30%, the distribution voltage shall correspond to the high-voltage load voltage.
The voltage of the distribution lines for the designed version is 10 kV because at this facility the percentage of high-voltage load of 6 kV is up to 30%.
Defining a Conditional Center of Electrical Loads
Currently, there are a number of mathematical methods that allow you to analytically determine the center of electrical loads (CEN) of both individual workshops and the entire industrial enterprise. Among them, three main methods can be distinguished.
The first method, using some positions from the course of theoretical mechanics, allows you to determine the CEN of the workshop (enterprise) with greater or lesser accuracy (approximately) depending on specific requirements. So, if you consider the loads of the workshop evenly distributed over the area of the workshop, then the center of the loads of the workshop can be taken to coincide with the center of gravity of the figure depicting the workshop in plan. If you take into account the actual distribution of loads in the workshop, then the center of loads will no longer coincide with the center of gravity of the workshop figure in plan, and finding the center of loads will reduce to determining the center of gravity of mass.
The presence of multi-storey workshop buildings determines the accounting of the third coordinate (Zi) in the calculations.
II. Drawing up of internal power supply diagrams
(in three versions)
A characteristic feature of intra-plant power distribution schemes is the large branching of the network and the presence of a large number of switching protection equipment, which has a significant impact on the technical and economic indicators and on the reliability of the power supply system. In order to create a rational power distribution scheme, a comprehensive accounting of many factors is required, for example, such as the design of network nodes of the scheme, the method of sewage of electricity, short-circuit currents in various versions, etc.
When designing a circuit, it becomes important to correctly solve power and lighting loads at night, on weekends and holidays. For mutual redundancy, it is recommended to use bus and cable jumpers between the nearest substations, as well as between the ends of low voltage networks supplied from different transformers.
In general, intra-plant power distribution schemes have a stepwise construction. It is considered inappropriate to use circuits with more than two stages, since in this case the switching and protection of the circuit becomes more difficult. In small enterprises, it is recommended to use single-stage schemes.
The power distribution scheme shall be connected to the object process diagram. Power supplies for electric power receivers of different parallel process flows should be carried out from different sources: substations, RP, different sections of buses of the same substation. This is necessary so that both process flows do not stop in case of an accident. At the same time, interconnected process units must be connected to one power source so that when the power supply disappears, all power receivers are simultaneously de-energized.
When constructing a general scheme of in-plant power supply, it is necessary to accept options that ensure rational use of switchgear cells, minimum length of the distribution network, maximum savings in switching protection equipment.
Select Plant Distribution Network Diagrams
Intra-plant distribution of electric power is performed according to main, radial or mixed scheme. The choice of the scheme is determined by the category of reliability of electricity consumers, their territorial location, and the features of operating modes.
Radial circuits are those in which electricity from the power source is transmitted directly to the receiving point. Most often, a radial circuit is used with a number of stages of no more than two.
Single-stage radial circuits are used in small-capacity enterprises to power concentrated consumers (pump stations, furnaces, converter units, workshop substations) located in various directions from the power center. Radial diagrams provide deep partitioning of the entire power supply system, starting from power supplies and ending with prefabricated buses up to 1 kV of workshop substations.
Power supply of large substations and substations or RP with the predominance of category I consumers is provided by at least two radial lines departing from different sections of the power supply.
Separately located one transformer substations with a capacity of 400630 kVA are powered on single radial lines without redundancy, if there are no consumers of the first and second categories and according to the conditions for laying the line, its quick repair is possible. If separate substations have consumers of category II, then their supply should be carried out by two cable lines with disconnectors on each cable.
Main power distribution circuits are used when many consumers and radial circuits are not suitable. The main advantage of the backbone circuit is the reduction of switching links. It is advisable to use them when the substations are located on the territory of the enterprise, close to linear, which contributes to the direct passage of the main line from the power source to the consumer and thereby reduces the length of the main line.
The disadvantages of the main circuit are lower reliability since one transformer substations can be reserved at a lower voltage when they are supplied along one line. It is recommended to supply from one line no more than two or three transformers with a capacity of 25001000 kVA and no more than four or five with a capacity of 630250kVA.
There are many varieties and modifications of trunk schemes, which, taking into account the degree of reliability, are divided into single and double through.
In practice, only radial or trunk ones are rarely used, since in such schemes they do not meet the best technical and economic indicators. Therefore, most often mixed schemes are used. The combination of mainly radial and main circuits makes it possible to create power supply systems with the best technical and economic indicators.
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