Mill agricultural complex - power supply

Contents

Introduction

1 Brief description of Agrocomplex CJSC

2 Brief description of the design object

3 Selection of electrified process equipment

4 Calculation and selection of ventilation and heating systems

4.1 Calculation of mill ventilation system

4.2 Heating system calculation

5 Calculation and selection of electrical installations of electric lighting systems

5.1 Selection of normalized illumination and type of lighting fixtures

5.2 Calculation of shop room lighting

6 Calculation and selection of wiring of internal lighting and power networks

6.1 Calculation and selection of internal group wiring

lighting networks

6.2 Calculation and selection of wiring of internal power networks

7 Calculation and selection of start-up equipment. Accounting of electric power consumption

7.1 Calculation and selection of circuit breakers

7.2 Calculation and selection of magnetic starters and thermal relays

7.3 Selection of power panels

7.4 Accounting of electric power consumption

8 Check of selected start-up equipment

8.1 Calculation of short-circuit currents

8.2 Check of selected start-up equipment

9 Power supply system development

9.1 Calculation of electrical loads

9.2 Reactive power compensation

9.3 Selection of TP power and type

9.4 Calculation of 0.4 kV line

10 Development of electric motor protection device from emergency operation modes

10.1 Terms of Reference

10.2 Technical Specifications

11 Operation of electrical equipment

11.1 General issues of electrical equipment operation

11.2 Calculation of required number of electricians for mill maintenance

12 Economic efficiency of electric motor protection device from emergency operation modes

13 Life safety and environmental friendliness of the project

13.1 TB Technical Measures

13.2 Organizational measures for TB

13.3 Project Environmental Friendliness

13.4 Explosion and fire safety

Conclusion

List of literature used

Applications

Introduction

One of the main conditions for the success of any production is its technical equipment. However, in most industries, there are many examples where highly equipped industries give way to lower-capacity enterprises for technical reasons. Such industries currently include grain processing, where a significant part of industrial capacity is systematically idle. At the same time, it is no secret that agricultural flour produces about half of all produced flour and cereals. The situation described is an illustration that the technical policy of an established or existing enterprise cannot be limited to the level of its equipment. In our opinion, there is a question of the production format, understood as a lot of mutually agreed technical elements (processing depth and energy intensity, assortment width and capacity in each of its sectors, the degree of development of supporting communications and the level of process management, etc.), linked into the system by unified marketing goals and objectives. On this basis, technical policy should focus on ensuring a format of production that best meets the market prospects of the enterprise.

Domestic grain processing has been working for a long time and is likely to work in conditions of lack of stability. But the most important thing is the limited implementation by scale of the only truly reliable partner - a saturating internal market. It is clear that in such a situation, the structure of grain processing will be represented by a dozen enterprises of national scale, supported by state orders with corporate "binding" to large consumers and a number of enterprises of regional scale, prevailing in terms of total volumes of products.

Grain processing, from the point of view of economic expediency, gravitates to the places of grain production, which are also places of accommodation of cheap production areas and labor. At the same time, in terms of the sale of their products, such productions are aimed at large urban consumers. Given the constant increase in the cost of transportation, these trends will be aggravated. In addition, the creation of efficient grain processing industries, taking into account the level of their technical complexity and capital intensity, is quite "by the teeth" of regional business. Therefore, trade in Odessa, for example, Kiev flour testifies not so much to the success of Kiev flour, as to the non-rigidity of Odessa regional business.

Thus, the task of the overwhelming number of enterprises will be to ensure regional leadership in equal conditions of competition. The format of such productions should provide at least: "lavishing" within several "strong" items of the assortment, strict minimization of energy and raw material costs, a timely reaction to changing conditions and rapid filling of emerging product categories. At least, the immediate future of domestic flour is visible for today in this way. This path will probably be the most natural and rational if, in favor of someone's private interests, some other forms are not imposed by force.

In our opinion, existing mills and grits according to their equipment can be conditionally divided into three groups:

A. Industrial industries with complex processing schemes, typically over 100 tonnes per day;

B. Industries carrying out processing according to abbreviated schemes using industrial equipment, with a capacity of mainly up to 1000 t/day;

B. Small-capacity mills and grits with individual circuits and equipment.

Group A enterprises are overwhelmingly a legacy of the past. Such production is based on schemes and equipment (including "reproducible") developed more than half a century ago. However, moral and physical deterioration is not the main obstacle to their work. The enterprises in question were created in a different political and economic situation, in order to achieve marketing goals that are not characteristic of market relations. For their claims to GOSTOV quality and the "high coefficient of use of raw materials," such productions are forced to pay for increased energy intensity, inertia of "multi-tonnage," high operating costs. The reason for this is the excessive saturation of the technologies used with equipment, accessories and communications, which is the main negative feature of the traditional solutions introduced in some places today.

Group B production was created mainly after restructuring, but today it is they who produce more than half of all flour and cereals. Mini-industries are characterized by small investment in construction, low processing costs and flexibility, which so far ensures their competitiveness in some places. However, the vast majority of such industries are extremely primitive schemes, hastily equipped with the same primitive machines, produced, oddly enough, mostly by machine-building plants. Owners of such "capacities" are faced with intractable problems of yield and especially quality of products, which are aggravated as the market becomes saturated, which is characteristic of artisanal production. In addition, most of the enterprises in question are below the minimum productivity limit, which does not allow for the organization and full maintenance of the technological process, laboratory control and accounting. It seems that the formation of an entire industry called "agricultural flour mill" took place without the participation of flour scientists .

The intermediate position between the groups of enterprises considered is occupied by relatively recent small-scale production, which was created by "truncating" traditional processing schemes and equipped with domestic and foreign industrial equipment. The experience of Ukrainian processors operating such facilities (including those produced by foreign companies) shows that their authors did not have up-to-date knowledge and experience in creating such industries. Built on the basis of assumptions, mills and grits immediately required serious improvements and adjustments. However, these productions have in most cases been brought to yields, energy costs and quality ratios that give them significant advantages over Group A and Group B.

The analysis allows you to consider Group B enterprises as the main applicants for regional leadership. However, most of the Group A industries that are not national producers, as well as some Group B enterprises that will "outgrow" local markets, will be "formatted" at the regional level. These processes will entail the inevitable necessity of technical re-equipment of group A and B plants and additional equipment of group B.

The creation of production of a format that did not exist earlier by "adapting" equipment within the framework of schemes and cargo flows that were not characteristic of them cannot be a progressive way of development. Truly highly efficient production, as a new format, requires the development of appropriate technologies, schemes and equipment. It is quite true that such work should be carried out with the maximum use of domestic and foreign knowledge and experience, up to the use, where warranted, of existing technological solutions and machines.

. brief description of the design object

The mill is located on the domestic territory of the feed mill. Mill capacity is 100 t/day with three-day operation 300 days a year.

The mill belongs to the second category of power supply. Electric receivers of category II are recommended to be supplied with electricity from two independent mutually redundant power sources. Category II electric receivers are energized by one HF, including with a cable insert, if emergency repair of this line is possible for a period of not more than 1 day. Cable inserts of this line must be made by two cables, each of which is selected according to the longest current of the HF. Power supply of category II electric receivers is allowed along one cable line consisting of at least two cables connected to one common set. If there is a centralized reserve of transformers and it is possible to replace the damaged transformer for not more than 1 day. power supply of electric receivers of category II from one transformer [16]

Operation of the mill is provided by the operator from the central control panel or computer.

The mill building was built in 1982. Now the need for major repairs and reconstruction is ripe. Reconstruction and repair are carried out in stages.

It is necessary to replace the technological with a more modern one, which will stabilize the work of production. Regular mill stops until the machine is replaced will stop. Reconstruction of the mill is carried out without stopping the technological process of flour production.

Heating, ventilation and lighting equipment, wiring of power and lighting networks, as well as commissioning equipment also need to be replaced.

The installed power of electrical power stations after reconstruction will be 207.32 kW, which is 18 kW lower than before reconstruction. This will reduce the energy consumption of the process without reducing productivity.

To work at the mill, four people are required in the grain preparation department, four in the grinding room. The mill is headed by the head of the flour production site. Products are recorded by an accountant. Using an electric motor protection device will reduce downtime due to equipment failure and reduce repair costs.

7.3. Selection of power panels

As power board ShchS1 and ShchS2 we accept board BU33311UHL4, with the device on input. As lighting guards we accept ShchRN24 guards. As automatic control boards, we accept PDU boards made in accordance with the installed equipment.

7.4. Accounting of electric power consumption

Currently, meters with an accuracy class of at least 1.0 can be used for commercial accounting of electricity. Measurement and accounting of consumed electric energy is carried out by electric induction meters. Modern meters are divided into electromechanical, electronic and electronic with a mechanical meter. Electromechanical meters are the most common at the moment. They are most reliable, capable of withstanding long-term overloads, but have a number of drawbacks: measurement accuracy is significantly influenced by voltage fluctuations in the network, low temperatures. Electronic meters are free from these drawbacks, but have less resistance to overloads, in addition, they are easily disabled, and it will be impossible to restore meter readings. This fact significantly reduces the scope of such meters and some organizations do not allow their use for commercial accounting. Electronic meters with a mechanical counting device with all the advantages of electronic ones, keep the readings of the counting device yes after failure.

Counters are divided into single-phase and three-phase, which are two modifications - for a three- and four-wire network, the latter are divided into active and reactive energy counters. Payment for consumed electricity is made in accordance with the established tariffs. There are single, two-rate and time rates. For this enterprise, the most acceptable option is a two-rate tariff. It consists of an annual payment for each kW of the maximum power declared by the consumer, participating in the maximum load of the power system and a fee for each kWh released to the consumer of active energy.

When calculating with enterprises, surcharges and discounts to the tariff for compensation for reactive capacity are used.

The design current intensity at the input to the building is 285 A. For installation at the input to the BRU, we install an active energy meter SET42, two-tariff, accuracy class 1.0, the maximum current 100A to be taken into account, connected through the current transformer.

10 development of the device for protection of electric motors from emergency modes

Short-circuited asynchronous motor is considered the most reliable electrical machine. In practice, however, there is a relatively high rate of failure. This is mainly due to the fact that during operation there are conditions for which the machine is not designed during design. Statistical material collected in a number of research organizations and universities indicates that 20-25% of electric motors have to be replaced annually in individual collective farms and state farms. High accident rate of electrical equipment causes great damage to production. [25]

Due to its simple design, high reliability and low cost, an asynchronous motor with a short-circuited rotor (hereinafter referred to as BP) is the most common motor. Over 85% of all electrical machines are three-phase asynchronous motors. According to statistics, at least 50 million units of three-phase BP with a voltage of 0.4 kV are now in public production in Russia.

BP are usually designed for a service life of 15-20 years without major repairs, provided they are properly operated. However, in real life there is a significant deviation from the nominal operating conditions. These are, first of all, poor quality of supply voltage and violation of technical operation rules: technological overloads, environmental conditions (increased humidity, temperature), reduced insulation resistance, cooling failure. As a result of such deviations are emergency modes of BP operation. As a result of accidents, up to 10% of the used electric motors fail annually. Failure of BP leads to severe accidents and large material damage associated with the downtime of technological processes, elimination of the consequences of accidents and repair of a failed electric motor. It is obvious that the application of reliable and effective protection against emergency modes of operation will significantly reduce the number and frequency of emergencies and extend the life of BP, reduce power consumption and operational costs.

AD accidents are divided into two main types: mechanical and electrical. Mechanical accidents are: deformation or breakage of the rotor shaft, weakening of the stator core attachment to the bed, weakening of the rotor core compression, melting of the babbit in the sliding bearings, destruction of the separator, ring or ball in the rolling bearings, breakage of the impeller, deposition of dust and dirt in the movable elements, etc.

Electrical accidents BP, in turn, are divided into three types :

network accidents (voltage accidents) related to accidents in the power grid;

current accidents related to the breakage of conductors in the windings of the stator, rotor or cable, turn-to-turn and phase-to-phase closure of windings, violation of contacts and destruction of connections made by soldering or welding; accidents resulting in breakdown of insulation as a result of heating caused by overload or short circuit currents ;

Accidents related to reduction of insulation resistance due to its aging, destruction or humidification.

Network accidents AD. Due to accidents at supply substations, short circuit in distribution networks, switching and lightning disturbances, non-uniformity of load distribution by phases, the actual values ​ ​ of a number of indicators are more than permissible, which leads to emergency modes of BP operation. According to statistics, up to 80% of motor accidents are directly or indirectly related to network voltage accidents.

Analysis of the electrical energy quality indicators (PCE) relative to the BP operating conditions shows that, for example, when the voltage in the network decreases, the stator current increases, leading to intensive heating of the BP insulation and a reduction in the service life due to accelerated aging of the insulation and its breakdown, and an increase in voltage leads to an increase in the magnetic flux of the stator, magnetization current, core heating (up to "fire" in steel) consumed from a reactive power network that reduces the power factor.

It should be noted that there are several other types of network accidents that occur most often, but are not directly regulated by GOST, since they are extreme cases of the manifestation of asymmetric modes of AD operation. This is a break in one of the phases, disruption of the phase sequence and "sticking" of the phases.

A phase break is usually associated with a break in the core of the supply cable, a burnt fuse or disconnection of the machine in one of the lines, or a break in the line itself. When connecting the motor windings with a star, the voltage in two phases is divided equally and is half of the linear Uf = Ul/2, in the third it is absent. Such modes lead to increased power consumption from the network, overheating of the stator windings. The field from the rotating one turns into a pulsating one, the current in the broken phase will be absent, in the other two it will increase by 50%. The engine does not turn even at idle. In some types of engines, in the event that a break occurred during engine operation, in the broken phase, the so-called "recovery" voltage is generated, close in phase and amplitude to the network, the engine goes into braking mode and, if it is not switched off, burns out within a few minutes .

The emergency mode of "sticking" phases occurs in the event of a break of one of the supply phases and its closure from the engine side to another phase. In this case, the same phase voltage is supplied to two phases of the motor, on the third remains normal. With insignificant amplitude asymmetry, significant phase asymmetry is observed, leading to the appearance of significant reverse sequence voltages that cause the engine to overheat and fail .

Violation of the sequence of phases A-B-C (B-C-A, C-A-B) fixed by GOST to any other causes a reversible mode of operation - rotation of the engine in the other direction, which is often unacceptable according to the process conditions, because it causes rotation of the drive mechanism in the other direction and can lead, in addition to the accident of the engine itself, to severe, sometimes catastrophic consequences .

Constant monitoring of the presence and quality of the mains voltage, including harmonic analysis, calculation of the current or average voltage values ​ ​ before the engine is turned on, monitoring of its state during the operation of the BP, including changes in the parameters of phase voltages caused by the operating modes of the engine itself, will often avoid the causes of emergency modes, prevent the phenomenon of short-circuit and current overload modes .

Current accidents AD. The voltage at the terminals of the BP and the phase currents flowing through its windings are closely interconnected, and any, even small, changes in the network voltage cause significant changes in the phase currents. To effectively protect BP, it is necessary to measure phase currents as accurately as possible. According to recent studies, the continuous operation of an engine with a current overload of only 5% of the nominal reduces its service life by 10 times. Due to the strong non-sinusoidity of the current curve, especially during starts, it has a large number of higher-order harmonics that have a significant effect on the value of the current current. Therefore, if you decide on the operation of BP not by calculated current values, but by some averaged signals or, even worse, by peak values, this can lead to false conclusions about the presence or absence of current overload .

There are two types of current overload AD: symmetrical and asymmetric. Symmetrical current overload is usually associated with mechanical overloads on the engine shaft. Their value is directly related to BP operation modes and thermal overload, which will be discussed below .

Most of the BP current accidents are primarily associated with damage inside the engine itself, leading to asymmetric current overload. In all cases of internal accidents of the electric motor, significant asymmetry of phase currents is observed, which exceeds voltage asymmetry several times. Therefore, constant monitoring of currents, the ratio of current skew to voltage skew allows you to accept fairly reliable conclusions about the presence of such accidents and quickly disconnect the engine .

Methods of protection against emergency modes .

In an effort to protect engines from emergency modes, from the middle of the last century, various relay protection began to be used in the energy industry: thermal, current, temperature, filter and combined. Many years of experience in the operation of BP have shown that most existing protections do not provide emergency-free operation of BP. So, for example, thermal relays count on a long overload - 25-30% of the nominal. But most often they work when one phase breaks at a load of 60% of the nominal. With a lower load, the relay does not operate and the BP continues to operate in two phases and fails as a result of overheating of the insulation of the windings. The correct selection of the protective device is an important factor in ensuring the safe operation of the BP.

BP protection devices can be divided into several types:

a) thermal protective devices: thermal relays, disconnectors;

a) current-dependent protective devices: fuses, automatic machines;

c) thermally sensitive protective devices: thermistors, thermostats;

d) protection against accidents in the electrical network: voltage relays and phase control, mains monitors ;

e) MTZ devices (maximum current protection), electronic current relays;

f) combined protection devices.

Modern standards in most countries of the world, including Russia, place increasing demands on the safe operation of asynchronous motors. High reliability and durability of BP are possible only if they are operated in nominal or close to them modes, which can only be provided by installing proper protection. All of these protective devices are used to quickly, within a fraction of a second, determine the nature and degree of damage to the engine and localize the emergency section by disconnecting it from the rest of the power supply circuit. But, at the same time, each of them has a number of significant shortcomings that affect the quality of their work: some are unjustified selectivity, others do not have adjustment from the start-up process, others do not respond to short-circuit currents or overload, etc. In order to select the protective device correctly, it is necessary to know how and from what accidents the particular device, the principle of operation and design features protect.

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