Chemical Plant Power Supply - Diploma

Contents

Contents

Introduction

Source Data

1. Calculation of electrical loads         

2. Selection of quantity variant and location of shop TPs, 

number and capacity of transformers         

3. Selection of external power supply scheme         

4. Selection of internal power supply scheme         

5. Calculation of short-circuit currents         

6. Check cables for thermal resistance         

7. Lighting Calculation and Cable Selection in Mechanical Repair Shop        

8. Selection of electrical devices of         GPP

9. Relay         protection

9.1. Protection of GPP transformers         

9.2 Protection of 10 kV cable lines

9.3. Protection of shop TP transformers

9.4. Condenser plant protection             

10. Safety and         Environmental Friendliness

10.1. Protection against exposure to harmful substances contained in the air      

10.2 Cleaning air emissions         

10.3. Noise and vibration protection         

10.4. Protection against electromagnetic radiation         

10.5. Thermal radiation protection         

10.6. Calculation of grounding devices

10.7. Calculation of lightning protection of         GPP

11. Economy         

11.1. Determination of estimated cost of power supply scheme         

11.2. Calculation of depreciation deduction amount         

11.3. Headcount planning         

11.4. Personnel Payroll Planning         

11.5. Preparation of estimates of annual operating expenses for maintenance of the enterprise energy farm         

11.6. Determination of cost of energy consumption within the enterprise         

11.7. Final technical and economic indicators of power supply         of the enterprise

Conclusion         

List of literature

Paper

Page  – ; Fig. -  ; east. - 12; Table      

Keywords:

POWER SUPPLY, MILL, CABLE LINE, TRANSFORMER, DISTRIBUTION SUBSTATION, AIR LINE, RELAY PROTECTION, GROUNDING.

The following sections were worked out in the diploma project: calculation of electrical loads for the enterprise as a whole and for the workshop; selection of external power supply scheme; selection of number and power of transformer substations; selection and calculation of internal power supply scheme; calculation of short-circuit currents; selection of protection devices and cables; calculation of relay protection and automation; calculation of internal electric network; BJD.

 Consumers of electric power of the enterprise are receivers of three-phase alternating current, voltage 0.38 kV and 10 kV, frequency 50 Hz .

In the course of the project, calculations of reactive power to be compensated were carried out, the selection of switches, disconnectors, current transformers, substation auxiliary transformer, OPN, relay protection equipment was carried out.

Introduction

One of the main tasks of the modern electric power industry is the rational construction of the power supply system. To ensure the continuity of the production process and the constant renewal of equipment, modern power supply systems must have increased reliability and flexibility, be highly economical and meet electrical safety requirements. 

Power supply systems of industrial enterprises are created to provide power supply to industrial receivers, which include electric motors of various machines and mechanisms, electric furnaces, electric welding devices and machines, lighting installations and other electrical equipment.

On the territory there are workshops of the main production, various auxiliary workshops, warehouses and administration buildings.

To select the number and location of shop TPs and the capacity of transformers, we calculate the electrical loads of the enterprise. For clarity and analysis of load placement in the territory, a load cartogram is built. Internal power supply diagrams are considered. Based on the calculations of short-circuit currents, electrical equipment and relay protection equipment are selected.

Main design and maintenance parameters: design maximum load, power factor, power consumption level for transmission and distribution (power loss), relay protection.

Task 10. Option 2

Topic: ″ Chemical Mill Power Supply ″

Design Input:

Mill Plot Plan Diagram (Fig.1). Dimensions: 650x490 m.

Information on electrical loads by workshops (Table 1).

The mill can be fed from the CHP and from the LEP110 kV passing at a distance of 12 km from the mill. 4 turbine generators with a capacity of 25 MW and a voltage of 10.5 kV are installed at the CHP. Generators operate in parallel in two sections. The CHP has a step-up substation with two transformers with a capacity of 16 MV⋅A and a voltage of 10.5/38.5 kV. 

The distance from the substation to the mill is 10 km.

Calculation of electrical loads

Calculated loads are determined by the method of ordered diagrams, that is, by using coefficients (Ku) and calculated power (Kp). 

Cartogram of electrical loads

The cartogram of electrical loads is a circle located on the general plan, the areas of which in the accepted scale are equal to the calculated loads of the workshops. Each workshop and site corresponds to a circle, the center of which is combined with the center of loads of the workshop, that is, a symbolic point of their electricity consumption. Therefore, the location of the main lowering, distribution and workshop substations near the loads supplied by them makes it possible to bring high voltage closer to the center of electricity consumption and reduce the length of both high-voltage networks of the enterprise and workshop electric networks. This leads to a decrease in the consumption of conductor material and a decrease in the loss of electricity in the power supply system.

1.5 Finding the center of electrical loads

The center of electrical loads for the enterprise is determined to find the location of the GPP. If other conditions are met, it is desirable to position the GPP as close to the center of electrical loads as possible. Active and reactive load centers can have different points. To find the center on the plot plan, temporary coordinate axes are applied. Then the coordinates of the center of electrical loads

Conclusion

During the calculations, the following results were obtained: the design capacity of the plant was 10470.7 kVA; for the repair and mechanical workshop, the total design capacity was 472.149 kVA. These data will allow you to select and check the electrical equipment of the power supply system, determine power and power losses, and estimate capital costs for the power supply system.

The load cartogram allows you to clearly see the electrical loads of the workshops: power and lighting, according to which the number and location of transformer substations and distribution points are determined.

The coordinates of the center of electrical loads according to the design data lie in the area of ​ ​ building No. 13, in which the vinyl acid workshop No. 2 is located. Since the access roads, which are normalized by 5-7 meters, as well as the standard overall dimensions of the substation, must be observed between the buildings and the GPP, it is not possible to place it in the center of electrical loads. Therefore, the GPP will shift towards the power source outside the territory of the enterprise.

2.1 Compensation of reactive power at  the GPP

Selection of compensating devices is carried out taking into account power losses in CTP.

For predesigns we accept TDN10000/35 transformers,

At the same time, the preliminary selection of power and voltage class is due to previously made calculations of the plant capacity.

Conclusion

During the calculations, they received that all consumers are fed from two-transformer TPs.

We accept that transformer substations will be of package type external installation. Reactive power compensation on the 0.38 kV side is not required.

Taking this into account, the calculations showed that on side 10 (kV) it is required to install 1 compensating device of the CC type - 10 - 900 U3.

Selection of external power supply scheme

To select the standard voltage stage of the supply line, it is necessary to take into account: the distance of electricity transmission from the system power centers (CPU) to the GPC, the amount of transmitted power, the voltages that the CPU has, the cost of electricity, as well as the voltage adopted for in-plant distribution of electricity. Using these input data, the issue is solved by comparing several options for the given costs .

 Four embodiments are possible:

   110K and GPP transmission;

   35Q and GPP transmission;

 transmission at 10 kV voltage via VL and FRG.

 transmission at voltage of 10 kv by CL and GRP.

Based on the relatively large plant capacity (Sp = 9881.78 kVA) and the distance to the system substation (1012 km), it can be assumed in advance that option No. 1 is the most suitable.

For 1 and 2 options transformers are chosen: TDN10000/35 and TDN10000/110.

Conclusion

To determine the most reliable and cost-effective power supply option, calculations were made to select the section of wires and cable cores based on technical and economic conditions, which include: heating conductors with design current, voltage and power losses in lines, economic section of the line. The cost-effectiveness criterion is the minimum cost.

The most economical option is VL110 kV. For power supply of the enterprise, we accept an overhead line for 110 kV with a wire AC- 70/11  , and two transformers of TDN grade are installed on the MPP - 10,000/110.

Selection of internal power supply scheme

Internal power supply can be performed according to radial and mixed schemes. The selection of the scheme is carried out according to technical and economic calculation, when comparing the options, the same elements of the schemes are not taken into account. Cable line for 10kV is made by AAB cable and 0.4 kV by APB cable laid in trenches.

Calculation of short-circuit currents

Initial for calculation are accepted version of power supply scheme, transformers of shop TC and MPP, wires and cables selected for installation. An equivalent substitution scheme is compiled, where only network elements that significantly affect the value of short-circuit currents are introduced, points of short-circuit are applied.

We bring the design scheme to the type of series-connected resistances. After that, separate the active and inductive resistances to the short-circuit point

Check cables for thermal resistance

The cable lines selected by economic current density and heating are checked for thermal resistance in case of short circuits. Cable temperature at three-phase steady-state short-circuit current I∞ shall not exceed 2500С.

Lighting Calculation and Cable Selection in Mechanical Repair Shop

Lighting in the workshop based on arc-turn lamps.

Lighting in the workshop is made by UPDDRL400 lamps with wide (W) light distribution with DRL400 gas discharge lamps.

 The workshop will be divided into four sections:

Section 1 (electric receivers 116);

Section 2 (electric receivers 1732);

Section 3 (electric receivers 3341);

Section 4 (electric receivers 4266).

The lamps must be arranged evenly, for this it is necessary to know the area of ​ ​ each section .

F1 = 17*27 =459 sq.m;

F2 = 17*28.8 =490 sq.m;

F3 = 17*27 =459 sq.m;

F4 = 17*28.8 =490 sq.m.

Finding the area, according to the directories we find lamps with a wide distribution of light, learning their specific lighting, divide it by the area and find the necessary number of lamps that need to be arranged evenly.

 Gas protection

   The use of gas protection is mandatory on transformers with a capacity of 6300 kV∙A or more, as well as on transformers with a capacity of 10004000 kV∙A that do not have differential protection or cut-off and if the maximum current protection has a time delay of 1s or more.   

   The effect of the protection is based on the fact that any, even minor, damage, as well as increased heating inside the transformer tank, cause the decomposition of oil and organic insulation, which is accompanied by the release of gas.

  The intensity of gas formation and the chemical composition of the gas depend on the nature and size of the damage. Therefore, protection is performed so that during slow gas generation a warning signal is given, and during violent gas generation, which occurs at K.Z., the damaged transformer is disconnected. In addition, the gas protection acts on the signal in case of a dangerous decrease in the oil level in the transformer tank.

9.2 Protection of 10 kV cable lines

Distribution networks of industrial plants with rated voltage of 635 kV have one-way power supply and are performed with isolated neutral. The most common type of protection of such networks is maximum current protection (MTZ). Against interfacial faults, it is recommended to perform such protection in a two-phase version and include it in the same phases throughout the entire network of this voltage in order to turn off in most cases double faults to the ground of only one fault site. This protection is carried out: 1) in the section of the line between the substation and the plant MPP with the protection of the supply substation, since the line length is small 2) in the section from the MPP tires to the workshop substations with the protection installed on the MPP.

Ground fault of one phase in networks with isolated neutral is not short-circuit. Therefore, the protection is performed acting on the signal and only when necessary according to the safety requirements acting on the shutdown.

Typically, ground fault current protection is performed by including zero sequence currents on the filter. It comes into effect as a result of zero sequence currents passing through the damaged section due to the capacity of the entire electrically connected network without taking into account the capacity of the damaged line.

Safety

10.1.Protection against harmful substances contained in the air

Ventilation is an organized and controlled air exchange that ensures the removal of air contaminated with harmful vapors, gases, dust from the room, as well as improving meteorological conditions in the workshops. According to the method of fresh air supply to the room and removal of contaminated ventilation system, it is divided into natural, artificial and mixed. As intended, ventilation can be general and local.

One type of natural air exchange is aeration, which is a natural organized controlled ventilation. The physical basis of such ventilation is thermal as well as wind pressure. Aeration, as a rule, is used in workshops with significant heat emissions, if the concentration of dust and harmful gases in the plenum air does not exceed 30% of the maximum permissible in the working zone. During aeration, air exchange is controlled using framugs located in the lower part of the building, through which usually colder air flows from the outside, and warm contaminated air exits through the exhaust lamp on the roof of the building.

Mechanical (artificial) ventilation ensures the maintenance of constant air exchange regardless of external meteorological conditions. Air entering the room is heated or cooled if necessary, moistened, drained or cleaned of dust. Cleaning of the air ejected from the outside is also provided. Mechanical ventilation can be plenum, exhaust, as well as plenum.

The plenum general exchange ventilation system takes air from the outside by a fan, supplies air to the heater, where the air is heated and moistened, and then enters the room. The amount of air supplied is controlled by valves and dampers installed in the branches. Contaminated air is displaced fresh through doors, windows, lights and slots of building structures.

The exhaust common ventilation system removes superheated and contaminated air through a network of air ducts using a fan. Clean air is sucked through windows, doors, looseness of structures. Contaminated air is cleaned before being ejected to the outside.

The supply and supply general exchange ventilation system consists of two separate systems - plenum and exhaust, which simultaneously supply clean air to the room and remove contaminated air from it. Plenum ventilation systems, in addition, compensate for air removed by local suction and consumed for technological needs.

Local ventilation provides ventilation directly at the workplace, and not in the volume of the entire workshop. It can be plenum and exhaust.

Protection of a person from harmful gases, steam and dust discharges provides for the device of local exhaust ventilation for the suction of poisonous substances directly from the places of their formation. Local suction is arranged structurally built-in and interlocked with the equipment so that the unit cannot be put into operation when the suction is turned off.

Air conditioning is the creation and maintenance in the working area of ​ ​ production rooms of constant or changing air medium parameters according to a given program, which is carried out automatically.

Air conditioners are full and incomplete air conditioning. Complete air conditioning units ensure constant temperature, relative humidity, mobility and cleanliness of air. In addition, ionization, ozonation, deodorization, etc., can be carried out. Partial conditioning units support only part of the parameters given.

The efficiency of the ventilation plant will be determined by technical tests before the start-up of the plant, and the installation quality, capacity, temperature and humidity of the supply air are checked periodically according to the schedule. During sanitary and hygienic tests, air cleanliness and meteorological conditions in the room are checked.

Individual means of protection. When working with poisonous and polluting substances, they use overalls - overalls, robes, aprons, etc., to protect against alkalis and acids - rubber shoes and gloves. To protect the skin of hands, face, neck, protective pastes are used: anti-toxic, oil-resistant, water-resistant. Eyes from possible burns and irritation are protected with glasses with a sealed frame, masks, helmets.

Respiratory organs are protected by filtering and isolating devices. Filtering devices are industrial gas masks and respiratory devices.

10.2 Cleaning air emissions

It is possible to prevent contamination of the air pool with poisons and dust removed from the production premises by passing contaminated air through special cleaning filtering and neutralizing devices; fumes after cleaning disperse in the atmosphere.

The sufficient height of the chimneys ensures the scattering of emissions over large areas, so that the concentrations of hazards in the atmosphere become insignificant.

Cleaning of air removed from the premises from dust can be thin, medium and coarse. Sometimes two-stage cleaning of exhaust and especially recirculation air from dust is used: large dust is caught at the first stage, and fine dust at the second stage.

The choice of a dust cleaner is determined by the dispersion and physicochemical characteristics of the dust. Significant considerations are the possibility of disposing of retained dust.

For fine cleaning, oil and paper filters are used, which are collected in installations from separate cells.

Coarse and medium and, in some cases, fine cleaning of air from dust used in exhaust ventilation plants is carried out in dust separators of various design. In dust settling chambers, the principle of dust deposition is based on a sharp decrease in the speed of movement of contaminated air in the chamber, where dust, losing speed, under the influence of gravity, settles to the bottom. In inertial dust separators, the direction of dust air movement changes dramatically, as a result of which the dust, hitting the walls, lose speed and drop into the dust collector.

In centrifugal dust separators (cyclones), contaminated air supplied to the annular space between the cylinders receives rotational movement. The dust is centrifugally pressed to the walls of the outer cylinder, lost speed and slid down the conical part into the hopper.

Finer air cleaning occurs in filters - oil, ultrasonic, electric. In electric filters along the axis of the metal grounded cylinder, a corona electrode is installed, to which a voltage of 50100 kV is supplied. When dust enters a strong electric field inside the cylinder, a negative electric charge is obtained from the coronating electrode and directed to the positive settling electrode, which is the cylinder. On the inner wall of the cylinder, the dust, having given its charge, is held by clutch forces. Settled dust is shaken off from the precipitator using a special mechanism without stopping the supply of voltage and air and is removed through the hopper.

Larger dust traps are easier, so they use simpler and cheaper dust collectors. It is advisable to enlarge the dust before supplying contaminated air to the treatment facilities. You can increase the size of the dust using ultrasound.

Purification of air from gaseous impurities is carried out by absorption (absorption of impurities by solid substances) or conversion of gaseous impurities to a liquid or solid state with their subsequent removal.

10.3. Noise and vibration protection

One of the main methods of reduction of noise on production objects is noise reduction in its sources - in electrical machines, machines, mechanisms, compressors, fans, etc. According to GOST 12.2.00374, the design of production equipment should ensure the elimination or reduction to the regulated level of noise, ultrasound, vibrations.

In mechanical devices, often the reasons for unacceptable noise are bearing wear, inaccurate assembly of parts during repairs, etc. Therefore, during the operation of all types of machines and mechanical equipment, it is necessary to accurately comply with all the requirements of the Maintenance Rules.

Construction codes and SNiP II1277 provide for noise protection by construction and acoustic methods, with the following measures to reduce noise levels:

a) sound insulation of enclosing structures; sealing along the perimeter of windows, gates, doors; sound insulation of crossing points of enclosing structures by engineering communications; device of soundproofed observation cabins and remote control of process equipment; noise source shelters and enclosures;

b) installation of sound absorbing structures and screens in rooms;

c) use of aerodynamic noise silencers, sound-absorbing lining in gas-air paths of mechanical ventilation systems and air conditioning systems;

As individual noise protection, special headphones, inserts in the auricle, and anti-noise helmets are used.

Protection of people from vibrations at workplaces, as well as equipment and building structures is carried out by the method of vibration isolation, by means of the device of elastic elements placed between the vibrating machine and the base on which it is installed. Steel springs or rubber gaskets are used as vibration absorbers.

To reduce the vibrations of casings, enclosures and other parts made of steel sheets, vibration absorption is used by applying a layer of rubber, mastic, plastics to the vibrating surface, which dissipate the energy of vibration, while also reducing the level of production noise.

As a personal protection against vibrations transmitted to a person through the legs, it is recommended to wear shoes on felt or thick from microporous rubber sole. Vibration damping gloves are recommended for hand vibration protection.

10.4. Protection against electromagnetic radiation

Organizational protection measures. People under the age of 18 are not allowed to work on HF and microwave installations, as well as with the following diseases: all blood diseases, organic diseases of the nervous system of a progressive nature, chronic eye diseases, tuberculosis in an active form, pronounced endocrine diseases, functional disorders of the nervous system. Every year a medical examination is carried out. If it is necessary to work under irradiation conditions exceeding 10 μW/cm2, the workers are given additional leave and the working day is reduced.

Rooms where high-frequency installations operate are equipped with general exchange ventilation. Ventilation devices to avoid heating are made from non-metal.

In technical means of protection against electromagnetic radiation, the phenomena of reflection and absorption of energy of the emitter are used, using various types of screens and power absorbers. Due to high absorption coefficients and almost no wave resistance, metals have high absorption and reflectivity and are therefore widely used for shielding.

The penetration depth of electromagnetic energy of high and ultra-high frequencies is very small, for example, for copper it leaves tenths and hundredths of a millimeter, so the thickness of the screen is chosen for design reasons.

In some cases, metal nets are used to shield radiation, through which installations can be observed or ventilation can be carried out.

Screens of high-frequency radiation sources must meet two conditions - provide the necessary shielding efficiency and do not reduce the field inside the coil more than the permissible limits.

The screens are made of sheet metal; seams connecting individual screen sheets to each other shall provide reliable electrical contact between the connected elements. Each screen is grounded.

Protection against ultra-high radiation, in addition to shielding the sources themselves, can be provided by absorbing loads, shielding of workplaces and the use of individual protective equipment. The shields may also be provided with an absorption or interference coating which provides the best conditions as electromagnetic energy is dissipated in the absorption coatings as heat loss.

When performing a number of works on setting up and testing equipment, the operator inevitably has to be in the electromagnetic radiation zone sometimes with a higher density of power flow. In these cases, personal protective equipment should be used, which in principle are screens made of metallized materials.

To protect the eyes, special ORZ-5 radio protection glasses made of glass reflecting electromagnetic radiation are used. They fit tightly against the skin of the face.

To protect the whole body, hoods, robes, overalls made of metallized cotton fabric are used.

10.5. Thermal radiation protection

Heat protection measures of particular importance in the hot shops of industrial enterprises can be divided into the following groups: 1) eliminating the source of heat 2) protecting against heat radiation 3) facilitating the heat transfer of the human body 4) personal protective equipment.

Elimination of heat sources is possible when the technology changes (for example, replacing plasma furnaces with electric ones), when automation and mechanization of manual labor, reducing the length of the line of steam pipelines and gas ducts, etc.

Protection against the direct action of thermal radiation is carried out mainly by shielding - installing thermal resistance on the path of heat flow. Screens are very diverse, but according to the principle of action, they are divided into absorbing and reflecting thermal radiation and can be stationary and mobile. Screens not only protect against thermal radiation, but also protect against sparks, spills of molten metal, scale, slag.

Reflecting screens are made of brick, aluminum, tin, asbestos, aluminum foil on asbestos (alphol) or metal mesh and other materials. Screens can be single or multi-layered, and the air layer increases the efficiency of shielding.

Absorbing screens are curtains, as well as shields and screens made of low heat conducting materials. Curtains are installed against radiating openings and are made of small metal chains that reduce radiant flux by 6070%, or from water film that absorbs up to 90% of thermal radiation and transmits visible rays.

Often it is not necessary to create certain meteorological conditions in the entire volume of the hot workshop; Optimal conditions are provided at individual workplaces. This is done by creating oases and showers. Air oasis - fenced from the sides with shields and an open volume from above in the workshop, where cooled air is supplied. The air shower supplies cooled air to the workstation through the air distributor.

Individual protection in hot shops is workwear made of heat radiation resistant, strong, soft and breathable material. Depending on the protection requirements, the suit is made of cloth, tarpaulin, synthetic fiber, chemically treated, with a metal coating of fabrics.

The head is protected from overheating and burns with a hat of felt, felt or rough cloth. The suit is supplemented by a special, resistant to elevated temperature and irradiation of shoes and sleeves.

Eyes are protected from exposure to radiant heat with glasses with light filters, spectral absorption of which corresponds to spectrum of radiant flux.

11.5. Preparation of estimates of annual operating expenses for maintenance of the enterprise energy farm

Calculation of payroll accruals.

Under this article, social contributions are planned with basic and additional wages. These charges are accepted in the amount of 26.2% of the annual fund of basic and additional wages. 

Operational materials.

This article plans and takes into account the cost of auxiliary materials for the main production: lubricants, wipers, emulsions for cooling and other auxiliary materials necessary for the care of equipment.

The cost of operating materials is accepted in the amount of 15% of the main and additional board of operating workers.

Maintenance costs.

Maintenance costs include: 

basic and additional salaries of repair workers;

26.2 per cent of social insurance salaries;

cost of materials, semi-finished products and purchased components. Accepted as a percentage of the wage fund of repair workers in the amount of 45%, to the value of fixed assets 

Other expenses.

This item includes expenses for travel expenses, rent, expenses for labor, safety, test costs, research, deductions for the maintenance of higher organizations, training costs, etc. 

Conclusion

In this diploma project, as a result of comparing external power supply options, the most economical circuit turned out to be 110 kV, so the enterprise receives power from the substation of the power system via a 110 kV double-circuit overhead line.

Power distribution inside the plant is carried out according to a mixed scheme for 10 kV voltage.

GPP with two 10000 MVA transformers is to be installed at the mill.

In the economic part of the project, the number of maintenance personnel, wages of workers and the intra-plant cost of 1 kWh of electricity received are determined.

In accordance with the specifics of production, the issue of labor protection and ecology was considered.