No. according to the plan

Name of electrical receivers

Р nom, kW

lathe

lathe

lathe

lathe

lathe

lathe

CNC carousel

Milling machine

Milling machine

Milling machine

Milling machine

Fan

Fan

Crane - beam PV = 40%

Crane - beam PV = 40%

Fan

Fan

name site

Lamp type

Plot area, m²

Naim. node gr. EP

R set kW

P nom kW

Cosφ tgφ

1) milling machines

2) lathe

3) machine carousel. CNC

0,5 1,73

4) crane-beam PV=40%

0,5 1,73

On tires ШР-1

1) milling machines

0,4 2,35

2) Fans

0,8 1,73

On tires ShR-2

1) lathes

0,4 2,35

2) Fans

0,8 1,73

3) crane-beam PV=40%

0,5 1,73

On tires ШР-3

Lighting

On tires 0.38 TP

Name of parameters

Option 1 - 1 x 160 kVA

Option 2 - 2 x 63 kVA

ΔR x.x kW

ΔR short-circuit kW

C o, tn/kW∙h

Estimated coordinates

Installation coordinates

conductor

fuse

Number of conductors

Name of electrical equipment

Brand Type

unit of measurement

Quantity

Three-pole disconnector

Oil switch

VMM-10-320-10tz

160kv*A oil transformer

Fuse

also I nom \u003d 600A I pl.vs \u003d 500A

also I nom \u003d 250A I square.vs \u003d 200A

also I nom \u003d 250A I square.vs \u003d 120A

also I nom \u003d 100A I pl.vs \u003d 80A

also I nom \u003d 100A I square.vs \u003d 50A

also I nom \u003d 100A I pl.vs \u003d 40A

also I nom \u003d 100A I pl.vs \u003d 30A

Cable for voltage 6Kv Cross section 3/10mAPV

Postnikov N.P., Rubashov G.M. Power supply of industrial enterprises. L.: Stroyizdat, 1980.

Lipkin B.Yu. Power supply of industrial enterprises and installations. - M .: Higher school, 1981.

Kryuchkov I.P., Kuvshinsky N.N., Neklepaev B.N. Electric part of stations and substations. - M.: Energy, 1978.

6. Handbook of power supply and equipment / Ed. Fedorova A.A., Barsukova A.N. M., Electrical equipment, 1978.

7. Rules for the installation of electrical installations / Ministry of Energy of the USSR. - M .: Energy, 1980.

Khromchenko G. E. Designing cable networks and wiring - M .: Higher school, 1973.

9. E.F. Tsapenko. Devices for protection against single-phase earth fault. - M.: Energoatomizdat 1985 - 296 p.

10. Shidlovsky A.K., Kuznetsov V.G. Improving the quality of energy in electrical networks. - Kyiv: Naukova Dumka, 1985 - 354 p.

Zhelezko Yu.S. Selection of measures to reduce electricity losses in electrical networks. Guide for practical calculations. - M.: Energoatomizdat, 1989 - 176 p.

The choice of a power supply scheme is inextricably linked with the issue of voltage, power, EP category in terms of reliability, EP remoteness.

With regard to ensuring the reliability of power supply, power receivers are divided into the following three categories.

Power receivers of the first category are power receivers, the interruption of power supply of which may entail: a danger to people's lives, a threat to the security of the state, significant material damage, disruption of a complex technological process, disruption of the functioning of especially important elements of public utilities, communication and television facilities.

From the composition of power receivers of the first category, a special group of power receivers stands out, the uninterrupted operation of which is necessary for an accident-free shutdown of production in order to prevent a threat to human life, explosions and fires.

Power receivers of the second category are power receivers, the interruption of power supply of which leads to massive undersupply of products, massive downtime of workers, mechanisms and industrial transport, disruption of the normal activities of a significant number of urban and rural residents.

Power receivers of the third category - all other power receivers that do not fall under the definitions of the first and second categories.

Power receivers of the first category in normal modes must be supplied with electricity from two independent mutually redundant power sources, and a break in their power supply in the event of a power failure from one of the power sources can only be allowed for the period of automatic power restoration.

For the power supply of a special group of power receivers of the first category, additional power must be provided from a third independent mutually redundant power source.

As a third independent power source for a special group of power receivers and as a second independent power source for the remaining power receivers of the first category, local power plants, power plants of power systems (in particular, generator voltage buses), uninterruptible power units designed for these purposes, batteries and etc.

If it is impossible to ensure the continuity of the technological process by redundant power supply, or if redundant power supply is not economically feasible, technological redundancy should be carried out, for example, by installing mutually redundant technological units, special devices for trouble-free shutdown of the technological process, operating in the event of a power failure.

Power supply of power receivers of the first category with a particularly complex continuous technological process that requires a long time to restore the normal mode, in the presence of feasibility studies, it is recommended to carry out from two independent mutually redundant power sources, to which additional requirements are imposed, determined by the characteristics of the technological process.

Power receivers of the second category in normal modes must be provided with electricity from two independent mutually redundant power sources.

For power receivers of the second category, in the event of a power failure from one of the power sources, power supply interruptions are permissible for the time necessary to turn on the backup power by the actions of the duty personnel or the mobile operational team.

For power receivers of the third category, power supply can be carried out from one power source, provided that power supply interruptions necessary to repair or replace a damaged element of the power supply system do not exceed 1 day.

The issue of choosing a power supply scheme, voltage level is decided on the basis of a technical and economic comparison of options.

For industrial power supply, enterprises use electrical networks with a voltage of 6, 10, 35, 110 and 220 kV.

In the supply and distribution networks of medium-sized enterprises, a voltage of 6–10 kV is accepted. Voltage 380/220 V is the main voltage in electrical installations up to I000 V. The introduction of voltage 660 V is cost-effective and is recommended to be used primarily for newly built industrial facilities.

Voltage 42 V (36 and 24) is used in rooms with increased danger and especially dangerous, for stationary local lighting and hand-held portable lamps.

The 12 V voltage is used only under particularly unfavorable conditions with regard to the risk of electric shock, for example, when working in boilers or other metal tanks using hand-held portable lights.

Two main power distribution schemes are used - radial and main, depending on the number and relative position of workshop substations or other power supplies in relation to the point that feeds them.

Both schemes provide the required reliability of power supply to EA of any category.

Radial distribution schemes are used mainly in cases where the loads are dispersed from the power center. Single-stage radial circuits are used to power large concentrated loads (pumping, compressor, converter units, electric furnaces, etc.) directly from the power center, as well as to power workshop substations. Two-stage radial circuits are used to power small workshop substations and HV power receivers in order to unload the main energy centers (Fig. Z.1). At intermediate distribution points, all switching equipment is installed. The use of multi-stage schemes for intrashop power supply should be avoided.

Rice. 3.1. Fragment of a radial power distribution scheme

Distribution points and substations with electrical receivers of categories I and II are usually powered by two radial lines that operate separately, each for its own section, when one of them is disconnected, the load is automatically taken by the other section.

Main power distribution schemes should be used for distributed loads, when there are many consumers and radial schemes are not economically feasible. The main advantages: allow better loading of cables in normal mode, save the number of cabinets at the distribution point, reduce the length of the trunk. The disadvantages of trunk circuits include: the complication of switching circuits, the simultaneous shutdown of the EP of several production sites or workshops powered by this trunk when it is damaged. For power supply of VP of categories I and II, schemes with two or more parallel through mains should be used (Fig. 3.2).

Rice. 3.2. Scheme with double through highways

Power supply of EP in networks with voltage up to 1000 V of II and III categories in terms of power supply reliability is recommended to be carried out from single-transformer packaged transformer substations (KTS).

The choice of two-transformer PTS must be justified. The most expedient and economical for intrashop power supply in networks up to 1 kV are the main circuits of transformer-trunk blocks without switchgears at a substation using complete busbars.

Radial circuits of intrashop supply networks are used when it is impossible to perform trunk circuits due to the conditions of the territorial distribution of electrical loads, as well as environmental conditions.

For the power supply of shop consumers in design practice, radial or main circuits in their pure form are rarely used. The most widespread are the so-called mixed circuits of electrical networks, combining elements of both radial and trunk circuits.

Power supply circuits and all electrical installations of alternating and direct current of an enterprise with a voltage of up to 1 kV and above must meet the general requirements for their grounding and protection of people and animals from electric shock both in normal operation of the electrical installation and in case of damage to the insulation.

Electrical installations in relation to electrical safety measures are divided into:

- electrical installations with voltages above 1 kV in networks with a solidly grounded or effectively grounded neutral;

- electrical installations with voltages above 1 kV in networks with isolated or grounded neutral through an arcing reactor or resistor;

- electrical installations with voltage up to 1 kV in networks with dead-earthed neutral;

- electrical installations with voltage up to 1 kV in networks with isolated neutral.

For electrical installations with voltage up to 1 kV, the following designations are accepted: system TN- a system in which the neutral of the power source is solidly grounded, and the open conductive parts of the electrical installation are connected to the solidly grounded neutral of the source by means of zero protective conductors (see Fig. 3.3–3.7).

Rice. 3.3. System TN-C- system TN, in which zero protective

and zero working conductors are combined in one conductor

throughout its length

The first letter is the state of the neutral of the power supply relative to earth:

T– grounded neutral;

I– isolated neutral.

The second letter is the state of open conductive parts relative to ground:

T– exposed conductive parts are grounded, regardless of the relation to the earth of the neutral of the power supply or any point of the supply network;

N– exposed conductive parts are connected to a dead-earthed neutral of the power source.

Subsequent (after N) letters - combination in one conductor or separation of the functions of the zero working and zero protective conductors:

S– zero worker ( N) and zero protective ( PE) conductors are separated;

C- the functions of the zero protective and zero working conductors are combined in one conductor ( PEN-conductor);

N- zero working (neutral) conductor;

PE- protective conductor (grounding conductor, zero protective conductor, protective conductor of the potential equalization system);

PEN- combined zero protective and zero working conductor.

Rice. 3.4. System TN-S- system TN, in which zero protective

and zero working conductors are separated along its entire length

Rice. 3.5. System TN-C-S- system TN, in which the functions of zero

protective and zero working conductors are combined in one

conductor in some part of it, starting from the power source

Rice. 3.6. System TT– a system in which the neutral of the power supply

deafly grounded, and open conductive parts of the electrical installation

earthed with a grounding device, electrically

source independent of the dead-earthed neutral

Rice. 3.7. System IT– a system in which the neutral of the power supply

isolated from earth or earthed through appliances or devices,

with high resistance, and exposed conductive parts

electrical installations are grounded

Zero working (neutral) conductor ( N) - a conductor in electrical installations up to 1 kV, designed to power electrical receivers and connected to a solidly grounded neutral of a generator or transformer in three-phase current networks, with a solidly grounded output of a single-phase current source, with a solidly grounded source point in DC networks.

Combined zero protective and zero working ( PEN) conductor - a conductor in electrical installations with voltage up to 1 kV, combining the functions of zero protective and zero working conductors.

To protect against electric shock in normal operation, the following protective measures against direct contact must be applied individually or in combination:

– basic insulation of current-carrying parts;

- fences and shells;

– installation of barriers;

– placement out of reach;

– use of extra-low (small) voltage.

For additional protection against direct contact in electrical installations with voltages up to 1 kV, if there are requirements of other chapters of the PUE, residual current devices (RCDs) with a rated differential breaking current of not more than 30 mA should be used.

In order to protect against electric shock in the event of insulation failure, the following protective measures against indirect contact must be applied individually or in combination:

– protective grounding;

– automatic power off;

– equalization of potentials;

– equalization of potentials;

– double or reinforced insulation;

– extra-low (small) voltage;

– protective electrical separation of circuits;

- insulating (non-conductive) rooms, zones, sites.

Electrical installations up to 1 kV in residential, public and industrial buildings and outdoor installations should, as a rule, be powered from a source with a solidly grounded neutral using a system TN.

Power supply of electrical installations with voltage up to 1 kV AC from a source with isolated neutral using the system IT should be carried out, as a rule, if a power interruption is unacceptable at the first fault to the ground or to open conductive parts connected to the potential equalization system. In such electrical installations, for protection against indirect contact during the first earth fault, protective grounding must be performed in combination with network insulation monitoring or RCDs with a rated differential breaking current of not more than 30 mA should be used. In case of a double ground fault, automatic power off must be performed in accordance with the PUE.

Power supply of electrical installations with voltage up to 1 kV from a source with a dead-earthed neutral and with grounding of open conductive parts using a grounding conductor not connected to the neutral (system TT), is allowed only in those cases when the electrical safety conditions in the system T N cannot be provided. To protect against indirect contact in such electrical installations, automatic power off must be performed with the mandatory use of RCDs.

In this case, the following condition must be met:

R a I a ≤ 50 V,

where I a is the operating current of the protective device;

R a is the total resistance of the grounding conductor and the grounding conductor of the most remote electrical receiver, when using RCD to protect several electrical receivers.

When using the system TN re-grounding is recommended PE- And PEN- conductors at the input to the electrical installations of buildings, as well as in other accessible places. For re-grounding, first of all, natural grounding conductors should be used. The resistance of the re-grounding earth electrode is not standardized.

In electrical installations with a voltage above 1 kV with an isolated neutral, to protect against electric shock, protective grounding of exposed conductive parts must be made.

App. 3 shows the power supply schemes of individual buildings, and in App. 4 - graphic and letter designations in electrical circuits.

Electrical networks serve to transmit and distribute electrical energy to shop consumers of industrial enterprises. Energy consumers are connected through intrashop substations and distribution devices using protective and starting devices.

Electric networks of industrial enterprises are carried out internal (workshop) and external. External voltage networks up to 1 kV are very limited in distribution, since at modern industrial enterprises the power supply of shop loads is produced from intra-shop or attached transformer substations.

The choice of electrical networks radial power circuits are characterized by the fact that from the power source, for example, from a transformer substation, lines depart directly to power powerful electrical receivers or separate distribution points, from which smaller electrical receivers are fed by independent lines.

Radial circuits provide high reliability of power supply to individual consumers, since accidents are localized by turning off the automatic switch of the damaged line and do not affect other lines.

All consumers can lose power only in case of damage on the PTS busbars, which is unlikely. As a result of a fairly reliable design of cabinets of these PTS.

Main power supply circuits are widely used not only to power many electrical receivers of one technological unit, but also to compare a large number of small receivers that are not connected by a single technological process.

Trunk circuits allow you to abandon the use of a bulky and expensive switchgear or shield. In this case, it is possible to use the transformer-trunk block scheme, where bus ducts (bus ducts) manufactured by the industry are used as the supply line. Trunk schemes made by busbars provide high reliability, flexibility and versatility of workshop networks, which allows technologists to move equipment inside the workshop without significant installation of electrical networks.

Due to the uniform distribution of consumers within the mechanical repair shop, as well as low cost and ease of use, the main power supply scheme is selected.

The location of the main equipment is shown in the diagram (Fig. 1).

When designing a power supply network for large consumers, which also includes individual workshops of enterprises, it is important to take into account a lot of conditions. The initial data for the design depend on many factors, ranging from the specialization of the enterprise to the geographical location, since it is necessary to take into account not only the power consumed by the equipment, but also the costs of lighting and heat supply. Competently and rationally executed shop power supply project significantly affects the reliability of the installed equipment with the minimum allowable power consumption. The power supply of the enterprise must ensure safe working conditions and not have a harmful effect on the environment.

The most complex and time-consuming stage in the design of internal power supply is the determination and calculation of the power consumption of the load. The calculation is based on data, both on the passport power consumption of the equipment, and its modes of operation. All factors are taken into account, including reactive power, which requires compensation with the help of special equipment - reactive power compensators to ensure a uniform load on a three-phase network.

A separate column in determining the power is the calculation of the lighting system of the workshop, which allows you to select and optimize the location and types of lamps, depending on the lighting requirements of various areas. The presence or absence of central heating may require the introduction of seasonal connection of electric heating systems to the number of consumers.

Most of the workshops of an industrial enterprise require the design of ventilation systems.

These conditions show how time-consuming the calculation of the power supply system can be at the first stage of design, especially when it comes to the power supply of the non-standard equipment shop.

At the second stage of design, using the data of the first stage and a large-scale equipment layout plan, the type of distribution network is selected. In doing so, the following factors must be taken into account:

• Location of power receivers on the territory of the workshop;
• The degree of responsibility of the receivers (requirements for the reliability of the power supply);
• Operating mode.

The consumption of materials for power lines, the location of transformer substations, switchboards depend on the chosen distribution network scheme.

The following types of distribution networks are used:

• Radial schemes;
• Trunk;
• Combined.

With a radial scheme, each receiver is powered by a separate line laid from the switchboard. This type of networks is used to connect powerful receivers located at a sufficient distance from one another, and the substation is located near the geometric center of the load.

The main circuit is characterized by the fact that it is used with a concentrated load, when energy receivers are grouped in series and at a small distance from each other. In this case, they are connected to a single line laid from a transformer substation or switchboard.

The combined circuit includes a main circuit with concentrated loads, when several mains depart from the switchboard, each for its own group of loads. A combined network can also be called a radial construction, when powerful consumers are powered directly from the supply substation, while less powerful ones are combined into groups and receive power from switchboards.

It is the combined networks that have become most widespread, since they allow the most optimal use of material resources without reducing reliability. At this stage, the requirements of receivers for power reliability are also taken into account and schemes for redundant power supply are laid.

The third stage of project development is based on the two previous ones and involves the calculation of the required number and power of switchgear, substations, reactive power compensators.

Calculation of the power of electrical energy receivers

The load power on the supply network largely depends on the type of production. For example, the equipment of the metal-cutting machine shop of a metalworking plant, with the same number of devices, consumes much more power than the machines of a woodworking shop. Thus, the power supply of the mechanical workshop of heavy engineering requires a more rigorous approach regarding the choice of the number and capacity of converter substations and power lines.

When designing, the daily work schedule of consumers should be taken into account, and the calculations should be based on the average power consumption during peak hours. If we take into account the total power of consumers, then most of the time the substation transformers will operate in an underloaded mode, which will lead to unnecessary financial costs for servicing the supply equipment.

It is believed that the optimal mode of operation of the transformer should be 65 - 70% of the rated power.

The required section of the power supply lines is also selected taking into account the average power consumption, since the allowable current density, heating and power losses must be taken into account.

Similarly, at this stage, the characteristics of the consumption of the reactive component of power should be taken into account, for the rational use of compensators. Incorrect placement and parameters of compensators will lead to energy overruns, incorrect accounting, and, most importantly, to increased losses and load on power lines.

This task is posed primarily where there are many powerful consumers with inductive loads. The most common example is induction motors, which are found in most machine tools.

Second stage of design

The choice of the type of distribution network is partly determined by the characteristics of the equipment according to the categorization of the receivers. There are three categories according to the requirements for power supply reliability:

1. The first category - a power outage leads to a safety hazard, accidents, a complete disruption of the technological process. This category includes a large number of machine-building and metal-working equipment, as well as mass production enterprises based on a conveyor, for example, a machine-building profile.
2. The second category is a violation of the production cycle, interruptions in the production of products that do not lead to serious economic consequences. Most industries fall into this category. Here you can specify the equipment of the mechanical repair shop (RMC).
3. The third category includes consumers with more forgiving power requirements than the first two categories. This includes most of the production equipment of the sewing workshop, and some of the hardware workshops.

Equipment belonging to the first category requires the design of power supply, taking into account the mutual redundancy of several (usually two) sources of external electrical supply.

The optimal combination of power supply reliability at minimal cost is achieved by the right choice of power supply system in accordance with the category of the equipment and the location of the equipment on the area of ​​the production workshop.

In most cases, the most rational is a combined trunk scheme with concentrated loads. The equipment of a forging shop or a welding shop has its own characteristics in terms of energy consumption and requires the laying of separate supply lines, and the power supply of the machine-assembly shop, on the contrary, can be performed according to the main scheme. And when several production lines are installed in the workshop, then several supply lines are indispensable. The same must be taken into account when calculating the power supply of the tool shop.

Separate power lines are laid for the lighting and ventilation system, whether it is an electrical project for a woodworking plant or an electrical project for an aircraft factory of an aviation enterprise.

The final stage

Based on the data of previous calculations, an electrical project is drawn up, consisting of several sets of documents. First, a working draft is developed, which in the process of performing work can be adjusted depending on local conditions and at the end of the work will differ from the calculated one. One of the main documents in the design of power supply is a single-line power supply diagram of the workshop. A drawing of a single-line diagram allows you to quickly navigate the intricacies and features of the power supply of the workshop.

Summing up

Designing the power supply system of a separate workshop or a whole plant is one of the most important activities, the implementation of which is possible only by specialized organizations that have the right to such work. It makes no sense to waste time developing the project yourself. No matter how it is executed competently and accurately, it still will not receive approval from energy sales organizations. By ordering a typical design of an intrashop power supply scheme of up to 1000 V or more from a licensed organization, you can not worry about the safety and legality of all activities for the construction and operation of electrical equipment. The finished project will have all the necessary approvals and approvals, starting from the sketch and ending with fully corrected documentation when the facility is put into operation.

You can order a project at Mega.ru. The company's website has many articles that reveal the essence and subtleties of design, with examples of projects. Particular attention should be paid to the article, which explains in detail what are the stages of an electrical project.

But still, much more information of interest can be obtained by contacting the company directly for advice. The section indicates how you can contact our specialists and get answers to all questions.

We carry out all types of student work

The electrical load is calculated jointly for working and emergency lighting. The initial data for the calculation are given in Table 8. Table 8 - Lighting load parameters of the workshop. Active replaceable powers of working, kW, and emergency, kW, lighting are determined by the formula. For = 0.83. Reactive replaceable powers of working, kvar, and emergency, kvar, lighting are determined by the formula (2) ...

Power supply of the machine shop for mass production (abstract, term paper, diploma, control)

• Introduction
• 1. General part
• 1.3 Reliability category of shop power supply
• 2. Special part
• 2.3 Calculation of the electrical load of the power equipment of the workshop
• 2.8.4 Calculation and selection of pipes

Introduction

One of the most urgent tasks in our country is the systematic development of its economic complex. In a market economy, the main factor in increasing the efficiency of the national economy is not the individual achievements of science and technology, but the high scientific and technological level of the entire production complex. This level is determined primarily by the state of engineering as an industry. In this regard, the most acute issues related to the improvement, reorganization, development and modernization of the industry as a whole and each enterprise separately. In turn, any modernization of industrial machine-building enterprises, or the creation of new ones, sets the priority task of organizing a full-fledged, economical and efficient power supply for production facilities, including machine tools.

This course project discusses some experience in designing the power supply of a separate section of the machine shop for serial production, intended for serial production of products for a heavy engineering plant.

The course project consists of general and special parts. The general part deals with the basic data of the premises, equipment, etc., necessary for the calculations. In a special part, the methods and directly the calculations themselves for organizing the power supply of the site of the machine-building production shop are given.

power supply machine shop network

1. General part

1.1 Characteristics of the premises of the workshop

The mass production machine shop (MCSP) is divided into the following sections:

machine department;

transformer substation (TP);

repair site;

household premises;

milling section;

grinding area;

ventilation.

In the premises of the machine department, the main production activities of the MCSP, the processing of blanks and parts, are carried out. The machine room is a dry room with a normal environment, the ambient temperature does not exceed 30 ° C, there is no chemically active environment, fire and explosive substances. The degree of protection of the shell of electrical equipment is IP 44.

The characteristics of the sites in terms of environmental conditions, technological purpose, the presence of fire and explosion hazard zones are given below in Table 1.

Table 1 - Characteristics of the premises of the workshop

1.2 Analysis of shop electrical consumers

This workshop uses electrical equipment that has the following technological purposes:

metalworking equipment (turning, milling machines, etc.);

handling equipment (overhead crane);

metalworking machines (grinding, drilling, turning, grinding, milling, bolt-cutting, thread-cutting machines);

woodworking machinery;

household appliances (refrigerator, electric stove);

welding equipment (welding transformer, welder's table);

sanitary equipment (fans);

Electrical consumers are connected to a three-phase voltage of 380 V (fans, machines), to a single-phase voltage of 220 V (refrigerator) and a single-phase voltage of 380 V (welding transformer, electric stove). The rest of the electrical equipment operates in a continuous mode.

Most of the electrical receivers are connected to a three-phase voltage of 380 V (metalworking, handling equipment), except for single-phase electrical receivers of 220 V (emery, grinding machines, magnetic flaw detector) with a frequency of 50 Hz. The electric consumers of the workshop operate both in long-term mode (metal-working equipment) and in intermittent mode (handling equipment).

The category of power supply reliability is the ability of the electrical system to provide the enterprise and individual facilities with electricity of the proper quality without emergency interruptions. With regard to ensuring the reliability of power supply, power receivers (EP) are divided into three categories according to the rules for the installation of electrical installations (PUE).

Category 1 - it includes electrical consumers, the interruption in the power supply of which can cause a threat to human life, damage to expensive equipment, mass defective products, etc. Consumers of this category are powered by two independent sources of electricity. Power supply interruption is allowed for the period of automatic switching from one source to another.

Category 2 - this category includes electrical consumers, a break in the power supply of which can cause a massive underproduction and downtime of workers, disruption of the life of urban and rural residents. Consumers are fed from two independent sources. When one power source fails, switching to another power source is carried out by a mobile operational team or operational personnel.

Category 3 - this category includes electrical consumers that do not belong to the 1st and 2nd categories. Consumers of this category are powered by one source of electricity, and interruption of their power supply is allowed for a period of not more than a day.

For power receivers of this category, interruptions in power supply are allowed for the time required to turn on the backup power by the on-duty personnel or the mobile operational team. In the presence of a centralized reserve, it is allowed to supply power consumers of category II with one transformer, since a break in power supply can cause a massive underproduction and downtime for workers.

1.4 Design input

To perform the power supply of the workshop, it is necessary to indicate the main indicators of the workshop, the load parameters of the workshop and the technical parameters of the electrical consumers, which are entered in tables 2, 3 and 4, respectively.

Table 2 - Main indicators of the workshop

Table 3 - Workshop load parameters

Table 4 - Technical parameters of electrical consumers

2. Special part

2.1 Choice of method and scheme of power supply of distribution networks

A distribution network is a network from distribution cabinets to electrical consumers.

Distribution cabinet (SHR) is an electrical device that serves to receive and distribute electricity between electrical consumers, as well as to protect them from emergency conditions. Distribution cabinets are installed, as a rule, in the center of loads, as well as in places that do not interfere with the technological process and are convenient for operation and repair. In this workshop, distribution cabinets are located near the walls.

There are 3 schemes for the implementation of distribution networks.

The radial scheme (Figure 1) is a distribution network power supply scheme in which the power consumer receives power through its own separate line. Thus, if one supply line fails, the remaining electrical consumers continue to receive power. However, with such a scheme, a large number of starting-protective equipment and cable products are used.

Figure 1 - Radial diagram of the distribution network

The main circuit (Figure 2) is a distribution network power supply scheme in which several electrical consumers are powered from one line.

Figure 2 - Main distribution network diagram

A mixed scheme (Figure 3) is a power supply scheme for distribution networks, in which power consumers receive electricity both through radial and main schemes.

Figure 3 - Mixed distribution network scheme

The connection of electrical consumers to switch cabinets in the machine shop is carried out both according to radial and mixed distribution network schemes.

This course project uses a radial distribution network.

To connect electrical consumers, both open (in structures, in boxes) and hidden (in floor preparation pipes) electrical wiring are used. The method of laying electrical wiring depends on the technological process, environmental conditions, the presence of dust, a chemically active environment, and zones of explosion and fire hazard. For example, the electrical wiring in the ventilation chamber is carried out openly in a box to protect the wiring from process dust.

2.2 Calculation of the electrical load of the switch cabinet using the ordered diagram method

The electrical load for the workshop is power equipment and electric lighting. The calculation of the electrical load is an important element in the design of workshops, enterprises, sites. Depending on the calculated power, the number and power of power transformers, the brand and cross section of the high and low voltage supply lines, as well as the type of start-protective devices of distribution cabinets are selected.

An example of the calculation of power equipment for a distribution cabinet (SR) No. 1 (according to the plan) is given.

Initial data are selected from table 4 and entered in table 5

According to the reference data, the values ​​of ki, cosц, tgц are found and are entered in table 5

Table 5 - Data of electrical consumers connected to ШР1

The layout of the switch cabinet is shown in Figure 4.

Figure 4 - Schematic diagram of ShR1

All EPs belong to the same technological group.

The active replaceable power Rcm, kW, is determined by the formula Rcm \u003d ku x? Рн1…8 (1)

Rcm=0.12×81.5 = 9.78 kW Reactive power Qcm, kvar, is determined by the formula

Qcm \u003d Rcm x tgc (2)

Qcm= 9.78×2.30 =22.494 kvar = Rcm (3)

rsm? = 9.78 kW

Qcm? = Qcm (4)

Qcm? = 22.494 kvar The weighted average value of the function tgц is determined by the formula

tgcsrv = Qcm? / rsm? (five)

tgcrv = 22.494 / 9,78 = 2,3

The total average shift power ShR1 Scm?, kVA, is determined by the formula

Scm? =v 9.78 I + 22.494I = 24.53 kVA

coscrv = Rcm? / Scm? (7)

coscrv = 9.78/24.53 = 0.399

The total installed power E P Ru?, kW, connected to ShR1, is determined by the formula Ru? =? Pn1+ Pn2+ Pn3+ Pn4+ Pn5+ Pn6+ Pn7+ Pn8 (8)

RU? = 9.5+9.5+9.5+9.5+9.5+10+12+12 = 81.5 kW

The weighted average value of the utilization factor is determined by the formula

kUav = Rcm? / RU? (nine)

kUav = 9.78/81.5 = 0.12

The effective number of EP nef, pcs, is determined by the formula

6642, 25

nef = 839.25 = 7.91

According to the values ​​of nef and k and av, the value of the coefficient of maximum km is found

km = f (nef; kUav) (11)

km \u003d f (7.91; 0.12) \u003d 2.59

Active design power ШР1 Рр kW, is determined by the formula Рр = km x Rcm? (12)

Рр = 2.59 × 9.78 = 25.33 kW Reactive calculated power ШР1 Qр, kvar, is determined by the formula

Qp \u003d 1.1 x Qcm ?, because nef<10, nэф = 7,91 (13)

Qр = 1.1×22.494 = 24.7434 kVAr Total reactive power ШР1 Sр, kVA, is determined by the formula

Sp =v 25.33 I + 24.7434 I = 35.41 kVA Rated current ШР1, A, is determined by the formula

Ir = 35.41 / 1.73 × 380 = 53.86 A The electric power supply with the highest starting current is selected. For ShR1, this is EP13 (Semi-automatic gear hobbing). Its rated current, A, is found by the formula

In1= 1.73×380×0.4×0.83 = 54.98 A Starting current of a given EA, A, is determined by the formula

where is the start factor (for).

In1 \u003d 6 × 54.98 \u003d 329.88 A Peak current ШР1, A, is calculated by the formula

Ipeak \u003d 53.86 + 329.88 - 0.12 × 54.98 \u003d 377.1424 A The calculation data are entered in table 6.

Table 6

Active replaceable total power of power equipment, kW, is determined by the formula

P cm Force = 710 × 0.3 = 213 kW The weighted average value of the mathematical function of the power equipment is determined corresponding to

at = 0.7 = 0.9 (20)

Reactive replaceable total power of power equipment, kvar, is determined by the formula

Qcm? force = 213 × 1.02 = 217.26 kvar Active rated power of power equipment, kW, is determined by the formula Pp force = P cm Y force x km force (12)

Рр forces = 213 × 1.3 = 276.9 kW The reactive rated power of power equipment, kvar, is determined by the formula

QР forces = 217.26 kvar The total rated power of power equipment, kVA, is determined by the formula

Sp force = v 276.9 І + 217.26 І = 351.96 kVA Rated current of power equipment, A, is determined by the formula

Ip = 351.96 / 1.73 × 380 = 535.38 A ) respectively

In strength \u003d 1.73 × 380 × 0.8 × 0.83 \u003d 27.49 A

In1 = 6 × 27.49 = 164.94 A Peak current of power equipment, A, is determined by formula (27)

I peak force \u003d 535.38 + 164.94 - 0.12 × 27.49 \u003d 697.0212 A

2.4 Calculation of working and emergency lighting of the workshop

The electrical load is calculated jointly for working and emergency lighting. The initial data for the calculation are given in table 8

Table 8 - Shop lighting load parameters

Active replaceable power of working, kW, and emergency, kW, lighting are determined by the formula

Pcm RO \u003d 0.9 × 54 \u003d 48.6 kW

Pcm AO = 1×11 = 11 kW Weighted average values ​​of the mathematical function of working and emergency lighting are determined by the corresponding values

Reactive replaceable powers of working, kvar, and emergency, kvar, lighting are determined by the formula (2)

Qcm RO \u003d 48.6 × 0.48 \u003d 23.33 kvar

Qcm AO = 11×0 = 0 kvar Active design power of working, kW, and emergency, kW, lighting are determined by the formula

Pr RO = Pcm RO = 48.6 kW

Pr AO = Pcm AO = 11 kW Reactive design power of working, kvar, and emergency, kvar, lighting are determined by the formula

Qr RO \u003d Qcm RO (31)

Qr RO \u003d Qcm RO \u003d 23.33 kvar

Qр AO = Qcm AO = 0 kVAr The total design power of the working, kVA, and emergency, kVA, lighting is determined by the formula (14)

Sp RO \u003d v 48.6 I + 23.33 I \u003d 53.9 kVA

Sp RO \u003d v 11 I + 0 I \u003d 11 kVA The rated currents of the working, A, and emergency, A, lighting are determined by the formula (15)

Ir RO \u003d 1.73 × 0.38 \u003d 81.67 A

Ir RO \u003d 1.73 × 0.38 \u003d 16.67 A The total active replaceable power of working and emergency lighting, kW, is determined by the formula

Pcm? sv \u003d 48.6 + 11 \u003d 59.6 kW The total installed power of working and emergency lighting, kW, is determined by the formula

Pу sv = 54 + 11 = 65 kW Total reactive replaceable power of working and emergency lighting, kvar, are determined by the formula

(34) Qcm? sv = 23.33 + 0 = 23.33 kvar Active rated power of working and emergency lighting, kW, are determined by the formula

Pr sv = 59.6 kW Reactive rated power of working and emergency lighting, kvar, are determined by the formula

Qr sv \u003d 23.33 kvar

2.5 Reactive power compensation

The operation of alternating current machines and devices, based on the principle of electromagnetic induction, is accompanied by a process of continuous change by changing the magnetic flux in their magnetic circuits and stray fields. Therefore, the power flow supplied to them must contain not only the active component P, but also the reactive component of the inductive nature Q, necessary to create magnetic fields, without which the processes of energy conversion, the type of current and voltage are impossible.

Reactive power compensation can be performed both naturally (reducing reactive power consumption) and artificially (installing reactive power sources) in ways.

2.5.1 Calculation of the electrical load of the shop before compensation

The calculation of the total electrical load of the workshop is carried out on the basis of the data of the calculation of the electrical load on the low voltage side of the PTS and the calculation of the electrical load of the electric lighting of the workshop, which are given in table 9

Table 9 - Parameters of electrical loads of power equipment and electric lighting of the workshop

The active installed capacity of the workshop, kW, is determined by the formula

Pу shop = 710 + 54 = 764 kW Active replaceable total power of the shop, kW, is determined by the formula

(38) P cm? shop = 196 +59.6 = 255.6 kW Reactive replaceable total power of the shop, kvar, is determined by the formula

Qcm? workshop = 217.26 + 23.33 = 240.59 kvar The total shift power of the workshop, kVA, is determined by the formula (6)

Scm workshop =v 255.6 І + 240.6І = 351.03 kVA The weighted average value of the workshop power factor is determined by the formula (7)

soscsrv shop = 255.6 / 351.03 = 0.73

The weighted average value of the mathematical function of the workshop is determined by the formula (5)

tgcsrv workshop = 240.6 / 255,6 = 0,941

The active design power of the workshop, kW, is determined by the formula

— coefficient of mismatch of the maximum load for active power.

P p shop \u003d 0.95 x (276.9 + 59.6) \u003d 319.7 kW The reactive design power of the shop, kvar, is determined by the formula

Qр workshop = 0.98 x (217.26 + 23.33) = 235.78 kVAr The total rated power of the workshop, kVA, is determined by the formula (14)

Scm shop \u003d v 319.7 I + 235.78 I \u003d 397.24 kVA The rated current of the shop, A, is determined by the formula (15)

Ir workshop = 397.24 / 1.73 × 380 = 604.26 A The peak current of the workshop, A, is determined by the formula (18)

Ipeak shop \u003d 604.26 + 329.88 - 0.12 × 54.98 \u003d 930.54A

2.5.2 Calculation and selection of a complete condensing unit

To select the power and type of complete capacitor units, the calculation data of the electrical load of power equipment and electric lighting of the workshop are used, which are given in table 10

Table 10 - Parameters of the electrical load of the shop

The weighted average of a mathematical function is determined by is determined by the value of the function

The desired power value of the KKU, kvar, is determined by the formula

QKKU zhel \u003d 255.6 x (0.941 - 0.36) \u003d 148.5 kvar

The power value of the KKU is selected - 150 kvar, since 150 kvar ‹ 240.59 kvar.

The reactive replaceable total power of the shop after compensation, kvar, is determined by the formula

Qcm? shop PC = 240.59 - 150 = 90.59 kvar Total replaceable total power of the shop after compensation, kVA, is determined by the formula (6)

Scm? shop PC = v 255.6І + 90.59І = 271.18 kVA The weighted average value of the power factor of the shop after compensation is determined by the formula

(45) soscav PC = 255.6/ 271.18 = 0.942

The obtained values ​​are compared with the value

0.942? 0.94 - true This means that a CCGT with a rated power of 150 kvar is selected, and its technical data are entered in table 11

Table 11 - Technical parameters of the CCU

The rated current of the KKU, A, is determined by the formula

In KKU = 150 / (1.73 × 0.38) = 288.17 A The reactive design power of the workshop after compensation, kvar, is determined by the formula

Qcm? shop PC = 235.78 - 150 = 85.78 kvar The total design power of the shop after compensation, kVA, is determined by the formula (14)

Sp workshop PC = v 319.7І + 85.78І = 331.01 kVA The rated current of the workshop after compensation, A, is determined by formula (15) A, by formula (25)

Ir shop PC = 331.01/ (1.73 × 0.38) = 503.51A Peak current of the shop after compensation, A, is determined by the formula (18)

Ipeak shop PC = 503.51 + 329.88 - 0.12 × 54.98 = 826.79 A

2.6 Calculation and selection of the number and power of power transformers

In the mechanical workshop of serial production, there are electrical consumers of the first and second categories of power supply reliability.

The consumer of the first category includes emergency lighting of the workshop, and the consumer of the second category - the working lighting of the workshop.

The initial data for the calculation and selection of the number and power of power transformers are given in table 12

Table 12 - Initial data for the calculation and selection of the number and power of power transformers

The weighted average value of the mathematical function is determined by the corresponding value

The reactive replaceable total power of the workshop after compensation, kvar, is determined by the formula (21)

Qcm? workshop PK = 255.6 × 0.035 = 8.95 kvar Total replaceable total power of the workshop after compensation, kVA, is determined by the formula (6)

S cm? shop PC = v 255.6І + 8.95І = 255.77 kVA The reactive design power of the shop after compensation, kvar, is determined by the formula (22)

Qr shop PC = 8.95 kvar Total rated power on the low voltage side, kVA, is determined by the formula (14)

S p workshop PC = v319.7І + 8.95І = 319.83 kVA Active, kW, and reactive, kvar, power losses in the power transformer and in high-voltage lines, kW, are determined by the formulas

P T \u003d 0.02 × 319.83 \u003d 6.4 kW

Q T \u003d 0.1 × 319.83 \u003d 31.98 kvar

R P= 0.03×319.83 = 9.6 kW Total rated power on the high voltage side, kVA, is determined by the formula

S p HV = v (319.7 + 6.4 + 9.6) I + (8.95 + 31.98) I = 338.19 kVA The calculated power of the power transformer, kVA, taking into account the load factor, is determined by the formula

- permissible load factor, which, with the predominance of consumers of the III category of reliability of power supply, is 0.92

S Т1 = 338, 19/ 0.92 = 367.59 kVA Select the nearest higher standard power transformer power value, kVA

The actual value of the load factor is determined and compared with the value of the allowable load factor

in Tf = 338, 19/400 = 0.85

Comparable, provided

0.92 > 0.85 - correct The value of the load curve fill factor, determined by the formula

The number of use of the maximum load, h, is determined by the formula

According to the values ​​\u200b\u200band, as well as the curves of the multiplicity of permissible loads of transformers, the coefficient of permissible overload is determined

The calculated power of the power transformer, kVA, taking into account, is determined by the formula

ST2 \u003d 297.73 / 1.02 \u003d 297.73 kVA Taking into account the values ​​\u200b\u200bof ST1 and ST2 The standard power value of the power transformer is selected and its technical data are entered in table 13

Table 13 - Technical data of the power transformer

The active calculated total power of consumers of the I and II categories of power supply reliability, kW, is determined by the formula

The reactive calculated total power of consumers of the I and II categories of power supply reliability, kvar, is determined by the formula

The total rated power of consumers of the I and II categories of reliability of power supply, kVA, is determined by the formula (14)

The percentage of consumers of the I and II categories of reliability of power supply,%, is determined by the formula

Since the percentage of consumers of the I and II categories of power supply reliability does not exceed 30%, then 1 power transformer is selected with redundancy on the low side from the nearest workshop transformer substation.

2.7 Calculation and selection of protective equipment

Start-up equipment are called devices designed for switching and protecting electrical networks from overloads and short circuits. These devices include circuit breakers, magnetic starters and fuses.

Circuit breakers are used to automatically open electrical circuits during overloads and short circuits, with unacceptable voltage drops, as well as for infrequent manual switching on of circuits.

Magnetic starters are designed to start motors and protect against overloads.

Fuses are designed to protect circuits from short circuit modes and, occasionally, from overloads.

Below is a diagram of a switch cabinet with protective devices installed in it, supply and distribution networks (Figure 5).

Figure 5 - Schematic diagram of ShR1

2.7.1 Fuse selection FU1

The rated current of the electric consumer, A, is determined by the formula (16)

The starting current of the electric consumer, A, is determined by the formula (17)

The desired value of the fuse-link current of the fuse installed in the box, A, is determined by the formula

where is the coefficient of starting conditions: with a difficult start = 1.6; with light = 2.5.

By value, a larger standard value of the current of the fuse fuse, A, is selected, provided

A fuse of type PN - 2 - 150 is selected; .

According to the reference data, the type of fuse is determined, which are entered in table 14

Table 14 - Technical data of box 1I

2.7.2 Selecting the type of fuses installed in switch cabinets

The choice of fuse types installed in the switch cabinet is considered using the FU1 fuse as an example.

The rated current of the consumer, A, which is protected by a fuse, is determined by the formula (25)

The starting current of the consumer, A, which is protected by a fuse, is determined by the formula (17)

The desired value of the fuse fuse current, A, is determined by the formula (63)

By value, a larger standard value of the fuse fuse link current, A, is selected, subject to (64)

The types of other fuses are determined similarly.

Calculation data are entered in table 15

Table 15 - Technical data of the fuses installed in ШР1

2.7.3 Selection of enclosure types

The choice of distribution cabinets is made according to the number of fuses, their rated currents, and the degree of protection. The technical data of the ShR1 cabinet are entered in table 16

Table 16 - Technical data of switch cabinet ШР1

2.8 Calculation and selection of distribution networks

A distribution network is a network from distribution cabinets to electrical consumers. Electrical consumers are connected to the SR by means of wires or cables, the totality of which is electrical wiring. Electrical wiring can be open (suspensions, trays, boxes, etc.), or hidden, in which cables or wires are laid hidden in the cable channels of walls and ceilings or in floor preparation pipes.

2.8.1 Selection of cross-sections of conductors for continuous current

To connect electrical consumers to ШР1, hidden laying of cables in floor preparation pipes at a temperature of 25ºС is used. The wiring is made with a VVG brand cable with three phase and one neutral conductors. The cable cores are made of copper, the insulation and sheath are made of polyvinyl chloride, there is no protective cover. The choice of cable sections is considered on the example of one of the sections of the distribution network from ShR1 - section 18N-1.

The rated current connected by this cable, the consumer, A, is determined by the formula (25)

According to the reference data, the nearest higher value of the continuous-admissible current, A, to the rated current of the EA is determined

- the condition is met

In accordance with the value, the VVG cable 31.5 + 11.5 mm² is selected.

The selection of the conductor cross-sections of the remaining sections of the distribution network from ШР2 is carried out in a similar way.

Table 17 - Data for the selection of cross-sections of conductors of the distribution network

2.8.2 Checking the selected sections of conductors for compliance with protective devices

The distribution network from ШР1 is protected by fuses installed in the distribution cabinet.

To perform a check, you need to know the following parameters:

protection factor, the value of which is determined from the reference data for a particular protective device (for fuses, since the network does not require overload protection);

operating current of the protective device, A - for fuses, the value is equal to the value of the fuse-link current, A;

value of continuous current, A.

The algorithm for checking the selected sections of conductors for compliance with protective devices is given on the example of one of the sections of the distribution network - section 21-H1.

The condition must be met

- the condition is met

Therefore, the selected cable section corresponds to the protective device. Checking for compliance with other selected sections of conductors is carried out similarly. The verification data are entered in table 17.

2.8.3 Checking the selected conductor cross-sections for allowable voltage loss

Voltage loss is the algebraic difference between the voltage of the power source and the voltage at the connection point of the consumer. The sum of allowable voltage losses of the supply and distribution networks should not exceed 3%.

To determine the voltage loss of a given distribution network, the voltage loss is determined in the section from switch cabinet No. 1 to the most remote consumer, that is, in section 34-H1.

Resistivity, determined by the formula

- specific conductivity, (for copper).

Specific reactance, determined from the reference data ().

The calculated value of voltage loss,%, is determined by the formula

The resulting calculated value, %, is compared with the allowable value for distribution networks, %, provided

- the condition is met

2.8.4 Calculation and selection of pipes

For hidden laying of conductors in floor preparation pipes, steel (electric-welded or water-gas), PVC, polyethylene and polypropylene pipes are used. The choice of pipe material depends on the environmental and process conditions. So, for example, when laying wiring, it is recommended to use steel pipes - in explosion and fire hazardous areas of premises, PVC pipes - when laying on non-combustible bases, and polyethylene and polypropylene pipes - only on fireproof bases.

To connect electrical consumers to switch cabinet No. 2, pipe laying of cables of the VVG brand using PVC and steel pipes is used. Pipes are laid at a depth of 0.3 m from the level of the clean floor. Steel pipes are used to carry out the exit of the cable from the floor, as it needs protection from mechanical damage. The cable connection from the steel pipe to the electrical consumer is carried out using a flexible input.

To perform pipe laying of electrical wiring, it is necessary to draw up a special project document “Pipe Procurement List”, which indicates the marking of the route, the material and diameter of the pipes, the beginning and end of the route, sections of pipe blanks.

Table 18 - Pipe procurement list

Then a summary of pipes is performed, indicating the pipe material and diameter in ascending order: Polyvinyl chloride pipe TU6 - 0.5.1646 - 83 Sh 20 mm = 71.6 m Gas-welded steel pipe GOST 10 704- - 76 Sh 20 mm = 7.7 m

2.9 Choice of location and type of complete transformer substation

Complete transformer substation (KTP - for indoor and KTPN - for outdoor installation) - a substation consisting of transformers and complete switchgear units (KRU or KRUN), supplied assembled or fully prepared for assembly.

Power transformers are divided into dry, oil and non-combustible liquid filled dielectric.

By location on the territory of the facility, the following transformer substations (TS) are distinguished:

separately standing at a distance from buildings;

attached, directly adjacent to the main building from the outside;

built-in, located in separate rooms inside the building, but with transformers rolled out;

intrashop, located inside industrial buildings with

placement of electrical equipment directly in the production or

a separate closed room with the roll-out of electrical equipment to the workshop.

2.10. Selection of the power supply scheme and calculation of supply networks with voltage up to 1 kV

The supply network is a network from the switchgear of a transformer substation to distribution cabinets, lighting panels, and powerful electrical consumers.

The supply network of the workshop is shown in Figure 9.

Figure 9 - Scheme of power supply of the mains

Data for calculation are given in table 19

Table 19 - Data of rated and peak currents of the supply network

2.10.1 Calculation and selection of types of nominal parameters of circuit breakers

Circuit breakers are used in the power supply network to protect them from emergency operation (overloads, short circuits, etc.). The algorithm for selecting the type and nominal parameters of automatic switches is considered on the example of a machine.

The condition must be met

The desired value of the operating current of the thermal element, A, is determined by the formula

The desired value of the current of the magnetic release, A, is determined by the formula

The condition must be met

where is the standard value of the operating current of the thermal element, the value of which is determined from the reference data.

The standard value of the current of the magnetic release, A, is determined by the formula

where k is the cutoff factor, the value of which is determined from the reference data.

The condition must be met

According to the reference data, the type and rating parameters of the circuit breaker are determined. The types of other circuit breakers are defined similarly. The calculation data are entered in table 20.

Table 20 - Type and ratings of circuit breakers

2.10.2. Calculation and selection of supply networks with voltage up to 1 kV

The supply networks of this workshop are carried out with cables of the ANRG brand.

An example of the selection of the cross section of the supply line cable is considered on the example of section M1. This section is made with an ANRG brand cable applied openly in the air on cable hangers at a temperature of 25ºC. The selection of the section is made according to the long-term permissible current. Data for selection are given in table 19.

According to the reference data, the nearest higher value of the continuous-admissible current, A, is determined, provided

- the condition is met

In accordance with the value, an ANRG 3120+135 mm2 cable is selected.

The selection of the sections of the remaining cables of the supply network is carried out in a similar way.

The selected cable section is checked for compliance with the protective device - the QF2 circuit breaker (according to Figure 9).

The condition must be met

- the condition is met

Therefore, the selected cable section corresponds to the protective device.

The calculated value of voltage loss is determined,%, according to the formula (68)

- resistivity, the value of which is determined by the formula (67)

- specific reactance, the value of which is determined from reference data (for a cable line up to 1 kV,).

The value of a mathematical function is determined by the corresponding value

The resulting calculated value, %, is compared with the allowable value for distribution networks, %, provided that the condition is met

Therefore, the selected cable section satisfies the requirements.

2.11 Calculation selection of the high voltage supply network

The high-voltage cable is designed to transmit electricity from the central distribution substation (CRS) to the transformer substation (TS). The choice of brand and section of the high-voltage cable depends on the laying conditions, environmental conditions and corrosion.

To connect a complete transformer substation, a high-voltage cable of the AAP2LShVU brand is used, that is, a cable with aluminum conductors, improved paper insulation, and an aluminum sheath.

Armor made of flat metal. The cable is laid in the ground in a trench one at a time. The cable length is 0.9 km. The soil is aggressive towards steel.

The selection of the cable section is made according to the long-term permissible current and the economic current density.

The value of the current flowing through the high side of the transformer, A, is determined by the formula

According to the reference data, the nearest greater value of the continuous-admissible current, A, to the current is determined

In this case, the condition

- the condition is met

In accordance with the value, the cable AAP2LShVU 310 mm2 - 6kV is selected.

The desired value of the cable cross-section is determined by the economic current density, mm2, according to the formula

where - economic density, the value of which is determined from the table

From among the standard values ​​of cable cross-sections, the nearest greater to the value, mm2, is selected, provided

Therefore, the cable m. AAP2LShVU 335 mm2 - 6 kV is selected.

From the found values ​​of the cable cross-sections for continuous current and economic current density, a larger one is selected

Therefore, the cable AAP2LShVU 335 mm2 - 6kV is selected.

The calculated value of voltage loss,%, is determined by the formula (68)

where is determined by formula (67)

determined according to reference data (for a cable line of 6 kV and a cable cross section of 35 mm2).

The value of a mathematical function is determined by the corresponding value

The resulting calculated value, %, is compared with the allowable value for supply networks, % - the condition is met

Therefore, the selected cable section satisfies the requirements.

Then the calculated value of the total voltage loss in the power supply networks is determined,%, according to the formula

The resulting calculated value, %, is compared with the allowable total value for distribution, supply networks and high-voltage lines, % is correct.

2.12 Calculation and selection of a grounding device

For grounding devices, you can use both natural (water and other metal pipes, except for pipelines with combustible substances), and artificial ground electrodes (steel rods driven into the ground and interconnected by a steel strip).

To ground the electrical equipment of the KTP of this workshop, artificial ground electrodes are used - steel bars hammered into the ground and interconnected by a horizontal ground conductor (steel strip) laid at a depth of 0.6 m. The initial data for the calculation are given in table 21

Table 26 - initial data for the calculation and selection of a grounding device

Earth fault current, A, is determined by the formula

The calculated resistance of the grounding device is determined, Ohm

In accordance with the PUE, the value of the resistance of the grounding device, Ohm, is determined, common for high and low voltage installations

Since the ground electrode is made of round steel with a diameter of 20 mm and a length of 5 m each, its resistance is determined by the formula

Since the length of the vertical ground electrodes l and the distance between them a are 5 m, the screening coefficient is determined by the formula

Then, the number of grounding conductors n, pcs, is determined by the formula

Since pcs, it is necessary to take into account the resistance of the horizontal ground electrode

The length of the horizontal strip, m, is determined by the formula

The required resistance of vertical grounding conductors, Ohm, is determined by the formula

The specified number of vertical ground electrodes, pcs, is determined by the formula

List of sources used

1. Barybin Yu. G., Krupovich V. N. Handbook for the design of power supply. - M .: Energy, 1990

2. Barybin Yu. G., Fedorov L. E. Reference book on the design of electrical networks and electrical equipment. - M .: Energy, 1990

3. Konyukhova E. A. Power supply of objects. - M .: Publishing house "Mastery"; High School, 2001

4. Lipkin B. Yu. Power supply of industrial enterprises. - M .: Higher school, 1990

5. Postnikov N. P. Power supply of industrial enterprises. - M .: Stroyizdat, 1990

6. Rules for the installation of electrical installations (PUE). — M.: Energoatomizdat, 2002

7. Sibikin Yu. D., Yashkov V. A. Power supply of enterprises and installations of the oil industry. - M .: OAO Publishing House Nedra, 1997

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