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abstract

This course project for the course "Power supply industrial enterprises" consists of explanatory note(49 pages); graphic part (2 sheets of A1 format); 28 tables; 3 drawings.

POWER TRANSFORMER, THERMAL PULSE, FUSE, STROBOSCOPIC EFFECT, BUSLINE, VACUUM SWITCH, SYNCHRONOUS MOTOR, BASE INSULATOR.

Introduction

The purpose of this course project is to obtain new and consolidate existing knowledge, as well as the manifestation creativity in the field of power supply design for small workshops.

This course project (CP) is the final stage in the study of the main course of the specialty "Power supply of industrial enterprises".

In the process of performing the CP, it is necessary to choose the configuration option for the workshop network at 0.4 kV. In the design version, it is necessary to determine the short-circuit currents and select the switching equipment, while ensuring that the power supply system has high technical and economic indicators and would provide the appropriate degree of quality and the required degree of reliability of the power supply of the designed object.

Initial data for the course project

Figure number 1 (distribution network 0.4 kV)

Option number 2

Name of electrical receivers, their number and power

	ES name	Plan number	Power, kWt
	Circular grinding
	Turret turning
	Vertical drilling
	Lathe semi-automatic
	surface grinding
	CNC lathe
	horizontal flow
	Horizontal boring
	ventilation unit
	Radial drilling
	Centerless grinding
	screw-cutting
	Grinding and grinding
	heating furnace
	thermal oven
	Electrothermal furnace
	ventilation unit
	Point stationary
	Butt welding
	Welding seam roller
	Welding spot
	ventilation unit

1. Calculationthree-phase electrical loads in the distribution network 0.4 kV

The calculation of electrical loads is carried out using the calculation coefficient method. This method calculation allows you to determine the electrical loads of electrical receivers with voltage up to 1000 V. Let's make a calculation for the electrical receiver "circular grinding" machine.

Calculation algorithm

1) Rated power of the electrical receiver

2) Number of electrical receivers,

3) According to the reference data, we determine the values ​​​​of the utilization and power factors, as well as by;

4) The total power of the group of electrical receivers:

5) We determine the average active and reactive power of this group of electrical receivers:

6) Find the value of the quantity

A similar calculation is performed for all other types of electrical receivers, with the exception of the welding load. The data obtained are summarized in table No. 1

7) Calculate the effective number of electrical receivers:

8) Determine the weighted average utilization factor:

9) Determine the value of the calculated coefficient:

10) for the main bus duct we have:

11) Define the values:

Taking into account lighting and welding loads:

We enter the obtained data in table No. 1.1

Ep name

Circular grinding

Turret turning

Vertical drilling

Lathe semi-automatic

surface grinding

CNC lathe

horizontal flow

ventilation unit

Radial drilling

Centerless grinding

screw-cutting

Grinding and grinding

heating furnace

thermal oven

Electrothermal furnace

ventilation unit

ventilation unit

Horizontal boring

Lighting NG

Welding NG

Total for the workshop

Table 1.1 - Calculation of loads for the selection of a shop transformer and ShMA

2. Calculationweldingequivalent three-phase load

All contact electric welding machines are single-phase with intermittent operation.

The calculation of the electrical loads of resistance welding machines is carried out at full power, the rms load is taken as the calculated heating load.

Table 2.1 - Initial data for calculating the electrical loads of resistance welding machines

1. Load distribution over three pairs of phases (starting from the nominal values):

3. Determine the average power of each pair of phases:

6. The design power of all welding machines is determined by the two most loaded phase pairs:

7. Calculated active and reactive loads are found by the formulas:

3. Light load calculation

Lighting is calculated according to the specific load per unit of production area:

Determine the area of ​​the workshop:

where - specific electrical load per unit of production area, kW /. Let us assume that lighting is also produced by fluorescent lamps with cos

The obtained values ​​are entered in table No. 1

4. Crane load calculation

The crane has three engines: trolley, bridge, lift.

Power ratio 1:2:3. Crane power 50 kW

Trolley power:

Bridge power:

Lifting power:

Inclusion factors:

for trolley

for bridge

for lifting

Let's determine the power of the engines:

Determine the rated power of the crane:

The obtained values ​​are entered in table No. 1.1

5. Selection of the number and power of the workshop transformerincluding reactive power compensation

We use a single-transformer substation, because there are power receivers in the workshop that allow a power outage during the delivery of the warehouse reserve, i.e. for consumers of categories II and III, and they are also acceptable for a small number (up to 20%) of category I consumers.

Since there is mutual redundancy, we will take the load factor

The choice of the power transformer of the KTP is made taking into account reactive power compensation.

The power of the transformer is determined by the active design load:

where is the number of transformers equal to 1;

Load factor equal to 0.8

taken from table number 1

We select the transformer TM-1000/10-U1 with parameters: ;

Let's determine the reactive power, which is advisable to pass through the transformer to the network with voltage up to 1 kV:

The first component of the power of a capacitor bank in a network with a voltage of up to 1000 V:

The second component of the capacitor bank power, determined in order to optimally reduce losses in the transformer and reduce losses in the 10 kV network:

where - economic importance = 0,25

We choose standard compensating devices according to:

Let's determine the real load factor of the transformer, taking into account the KU:

Determine the losses in the transformer

Losses are determined by the following formulas:

6. Selection of trunk and distribution busbars

Choice of SHMA

We select the main bus duct according to the rated current. We choose ShMA type ShMA-73 on.

Choice of SRA

We will calculate the loads for the choice of SHRA. Let's make a table of loads for calculating SHRA1,2 (tables No. 7.1-7.2)

The calculation algorithm is the same as for SHMA, but design factor is according to table 1 (ref. data) where Kp 1, reactive power is from the condition

for n: Qp = Qav; Pр = Кр Рср

Based on the values ​​of the table No. for rated current. choose ShRA1 type ShRA-73 - 400

Based on the values ​​of the table No. for rated current. choose ShRA2 type ShRA-73 - 250

7. Choice of power points

Let's calculate the loads for choosing a joint venture. Let's make a table of loads for calculating the joint venture 1,2,3,4 (tables No. 7.3-7.6)

The calculation algorithm is the same as for SHRA, the calculated coefficient is found according to table 1 (ref. data) where Kp 1, reactive power is found from the condition

for n10: Qp =1.1 Qav; Pр = Кр Рср

Let's check the forcespoints for currents of outgoing lines

We select power points: No. 1.: ShRS1 - 54UZ on rated current cabinet 320 A with the number of outgoing lines 8 and rated current of fuses 100 A type PN2 - 100 (up to 100 A)

We select power points: No. 2.: ShRS1 - 53UZ for a cabinet rated current of 250 A with the number of outgoing lines 8 and a rated current of 60 A fuses of the NPN type - 60 (up to 63A)

Let's check the currents of the outgoing lines, take the most powerful receiver, taking into account tg

(grinding grinding) and determine its rated current:

We select the power point: No. 3: ShRS1 - 28 UZ for a cabinet rated current of 400 A with the number of outgoing lines 8 and the rated current of the fuses: 2x60 + 4x100 + 2x250 A type PN2 - 100 (up to 100 A), NPN2-60 (up to 63A) , PN2-250 (up to 250A)

Let's check the currents of the outgoing lines, take the most powerful receiver, taking into account Ki (heating furnace) and determine its rated current:

We select the power point: No. 4: ShRS1 - 54UZ for the rated current of the cabinet 320 A with the number of outgoing lines 8 and the rated current of the fuses 100 A type PN2 - 100 (up to 100 A)

Let's check the currents of the outgoing lines, take the most powerful receiver, taking into account tg (Electrothermal furnace) and determine its rated current:

Selected power points are chosen correctly

Table 7.1 - Calculation of SRA-1.

ES name

Circular grinding

Turret turning

Vertical drilling

ventilation unit

Table 7.2 - Calculation of SRA-2.

ES name

Lathe semi-automatic

surface grinding

CNC lathe

horizontal flow

Horizontally-gross

Table 7.3 - Calculation of SP-1.

ES name

Radial drilling

Centerless grinding

Turning - screw-cutting

Table 7.4 - Calculation of SP-2.

Table 7.5 - Calculation of SP-3.

ES name

heating furnace

thermal oven

Table 7.6 - Calculation of SP-4.

ES name

Electrothermal furnace

ventilation unit

Selection of power points of the welding department

Choice of power point No. 5

Let's make a table of downloads (table No. 7.7)

Table 7.7 - Calculation of SP No. 5

ES name
Point stationary
Welding spot

Calculation algorithm

2. Determine the average load of each machine:

Load factor of the i-th welding machine;

Turn-on factor of the i-th welding machine.

AB:

4. Determine the RMS power of each welding machine:

AB, is determined by the formula:

We select power point No. 5: ShRS1 - 53UZ for a cabinet rated current of 320 A with the number of outgoing lines 8 and a rated current of 60 A fuses of the NPN2 type - 60 (up to 63A)

Let's determine the rated current for one machine - point stationary with a maximum:

The power point is chosen correctly

Choice of power point No. 6

Let's make a table of downloads (table No. 7.8)

Table 7.8 - Calculation of SP No. 6

Calculation algorithm

1. We distribute the loads over three pairs of phases:

2. Determine the average load of each machine:

Load factor of the i-th welding machine;

Turn-on factor of the i-th welding machine.

3. Let's determine the average power of each pair of phases, for example, AB:

4. Determine the RMS power of each welding machine:

5. RMS load of each pair of phases, for example, AB, is determined by the formula:

6. The design power of all welding machines is determined by the 2 most loaded phase pairs:

7. Determine the calculated active and reactive and apparent power:

In addition to the welding load, two ventilation units are connected to SP-6, with We sum up the welding load and the load of the ventilation units.

We select power point No. 6: ShRS1 - 53UZ for a cabinet rated current of 320 A with the number of outgoing lines 8 and a rated current of 60 A fuses of the NPN2 type - 60 (up to 63A)

Let's check the power point for the currents of the outgoing lines:

Let's determine the rated current for one machine - welding - butt with a maximum:

The power point is chosen correctly

8. Selection of cables and cable jumpers

The cross section of the cores of the workshop network cables is selected according to heating by a long-term rated current according to the condition:

where is the rated current, A;

long-term permissible current of a given section, A.

rated power of the electric receiver, kW;

rated power factor of the electrical receiver.

For induction motors with a squirrel-cage rotor, the following condition must be met:

for furnaces and welding machines:

For the rated current for welding machines, we take the root mean square current:

Table 8.1 - Selection of cables for EP, in which AD with short circuit. the rotor is the drive.

ES name
Circular grinding
Turret turning
Vertical drilling
Lathe semi-automatic
surface grinding
CNC lathe
horizontal flow
Horizontal boring
ventilation unit
Radial drilling
Centerless grinding
screw-cutting
Grinding and grinding
ventilation unit
ventilation unit

Table 8.2 - Selection of cables for EP thermal separation

Table 8.3 - Selection of cables for the EA of the welding department

Table 8.4 - Selection of cables and cable jumpers between ShMA and ShRA, SP,

Busbar name
SHMA-SHRA - 1
SHMA-SHRA - 2
ShMA-SP - 1
ShMA-SP - 2
ShMA-SP - 3
ShMA-SP - 4
ShMA-SP - 5
ShMA-SP - 6

Check the cable for permissible voltage loss:

Check the cable for the circular grinder:

rated current of the cable line, A;

cable line length, km;

linear active and reactive resistance of cables,

the number of cables laid in parallel.

We enter the data in tables No. 8

Table 8.5 Checking cable lines for voltage loss.

ES name
Circular grinding
Turret turning
Vertical drilling
ventilation unit
Lathe semi-automatic
surface grinding
CNC lathe
horizontal flow
Horizontally-gross
Radial - drilling
Centerless grinding
Turning - screw-cutting
Grinding and grinding
heating furnace
thermal oven
Electrothermal furnace
ventilation unit
ventilation unit

All cables are tested.

Table 8.6 Checking cable lines from the WMA to the joint venture of the welding department

Name of foreign line

All cables are tested

Table 8.7 Checking the cable lines of the welding department for voltage loss.

ES name
Point stationary
Welding spot
Butt welding
Welding suture roller

All cables are tested

9. Calculation of short circuit currents

The calculation is carried out for the two most electrically remote power receivers. This is a radial drilling machine (No. 45) connected to SP-1, and a ventilation unit (No. 42) connected to ShRA-1.

Figure No. 9.1 Single-line diagram for calculating short-circuit currents

Define the parameters of the equivalent circuit

The resistance of cable lines to a straight line is determined by the formula:

linear active and reactive resistance of cable lines, respectively, .

length of cable lines, m

number of cables laid in parallel, pcs.

Zero sequence resistance of cable lines:

Table No. 9.1 Calculation of the resistance of the direct and zero sequence of cable lines

Name of CL

Positive sequence resistance of the main and distribution busbar trunking:

Zero sequence resistance of the main and distribution busbar:

Table No. 9.2 Calculation of resistances of positive and zero sequence busbars for various short circuit points

The resistance of the transformer is determined by the formula:

short circuit losses in the transformer, kW;

rated voltage on the secondary winding, kV;

rated power of the transformer, kVA;

transformer short circuit voltage, %.

From the reference book we find the resistance of circuit breakers and fuses:

for circuit breakers Electron E16V with

for circuit breakers BA 0436 with 400 A

for circuit breakers BA 0436 with 160 A

Contact resistance of busbar connections:

ShMA (K2,K3) 9 sections of 6 meters

ShMA(K4,K5) 1.7 sections of 6 meters

ShRA (K4,K5) 18 sections of 3 meters

Contact resistance of connecting cables (we take into account 2 contacts per 1 cable):

Figure No. 9.2 Equivalent circuit for calculating short-circuit currents

Calculation of single-phase and three-phase short-circuit currents

The three-phase short-circuit current is determined by the formula:

The single-phase short-circuit current is determined by the formula:

average rated voltage of the network, V, where the short circuit occurred;

the total respectively active and inductive resistances of the direct sequence equivalent circuit relative to the short circuit point, including the resistance of busbars, devices and contact resistances, starting from the neutral of the step-down transformer, mOhm;

the same, zero sequence.

The zero-sequence resistance of a transformer with a low voltage of up to 1 kV with the winding connection scheme tr-11 is taken equal to the positive sequence resistance.

We calculate the current of a three-phase short circuit at point K1.

We believe that the short circuit at the beginning of the SMA since. it is necessary to calculate the maximum value of the short-circuit current

The total active resistance is:

The total reactance is:

The current of a three-phase short circuit is equal to:

We calculate the current of a single-phase short circuit at point K1.

We determine the current of a single-phase short circuit. We find the resistance of the reverse (equal to direct because there are no rotating machines) and zero sequence. It should be noted that in the positive sequence resistance, the active resistance of the arc must be taken into account. The influence of the active resistance of the arc on that short circuit is taken into account by multiplying the calculated short circuit current, found without taking into account the resistance of the arc at the short circuit location, by the correction factor K s, which depends on the resistance of the short circuit circuit.

For all other points, we find the short-circuit current without taking into account the arc.

We believe that the short circuit at the end of the SHMA since. it is necessary to calculate the minimum value of the short-circuit current.

Then, taking into account the resistance of the arc, we have a single-phase short-circuit current.

For all other points, we perform a similar calculation. We summarize the results in table No. 8.3

Table 9.3 Calculation of short-circuit currents

10. Calculation of starting and peak currents.

Calculation of starting currents

The starting current is determined for receivers with a squirrel-cage rotor to check the fuse inserts.

The starting current of the receiver is determined by the formula:

The normal current of the EA, which is determined by the following formula:

The multiplicity of the starting current, because there are no data, we will accept: = 5

Table No. 10.1 Values ​​​​of starting currents for receivers with AD

ES name
Circular grinding
Turret turning
Vertical drilling
Lathe semi-automatic
surface grinding
CNC lathe
horizontal flow
Horizontal boring
ventilation unit
Radial drilling
Centerless grinding
screw-cutting
Grinding and grinding
ventilation unit
ventilation unit

Peak current calculation

Determination of peak currents of main, distribution busbars and SP

To calculate the peak currents of trunk, distribution busbars and joint ventures, use the following formula:

I p - rated current SHMA, SHRA, SP, A;

I p.ma x - starting current of the highest power EP connected to ShMA, ShRA, SP, A;

K and - utilization factor of the largest electric power supply, A;

I n. max is the rated current of the EP with the highest power.

Calculation of the peak current of the SMA

Let's determine the rated current of the receiver with the highest power (in this case, it is a CNC lathe with K and = 0.2):

Maximum rated load node current (SHMA), taking into account reactive power compensation;

Peak current calculation ShRA-1

The largest electrical receiver in terms of power is vertical drilling with

Maximum rated current ShRA-1

Peak current calculation ShRA-2

The largest electrical receiver in terms of power is a CNC lathe with

Maximum rated current ShRA-2

Peak current calculation SP-1

The largest power receiver is a radial drilling machine with

Maximum rated current SP-1

Peak current calculation SP-2

The largest power receiver is a turret lathe with

Maximum rated current SP-2

Peak current calculation SP-4

In addition to the ventilation unit, SP-4 feeds electrothermal furnaces, the peak current of which practically does not differ from the nominal current, therefore we use the power of the ventilation unit motor with

Maximum rated current SP-4

Calculation of peak currents of resistance electric welding machines

Contact electric welding machines are consumers with a sharply variable mode of operation and create peak loads with a high frequency, as a result of which voltage fluctuations occur in the network.

The peak power of the machine at the time of welding is determined by the formula:

The calculated peak of any pair of phases, for example phase AB, is determined by the formula:

Where - the number of simultaneously working machines, determined from the probability curves

Number of machines connected to a given phase pair

When determining, the weighted average is calculated

The peak load for a linear wire is determined by the formula, according to the peaks of two phase pairs, for example in phase B:

Where, - peak load for a pair of phases AB and for a pair of phases BC

Peak line current:

Where - line voltage, kV

Peak current calculation SP-5

Table 10.2 Calculation of SP No. 5

6. Determine the peak power of the busiest phase by the two busiest phase pairs, hence the busiest phase B:

Determine the peak current

Peak current calculation SP-6

Table 10.3 Calculation of SP No. 6

Calculation algorithm

1. We distribute the loads over three pairs of phases:

2. Determine the peak power of each group of machines:

3. In each pair of phases, we find the weighted average switching coefficient:

the curves determine the number of simultaneously operating machines m out of the total number n in each pair of phases:

5. In each pair of phases, we select the machines with the highest peak power in accordance with the obtained number of simultaneously operating machines m, determine the total value of the peak power in each pair of phases:

6. Determine the peak power of the most loaded phase for the two most loaded pairs of phases:

Determine the peak current

But in addition to the welding load, SP-6 feeds two ventilation units, so we will determine the starting current of the AD of ventilation units.

Engine power of the ventilation unit with

Maximum rated current SP-6

i.e., the starting current turned out to be less than the welding current, therefore, in the future, we are guided by the peak welding current.

11 . Protection of shop electrical networks

In networks with voltage up to 1000 V, protection is carried out by fuses and circuit breakers.

The fuse is designed to protect electrical installations from overloads and short circuit currents. Its main characteristics are: rated current of the fuse link rated current of the fuse rated voltage of the fuse rated current of the fuse cut-off protective (ampere - second) characteristic of the fuse.

Designations in the calculation:

Rated mains voltage, kV;

Maximum short-circuit current networks, A;

Maximum rated current, A;

Starting current of the engine, A.

Long-term permissible current of the protected section of the network;

Minimum short-circuit current

Calculation algorithm

Consider, for example, the choice of a fuse for a circular grinding machine (No. 1).

We select a fuse of the NPN type - 60 s; ;

since the fuse is selected for an individual receiver, then the rated current is taken as the rated current:

4) , where 46.6 = 233 A;

The overload coefficient, which takes into account the excess of the motor current in excess of the rated value in the starting mode, taken 2.5 - for light starting conditions.

i.e. = 93.2 A - the selected fuse is not suitable. Let's choose a fuse type PN-2 100 s = 50 kA; ; , where

The fusing currents of the inserts must correspond to the multiplicity of permissible long-term currents (matching with the cross section):

Checking the fuse for:

6) - for sensitivity

7) - for breaking capacity

50 kA 5.01 kA, where = = 5.01 kA

Choose a fuse type PN-2 100: = 50 kA; ;

According to this algorithm, we select fuses and summarize the choice in table No. 11.1

Table No. 11.1 Selection of fuses for EP driven by IM with short circuit rotor

ES name

Circular grinding

Turret turning

Vertical drilling

Lathe semi-automatic

surface grinding

CNC lathe

horizontal flow

Horizontal boring

ventilation unit

Radial drilling

Centerless grinding

screw-cutting

Grinding and grinding

ventilation unit

ventilation unit

Table 11.2 - Choice of fuses for EA thermal compartment

Table 11.3 - Selection of fuses for the EA of the welding department

ES name

Point stationary

Welding spot

Butt welding

Welding seam roller

1 2 . Selection of circuit breakers

Let's write down the conditions for choosing circuit breakers:

where is the maximum rated load current;

Rated current of the circuit breaker release.

peak current of a group of electrical receivers, A

3) Detuning from long-term permissible currents:

For circuit breakers with only electromagnetic release (cut-off):

4) Detuning from the minimum short-circuit currents:

5) Breaking capacity test:

Let's consider the choice of a switch to the ShMA (SF1) as an example.

Table No. 12.1 Selection of circuit breakers

Installation location

Estimated data

Passport data

Breaker type

E25V: - SMA

BA 04-36: - SHRA1

VA 04-36: - SHRA2

VA 04-36: - SP1

VA 04-36: - SP2

VA 04-36: - SP3

VA 04-36: - SP4

BA 04-36: - SP5

VA 04-36: - SP6

Listusedliterature

1. Burnazova L.V. Guidelines for the course project. Mariupol 2010

2. Blok V.M. Manual for course and diploma design, second edition, revised and supplemented. Moscow "Higher School", 1990

3. Neklepaev B.N. Electrical part of power plants and substations. - M.: Energoatomizdat, 1986.

4. GOST 28249-93 Interstate standard "Short circuits in electrical installations up to 1000 V".

5. Fedorov A.A., Starkova L.E. Tutorial for course and diploma design on the power supply of industrial enterprises. Textbook for universities - M. "Energoatomizdat", 1986

6. Gaisarov R.V. Choice of electrical equipment. Chelyabinsk 2002

7. Media "Internet"

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Characteristics of consumers. Calculation of electrical loads. Selection of supply voltages, power and number of workshop transformers. Reactive power compensation. Selection of current-carrying parts and calculation of short-circuit currents. Selection and calculation of devices.

To calculate the load of the workshop, we use the method of ordered diagrams. This method is used for mass electrical receivers. He makes a connection workload with the operating mode of power receivers based on a probabilistic scheme for generating a group load graph.

General information about the calculation of electrical loads

The load of industrial enterprises or individual workshops usually consists of electrical receivers of various capacities. Therefore, all electrical receivers of the workshop are divided into groups of receivers of the same type of operation mode, with the allocation in each group of characteristic subgroups of electrical receivers with the same power, utilization factors and power factors.

When determining electrical loads, we use the method of utilization of the maximum electrical loads. This method establishes a connection between the calculated load and the operating modes of power receivers (EP) based on a certain probabilistic scheme for generating a group load schedule. The method is used as the main one for mass EP.

The procedure for determining the design loads:

All electrical receivers are divided into groups according to the value of the utilization factor K and, power factor cos, rated active power Rn. We determine according to table 4.10 2 the utilization factor and the power factor, we determine tg by the value of the power factor.

We count the number of EPs in each group and for the object as a whole.

In each group, the minimum and maximum powers are indicated at PV = 100%, if PV<100%, то номинальная мощность определится по формуле:

where: R pass- EP power according to the passport, kW;

PV - duration of inclusion.

The total power of all EPs is calculated by the formula:

P n=P none ; (2)

For each supply line, the power assembly indicator m is determined by the formula:

where: - rated power of the maximum consumer, kW;

Rated power of the minimum consumer, kW.

The average loads for the most loaded shift of power EDs of the same operating mode are determined by the formulas:

where: R cm- average active power of one or a group of receivers for the busiest shift, kW;

R nom- we take the rated power of electrical receivers according to table 1, kW;

To and- utilization factor, we take according to table 4.10 2;

Q cm- average reactive power of one or a group of receivers for the busiest shift.

For several groups of electrical receivers, we determine by the formula

We determine the average utilization factor of the EP K group and according to the formula:

The effective number of electrical receivers is determined by the formulas based on the following relationships.

At n5, K u 0.2, m3 and P nom const ne is determined by the formula:

Formula 9 can also be used when none of the cases listed below are suitable for the calculation.

For n>5, K u 0.2, m 3 and P nom const we take ne=n.

For n >5, K u 0.2, m< 3 и Р ном const принимаем nэn.

At n 5, K u 0.2, m 3 and R nom const ne is determined by the formula:

where: n* E is the relative value of the number of EP, the value of which is found in the table based on the dependence n* E = f(n*; P*).

According to formula 10, n * is found:

where: n 1 - the number of EPs in the group, the power of each of which exceeds the value of the maximum power of the EP of this group divided by 2.

P* is determined by the formula:

P nom- maximum unit power of the EP group, kW;

R nom1- the total rated power of a group of electrical receivers, the power of which exceeds the value of the maximum power of this EP group divided by 2, kW.

The maximum active power is determined by the formula:

where: To m - the coefficient of the maximum is determined according to table 3.2 5;

R nom - rated power of the electrical receiver.

Maximum reactive power is determined by the formula:

where: - coefficient of maximum reactive power, at n E? 10 \u003d 1, with n E<10 -=1,1

The total maximum power is determined by the formula:

The maximum current is determined by the formula:

We distribute the load:

RP-1: EP No. 1,2,3,4,5,6,7;

RP-2: EP No. 17,18,19,21,22,23;

RP-3: EP No. 8,9,12,13,14,15;

RP-4: EP No. 23,24,25,26,29,30,31;

RP-5: EP No. 10,11,16,27,28;

Determination of the design load of the workshop

For example, consider the definition of the load on the RP-1.

table 2

1) We determine the average load of the EP for the busiest shift using formulas (6), (7):

P cm.1 \u003d 0.65 2 3 \u003d 3.9 kW; Q cm.1 \u003d 0.75 3.9 \u003d 2.92 kvar;

P cm.2 \u003d 0.35 2 76 v0.65 \u003d 42.9 kW; Q cm.2 \u003d 1.73 42.9 \u003d 74.2 kvar;

P cm.3 \u003d 0.12 1 4.4 \u003d 0.53 kW; Q see 3 \u003d 2.29 0.53 \u003d 1.21 kvar;

P cm.4 \u003d 0.2 1 3 \u003d 0.6 kW; Q see 4 \u003d 1.17 0.6 \u003d 0.7 kvar;

P cm.5 \u003d 0.1 1 115.5 v0.4 \u003d 7.3 kW; Q cm.5 \u003d 1.73 14.6 \u003d 12.6 kvar.

2) Determine K and groups according to the formula (8):

3) The index of the power assembly according to the formula (3) will be equal to:

4) Since n > 5, To and > 0.2, m>3, then n e \u003d n \u003d 7

5) The maximum coefficient is determined according to table 4.3 2 . A more accurate value of Km is determined using the interpolation method:

6) The maximum active and reactive powers are determined by formulas (13) and (14):

P max \u003d 1.89 55.22 \u003d 104.36 kW.

Because n e<10, то принимаем значение К" М = 1,1:

Q max \u003d 1.1 91.67 \u003d 100.84 kvar.

The total maximum power is found by formula 15:

The rated current is determined by formula 16:

Similarly, we determine the calculated load for the remaining receivers and enter the results of the calculation in Table 2.

1) We divide all the EP of the shop into groups with the same operating modes and determine the total rated power of the shop:

2) Determine the indicator of the power assembly:

3) Determine the total load of the shop for the busiest shift:

4) We determine the load utilization factor of the EP shop:

5) Since n > 5, To and > 0.2, m> 3, then n e \u003d 31.

6) The maximum coefficient is determined according to table 4.3 2 . A more accurate value of Km is determined using the interpolation method:

where: K u1 K u2, K m1, K m2 - boundary values ​​of the coefficients K and and K m.

We determine the calculated active and reactive powers:

Since, we take the value:

8) Gross rated power:

9) Rated current:

The results of all calculations are entered in table 2.

table 2

	Coeff. maximum	Max. active power	Max. reactive power Q MAX , kvar	Max. full power		Coeff. Use	Effect. number of EP n E

Workshop lighting calculation

According to research, in modern conditions, the use of LED spotlights and industrial lamps in production workshops is very effective, as it meets all the requirements for operation. They are also an economical solution, as they allow you to reduce electricity costs by about 2.5 times. Particularly effective are LED spotlights with a narrow luminous flux distribution diagram. The most common and universal industrial lamps.

Industrial LED lamps have a number of undeniable advantages, which include:

* they provide high efficiency;

* are highly resistant to temperature extremes;

* do not emit mercury vapor and other harmful substances;

* Possess high moisture protection and protection against dust;

* can be used in difficult climatic conditions, where they provide instant switching on and stable operation;

* are economic also on the maintenance of power supply networks;

* easy to install;

* do not require special maintenance;

* have a long service life

When choosing light sources, one should take into account their advantages, disadvantages, and their efficiency.

Fluorescent lamps, compared to incandescent lamps, have a more favorable emission spectrum, 4-5 times greater luminous efficiency, longer service life and significantly lower glare. However, fluorescent lamps need starting equipment, they create a pulsation of the light flux, they ignite poorly at low temperatures, and they are less reliable.

Let us determine the luminous flux necessary to create normal working lighting in the workshop. For the calculation, we use the method of luminous flux utilization coefficients.

Work lighting is the main type of lighting. It is designed to create normal vision conditions in a given room and is usually performed by general lighting fixtures.

Emergency lighting is used to continue work or evacuate people when the working lighting is extinguished. It should provide at least 5% illumination at the workplace set for normal conditions. Workshop dimensions - 36 x 24 m.

For lighting, we will use industrial LED lamps.

GSSN-200, the parameters of which are specified in the appendix.

Let's calculate the lighting of the workshop:

The height of the room is 7 m. The height of the design surface above the floor is h p = 1.5 m. The design height can be determined by the formula:

H P \u003d h p - h p - h c m .; (eighteen)

H P \u003d 7 - 1.5 -1 \u003d 4.5 m;

To determine the distance between the rows of lamps, we use the formula:

L = H R L opt, m.; (nineteen)

where: L opt is the lighting engineering most advantageous optimal relative distance between the lamps, table. 2.1 [L.7]

L \u003d 4.5 1.2 \u003d 5.4 m .;

L opt \u003d 0.8 h 1.2-deep

Then the number of rows of fixtures can be determined by the formula:

where: B is the width of the design room, m.

Let's take the number of rows of lamps n p = 5.

We determine the actual distance between the rows by the formula:

where: L ST.V - the distance from the last row of fixtures to the wall, (m). We accept L ST.V = 2 m.

The number of fixtures is defined as:

where Ф 1 - the flux of lamps in each lamp.

Coefficient z, characterizing the unevenness of illumination, for LED lamps z = 1.

To determine the utilization factor, the index of the room i is found and the reflection coefficients are presumably estimated: ceiling - p, walls - c, design surface or floor - p, (Table 2.13 [L.7]) Determine. The index is found by the formula:

where: A is the length of the design room, m.

According to table 2.15 [L.7], we determine = 37%

We take the safety factor k equal to k = 1.5 (according to table 2.16 [L.7])

The area of ​​the room is determined by the formula:

S \u003d A B, m 2 (23)

S \u003d 36 24 \u003d 864 m 2

The specified minimum illumination is determined from the table. 4-1 [L.3] for visual work of medium accuracy, total illumination E = 200 lx.

For lighting, we accept GSSN-200 lamps with a luminous flux of 24,000 lm. Let's determine the number of lamps according to the formula 21:

Then the number of lamps in the row. We accept N St. row \u003d 7 N St \u003d 35.

Let's find the distance between the lamps in one row using the formula:

where: A - the length of the room without taking into account the thickness of the walls,

L A. ST - the distance from the first lamp in a row is determined by the formula:

The layout of lighting fixtures throughout the workshop is shown in Figure 3.

Active installed lighting power:

P mouth = N P o.p, (27)

where: P o.p. - lamp power, 200 W;

P mouth..\u003d 35 200 \u003d 7 kW

Reactive installed lighting power:

where: tg = 0.25 for LED lamps.

Let's determine the total lighting power:

Calculation of the total load of the workshop

The total design capacity of the workshop, taking into account lighting:

Estimated current of the workshop, taking into account lighting:

Introduction

In the power supply systems of industrial enterprises and installations, energy and resource saving is achieved mainly by reducing the loss of electricity during its transmission and transformation, as well as the use of less material-intensive and more reliable designs of all elements of this system. One of the proven ways to minimize power losses is to compensate for the reactive power of consumers using local sources of reactive power, and the correct choice of their type, power, location and automation method is important.

The main task of designing enterprises is to develop a rational power supply, taking into account the latest achievements of science and technology based on a feasibility study of solutions that ensure optimal reliability of supplying consumers with electricity in the required size, the required quality at the lowest cost. The implementation of this task is associated with the consideration of a number of issues that arise at various stages of design. When making technical and economic comparisons of power supply options, the main criteria for choosing a technical solution is its economic feasibility, i.e. the decisive factors should be: cost indicators, namely the reduced costs, taking into account one-time capital investments and estimated annual production costs. The reliability of the power supply system is primarily determined by the circuit and structural design of the system, the reasonable amount of reserves incorporated into it, as well as the reliability of the incoming electrical equipment. When designing power supply systems, it must be taken into account that at present, the input is becoming more widespread, which makes it possible to bring the highest voltage (35 - 330 kV) as close as possible to consumer electrical devices with a minimum number of stages of intermediate transformation. The fundamental principle in the design of power supply schemes is also the rejection of the "cold" reserve. Rational solution schemes should ensure the limitation of short-circuit currents. When necessary, when designing power supply systems, reactive power compensation should be provided. Measures to ensure the quality of electricity should be addressed in a comprehensive manner and based on rational technology and production mode, as well as on economic criteria. When choosing equipment, it is necessary to strive for unification and focus on the use of complex devices (camera team of one-way service (KSO), complete switchgears (KRU), etc.) of various voltages, power and purpose, which improves the quality of the electrical installation, its reliability, convenience and safety. service.

1. Design of electrical networks of industrial enterprises

Power supply design is the impact and cable lines from the substation of the power system to the main step-down substation or distribution point, industrial facility.

Internal power supply is a scheme for distributing energy between consumers of a machine shop. Radial, main or mixed (combined) power supply schemes are used to power the workshop equipment.

Radial schemes are used in the presence of groups of concentrated loads with their uneven distribution over the area of ​​the workshop, in explosion and fire hazardous workshops, in workshops with a chemically active and similar environment. Radial circuits are widely used in pumping and compressor stations, petrochemical industry enterprises, foundries and other shops. Radial circuits of intrashop networks are performed with cables or insulated wires. They can be used for dune loads of reliability category.

The advantage of radial circuits is their high reliability, since an accident on one line does not affect the operation of EP connected to another line. The disadvantages of radial circuits are: low efficiency associated with a significant consumption of conductor material, pipes, distribution cabinets; a large number of protective and switching equipment; limited flexibility of the network during the movement of the EA caused by a change in the technological process; low degree of industrialization of installation.

It is advisable to use trunk circuits to power power and lighting loads distributed relatively evenly over the workshop horse, as well as to power a group of EAs belonging to the same line. With backbone systems, one supply line serves several switch cabinets and large EPs of the workshop.

The advantages of trunk circuits are: simplification of the RUNN of transformer substations; high flexibility of the network, which makes it possible to rearrange technological equipment without altering the network; the use of unified elements (bus ducts) that allow installation by industrial methods. The disadvantage is their lower reliability compared to radial circuits. Since in the event of an accident on the highway, all EPs connected to it lose power. (However, the introduction of redundant jumpers between the nearest trunks into the circuit significantly increases the reliability of trunk circuits.)

The use of wine pipelines of constant cross section leads to some overspending of the conductor material.

In practice, for the power supply of shop EPs, radial or trunk circuits are rarely found in their pure form. The most common are mixed schemes that combine elements of radial and main schemes. The workshop equipment is not interconnected and operates continuously. With two shifts, the shop works 4500 hours a year.

The quality of electrical energy is determined by the totality of its characteristics, under which power receivers can operate normally and perform their functions.

Continuous mode is the mode of operation of the electric receiver for such a long time that the excess of the heating temperature of all its parts over the ambient temperature reaches a practically steady value.

In this shop at the enterprise, electric receivers of the second and third categories are used.

Electric receivers of the second category are consumers, a break in power supply, which leads to massive undersupply of products, massive downtime of working mechanisms.

Power receivers of the third category are consumers that do not fit the definition of power receivers of the second and first categories, the interruption in the power supply of which does not exceed one day.

For these consumers, one or two transformer substations are used, which are backed up using a warehouse or mobile reserve with an acceptable power outage for the time necessary to turn on the backup action of the on-duty personnel or mobile operational team. Power supply via one high-voltage line with the possibility of emergency repair of this line per day.

The power supply of the workshop receives from the workshop transformer substation 10/0.4 kV located on the territory of the workshop. The workshop TP receives electricity from the plant's GPP via a cable line. All electrical receivers in this workshop are of category 2. Number of shifts 2. The turning shop is located in the temperate climate zone, the temperature inside the shop is +32C. The workshop is located on sandy loam with a temperature of -8C.

Table 1 - Initial data

Name of equipment	No. according to plan	Number of equipment	Type of equipment	pH.tech, kW	Rn.dv, kW	ηnom%	Cos	Ip/In
Aggregate-drilling machine	1-3	3	4А225М4Y3	53,50	55,00	92.5	0.90	7
Finishing and boring machine	4-6	3	4A225M4Y3	52,20	55.00	92,5	0.90	7
Machine specially bored	7-9	3	4A180S4Y3	19.00	22.00	90.0	0.90	7
Diamond-bored machine	10-12	3	4A200M4Y3	34,60	37,00	91,0	0.90	7
Semi-automatic drilling and threading	13-15	3	4A180S4Y3	36.90	37,00	91.0	0.90	7
Semi-automatic circular grinding	16-18	3	4A280S4Y3	92.80	110.00	92.5	0.90	7
Hydrocopy lathe	19-21	3	4A180M4Y3	29.30	30.00	91,0	0.89	7
Horizontal slot milling machine	22-24	3	4A180M4Y3	22,85	30,00	91,0	0.89	7
Milling machine	25-27	3	4А180S4Y3	18,70	22,00	92,5	0,90	7
drilling machine	28-30	3	4A132S4Y3	6,3	7,50	87,5	0,86	7,5

2. Calculation of electrical loads

The electrical loads of power supply systems are determined to select the power of transformers, the power and place of connection of the compensating installation (CU), the selection and verification of current-carrying elements according to the condition of permissible heating, the calculation of voltage losses and the choice of protection devices.

For each group, we determine the installed power:

, - rated power on the motor shaft, kW

Electrical loads determine the choice of the entire power supply system. For their calculation, the demand factor method and the chart ordering method are used. The first method is usually used at the design stage, when the power of individual power receivers (EP) is unknown.

The method of ordering diagrams or the method of the maximum coefficient is the main one in the development of technical and working projects of power supply. It allows you to determine the estimated load of any node of the power supply circuit by the rated power of the EP, taking into account their number and characteristics. According to this method, the calculated maximum load of the EA group is:

Group rated power R n is defined as the sum of the rated powers of the EP, with the exception of the reserve ones.

Utilization factor To and one or a group of EP (Table 2.1) characterizes the use of active power and is the ratio of the average active power of one or a group of EP for the busiest shift to the rated power.

Maximum factor To m is the ratio of the calculated maximum active power of the load of the EP group to the average load power for the most loaded shift.

For an EA group of one operating mode, the average active and reactive loads for the most loaded shift are determined:

;
. (2.2)

Rated power P of the same type of EP

. (2.3)

Table 2.1

Design coefficients of electrical loads

Electrical receivers
Pumps, compressors
Industrial fans, blowers, smoke exhausters
Welding transformers: manual electric welding
automatic welding
Resistance Furnaces
Incandescent lamps
Fluorescent lamps
Overhead cranes, overhead cranes, telphers, elevators

For consumers with variable load (group A), the calculated active load R p (A) of the EP group of the department (section, workshop) is determined taking into account the maximum coefficient To m and medium load compartments:

, (2.4)

where To m (A) - is determined depending on the effective number of EP n e and from the group utilization factor To and for the busiest shift (Table 2.2).

Table 2.2

Maximum odds To m for various utilization rates

depending on the n uh

	Meaning To m at To and

The weighted average utilization factor of the EP department of group A

, (2.5)

where R n (A) - the total rated active power of the EP of the group

;

R cm (A) - the total average shift active power of the EP of group A

.

The effective number of EPs of group A is found by the formula

, (2.6)

or in simplified terms.

The calculated reactive load of the EP group with a variable load for the department and the shop as a whole is determined taking into account the given number of EP:

at n e >10
, (2.7)

at n e £10
. (2.8)

For group B consumers with a constant load schedule ( To m = 1) the load of the EP group is equal to the average load for the busiest shift. Estimated active and reactive power of the EP of group B of the department:

;
. (2.9)

Such EA can include, for example, electric motors of water supply pumps, fans, unregulated smoke exhausters, compressors, blowers, unregulated resistance furnaces.

After determining the loads of the departments, the calculated load for the workshop is found:

,
, (2.10)

where R cm j , Q cm j– active and reactive loads of ED j-th department; m- the number of departments.

Estimated active and reactive power of the workshop:

kW;
kV∙Ar. (2.11)

If there are single-phase EAs in the workshop, distributed over the phases with a non-uniformity £ 15%, they are taken into account as three-phase ones of the same total power. Otherwise, the calculated load of single-phase EA is taken equal to the triple value of the load of the most loaded phase.

With the number of single-phase EA up to three, their conditional three-phase rated power is determined by:

a) when a single-phase ED is switched on for phase voltage in a three-phase system

where S n- nameplate power; R n.f. - rated power of the most loaded phase;

b) when one EP is switched on for line voltage

. (2.13)

The maximum loads of single-phase EA with more than three of them with the same To and and cosj connected to the phase or line voltage are determined by:

;
. (2.14)

To determine the electrical loads of the workshop, a summary sheet is compiled (Table 2.3) with filling in all the calculated data.

Table 2.3

Summary sheet of electrical loads of the workshop

Name of the characteristic group of EP	Number of EP	Installed power of the electric power supply, reduced to PV = 100%		Coefficient use To and		Average load for the busiest shift				Maximum rated power
		one, kW	total, kW			R cm,	Q cm, kW			R m, kW	Q m, kV∙Ar

Lighting loads are calculated by the approximate method according to the specific power per illuminated area.

;
(2.15)

where R udo - specific design power per 1 m 2 of the production area of ​​\u200b\u200bthe department ( F);

To co - lighting demand coefficient (Table 2.4).

Table 2.4

Estimated coefficient To and, cosj, R ud0 and To from individual workshops of industrial enterprises

	Name of workshops				R ud0 ,
	Compressor
	Pumping
	Boiler houses
	welding shop
	Electrical shop
	assembly shops
	Mechanical
	Administrative and amenity premises

When using the known values ​​of the specific power of general uniform lighting, depending on the type of lamp and, based on their optimal location in the room, the power of one lamp is determined.

To illuminate the main workshops with a height of more than 6 m and in the presence of open spaces, gas-discharge lamps of the DRL type with cosj = 0.58 are used. For administrative and amenity premises, fluorescent lamps with cosj = 0.85 are used, incandescent lamps with cosj = 1 are used to illuminate small rooms.

The total design load of the workshop is determined by summing the design loads of power and lighting groups of electrical receivers

According to the value of the full design load, a transformer is selected taking into account reactive power compensation.

Note : examples for determining electrical loads are presented in.

FGOU SPO "Penza College of Management

and industrial technologies. E. D. Basulina

EXPLANATORY NOTE

TO COURSE PROJECT

Introduction

1. Theoretical part

1.1 Brief description of the workshop, a brief description of the technological process

1.2 Characteristics of electricity consumers and definition of the category of power supply. List of electricity consumers

1.3 Selecting the supply voltage

1.4 Choice of shop power supply scheme

1.4.1 The tasks of the power supply of the workshop

1.4.2 Selecting a power supply scheme for the workshop

2. Settlement part

2.1 Calculation of electrical loads

2.2 Reactive power compensation and choice of compensating device

2.3 Selection of the number and power of power transformers of the workshop substation

2.4 Calculation and selection of the power network, cross-sections of wires and cables

2.5 Selection of protection and automation devices

3. Economic part of the project

3.1 Preventive maintenance system

3.2 Features of the repair of electrical equipment and its technical characteristics

3.3 Calculation of the repair complexity of electrical equipment

Conclusion

List of sources used

Introduction

The most important role in the country's economy belongs to mechanical engineering. The growth of mechanical equipment in all branches of the national economy characteristically depends on the rate of development of mechanical engineering.

Mechanical engineering is characterized by an extraordinary variety of technological processes that use electric power: foundry production and welding, metal forming and cutting, hardening heat treatment, application of protective and finishing coatings, etc.

Mechanical engineering enterprises are widely equipped with electrified hoisting and transport mechanisms, pump compressor units, machining and welding equipment. Automation in mechanical engineering affects not only individual technological units and auxiliary mechanisms, but also entire complexes, automated production lines, workshops and factories.

Scientific and technological progress implies an increase in the power supply in industry through the improvement and introduction of new, economical and technological electrical equipment. Electrical receivers that convert electrical energy into other types of energy firmly occupy a leading position in the vast majority of production processes.

A constant increase in the power-to-weight ratio of production is ensured by the advanced development of the electric power industry.

Production efficiency and product quality are largely determined by the reliability of the means of production and, in particular, the reliability of electrical equipment.

The intensive development of technical means necessitated the improvement of the design methodology and the creation of new highly efficient enterprises on its basis. In modern conditions, the operation of electrical equipment requires more and more profound and versatile knowledge, and the tasks of creating a new or upgrading an existing electrified technological unit, mechanism or device are solved by the joint efforts of technologists, mechanics, and electricians.

Reconstruction of existing industries using modern equipment, based on energy-saving technologies is one of the main tasks of re-equipment of production.

In the conditions of scientific and technological progress, the relationship between man and nature has become much more complicated. Scientific and technological progress has created enormous opportunities for conquering the forces of nature, and at the same time for its pollution and destruction. Industrial progress is accompanied by the entry into the biosphere of a huge amount of pollution, which can upset the natural balance and threaten human health.

The course towards the intensification of economic development requires a further increase in the efficiency of the use of natural resources. Based on this, it is planned to expand the scientific development of fundamental and applied problems of nature protection, as well as to increase the efficiency of the use of existing equipment.

The relevance of the topic of the course project corresponds to the task of technical re-equipment - the creation of highly efficient energy-saving production.

1. Theoretical part

1.1 Brief description of the workshop, a brief description of the technological process

The main electrical equipment of the metal-cutting machine shop is a group of turning, grinding and tool-grinding machines. Consider these groups:

1. The turning group can include screw-cutting lathes of the brand 16K25 with a power of 11 kW.

2. Grinding equipment includes round, flat, internal and thread grinding machines with a power of 0.4 kW for an internal grinding machine of the 3M225V brand to 5.5 kW for a thread grinding machine of the 5K823V brand.

3. The grinding group includes: universal grinding machines, grinding machines, grinding machines for worm cutters and grinding machines for round dies. The power ranges from 0.4 kW for universal grinding machines to 2.2 kW for grinding machines.

There are three operating modes for machines:

1. Continuous, in which the machines can work for a long time, and the temperature rise of individual parts of the machine does not go beyond the established limits;

2. Repeated-short-term, here the working periods t p alternate with periods of pauses t 0, and the duration of the entire cycle does not exceed 10 minutes. In this mode, the electric motors of overhead cranes, hoists, welding machines operate.

3. Short-term, in which the operating period is not so long that the temperatures of individual parts of the machine reach a steady value, and the stop period is so long that the machine has time to cool down to ambient temperature.

Reliability of power supply - the ability of the system to provide the enterprise with electricity of good quality.

To ensure the reliability of power supply, power receivers are divided into three categories:

I. Electric receivers, where a power outage will cause danger to people's lives, damage to expensive equipment, mass product defects.

II. Electric receivers, here a break leads to a massive undersupply of products, downtime of workplaces, mechanisms and industrial processes.

III. Electrical receivers for non-serial production of products, auxiliary workshops, utility consumers, agricultural plants. Break in power supply up to 24 hours.

1.2 Characteristics of electricity consumers and definition of the category of power supply. List of electricity consumers

Consumers of electricity in this workshop are lathes, sharpening grinding groups.

Screw-cutting lathes are designed to perform a variety of jobs. On these machines, it is possible to grind external cylindrical, conical and shaped surfaces, bore cylindrical and conical holes, process end surfaces; cut external and internal threads; drilling, countersinking and reaming holes; perform cutting, trimming, and other operations.

Grinding machines are designed for processing parts with polished wheels. They can process external and internal cylindrical, conical and shaped surfaces and planes, cut workpieces, grind threads and gear teeth, sharpen cutting tools, etc. Depending on the shape of the surface to be ground and the type of grinding, general-purpose machines are divided into cylindrical grinding, centerless grinding, internal grinding, surface grinding and special.

Sharpening machines. Depending on the nature of the operations, grinding machines are divided into simple, universal, special, and according to the type of processing - into machines for abrasive sharpening and finishing and non-abrasive (anode-mechanical, electric spark, etc.). Universal grinding machines are used for sharpening and finishing cutters, drills, countersinks, reamers, taps, cutters, cutters, worm cutters and perform external and internal grinding. Special grinding machines are designed for sharpening cutters, drills, worm cutters, etc.

All equipment is presented in the list of electricity consumers.

1.3 Selecting the supply voltage

Considering that the main parameter of technical and economic indicators is the accepted voltage, possible options for power supply are considered, i.e. supply voltage is selected.

A voltage of 10 kV is used for intra-factory power distribution:

At large enterprises with the presence of engines that allow direct connection to a 10 kV network;

At enterprises of small and medium power, in the absence or small number of engines that can be connected directly to the 6 kV network;

In the presence of a factory power plant with a generator voltage of 10 kV.

Voltage 6 kV is used:

If the enterprise has a significant number of electrical receivers for this voltage;

In the presence of a factory power plant for a voltage of 6 kV;

At reconstructed enterprises with a voltage of 6 kV.

For the intrashop power supply system, voltages of 380 and 660V are used.

A voltage of 380 V is used to power general industrial power receivers.

if, according to the conditions of the general plan, technology and the environment, deep inputs, crushing of workshop substations and their approach to the centers of the groups of electrical receivers fed by them cannot be carried out, and in connection with this there are extended and branched networks up to 1000 V, as well as large concentrated loads.

The feasibility of using a voltage of 660 V should be justified by technical and economic comparisons with a voltage of 380/220 V, taking into account the prospective development of the enterprise, the reduction in the cost of 660 V electric motors and their better efficiency compared to 6 kV electric motors, and also taking into account the reduction of electricity losses in the 660 V network by compared to a 380 V network.

For lighting installations, AC lighting networks with a grounded neutral voltage of 380/220 V are mainly used.

Networks with an isolated neutral voltage of 220 V and below are used mainly in special electrical installations with increased electrical safety requirements.

Direct current is used for backup power supply of critical lighting receivers and in special electrical installations.

With a voltage of power receivers of 380 V, lighting is usually powered from 380/220 V transformers, common for power and lighting loads.

Ensuring the quality of electricity at the terminals of electricity receivers is one of the most difficult tasks to be solved in the process of designing and operating power supply systems. For the rational operation of electrical receivers, it is necessary that the quality of electricity of three-phase networks correspond to the quality indicators regulated by GOST 13109-77:

Voltage deviation (+ - 5% for the lighting network, + - 5-10% for the power network);

Frequency deviation (from 1.5 to 4%);

Coefficients of non-symmetry and unbalance of stresses (K and<=2%)

Based on the above requirements, we set the voltage for the workshop of metal-cutting machines 380/220 V for the power and lighting network, taking into account the requirements for quality indicators of the voltage of the intra-factory power distribution - 10 kV

1.4 Choice of shop power supply scheme

1.4.1 The tasks of the power supply of the workshop

The main task of power supply is to provide consumers with electricity. With the help of electrical energy, millions of machine tools and mechanisms are set in motion, rooms are illuminated, production processes are automatically controlled, etc.

To ensure the continuity of the production process and the constant updating of equipment, modern power supply systems of an enterprise must have increased reliability and flexibility, provide the specified power quality indicators, be highly economical, easy to use and meet the requirements of fire, explosion and electrical safety.

The reliability of the power supply system is affected by:

Compliance with network bandwidth;

Connection diagrams of network elements;

The presence of sensitive high-speed and selective protection;

The presence or absence of a power shortage in the power system and spare reserve elements and other factors.

The power supply systems of the enterprise must also meet the following requirements:

1. Ensuring proper power quality, voltage levels and deviations, frequency stability, etc.;

2. Saving non-ferrous metals and electricity;

3. Maximum approximation of higher voltage sources to electrical installations of consumers, providing a minimum of network links and stages of intermediate transformation, reducing primary costs and reducing electricity losses while increasing reliability.

The fulfillment of these requirements is ensured, first of all, properly on the basis of appropriate calculations of the power of power sources and the throughput of all elements of the power supply system, the selection of their highly reliable design and resistance in emergency modes, the use of modern protection and automation systems, proper operation.

Through the power supply systems, electricity is accounted for and control over its rational use.

The most important tasks that must be solved in the process of designing power supply systems for industrial enterprises include the following:

1. Selection of the most rational in terms of technical and economic indicators of the power supply system of the workshop;

2. Correct, technically and economically justified choice of the number and power of transformers for the main step-down and workshop substations;

3. Choice of economically expedient mode of operation of transformers;

4. The choice of rational voltages in the circuit that ultimately determines the size of capital investments, the consumption of non-ferrous metal, the amount of electricity losses and operating costs;

5. Selection of electrical apparatus, insulators and current-carrying devices in accordance with the requirements of technical and economic feasibility;

6. Selection of the cross-section of wires, tires, cables, depending on a number of technical and economic factors.

Electricity consumers have their own specific features, which determine certain requirements for their power supply - power supply reliability, power quality, redundancy and protection of individual elements, etc.

When designing structures and operating power supply systems for industrial workshops, it is necessary to correctly select voltages in the technical and economic aspect, determine electrical loads, select the circulation, number and power of transformer substations, types of their protection, reactive power compensation systems and voltage regulation methods.

1.4.2 Selecting a power supply scheme for the workshop

Workshop networks are divided into supply networks, which depart from the power source (substation), and distribution networks, to which electrical receivers are connected.

Intra-shop distribution of electricity can be carried out according to three schemes:

Radial;

Trunk;

Mixed.

Workshop electricity distribution networks should:

1. Ensure the necessary reliability of power supply to power receivers, depending on their category;

2. Be convenient and safe to operate;

3. Have a design that ensures the use of industrial and high-speed installation methods.

The main circuit is used for high currents (up to 6300A), can be connected directly to a transformer without a switchgear on the low voltage side, and is performed with a uniform distribution of electricity to individual consumers. Trunk circuits are universal, flexible (allow you to replace process equipment without changing the electrical network).

The radial power supply scheme is a set of shop electrical network lines extending from the low voltage switchgear of the transformer substation and designed to power small groups of power receivers located in different places of the shop. The distribution of electricity to individual consumers with radial circuits is carried out by independent lines from power points located in the center of the electrical loads of this group of consumers. The advantage of radial circuits is high power supply reliability and the possibility of using automation.

However, radial schemes require high costs for the installation of distribution centers, cabling and wires.

In the projected work for the power supply of the workshop of metal-cutting machine tools, based on the analysis of literature sources, the main circuit was chosen, presented on a sheet of A3 format. Design groups of electrical receivers are presented in table 2.

Table 2 Settlement groups of electrical receivers

	item number on the drawing	Name of equipment	Quantity	Model
		Universal sharpening
		Grinding tools for hobs
		Sharpening
		Turning and screw-cutting
		Sharpeners for round dies
		Thread grinding
		surface grinding
		Internal grinding
		Cylindrical grinding
		Fans

2. Settlement part

2.1 Calculation of electrical loads

This section discusses methods for determining electrical loads, calculates power loads and draws up a summary sheet.

The creation of each industrial facility begins with its design: determining the expected (calculated) loads.

When determining the calculated electrical loads, you can use the main methods:

1. ordered charts (maximum coefficient method);

2. specific electricity consumption per unit of production;

3. demand coefficient;

4. specific density of electrical load per 1 m 2 of production area.

The calculation of the expected loads is given by the method of ordered diagrams,

which is currently the main one in the development of technical and working projects of power supply.

The calculated maximum power of electrical receivers is determined from the expression:

P max \u003d K max * K and * P nom \u003d K max * P cm,

where: K and - utilization factor;

K max - coefficient of maximum active power;

P cm is the average active power of electrical receivers for a more loaded scheme.

For a group of power receivers for a more loaded change of operating mode, the average active and reactive loads are determined by the formula:

R cm \u003d K u * R nom

Q cm \u003d P cm * tg φ,

where tg φ - corresponds to the weighted average cos φ, typical for power receivers of this operating mode.

The weighted average utilization factor is determined by the formula:

To U.SR.VZ. = ∑R cm / ∑R nom,

where ∑Р cm is the total power of electrical receivers and groups for the busiest shift;

∑R nom - the total rated power of electrical receivers in the group.

The relative number of power receivers is determined by the formula:

N * \u003d n 1 / n,

where n 1 is the number of large receivers in the group;

n is the number of all receivers in the group.

The relative power of the largest power receivers is determined from the expression:

Р * = ∑Р n 1 /∑Р nom,

where ∑Р n 1 is the total active rated power of large power receivers of the group;

∑R nom - total active rated power of electrical receivers of the group.

The main effective number of power receivers in a group is determined by reference tables, based on the values ​​of n * and P *

n * e \u003d f (n * ; P *)

The effective number of power receivers in a group is determined by the formula:

N e \u003d n * e * n

The maximum coefficient is determined from the reference tables, based on the values ​​of n e and K U.SR.VZ .:

K max \u003d f (N e; K U.SR.VZ.)

Estimated maximum active power of the circuit:

R max = K max * ∑R cm

Estimated maximum reactive power in the circuit:

Q max = 1.1 ∑ Q cm

The total design capacity of the group is determined by the formula:

Smax = √Pmax 2 + Qmax 2

The maximum rated current of the group is determined by the formula:

I max \u003d S max / (√3 * U nom)

Calculation of the expected loads of the metal-cutting machine shop.

1. We determine the average active and reactive power for a more loaded circuit of power receivers.

Calculation example for machine positions 1-3

R cm1-3 \u003d R nom × K and \u003d 0.4 × 0.14 × 3 \u003d 1.68 kW

Q cm1-3 \u003d P cm1-3 × tgφ \u003d 1.68 × 1.73 \u003d 2.9 kvar

The rest of the data on the calculation are presented in table 4

2. Determine the total power for the group:

∑P nom = 3 P nom1-3 + 2 P nom4.5 + 2 P nom6.11 + 2 P nom7.10 + 2 P nom8.9 + 2 P nom12.18 + 3 P nom13-15 + 3 P nom16, 17.22 + 2 P rated 19.21 + 3 P rated fan = 193.5 kW

3. Summing up active and reactive loads:

∑P cm = P cm1-3 + P cm4.5 + P cm6.11 + P cm7.10 + P cm8.9 + P cm12.18 + P cm13-15 + P cm16.17.22 + P cm19.21 + P cm vent = 57.12 kW

∑Q cm = Q cm1-3 + Q cm4.5 + Q cm6.11 + Q cm7.10 + Q cm8.9 + Q cm12.18 + Q cm13.15 + Q cm16.17.22 + Q cm19.21 + Q cm vent = 36.53 kvar.

4. Determine the weighted average value of the utilization factor:

K and.av.vz \u003d 57.12 / 193.5 \u003d 0.3

5. Determine the relative number of electrical receivers:

N*=5/25=0.2

6. We determine the relative power of the largest electrical receivers in terms of power:

P * \u003d 160 / 193.5 \u003d 0.83 kW

7. The main effective number of power receivers in the group is determined according to table 2.2 based on the values ​​of N * and P *:

n*e = 0.27

8. Determine the effective number of power receivers in the group:

N e \u003d 0.27 × 25 \u003d 6.75

9. The maximum coefficient K max is used for the transition from the average load to the maximum. The active power maximum factor is determined according to Table 2.3, based on the values ​​of n e and K i.sr.vz:

K max = 1.8

10. Determine the calculated maximum active power of the circuit:

P max \u003d 1.8 × 57.12 \u003d 102.82 kW

11. Determine the calculated maximum reactive power of the circuit:

Q max \u003d 1.1 × 36.53 \u003d 40.18 kvar

12. Determine the total design capacity of the group:

13. Determine the maximum rated current of the group:

I max = 110.4 / (1.73 × 0.38) = 157.7 A

Table 3 Summary sheet of electrical power loads by workshop

	Name of equipment		Р nom, kW		Q cm, kvar
									R max, kW	Q max, kvar	S max, kVA
	Universal sharpening
	Grinding tools for hobs
	Sharpening
	Turning and screw-cutting
	Sharpeners for round dies
	Thread grinding
	surface grinding
	Internal grinding
	Cylindrical grinding
	Fans

2.2 Reactive power compensation and choice of compensating device

Reactive power compensation or increasing the power factor of electrical installations of industrial enterprises is of great economic importance and is part of the general problem of increasing the efficiency of power supply systems and improving the quality of electricity supplied to the consumer.

The transfer of a significant amount of reactive power from the power system to consumers causes additional losses of active power and energy in all elements of the power supply system.

The costs associated with this transmission can be reduced or even eliminated if the influence of reactive power in low voltage networks is eliminated.

To compensate for reactive power, special compensating devices are used, they are sources of reactive energy of a capacitive nature.

The power of the KU (compensating devices) is determined from the expression:

Q k \u003d α × P max × (tgφ max - tgφ e) kvar,

where P max is the maximum design power;

α - coefficient taking into account the increase in cosφ in a natural way, is taken equal to 0.9;

tgφ e is determined by cosφ e = 0.92 - 0.95 by the power factor set by the system. We accept tgφ e = 0.33

tgφ max - estimated maximum power factor

cosφ max = P max / S max

cosφ max = 102.82/110.4 = 0.93

Q k \u003d 0.9 × 102.8 / (0.39 - 0.33) \u003d 1542 kvar

According to the calculated value of reactive power, we select compensating devices of the type UKN - 0.38 - 900 in the amount of 2 pieces.

2.3 Selection of the number and power of power transformers of the workshop substation

Transformer workshop substations are the main link in the power supply system and are designed to power one or more workshops.

Single-transformer workshop substations are used when supplying loads that allow interruption of power supply for the time of delivery of the “foldable” reserve or when redundancy is carried out by jumpers on the secondary voltage.

Two-transformer substations are used when consumers of the 1st and 2nd categories predominate.

The choice of the number and power of transformers is determined by the magnitude and nature of the load, taking into account its overload capacity, which should be 40% of the power of the transformer.

When choosing a transformer, you need to know the power of the substation:

where S p is the power of the transformer consumed by the section after compensation, kvar;

P max - total active maximum power, kW;

Q max - total reactive maximum power, kvar

Q k - reactive power consumption of the compensating device, kvar.

The power of the transformer consumed, taking into account 40% of the reserve, is calculated by the formula:

S m = 0.75 × S p

where S p is the power of the transformer consumed by a group of power receivers after compensation, kVA;

The power of the transformer, taking into account climatic conditions (the average annual temperature differs from Q cf = 5 ° C), is determined from the expression:

where: S m - transformer power consumed, taking into account 40% of the reserve

Q cf - the average annual temperature of the area where the transformer is installed.

S m \u003d 0.75 × 125.7 \u003d 94.3 kVA

According to the estimated power equal to 94.3 kVA, taking into account the temperature of the area and 40% of the margin, we accept for installation a transformer of the type TM-100/10 U1

2.4 Calculation and selection of the power network, cross-sections of wires and cables

All power receivers are designed for three-phase alternating current and voltage of 380 V, industrial frequency of 50 Hz, they belong to the second category in terms of power supply reliability, are installed permanently and are evenly distributed over the area.

The wiring of electrical networks from the current passing through them, according to the Joule-Lenz law, heat up.

The amount of released thermal energy is proportional to the square of the current, resistance and current flow time. Excessively high heating temperature of the conductor can lead to premature wear of the insulation, deterioration of contact connections and fire hazard. Therefore, the maximum allowable values ​​for the heating temperature of the conductors are set depending on the brand and material of the conductor insulation in various modes.

The current flowing through the conductor for a long time, at which the longest allowable heating temperature of the conductor is established, is called the maximum allowable heating current.

When calculating the network for heating, the current is calculated for each electrical receiver and a group of electrical receivers powered by one power point:

Estimated current for a group of electrical receivers:

where: I p - rated current; U f - phase voltage.

Estimated current for each consumer:

where: R n - rated power of the electrical receiver - kW;

U n - rated voltage, V;

cosφ - power factor of the electrical receiver;

η is the efficiency of the electrical receiver;

An example of the calculation of electrical receivers of the power point of the joint venture.

I nr1 \u003d 400 / (1.73 * 380 * 0.5 * 0.9) \u003d 1.4 (A)

Table 4. Calculation and installation data for the workshop

on the drawing	Name equipment	Quantity
	Universal- grinding
	Grinding tools for hobs
	Sharpening
	Turning and screw-cutting
	Sharpeners for round dies
	Thread grinding
	surface grinding
	Internal grinding
	Cylindrical grinding
	Fans

According to the rated rated current, according to the tables, we select the cross section of wires and cables and determine the laying method.

The rated current for a group of electrical receivers is determined in paragraph 2.1

I max \u003d 110.4 / (1.73 × 0.38) \u003d 157.7 A

According to the rated current, we select ShRA 73 with a rated current of 250 A, and from the transformer to ShRA - a cable of the ASG type (95 × 4) (table) and a switch VA 52G-33 I n \u003d 160 A. sections. All wires are four-core with polyvinyl chloride insulation of the APV brand, with the exception of the workplace of an electrician, two-core ones are installed there.

The calculated data for this power point are summarized in the Settlement and Mounting Tables of the Appendix.

The plan of the workshop with the application of the power network is presented on a sheet of A1 format.

2.5 Selection of protection and automation devices

To receive and distribute electricity to groups of consumers of three-phase alternating current of industrial frequency with a voltage of 380 V, power distribution cabinets are used.

The microclimate in the workshop is normal, i.е. the temperature does not exceed +30 ° C, there is no technological dust, gases and vapors that can disrupt the normal operation of electrical equipment.

For workshops with normal environmental conditions, cabinets of the SP-62, ShRS-2P1U3, ShRS-53U3 and ShRS-54U3 series are manufactured.

Along with the indicated power cabinets, distribution points of the PR-9000 series are used. Distribution points have built-in circuit breakers to automate control.

Power points and cabinets are selected taking into account the conditions of the air environment and the number of connected power receivers.

For the cable from the transformer to the ShRA 73 switchgear, we select the circuit breaker of the VA 52G-33 series automatic switch from the table

3.3 Calculation of the repair complexity of electrical equipment

∑R \u003d R 1 + R 2 + R 3 + ... + R p

Calculation of the repair complexity of equipment by workshop:

1. For machines of the turning group R = 8.5. There are 2 machines of this group installed in the workshop, which means ∑R = 17

2. For machines of the grinding group R = 1.5. There are 9 machines of this group installed in the workshop, which means ∑R = 13.5

3. For machines of the grinding group R = 10. There are 11 machines of this group installed in the workshop, which means ∑R = 110

4. For fan R = 4. There are 3 fans installed in the shop, so ∑R = 12

For most electrical equipment, the category of repair complexity is defined and is a reference value.

Table 5 Repair complexity of electrical equipment

Conclusion

In the theoretical part of the project, the characteristics of electricity consumers and the category of power supply, internal power supply schemes.

In the design part of the project, calculations of electrical loads, calculation and selection of a compensating device, selection of a power transformer, sections of wires and cables, selection of protective devices were made.

In the economic part of the project, the issues of preventive maintenance of electrical equipment, its features were considered, and the calculation of the repair complexity of the electrical equipment of the site was made.