INTRODUCTION

The purpose of the section “Power supply and electrical equipment of an industrial enterprise” is graduation qualifying work is the systematization, expansion and consolidation of theoretical knowledge in electrical engineering, electrical machines, electric drives and power supply of industrial enterprises, as well as the acquisition of practical skills in solving problems necessary for a future specialist.

The power supply system of an industrial enterprise must ensure an uninterrupted supply of electricity to consumers while meeting the requirements for efficiency, reliability, safety, quality of electricity, availability of reserve, etc.

The selection of modern electrical equipment, development of control circuits, protection, automation, signaling of electrical receivers, development of a power supply circuit for the workshop and (or) the entire enterprise using progressive technical solutions are the tasks of the section “Power supply and electrical equipment of an industrial enterprise” of the final qualifying work.

The section “Power supply and electrical equipment of an industrial enterprise” of the final qualifying work includes consideration of the following issues:

5) select the number and type of workshop transformers 10/0.4 kV;

6) select switching equipment for the 0.4 kV network and 10 kV network;

7) calculate the costs of constructing a power supply network;

8) calculate the grounding loop of the transformer substation;

9) consider the use and operation of isolated bus systems.

The initial data for the electrical part of the final qualifying work are production (energy) equipment and mechanisms necessary to ensure technological processes, given terms of reference, as well as the area production premises workshops (enterprises), parameters of installed electrical receivers, existing circuits of the power supply system, etc. The automation object is indicated.

In the explanatory note of the final qualifying work, the electrical part is drawn up as a separate chapter. The volume and content of the graphic part are determined by the design assignment. The graphic part contains a power supply diagram for the enterprise (workshop).

Option 14

Calculation of the workshop power supply network

1.1 Initial data for design

The schematic plan of the enterprise is set on a scale of 1:1000

Table 1 specifies the rated powers of electrical receivers, utilization and start-up factors, power factors of the specified electrical receivers, and the lengths from electrical receivers to ShS-1.

Table 1 - Initial data for the first stage

№	Power receiver	N pcs.	Pnom kW	Ki	cos𝜑	Kp	PV%	L m
				0,16	0,61	5,35	-
	Slotting machine			0,14	0,43	6,40	-
	Overhead crane			0,1	0,5	6,79
	Lathe			0,4	0,75	5,58	-
	Exhauster		5,6	0,63	0,8		-
Average value	0,6

The design loads of the power cabinets of workshop No. 4, the weighted average utilization factor and the number of effective electrical receivers are specified. This information presented in Table 2.

Table 2 - Initial data for the second stage

№	Closet	P kW	Q kVAR	cos𝜑	Nef	K.av.vzv
	ShS-2		36,62	0,88		0,6
	ShS-3		21,05	0,88		0,54
	ShS-4		51,82	0,88		0,4
	ShS-5		23,73	0,86		0,8
	ShS-6		30,60	0,87		0,7
	ShS-7		13,49	0,88		0,7
	ShS-8		58,74	0,86		0,86
Average value	0,87

As initial data, the estimated capacities of the remaining workshops at the specified enterprise, the length of the supply cable is 10 kV from the GPP to the RP. The data is shown in Table 3.

Table 3 - Initial data for the third stage

The plan of an industrial enterprise is shown in Figure 1.

Figure 1 - Industrial plant plan

Calculation electrical loads ShS-1 consumers

The first and main stage of designing a power supply system for an industrial enterprise is determining the calculated values ​​of electrical loads. They are not a simple sum of the installed capacities of electrical receivers. This is due to the incomplete loading of some electronic devices, the non-simultaneity of their operation, the probabilistic random nature of turning on and off the electronic devices, etc.

The concept of “design load” follows from the definition of the design current, according to which all network elements and electrical equipment are selected.

The calculated current is the constant average current over a 30-minute time interval that leads to the same maximum heating of the conductor or causes the same thermal wear of the insulation as a real variable load.

Table 5 - Calculation of load ShS-1

Initial data	Calculation data
Naim EP	N pcs	Est. Power kW	Ki	Coefficient react	Wed.Change.Power	Ne	Kmax	Design power
1 EP	∑		cos𝜑	tg𝜑	Pcm kW	Qcm kvar	Ne	Kmax	Calculation kW	Qcalc kvar
Group A
Slitting machine				0,16	0,61	1,29	2,24	2,88	-	-	-	-
Slotting machine				0,14	0,43	2,09	1,96	4,09	-	-	-	-
Overhead crane				0,1	0,5	1,72		24,08	-	-	-	-
Lathe				0,4	0,75	0,88		10,56	-	-	-	-
Total				0,8	-	-	30,2	41,61		2,31	69,76	45,77
Group B
Exhauster		5,6	11,2	0,63	0,8	0,75	7,05	5,2	-	-	-	-
Total		5,6	11,2	-	-	-	7,05	5,2	-	-	7,05	5,2

Table 6

Parameter	cosφ	tgφ	Pm, kW	Q M , quar.	S M , kV*A
Total on NN without CG	0,83	0,68	495,81	287,02	572,89

The design power of the heat treatment unit is determined.

Q k.r = α R m (tgα – tgφ k) = 0.9“495.81“(0.68 – 0.29) = 174.02 kvar.

Cosφ k = 0.96 is accepted, then tanφ k = 0.29.

We find the transformer load after compensation and its load factor:

For installation, we select an automated capacitor unit type 2 AUKRM 0.4-100-20-4 UHL4

The current of the compensating device is found by the formula:

where 1.3 is the safety factor (30% nominal value);

Line voltage, 0.4 kV.

Since we have 2 bus sections with a sectional switch, the power of the heat exchanger for each section will be determined by the load of each section. In the first section, power cabinets 1,2,3,4 will be connected; in the second section 5,6,7,8 will be connected.

Table 7

where is the weighted average power factor of all loops;

Required power factor on transformer buses (not less than 0.95).

where k is the coefficient obtained from the table in accordance with the values ​​of power factors and ;

Section 1 requires more reactive power compensation due to ShS-1, which has a low power factor.

total amount compensated reactive power in both sections

For two transformer substations rated power

transformer is determined by the condition of permissible overload of one

transformer by 40%, subject to emergency shutdown of another within 6

hours per day for 5 working days.

In this case, the rated power of the transformer TP-10/0.4

determined by the expression:

where k=1.4 permissible transformer overload coefficient;

n=2 – number of transformers at the substation.

From a number of standard rated powers we select two

transformer TMG-400/10.

Reference data for the transformer is given in Table 8.

Table 8 – Passport data of transformer TMG-400/10

Snom, KVA	Unom, kV	∆Рхх, kW	∆Ркз, kW	Ukz, %	Iхх,%	dimensions	Weight, kg
		0,8	5,5	4,5	2,1	1650x1080x1780

Losses of active and reactive power in transformers at TP:

where n is the number of installed transformers, pcs;

– no-load losses in the transformer, kW;

– losses due to short circuit in the transformer, kW;

– rated power of the transformer, kVA.

where Iх.х – transformer no-load current, %;

Us.c – short circuit voltage, %.

The total power of the electrical receivers of the workshop, taking into account losses in

transformer:

Since the calculated power of 370.11 kVA satisfies the selected

rated power of the transformer, then we select 2 transformers TMG-400/10. And after recalculation when choosing centralized compensation, we connect the capacitor bank to the 0.4 kV busbars of the workshop substation. And as can be seen from the calculation, in this case the transformers of the main step-down substation and the supply network are unloaded from reactive power. In this case, the use of the installed capacitor power is the highest.

Individual compensation is most often used at voltages up to 660 V. This type of compensation has a significant drawback - poor use of the installed power of the capacitor bank, since when the receiver is turned off, the compensating installation is also turned off.

In many factories, not all equipment is running at the same time; many machines are used for only a few hours a day. Therefore, individual compensation becomes a very expensive solution when large quantities equipment and accordingly large number installed capacitors. Most of these capacitors will not be used for a long period of time. Individual compensation is most effective when most of the reactive power is generated by a small number of loads that consume the most power over a sufficiently long period of time.

Centralized compensation is used where the load fluctuates (moves) between different consumers during the day. At the same time, reactive power consumption varies throughout the day, so the use of automatic capacitor units is preferable to unregulated ones.

Load recalculation

Column 13 records the maximum reactive load from power

ED node Qcalc, kVar:

since ne< 10, то

Total maximum active and reactive loads according to the design

to the unit as a whole for electric drives with variable and constant load schedules

are determined by adding the loads of ED groups according to the formulas:

The maximum full load of power electric drives Scalc.uch, kVA is determined:

The calculated current Icalc, A is determined:

We will calculate currents and total power before installing the heat exchanger and after installing the heat exchanger.

Table 9 - Summary sheet before and after installation of the heat exchanger on TP buses

№	S, kVA	cos𝜑	I, A
BEFORE	AFTER	BEFORE	AFTER	BEFORE	AFTER
ShS-1	92,18	77,68	0,6	0,96	140,05
ShS-2	75,47	67,65	0,88	0,96	114,66	102,78
ShS-3	44,31	39,97	0,88	0,96	67,32	60,72
ShS-4	109,09	98,4	0,88	0,96	165,74	149,5
ShS-5	46,5	41,43	0,86	0,96	70,64	62,94
ShS-6	62,06	55,68	0,87	0,96	94,29	84,59
ShS-7	28,4	25,62	0,88	0,96	43,14	38,92
ShS-8	111,69	102,54	0,86	0,96	169,69	155,79

As can be seen from the statement, the result is obvious, the installation of the CU allowed us to:

Table 10 - Change in reactive power in the AL after installing the KU at the TP

№	power, kWt			K	kvar
ShS-1	76,81	0,6	0,96	1,04	71,89
ShS-2		0,88	0,96	0,25	14,85
ShS-3		0,88	0,96	0,25	8,77
ShS-4		0,88	0,96	0,25	21,6
ShS-5		0,86	0,96	0,30	10,8
ShS-6		0,87	0,96	0,28	13,6
ShS-7		0,88	0,96	0,25	5,62
ShS-8		0,86	0,96	0,30	26,73
Total 174.02

Table 11 - Recalculation of ShS-1 load

Initial data	Calculation data
Naim EP	N pcs	Est. Power kW	Ki	Coefficient react	Wed.Change.Power	Ne	Kmax	Design power
1 EP	∑		cos𝜑	tg𝜑	Pcm kW	Qcm kvar	Ne	Kmax	Calculation kW	Qcalc kvar
Group A
Unlocked				0,16	0,96	0,29	2,24	0,64	-	-	-	-
conveyor				0,14	0,96	0,29	1,96	0,56	-	-	-	-
Crane bridge.				0,1	0,96	0,29		4,06	-	-	-	-
Slotting Machine				0,4	0,96	0,29		3,48	-	-	-	-
Total				0,8	-	-	30,2	8,74		2,31	69,75	9,61
Group B
Exhauster		5,6	11,2	0,63	0,96	0,29	7,05	2,04	-	-	-	-
Total		5,6	11,2	-	-	-	7,05	2,04	-	-	7,05	2,04

Drilling machine

Calculation of EP peak loads

As a peak ED mode to check for voltage sag on

electrical receiver and selection of circuit breakers are considered

starting mode of the most powerful electric motor and the peak current is determined by

Ipeak cable line, supply transformer substation. Peak current for

where Inomm is the rated current of the most powerful blood pressure, A;

Кп – multiplicity of the starting current of the most powerful IM.

The current of the most powerful motor among the ShS-1 electrical receivers is calculated. Longitudinal planing machine Pnom = 14 kW and after compensation cosφ = 0.96.

The peak current will be equal to:

Characteristics of the premises

The turning shop room is classified as dry, since the relative air humidity does not exceed 60% of clause 1.1.6 c. A turning shop is a very dusty facility, so the premises are classified as dusty; due to the production conditions, process dust is released in such quantities that it can settle on the wires and penetrate inside the machines - clause 1. 1.11 c. The premises are non-explosive, since substances that form explosive mixtures with air are not located or used in them. 1.3 in. In terms of fire hazard, the premises of the turning shop are classified as non-fire hazardous, since they do not contain the conditions given in Chapter. 1.4 in.

Selecting a brand of 0.4 kV cables

Based on an analysis of the cable laying and the characteristics of the workshop environment, a conclusion is made about the possibility of using the VVGng(a)-Ls-0.66 cable (copper conductor, insulation made of PVC plastic of reduced fire hazard, sheath made of PVC composition) to power ShS 1-8 and electrical receivers reduced flammability) Cables of this brand are intended for vertical, inclined and horizontal routes. Unarmored cables can be used in areas subject to vibration. Do not propagate combustion when laid in bundles

(standards GOST R IEC 332-2 category A). They are used in cable structures and premises. The permissible heating of the conductor in emergency mode should not exceed +80ºC with a duration of operation of no more than 8 hours per day and no more than 1000 hours over the service life.

Service life – 30 years.

Table 12 - Selection of cable lines from transformer substations to shs for workshop No. 4 before installation of the heat exchanger

Naim	Route KL	S kVA	I A	K1	K2	Id A	Iadd A	L m	R Ohm	X Ohm	Z Ohm	Brand	Scab mm²
KL3-1	TP-ShS1	92,18	140,05		0,8	175,06			6,36	1,96	6,65	VVGng(a)-Ls-0.66
KL3-2	TP-ShS2	75,47	114,66		0,8	143,32			1,85	0,42	1,89	VVGng(a)-Ls-0.66
KL3-3	TP-ShS3	44,31	67,32		0,8	84,15			48,84		49,2	VVGng(a)-Ls-0.66
KL3-4	TP-ShS4	109,09	165,74		0,8	207,17			7,6	3,15	8,22	VVGng(a)-Ls-0.66
KL3-5	TP-ShS5	46,5	70,64		0,8	87,63			38,48	4,73	38,76	VVGng(a)-Ls-0.66
KL3-6	TP-ShS6	62,06	94,29		0,8	117,86			4,81	1,1	4,93	VVGng(a)-Ls-0.66
KL3-7	TP-ShS7	28,4	43,13		0,8	53,92			62,64	5,13	62,84	VVGng(a)-Ls-0.66
KL3-8	TP-ShS8	111,69	169,69		0,8	211,48			10,92	4,53	11,82	VVGng(a)-Ls-0.66

Table 13 - Selection of cable lines from transformer substations to shs for workshop No. 4 after installing the control unit on the transformer substation busbars

Naim	Route KL	S kVA	I A	K1	K2	Id A	Iadd A	L m	R Ohm	X Ohm	Z Ohm	Brand	Scab mm²
KL3-1	TP-ShS1	77,68			0,8	147,5			8,88	2,04	9,11	VVGng(a)-Ls-0.66
KL3-2	TP-ShS2	67,65	102,78		0,8	128,47			1,85	0,42	1,89	VVGng(a)-Ls-0.66
KL3-3	TP-ShS3	39,97	60,72		0,8	75,9			48,84		49,2	VVGng(a)-Ls-0.66
KL3-4	TP-ShS4	98,4	149,5		0,8	186,87			7,6	3,15	8,22	VVGng(a)-Ls-0.66
KL3-5	TP-ShS5	41,43	63,94		0,8	78,67			38,48	4,73	38,76	VVGng(a)-Ls-0.66
KL3-6	TP-ShS6	55,68	84,59		0,8	105,7			6,89	1,14	6,98	VVGng(a)-Ls-0.66
KL3-7	TP-ShS7	25,62	38,92		0,8	48,65			99,36	5,34	99,5	VVGng(a)-Ls-0.66
KL3-8	TP-ShS8	102,54	155,79		0,8	194,73			10,92	4,53	11,82	VVGng(a)-Ls-0.66

KL2-10

TP-KU

93,81

93,81

4,24

0,7

4,29

VVGng(a)-Ls-0.66-4x35.

Table 14 - Selection of cable from ShS-1 to EP

Name	Route KL	P kW	I A	cos𝜑	Iadd A	L m	R Ohm	X Ohm	Z Ohm	Brand	Ssection mm²
KL1-1	From ShS-1 to EP1		22,15	0,96			29,6	0,46	29,6	VVGng(a)-Ls-0.66	2,5
KL1-2	From ShS-1 to EP2		22,15	0,96			44,4	0,69	44,4	VVGng(a)-Ls-0.66	2,5
KL1-3	From ShS-1 to EP3		55,39	0,96			14,72	0,79	14,74	VVGng(a)-Ls-0.66
KL1-4	From ShS-1 to EP4		47,47	0,96			11,04	0,59	11,05	VVGng(a)-Ls-0.66
KL1-5	From ShS-1 to EP5	5,6	8,86	0,96			62,5	0,63	62,5	VVGng(a)-Ls-0.66	1,5
KL1-6	From ShS-1 to EP6	5,6	8,86	0,96			62,5	0,63	62,5	VVGng(a)-Ls-0.66	1,5

Table 15 - Checking cable lines KL1 in normal mode

KL	A	A	IN	IN	dU V	IN
KL1-1	22,15	29,6	1,13	1,85	2,99
KL1-2	22,15	44,4	1,7	1,85	3,55
KL1-3	55,39	14,72	1,41	1,85	3,26
KL1-4	47,47	11,04	0,9	1,85	2,75
KL1-5	8,86	62,5	0,95	1,85	2,8
KL1-6	8,86	62,5	0,95	1,85	2,8

Table 16 – Checking cable lines KL2 in normal mode

Name	A	Z Ohm	IN	dU%
KL2-1		9,11	1,85	0,48
KL2-2	102,78	1,89	0,33	0,08
KL2-3	60,72	49,2	5,16	1,35
KL2-4	149,5	8,22	2,12	0,55
KL2-5	63,94	38,76	4,28	1,12
KL2-6	84,59	6,98	1,02	0,25
KL2-7	38,92	99,5	6,69	1,76
KL2-8	155,79	11,82	3,18	0,83

Powerful engine

Metal-cutting machines are designed for mechanical processing of metal workpieces with cutting tools.

The purpose of metal-cutting machines is to produce parts of a given shape and size with the required accuracy and quality of the machined surface. The machines process workpieces not only from metal, but also from other materials, so the term “metal-cutting machine” is conditional.

According to the type of work performed, metal-cutting machines are divided into groups, each of which is divided into types, united by common technological characteristics and design features.

Metal-cutting machines represent a whole class of equipment designed to produce metal blanks: boring machines, lathes, etc.

As an example, we will calculate and select the electrical equipment of a screw-cutting lathe model 16D20.

Lathes are designed for the manufacture and processing of parts in the shape of bodies of revolution. They are used for processing cylindrical, conical, shaped surfaces, trimming ends, as well as for drilling and reaming holes, threading and other operations.

2.1 Selecting the type of current and voltage value for the workshop network

For power electrical networks industrial enterprises mainly use three-phase alternating current. Direct current is recommended to be used in cases where it is necessary under the conditions of the technological process (charging batteries, powering galvanic baths and magnetic tables), as well as for smooth control of the rotation speed

electric motors. If the need to use direct current is not caused by technical and economic calculations, then three-phase alternating current is used to power power electrical equipment.

When choosing voltage, you should take into account the power, number and location of electrical receivers, the possibility of their joint power supply, as well as technological features of production.

When choosing the voltage to power electrical receivers directly, you must pay attention to the following points:

1) Rated voltages applied to industrial enterprises for electricity distribution are 10; 6; 0.66; 0.38; 0.22 kV;

2) It is recommended to use voltages higher than 1 kV at the lowest level of power distribution only if special electrical equipment operating at voltages higher than 1 kV is installed;

3) If motors of the required power are manufactured for several voltages, then the issue of voltage selection must be resolved through a technical and economic comparison of options;

4) If the use of voltages above 1 kV is not caused by technical necessity, options for using voltages of 380 and 660 V should be considered. The use of lower voltages to power power consumers is not economically justified;

6) Using a voltage of 660 V, electricity losses and consumption of non-ferrous metals are reduced, the range of operation of workshop substations is increased, the unit power of the transformers used is increased and, as a result, the number of substations is reduced, and the power supply circuit at the highest level of energy distribution is simplified. The disadvantages of the 660 V voltage are the impossibility of jointly powering the lighting network and power electrical receivers from common transformers, as well as the lack of low-power electric motors for a voltage of 660 V, since currently such electric motors are not produced by our industry;

7) In enterprises with a predominance of low-power electrical receivers, it is more profitable to use a voltage of 380/220 V (unless the feasibility of using a different voltage has been proven);

8) Mains voltage direct current is determined by the voltage of the powered electrical receivers, the power of the converter installations, their distance from the center of electrical loads, as well as environmental conditions.

Electronic control and signaling circuits must be powered by a transformer.

For AC control circuits powered from a transformer, the following voltage values ​​are recommended: 1) 24 or 48V, 50 and 60 Hz; 2) 110V, 50Hz or 115V, 60Hz; 3) 220V, 50Hz or 230V, 60Hz.

For DC control circuits, the recommended voltage is: 24, 48, 110, 220, 250V. It is permissible to use other low voltage values ​​for electronic circuits and devices that are designed for such voltages. A ground fault in any control circuit must not cause the machine to turn on unexpectedly, cause the machine to move dangerously, or prevent the machine from shutting down.

The control circuit must be designed so that if the time limit has expired, both buttons must first be released and then pressed again to start the cycle.

It is recommended to connect the alarm circuit, which is not connected to the control circuit, to 24V AC or DC. In this case, lamps with voltages from 24V to 28V are used. If an individual transformer is used, then 6V or 24V lamps are used. In this case, the signaling circuit can be connected to the control circuit.

The use of fluorescent lamps for local lighting of lathes is prohibited. The most widely used are incandescent lamps with a voltage of 36V, connected through a step-down transformer. It is prohibited to use local lighting with a voltage higher than 36 V.

For a universal high-precision screw-cutting lathe, model 16D20, the most suitable parameters are:

Supply network: voltage 380V, current type - alternating, frequency 50 Hz;

Control circuit: voltage 110V, current type - alternating;

Local lighting: voltage 24 V.

FGOU SPO "Penza College of Management"

and industrial technologies named after. E. D. Basulina"

EXPLANATORY NOTE

FOR THE COURSE PROJECT

Introduction

1. Theoretical part

1.1 Brief description of the workshop, short description technological process

1.2 Characteristics of electricity consumers and determination of the category of electricity supply. Statement of Electricity Consumers

1.3 Selecting the supply voltage

1.4 Selecting a workshop power supply scheme

1.4.1 Workshop power supply tasks

1.4.2 Selecting a power supply scheme for the workshop

2. Calculation part

2.1 Calculation of electrical loads

2.2 Reactive power compensation and selection of compensating device

2.3 Selecting the number and power of power transformers for a workshop substation

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

2.5 Selection of protection and automation devices

3. Economic part of the project

3.1 System of preventive maintenance

3.2 Features of electrical equipment repair and its technical characteristics

3.3 Calculation of 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 sectors of the national economy typically depends on the pace of development of mechanical engineering.

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

Mechanical engineering enterprises are widely equipped with electrified lifting and transport mechanisms, pumping 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 involves an increase in the power supply in industry through the improvement and introduction of new, economical and technologically advanced electrical equipment. Electrical receivers that convert electrical energy in other types of energy, they firmly occupy a leading position in the vast majority of production processes.

The constant increase in the power supply of production is ensured by the rapid development of the electric power industry.

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

Intensive development technical means caused the need to improve the design methodology and create new highly efficient enterprises on its basis. In modern conditions, the operation of electrical equipment requires increasingly deeper and more versatile knowledge, and the tasks of creating a new or modernizing an existing electrified technological unit, mechanism or device are solved by the joint efforts of technologists, mechanics, and electricians.

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

In the conditions of scientific and technological progress, the relationship between man and nature has become significantly 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 disrupt the natural balance and threaten human health.

Course for intensification economic development requires further improvement in the efficiency of use of natural resources. Based on this, it is planned to expand the scientific development of fundamental and applied problems of nature conservation, as well as to increase the efficiency of using existing equipment.

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

1. Theoretical part

1.1 a brief description of workshops, brief description of the technological process

The main electrical equipment of the metal-cutting machine shop is a group of lathes, grinders and sharpening machines. Consider these groups:

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

2. Grinding equipment includes cylindrical, flat, internal and thread grinding machines with a power ranging from 0.4 kW for a 3M225V internal grinding machine to 5.5 kW for a 5K823V thread grinding machine.

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

There are three operating modes for machines:

1. Long-term, in which machines can operate for a long time, and the temperature rise of individual parts of the machine does not exceed established limits;

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

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

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

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

I. Electrical receivers, where a break in the power supply will result in danger to human life, damage to expensive equipment, and massive defective products.

II. Electrical receivers, here a break leads to a massive shortage of products, downtime of jobs, mechanisms and industrial processes.

III. Electrical receivers for non-serial production, auxiliary workshops, utility consumers, agricultural factories. Power supply interruption up to 24 hours.

1.2 Characteristics of electricity consumers and determination of the category of electricity supply. Statement of Electricity Consumers

The consumers of electricity in this workshop are lathes, sharpening and grinding machines.

Screw-cutting lathes are designed to perform a variety of jobs. These machines can be used to grind external cylindrical, conical and shaped surfaces, bore cylindrical and conical holes, and process end surfaces; cut external and internal threads; drill, countersink and ream holes; perform cutting, trimming and other operations.

Grinding machines are designed for processing parts with grinding wheels. They can be used to 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 being ground and the type of grinding, the machines general purpose They are divided into cylindrical grinding, centerless grinding, internal grinding, surface grinding and special.

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

All equipment is presented in the list of electricity consumers.

1.3 Selecting the supply voltage

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

A voltage of 10 kV is used for intra-plant energy distribution:

At large enterprises with motors that allow direct connection to the 10 kV network;

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

If there is 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;

If there is a factory power plant with a voltage of 6 kV;

At reconstructed enterprises with a voltage of 6 kV.

For the in-shop power supply system, voltages of 380 and 660V are used.

Voltage 380 V is used to power power general industrial electrical receivers.

if, according to the conditions of the general plan, technology and environment, deep penetrations, fragmentation of workshop substations and bringing them closer to the centers of the groups of power receivers they feed cannot be carried out properly, and in connection with this there are extended and branched networks up to 1000 V, and also when 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 promising development enterprises, cheaper 660 V electric motors and their better efficiency compared to 6 kV electric motors, as well as taking into account the reduction of electricity losses in the 660 V network compared to the 380 V network.

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

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

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

When the voltage of power receivers is 380 V, lighting power is usually supplied 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 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 in three-phase networks corresponds to the quality indicators regulated by GOST 13109-77:

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

Frequency deviation (from 1.5 to 4%);

Coefficients of non-symmetry and stress imbalance (K and<=2%)

Based on the above requirements, we set the voltage for the metal-cutting machine shop to 380/220 V for the power and lighting networks, taking into account the requirements for voltage quality indicators for in-plant energy distribution - 10 kV

1.4 Selecting a workshop power supply scheme

1.4.1 Workshop power supply tasks

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

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

The reliability of the power supply system is affected by:

Matching network bandwidth;

Connection diagrams of network elements;

Availability of sensitive, fast-acting and selective protection;

The presence or absence of power shortages and spare backup elements in the power system and other factors.

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

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

2. Saving non-ferrous metals and electricity;

3. Maximum proximity of high voltage sources to consumer electrical installations, ensuring a minimum of network links and intermediate transformation stages to reduce primary costs and reduce electricity losses while simultaneously increasing reliability.

Fulfillment of these requirements is ensured, first of all, properly based on 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, and proper operation.

Through power supply systems, electricity is accounted for and its rational use is monitored.

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, from the point of view of technical and economic indicators, power supply system for the workshop;

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

3. Selection of an economically feasible mode of operation of transformers;

4. Selection of rational voltages in the circuit, which ultimately determine the size of capital investments, consumption of non-ferrous metal, the amount of electricity losses and operating costs;

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

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

Electricity consumers have their own specific characteristics, which determine certain requirements for their power supply - power 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 methods of voltage regulation.

1.4.2 Selecting a power supply scheme for the workshop

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

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

Radial;

Magistralnaya;

Mixed.

Shop electrical distribution networks must:

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

2. Be convenient and safe to use;

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 the transformer without a switchgear on the low voltage side, and is carried out with a uniform distribution of electricity to individual consumers. Trunk circuits are universal and flexible (allow you to replace process equipment without changing the electrical network).

The radial power supply circuit is a set of lines of the workshop electrical network, extending from the low-voltage switchgear of the transformer substation and intended to power small groups of electricity receivers located in different places of the workshop. Distribution of electricity to individual consumers in radial schemes is carried out by independent lines from power points located in the center of the electrical loads of a given group of consumers. The advantage of radial circuits is high power supply reliability and the possibility of using automation.

However, radial schemes require large expenses for the installation of distribution centers, wiring and wiring.

In the project being designed, a main circuit diagram presented on an A3 sheet of paper was selected for the power supply of a metal-cutting machine shop based on an analysis of literature sources. Design groups of electrical receivers are presented in Table 2.

Table 2 Design groups of electrical receivers

	Position number on the drawing	Equipment identification	Quantity	Model
		Universal sharpening
		Grinding tools for hobs
		Sharpening
		Lathe-screw-cutting
		Grinding for round dies
		Thread grinding
		Surface grinding
		Internal grinding
		Cylindrical grinders
		Fans

2. Calculation part

2.1 Calculation of electrical loads

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

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

When determining design electrical loads, you can use the following basic methods:

1. ordered diagrams (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 expected loads are calculated using the ordered diagram method,

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

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

P max =K max * K and * P nom = K max * P cm,

where: K and – utilization factor;

K max – maximum active power coefficient;

P cm – average active power of electrical receivers for a more loaded circuit.

For a group of electrical receivers for a busier shift of operating mode, the average active and reactive loads are determined by the formula:

P cm = K u * P nom

Q cm = P cm * tan φ,

where tg φ – corresponds to the weighted average cos φ, characteristic of electrical receivers of this operating mode.

The weighted average utilization rate is determined by the formula:

To U.SR.VZ. = ∑Р cm / ∑Р nom,

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

∑Р nom – total rated power of electrical receivers in the group.

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

N * = 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 electrical receivers of the group;

∑Р nom – total active rated power of the group’s electrical receivers.

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

n * e = f(n * ; P *)

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

N e = n * e * n

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

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

Estimated maximum active circuit power:

P max = K max * ∑P cm

Estimated maximum reactive power in the circuit:

Q max = 1.1 ∑Q cm

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

S max = √P max 2 + Q max 2

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

I max = S max /(√3 * U nom)

Calculation of expected loads in a metal-cutting machine shop.

1. Determine the average active and reactive power for a more loaded circuit of electrical receivers.

Calculation example for machines positions 1-3

P cm1-3 = P nom × K u = 0.4 × 0.14 × 3 = 1.68 kW

Q cm1-3 = P cm1-3 × tgφ = 1.68 × 1.73 = 2.9 kvar

The rest of the calculation data is 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 nom 19.21 + 3 P nom fan = 193.5 kW

3. Let’s sum up the 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 fan = 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 i.av.vz = 57.12/193.5 = 0.3

5. Determine the relative number of electrical receivers:

N* = 5/25 = 0.2

6. Determine the relative power of the largest power receivers:

P * = 160/193.5 = 0.83 kW

7. The main effective number of electrical receivers in a 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 electrical receivers in the group:

N e = 0.27 × 25 = 6.75

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

K max = 1.8

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

P max = 1.8 × 57.12 = 102.82 kW

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

Q max = 1.1 × 36.53 = 40.18 kVAr

12. Determine the total design power 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 of electrical power loads in the workshop

	Equipment identification		R nom, kW		Q cm, kvar
									R max, kW	Q max, kvar	S max, kVA
	Universal sharpening
	Grinding tools for hobs
	Sharpening
	Lathe-screw-cutting
	Grinding for round dies
	Thread grinding
	Surface grinding
	Internal grinding
	Cylindrical grinders
	Fans

2.2 Reactive power compensation and selection of compensating device

Reactive power compensation or increasing the power factor of electrical installations of industrial enterprises is of great national 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 consumers.

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, which are sources of reactive energy of a capacitive nature.

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

Q k =α × P max × (tgφ max – tgφ e) kVar,

where P max – 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 – calculated maximum power factor

cosφ max = P max / S max

cosφ max = 102.82/110.4 = 0.93

Q k = 0.9 × 102.8 / (0.39 – 0.33) = 1542 kVAr

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

2.3 Selecting the number and power of power transformers for a workshop substation

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

Single-transformer workshop substations are used when powering loads that allow an interruption of power supply during the delivery of a “folding” reserve or when redundancy is carried out via jumpers at 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 size 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 transformer power 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 transformer power consumed taking into account 40% of the reserve is calculated using the formula:

S m = 0.75 × S p

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

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

where: S m – transformer power consumed taking into account 40% reserve

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

S m = 0.75 × 125.7 = 94.3 kVA

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

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

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

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

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

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

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

Estimated current for a group of electrical receivers:

where: I r – design current; U f – phase voltage.

Rated 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 – efficiency factor of the electrical receiver;

An example of calculating the electrical receivers of a power point of a joint venture.

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

Table 4. Design and installation data for the workshop

on the drawing	Name equipment	Quantity
	Universal- sharpening
	Grinding tools for hobs
	Sharpening
	Lathe-screw-cutting
	Grinding for round dies
	Thread grinding
	Surface grinding
	Internal grinding
	Cylindrical grinders
	Fans

Based on the rated current, use the tables to select the cross-section of wires and cables and determine the installation method.

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

I max = 110.4/(1.73 × 0.38) = 157.7 A

Based on the design current, we select ShRA 73 with a rated current of 250 A, and from the transformer to ShRA - an ASG type cable (95 × 4) (table) and a VA 52G-33 switch I n = 160 A. For electrical receivers, based on the rated current, we determine the AR wire of various sections. All wires are four-core with polyvinyl chloride insulation of the APV brand, with the exception of the electrician’s workplace, where two-wire wires are installed.

The calculated data for this power point are summarized in the Calculation and installation tables of the Appendix.

The workshop plan with the drawing 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.e. the temperature does not exceed +30 o 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 specified 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 air conditions and the number of connected power receivers.

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

3.3 Calculation of repair complexity of electrical equipment

∑R = R 1 + R 2 + R 3 + … + R p

Calculation of repair complexity of equipment for a workshop:

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

2. For sharpening group machines 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 a fan R = 4. There are 3 fans installed in the workshop, which means ∑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 power supply categories, internal power supply diagrams.

In the calculation 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, and selection of protective devices were made.

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

To calculate the workshop load we use the method of ordered diagrams. This method is used for mass electrical receivers. It establishes a connection between the workload and the operating mode of electrical receivers based on a probabilistic scheme for generating a group load schedule.

General information about calculating electrical loads

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

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

The procedure for determining 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 Рн. We determine the utilization factor and power factor from Table 4.10 2, and determine tg from the value of the power factor.

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

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

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

PV - duration of switching on.

The total power of all electric devices is calculated using the formula:

P n=P neither ; (2)

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

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

Rated power of the minimum consumer, kW.

Average loads for the busiest shift of power electric drives of the same operating mode are determined by the formulas:

where: P 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, 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 rate of the EP group K using the formula:

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

For n5, Кis 0.2, m3 and Р nom const ne is determined by the formula:

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

For n >5, К is 0.2, m 3 and Р nom const we accept ne=n.

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

For n 5, K is 0.2, m 3 and P nom const ne is determined by the formula:

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

Using formula 10, n* is found:

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

P* is determined by the formula:

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

R nom1- the total rated power of a group of electrical receivers whose power exceeds the maximum power of a given group of electrical equipment divided by 2, kW.

The maximum active power is determined by the formula:

Where: TO m - maximum coefficient 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: - maximum reactive power factor, at n E? 10 =1, at n E<10 -=1,1

The total maximum power is determined by the formula:

The maximum current is determined by the formula:

Distributing 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 determining the load on RP-1.

table 2

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

P cm.1 = 0.65 · 2 · 3 =3.9 kW; Q cm.1 = 0.75 · 3.9 = 2.92 kVAr;

P cm.2 = 0.35 · 2 · 76 · v0.65 =42.9 kW; Q cm.2 = 1.73·42.9=74.2 kVAr;

P cm.3 = 0.12 · 1 · 4.4 =0.53 kW; Q cm.3 = 2.29·0.53=1.21 kVAr;

P cm.4 = 0.2 1 3 = 0.6 kW; Q cm.4 = 1.17· 0.6= 0.7 kVAr;

P cm.5 = 0.1 1 115.5 v0.4 =7.3 kW; Q cm.5 = 1.73· 14.6 = 12.6 kVAr.

2) Define K and groups using formula (8):

3) The power assembly indicator according to formula (3) will be equal to:

4) Since n > 5, TO and > 0.2, m>3, then n e =n=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) Maximum active and reactive power is determined by formulas (13) and (14):

P max = 1.89 55.22 = 104.36 kW.

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

Q max = 1.1 91.67= 100.84 kVAr.

We find the total maximum power using formula 15:

The calculated current is determined by formula 16:

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

1) We divide all electrical equipment of the workshop into groups with the same operating modes and determine the total rated power of the workshop:

2) Determine the power assembly indicator:

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

4) Determine the load utilization factor of the workshop electrical equipment:

5) Since n > 5, TO and > 0.2, m> 3, then n e =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 and1 K and2, K m1, K m2 - boundary values ​​​​of the coefficients K and and K m.

We determine the calculated active and reactive powers:

So, we take the value:

8)Full design power:

9) Rated current:

The results of all calculations are recorded in Table 2.

table 2

	Coeff. maximum	Max. active power	Max.reagent- rated 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, since it meets all operating requirements. They are also an economical solution, as they allow you to reduce electricity costs by about 2.5 times. LED spotlights with a narrow luminous flux distribution pattern are especially effective. 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 changes;

* do not emit mercury vapor or other harmful substances;

* Have high moisture resistance and dust protection;

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

* economical in terms of maintenance of electrical networks;

* easy to install;

* do not require special maintenance;

* have a long service life

When choosing light sources, you should take into account their advantages, disadvantages, and their cost-effectiveness.

Compared to incandescent lamps, fluorescent lamps have a more favorable emission spectrum, 4-5 times greater luminous efficiency, longer service life and significantly lower glare. However, fluorescent lamps require starting equipment; they create a pulsating light flux, do not light well at low temperatures, and are less reliable.

Let's determine the luminous flux necessary to create normal working lighting in the workshop. To calculate, we use the luminous flux utilization coefficient method.

Task lighting is the main type of lighting. It is intended to create normal vision conditions in a given room and is carried out, as a rule, with general lighting lamps.

Emergency lighting is used to continue work or evacuate people when the working lighting goes out. It must provide workplace illumination of at least 5% of that established 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 application.

Let's calculate the lighting of the workshop:

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

H P = h p - h p - h c m.; (18)

H P = 7 - 1.5 -1 = 4.5 m;

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

L = Н Р L wholesale, m.; (19)

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

L = 4.5 1.2 = 5.4 m;

L opt =0.8h1.2-deep

Then the number of rows of lamps 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 using the formula:

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

The number of lamps is determined as:

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

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

To determine the utilization coefficient, the index of the room i is found and the reflection coefficients are presumably estimated: ceiling - p, walls - s, calculated 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 = A B, m 2 (23)

S = 36 24 = 864 m2

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

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

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

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

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

L A. ST - the distance from the first lamp in the 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 Р o.p., (27)

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

P mouth..=35 200 = 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

Total design power of the workshop including lighting:

Estimated current of the workshop taking into account lighting:

Electrical loads determine the choice of the entire power supply system. To calculate them, the demand coefficient method and the diagram ordering method are used. The first method is usually used at the design stage, when the power of individual electrical receivers (ER) is unknown.

The diagram ordering method or the maximum coefficient method is fundamental in the development of technical and operational power supply projects. It allows you to determine the design load of any node of the power supply circuit based on the rated power of the electric power supply, taking into account their number and characteristics. According to this method, the calculated maximum load of the electric group is:

Group rated power R n is defined as the sum of the rated capacities of the electric power plant excluding reserve ones.

Usage rate TO and one or a group of electric power plants (Table 2.1) characterizes the use of active power and is the ratio of the average active power of one or a group of electric power plants for the busiest shift to the rated power.

Maximum coefficient TO m is the ratio of the calculated maximum active load power of the electric power group to the average load power for the busiest shift.

For a group of electrical equipment of one operating mode, the average active and reactive loads for the busiest shift are determined:

;
. (2.2)

Rated power P same type of electronic signatures

. (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, beam cranes, hoists, elevators

For consumers with variable load (group A) the calculated active load R p (A) groups of electronic equipment of a department (section, workshop) are determined taking into account the maximum coefficient TO m and average compartment load:

, (2.4)

Where TO m (A) – 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 coefficients TO m for different utilization rates

depending on the n uh

	Meaning TO m at TO And

Weighted average utilization rate of group A ED department

, (2.5)

Where R n (A) – total rated active power of the electric group

;

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

.

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

, (2.6)

or in simplified terms.

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

at n e >10
, (2.7)

at n uh £10
. (2.8)

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

;
. (2.9)

Such electric motors may 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 ED j-th department; m– number of branches.

Estimated active and reactive power of the workshop:

kW;
kV∙Ar. (2.11)

If there are single-phase electric motors in the workshop, distributed among the phases with an unevenness of £ 15%, they are taken into account as three-phase ones of the same total power. Otherwise, the calculated load of single-phase electric motors is assumed to be equal to triple the load of the most loaded phase.

When the number of single-phase electric motors is up to three, their conditional three-phase rated power is determined by:

a) when a single-phase electric motor is switched on to phase voltage with a three-phase system

Where S n– nameplate power; R n.f. – rated power of the maximum loaded phase;

b) when one ED is switched on to line voltage

. (2.13)

Maximum loads of single-phase electric motors when their number is more than three at the same TO and and cosj connected to phase or line voltage are determined:

;
. (2.14)

To determine the electrical loads of the workshop, a summary statement is drawn up (Table 2.3) with all calculated data filled in.

Table 2.3

Summary sheet of workshop electrical loads

Name of the characteristic group of EP	Number of electronic devices	Installed power of the electric unit, 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 using an approximate method based on the specific power per illuminated area.

;
(2.15)

Where R udo – specific design capacity per 1 m 2 of production area of ​​the department ( F);

TOс – lighting demand coefficient (Table 2.4).

Table 2.4

Calculated coefficient TO and, cosj, R ud0 and TO from individual workshops of industrial enterprises

	Name of workshops				R ud0,
	Compressor
	Pumping
	Boiler rooms
	Welding shop
	Electrical shop
	Assembly shops
	Mechanical
	Administrative premises

When using 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 domestic premises, fluorescent lamps with cosj = 0.85 are used; for lighting small rooms, incandescent lamps with cosj = 1 are used.

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

The transformer is selected based on the full design load, taking into account reactive power compensation.

Note : examples for determining electrical loads are presented in.