Course design of electromechanical shop power supply

Introduction

Energy of our country provides electricity supply to the national economy and household needs of various consumers of electric energy. The main consumers are industrial enterprises, agriculture, municipal needs. Most of the electricity is spent on the technological processes of enterprises. To transfer electricity in the necessary quantity and of appropriate quality, the following power systems exist: Workshop - providing energy supply to consumers, Factory - serving for power supply to the main workshops and auxiliary facilities, City or District - serving for power supply to enterprises, agriculture, utility facilities. The design shall take into account the technical and economic aspects. When selecting the voltages of the supply lines, the network and the numbers of transformer substations, control systems, protection - we must take into account improvements in the technological process, power growth at nominal voltage.

1. General part

1.1. Brief characteristics of electromechanical workshop, electrical loads and its technological process

Electromechanical workshop (EMT) is designed to prepare metal blanks for electrical machines with their subsequent processing in various ways.

It is one of the workshops of the metallurgical plant, smelting and processing metal. The EMC has a machine compartment in which standard equipment is installed: ingot-cutting, turning, milling, strict, anode-mechanical machines, etc.

The workshop provides rooms for workshop TP, fan, tool, for household needs, etc. EMT receives ESN from the deep input substation (PGV). The distance from the PGV to the workshop TP is 0.5 km, and from the ENS to the PGV - 10 km. Voltage at SGV - 10 kV.

The number of working shifts is 2. EE shop consumers have ESN reliability category 2 and 3.

Soil in the EMC area - sand with temperature + 20 0С. The frame of the building is mounted of blocks-sections 8 and 9 m long each.

Shop dimensions A * B * H = 48 * 30 * 9 m.

Auxiliary rooms are two-storey with a height of 4 m.

List of EMC equipment is given in Table 1.

Power consumption capacity (Rep) is specified for one electric receiver.

The location of the main equipment is shown on the plan (Location Plan of the Electrical and Mechanical Workshop).

2. Design Part

2.1. ESN reliability category and ESN circuit selection

All electric receivers according to reliability of power supply are divided into three categories:

Electric receivers of category I - electric receivers, the interruption of power supply of which can entail: danger to people's lives, significant damage to the national economy; damage to expensive basic equipment, mass scrap of products, disorder of complex technological process, disruption of functioning of critical elements of public utilities. From the composition of electric receivers of category I, a special group of electric receivers is distinguished, the uninterrupted operation of which is necessary for accident-free shutdown of production in order to prevent the threat to people's lives, explosions, fires and damage to expensive basic equipment.

Electric receivers of category II - electric receivers, the interruption of power supply of which leads to mass underdelivery of products, mass downtime of workers, mechanisms and industrial transport, disruption of the normal activities of a significant number of urban and rural residents.

Power supply of category II electric receivers is allowed for one HF, including with a cable insert, if the possibility of emergency repair of this line is provided for a period of not more than 1 days. Cable inserts of this line must be made by two cables, each of which is selected according to the longest VL current. Power supply of category II electric receivers is allowed along one cable line consisting of at least two cables connected to one common set.

If there is a centralized reserve of transformers and the possibility of replacing the damaged transformer for a period of not more than one day, power supply of category II electric receivers from one transformer is allowed.

For category II electric receivers in case of failure of power supply from one of the power sources, power supply interruptions are allowed for the time required for switching on the backup power supply by the actions of the duty personnel or the field operational team.

According to PUE, electric receivers of category II are recommended to be provided with electricity from two independent, mutually redundant power sources.

Electric receivers of category III - all other electric receivers that are not suitable for the definitions of categories I and II .

For electric receivers of category III, power supply can be carried out from one power source, provided that the power supply breaks necessary for repair or replacement of the damaged component of the power supply system do not exceed 1 day.

Electromechanical workshop by ESN reliability category belongs to consumers of categories 2 and 3.

The main supply circuits are widely used not only to power many electric receivers of a single process unit, but also a large number of relatively small receivers that are not connected to a single process. Such consumers include metal cutting machines in metal machining shops and other consumers distributed relatively evenly over the area of the shop.

Backbone diagrams make it possible to avoid the use of a bulky and expensive switchgear or shield. In this case, it is possible to use the circuit of the transformer line unit, where current conductors (bus conductors) manufactured by industry are used as the supply line. Backbone diagrams made by busbars provide high reliability, flexibility and versatility of workshop networks, which allows technologists to move equipment inside the workshop without significant alterations of electrical networks.

To supply a large number of electric receivers of relatively small power, relatively evenly distributed over the area of ​ ​ the workshop, schemes with two types of main lines are used: supply and distribution. Supply or main lines are connected to the busbars of transformer substation cabinets specially designed for main circuits. The distribution lines to which the electric receivers are directly connected are powered by the main supply lines or directly by the transformer substation buses, if the main lines are not used.

As few individual electric receivers as possible are connected to the main supply lines. This improves the reliability of the entire power system.

The disadvantage of the backbone circuitry is that when the backbone is damaged, all the electric receivers supplied from it are simultaneously disconnected. This disadvantage is felt when there are some large consumers in the workshop that are not connected to a single continuous process.

Are connected to tires of the lowest tension of transformer substation via RP1,RP2,RP3,ShRA1,ShRA2 lead-in switches.

• RP1 through switch energizes electric receiver No. 1

• RP2 through the switch energizes electric receiver No. 21

• RP3 through switches energizes electric receivers No. 42, 43

• PSA1 energizes electric receivers No.2, 3, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 through line switches

• ShRA2 via linear switches powers electroreceivers No.

22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41

2.3 Calculation and selection of ESN elements

During operation of electrical networks, long-term G-loads of wires and cables, CP cause an increase in the temperature of conductive cores more than permissible.

This leads to premature wear and tear of their insulation, which can result in fire, explosion in explosive premises, personnel damage.

To prevent this, the ESN line has a protection device that turns off the damaged section.

Protection devices are: circuit breakers, fuses with fuses and thermal relays embedded in magnetic starters.

Circuit breakers are the most advanced protection devices, reliable, actuating during overloads and short circuit in the protected line.

The sensitive elements of the circuit breakers are: thermal, electromagnetic and semiconductor.

Thermal disconnectors are actuated during overloads, electromagnetic - during short-circuit, semiconductor - both during overloads and during short-circuit.

The most modern VA series circuit breakers are designed to replace the obsolete A37, AE, AVM and Electron.

They have reduced dimensions, perfect structural units and elements. They work in DC and AC networks. Table A.6 provides VA data, as they are the most modern and are used in packaged switchgears in the form of various combinations. VA Series Circuit Breakers

VA series switches of development 51, 52, 53, 55 are designed for disconnections during short circuit and overloads in electrical networks, disconnections at unacceptable voltage reductions, as well as for infrequent operational actuations and disconnections of electrical circuits.

VA series switches of development 51 and 52 have thermal (TP) and electromagnetic disconnectors, sometimes only EMF.

The VAs 51 have an average switching capacity.

VA 52 is elevated.

Circuit breakers are selected according to the following conditions:

for line without ED - In.a.≥ I.r.; In.r.≥ Idl;

for line with one ED - In.a.≥ I.r.; In.r.≥ 1.25 L;

for a group line with several EDs - In.a.≥ I.r.; In. river ≥ 1.1idl.

We make calculation and the choice of ShRA1, ShRA-2, RP1, RP-2, RP3 and lead-in switches:

Initial data for calculations of protection devices are taken from the summary load list.

Conclusion

During the course project on the topic "Electrical power supply of the electromechanical workshop," they studied technical and reference literature, learned to compile single-line and expanded power supply schemes. The replaceable and maximum active, reactive and full loads of electric receivers were calculated using the use factor and maximum factor. All coefficients were selected from reference literature.

Electric receivers operating in a re-short-term mode were brought to a long-term mode of operation. They justified the choice of a power transformer taking into account the power supply category of the mechanical workshop, determined the load factor of the transformer taking into account compensating devices .

During the course design, protection devices for all electric receivers were calculated and cable grades in cross section and permissible current were selected, according to PUE requirements.