Electrical (electrical, electrical power and equipment) is the production, transmission, distribution, use of electrical energy and the manufacture of electrical equipment and other disciplines or engineering fields collectively. is to electrical energy, electrical equipment and electrical technology as a means to create, maintain and improve the limited space and the environment of a science, covering the conversion of electrical energy, the use and research in three aspects, including basic theory, application technology, facilities and equipment.
Electrical Engineering (Electrical Engineering, referred to as EE) is one of the core disciplines in the field of modern science and technology, but also in today's high-tech field is indispensable to the key disciplines. It is the great progress of electronic technology to promote the computer network based on the arrival of the information age, and will change the human life, work mode. The prospects for the development of electrical engineering is also very promising, making today's students employment rate has been very high.
Control systems
Electrical control systems are generally referred to as secondary control loops for electrical equipment, with different control loops for different equipment and different control methods for high-voltage and low-voltage electrical equipment.
Main function
In order to ensure the reliability and safety of the primary equipment operation, there is a need for a number of auxiliary electrical equipment to serve, to achieve a certain control function of a number of electrical components of the combination, known as the control loop or secondary circuit. These devices to have the following functions:
1, automatic control function: the volume of high-voltage and high-current switchgear is very large? Need a set of detection of these fault signals and equipment and lines for automatic adjustment (disconnection, switching, etc.) of the protection equipment;
3, the monitoring function: electricity is invisible to the eye, whether a device is charged or disconnected, from the appearance can not be distinguished, which requires the setting of a variety of audio-visual signals, such as lights and sound, etc., the primary equipment for the electrical monitoring;
4, the measurement function: Lights and sound signals can only qualitatively indicate the working status of the equipment (power or power outage), if you want to quantitatively know the work of the electrical equipment, but also need to have a variety of instrumentation measurement equipment, measuring various parameters of the line, such as voltage, current, frequency and the size of the power and so on.
In the equipment operation and monitoring, the traditional operating components, control appliances, meters and signals and other equipment can be replaced by most of the computer control system and electronic components, but in the small equipment and in situ local control of the circuit still has a certain range of applications. This is also all the circuit to realize the basis of microcomputer automation control.
System Composition
The basic circuit of the commonly used control circuit consists of the following parts.
1, power supply circuit: power supply circuit power supply AC380V and 220V and so on;
2, protection circuit: protection (auxiliary) circuit of the power supply single-phase 220, 36V or DC 220, 24V and so on, the electrical equipment and lines for short-circuit, overload and loss of voltage and other kinds of protection, by the fuse, thermal relay, loss of voltage coil
3, signal circuit: can reflect or display the equipment and lines in a timely manner the normal and abnormal working state of the circuit information, such as different colors of the signal lights, different sound audio equipment, etc.;
4, automatic and manual circuit: electrical equipment in order to improve efficiency, generally have an automatic link, but in the installation, commissioning and emergency treatment, the control circuit, the control circuit, the control circuit, the control circuit, the control circuit, the control circuit, the control circuit, the control circuit, the control circuit, the control circuit, the control circuit, the control circuit, the control circuit, the control circuit, the control circuit, the control circuit and the control circuit. Emergency handling, control lines also need to set up a manual link, through the combination switch or changeover switch to realize the automatic and manual mode of conversion;
5, braking and parking circuit: cut off the power supply of the circuit, and take some braking measures, so that the motor to stop the control link quickly, such as energy braking, power reverse braking, reverse pull reverse braking and regenerative power generation braking, etc.;
6, self-locking and latching the same circuit: start button release, the line remains energized, the electrical equipment can continue to work the electrical link called self-locking link, such as contactor moving contacts in series in the coil circuit. Two or more electrical devices and components, in order to ensure the safety and reliability of equipment operation, only one energized to start, the other can not be energized to start the protection link, called the interlocking link. Such as the two contactor moving contacts are connected in series in each other's coil circuit.
Operation principle
The digital core of the microcomputer protection device of the electrical system generally consists of CPU, memory, timer/counter, Watchdog and so on. The mainstream of the digital core for the embedded microcontroller (MCU), that is, usually referred to as a microcontroller; input and output channels including analog input channels (analog input conversion loop (CT, PT measured into a lower amount of suitable for internal A/D conversion of voltage, ± 2.5V, ± 5V or ± 10V), low-pass filter and sampling, A/D conversion) and digital input and output channels (human-machine interface and a variety of alarms), and the digital input and output channels (the digital input and output channels). human-machine interface and various alarm signals, trip signals and power pulses, etc.).
Protection device
Microcomputer protection device of the electrical system is a microcomputer composition of the relay protection, is the direction of the development of power system relay protection (now basically realized, still need to develop), it has a high degree of reliability, high selectivity, high sensitivity. Microcomputer protection device hardware including microprocessor (microcontroller) as the core, with input and output channels, human-machine interface and communication interface. The system is widely used in electric power, petrochemical, mining and smelting, railroad and civil buildings. The hardware of the microcomputer is universal, while the performance and function of the protection is determined by the software.
Electrical diagram
Commonly used electrical diagrams include: electrical schematic diagrams, electrical components layout, electrical installation wiring diagram. Various drawings of the drawing size generally choose 297 × 210, 297 × 420, 297 × 630, 297 × 840mm, four kinds of format, special needs can be GB126-74 "Mechanical Drawing" national standard selection of other sizes.
Electrical principle
With graphic symbols, text symbols, item code, etc. indicates the relationship between the electrical components of the circuit and the principle of operation of the diagram is called the electrical schematic diagram. Electrical schematic structure is simple, hierarchical, applicable to the study and analysis of circuit working principle, and can provide help to find faults, but also the preparation of electrical installation wiring diagrams based on the design department and production site is widely used.
The electrical schematic diagram is an electrical component of the various parts of a separate form of drawing, the scene is also the same electrical parts are concentrated together, in accordance with the actual location of the circuit structure of the drawings.
The structure of the drawing method is easier to identify the electrical appliances, easy to install and maintenance. However, when the line is more complex and use more appliances, the line is not easy to see clearly. Because of the same appliance parts in the mechanical although linked together, but the circuit is not necessarily related to each other.
Drawing principles:
1, the electrical schematic diagram of the electrical components are not energized and not subject to external forces when the state of drawing. In different stages of work, the action of each appliance is different, the contacts are closed and open. In the electrical schematic diagram can only indicate a situation. Therefore, it is stipulated that the contacts of all electrical appliances are represented in the original situation, i.e., in the position when there is no energization or no mechanical action taking place. For the contactor, the coil is not energized, the position of the contact is not in action; for the button, the finger is not pressed the button when the position of the contact; for the thermal relay, is a normally closed contact in the absence of overload action and so on.
2, the drawing position of the contact. Make the contact action of the direction of the external force must be: when the graph is placed vertically from left to right, that is, the left side of the vertical line of the contacts for the normally open contacts, the right side of the vertical line of the contacts for the normally closed contacts; when the graph is placed horizontally from the bottom to the top, that is, below the horizontal line
square contacts for the normally open contacts, the horizontal line of the contacts above the normally closed contacts.
3, the main circuit, control circuit and auxiliary circuit should be drawn separately. The main circuit is the driving circuit of the equipment, is the path from the power supply to the motor through the high current; control circuit is composed of contactors and relay coils, various electrical contacts of the logic circuit, to achieve the required control functions; auxiliary circuits, including signaling, lighting, protection circuit.
4, the power circuit of the power circuit is drawn as a horizontal line, the powered power unit (motor) and its protection of electrical branches should be perpendicular to the power circuit.
5, the main circuit is drawn with vertical lines on the left side of the diagram, the control circuit is drawn with vertical lines on the right side of the diagram, and the energy-consuming components of the control circuit are drawn at the bottom of the circuit.
6, the diagram from left to right or top to bottom to indicate the order of operation, and minimize the lines and avoid line crossing.
7, there is a direct electrical connection in the diagram of the cross-wire connection point (i.e., where the wires cross) to be indicated by a black dot. No direct electrical connection of crossed wires, the intersection can not draw black dots.
8, in the schematic diagram at the top of the diagram will be divided into a number of diagram area, and marked the use of the circuit and the role of the district; in the relay, contactor coils below the contact table to illustrate the relationship between the coil and the contacts of the subordinate.
Component layout
Electrical component layout diagram mainly indicates the actual location of all electrical components on the electrical equipment, electrical equipment installation and maintenance to provide the necessary information. Electrical component layout can be drawn according to the complexity of the electrical equipment centrally or separately. Figure does not need to mark the size, but the electrical code should be with the relevant drawings and electrical list of all the components on the same code, in the figure often leave more than 10% of the spare area and the location of the wire tube (slot) for the improvement of the design.
Drawing principles:
1, drawing electrical components layout, the machine tool outline with a fine solid line or dotted line, electrical components are drawn with a thick solid line with a simple outline.
2, drawing the layout of electrical components, the motor should be drawn together with the dragged mechanical devices; travel switch should be drawn in the place of access to information; operating handle should be drawn in the place of easy operation.
3, drawing electrical components layout, between the electrical components, up, down, left, right should maintain a certain distance, and should take into account the device's heat and heat dissipation factors, should be easy to wiring, wiring and maintenance.
Installation and wiring
Electrical installation and wiring diagrams are mainly used for electrical equipment installation and wiring, line inspection, line maintenance and troubleshooting. In the diagram to indicate the actual wiring between the electrical equipment, electrical components, and label the data required for external wiring. In the electrical installation wiring diagram of the electrical components of the text symbols, components connected to the order, line number preparation must be consistent with the electrical schematic diagram.
Drawing principles:
1, drawing electrical installation wiring diagram, the electrical components are drawn according to their actual position in the installation of the base plate. Components accounted for by the actual size of the drawing surface to a uniform ratio will address.
2, drawing electrical installation wiring diagram, a component of all the parts drawn together, and with a dotted line box, sometimes more electrical components with a dotted line box, that they are installed in the same mounting plate.
3, drawing electrical installation wiring diagram, the installation of the base plate inside and outside the electrical components of the wiring between the connection through the terminal board, the installation of the base plate has a few leads to the external circuit, the terminal board should be drawn on a few lines of the point of contact.
4, drawing electrical installation wiring diagram, toward the same neighboring wires can be drawn as a line.
Secondary circuits
(1) DC circuits from the positive pole to the negative pole: columns such as control circuits, signaling circuits. Starting from the positive DC pole of a circuit, the current flows in the direction of the negative pole until you see it.
(2) AC circuit from the fire wire to the neutral: such as current and voltage circuits, transformer air-cooled circuits. Starting from the fire line of a circuit (A, B, C phase), according to the direction of current flow, see the neutral line (N pole) until.
(3) see the contact to find the coil, see the coil to find the contact: see the contact that is to find the relay or contactor to control the contact coil position. The coil is located in the loop is the control loop of the contact to analyze the conditions of the contact action. See the coil to find out all its contacts in order to find out all the contacts (objects) controlled by the relay.
(4) Using Ohm's law to analyze the relay to determine whether the action: the basis for discrimination is that the voltage-type coil is added to the ends of a sufficiently large voltage, current-type coil through the ends of a sufficiently large current. For voltage type relay coil circuit, when the coil ends through a number of relay contacts or current coil and respectively power supply positive and negative poles through, it is considered that the relay (contactor) action (excitation), when there is a short open circuit contacts, or coil circuit series has a relatively large resistance, or the coil is shorted by the parallel contacts, it is considered that the relay (contactor) does not act (not excitation). For example, when the switch is in the closing position and the positive terminal of the switching coil is connected with a closing relay (high resistance), it is considered inoperative. When the protection trip contact is closed and the coil is connected directly to the positive pole of the power supply, the tripping coil is considered to operate. For the current type (such as trip circuit of the anti-jump relay), when the ends of the coil through a number of relay contacts or coil with smaller resistance and respectively the positive and negative poles of the power supply through, it is considered that the relay (contactor) action (excitation). When there is a short open contact in the circuit, or the coil circuit is connected in series with a relatively large resistance, or the coil is shorted by the parallel contact, it is considered that the relay (contactor) does not operate (not excitation).
(5) Look at all the branches: when a circuit, from the positive pole to the negative pole to see the circuit, such as the middle of more than one branch to the negative pole, each branch must be seen. Otherwise, analyzing the circuit will miss part of the important situation.
(6) the use of relative numbering method, circuit labeling to clarify the installation diagram and the wiring schematic diagram of the wiring diagram of the corresponding relationship: verification of the installation diagram and the corresponding relationship between the main purpose of the diagram: the first is to check whether the installation diagram corresponds to the expansion of the diagram. Secondly, to clarify the location of each device in the unfolding diagram at the site. From the installation diagram (such as protection screen terminal wiring diagram) to find a terminal row of terminals in the expansion of the location of the diagram, the first to find out where the terminal circuit labeling, and then check the expansion of the circuit labeling diagram, the same circuit labeling that is, the same circuit, you can quickly find the circuit in the expansion of the diagram in the expansion of the diagram to find out the role of the circuit in the whole circuit. If the hand only installation drawings or found that the installation drawings and schematic wiring diagrams can not correspond to the expansion of the diagram, from the installation of each of the equipment in the diagram of the terminal number labeled, based on the relative number of the method, to the other equipment connected to the terminal, and then check out the terminal connected to the other equipment until the positive and negative poles of the DC power supply or the AC circuit of the fire wire and the neutral wire until the check. Finally, you can check the whole circuit and analyze whether the connection is in accordance with the action principle after drawing the diagram. When you want to find out the position of the equipment on the unfolding of the map, then one is to use the equipment table on the unfolding of the map to provide the location, and then go to the corresponding installation plan to check. The second is to clarify the terminal symbols in the unfolding of the map, which is the terminal row of the screen cabinet terminals, which is (protection or automatic) device terminals, and then go directly to the possible screen cabinet, terminal box to find.
(7) The solution to the special problems of map reading.
A. How to use the actual state of the equipment (the state of the equipment that can be seen on the scene) to describe the operating conditions of the circuit or relay: first, describe the conditions of the circuit in terms of the contact's split and close states, and then, according to the corresponding relationship between the contact's split and close states and the state of the equipment, replace the descriptions (e.g., by using the switching mechanism box's "remote/near-control diverter switch" in the "remote/near-control diverter switch" box). For example, use the "far/near control diverter switch" of the switching mechanism box in the "far" position to replace the contact state of the "far/near control diverter switch" in the far control loop. This ability must be gradually formed, otherwise the drawings will remain in the original state, can only see the contact points of the split, close and relay excitation or not, can not be combined with the operation of the equipment state monitoring and operation.
B, how to figure out how to expand the part of the drawing using the box drawing equipment and other parts of the external connection? First, find out the terminal number of the box drawing equipment, and then use the device manual or manufacturer's drawing that shows the internal wiring diagram of the equipment, find the terminal number of the external connection in these drawings, and then connect it to the internal circuit, and then connect it to the external circuit through the terminal of the external connection.
Operation Management
1, reasonable adjustment of the peak hour load
Normal conditions should try to make the transformer load rate control at about 60%, when the transformer loss is lower. Therefore, in the peak hours of electricity consumption, should optimize the equipment operation program, choose to unload certain relatively unimportant mechanical and electrical loads and lighting loads, so that the peak load reduction.
2, public **** lighting and office equipment operation and management
In the case of not affecting the office, should try to lower the illumination or timely closure of lamps and lanterns, no special needs, decorative lamps and lanterns as far as possible do not open for a long time. For the less mobile area, the lamp control switch should be used inductive, voice-activated, touch delayed closure and other control methods, conditions can be on the public **** real-time monitoring of the lighting system. Office equipment such as computers not used for a long time should be cut off in time to reduce standby losses.
3, air-conditioning system operation management
Summer will be the air-conditioning set temperature value down 1 ℃, will increase the energy consumption by 9%; winter will be the set temperature up 1 ℃, will increase the energy consumption by 12%. Therefore, the appropriate adjustment of the air conditioning set temperature value is an effective measure of air conditioning energy saving. At the same time, the use of equipment monitoring system to strengthen the air conditioning system unit equipment operation management, and according to changes in the system load and meteorological environment, timely adjustment of the air conditioning system operation program, reduce the total power of equipment operation, control the optimal start and stop time of the air conditioning equipment can be in the premise of ensuring a comfortable environment to shorten the air conditioning unnecessary operation time in order to achieve energy-saving operation.
4, elevator operation management
In the low peak operation, should be adjusted in a timely manner procedures to stop part of the elevator, and minimize the elevator's empty or low load operation. In peak operation, each elevator can be taken according to the plan to reduce the layer station or staggered layer stop measures to extend the elevator trip, shorten the operating cycle, the operating speed will have a greater increase, thus improving its operating efficiency.