How to understand electrical quadratic diagram? What is the difference between an electrical secondary diagram and a secondary circuit diagram?
Speaking of electrical secondary diagram, we must first understand what is the electrical secondary circuit, the following Jiangxi Electric will share the basic knowledge of electrical secondary diagram to you.
The secondary circuit is the electrical circuit that detects, controls, regulates and protects the operation of the power system and the primary equipment.
The electrical secondary diagram contains the control loop, the signal loop, the measurement loop, the regulation loop, the relay protection and automatic device loop, and the operating power system.
Control loop
It is composed of a transmission mechanism and an execution (or operation) mechanism of a control switch and a control object (such as a circuit breaker, an isolation switch).
Its function is to "separate" and "combine" the primary equipment to meet the requirements of changing the system operation mode and troubleshooting.
For example, the VS1 circuit breaker in the switchgear opens and closes the control loop.
Control loop classification
1, according to the degree of automation: manual control and automatic control;
2, according to the control distance: local control and remote control;
3, according to the control mode divided: decentralized control and centralized control;
4, according to the nature of the operating power supply division: DC control and AC control;
5, according to the operating power supply voltage and current division: strong current control and weak current control.
Strong current control uses higher voltage (110V, 220V) and larger current (AC 5A), weak current control uses lower voltage (DC below 60V) and smaller current (AC 0.5-1A).
Signal loop
It is composed of a signal sending mechanism, a transmission mechanism and a signal relay.
Its function is to accurately and timely reflect the working status of the corresponding primary and secondary equipment, and provide a reliable basis for operation, adjustment and troubleshooting.
For example, a switchgear light indicates a circuit.
Signal loop classification
1, according to the nature of the signal: accident signal, warning signal, command signal and position signal;
2, according to the signal display mode: light signal and sound signal;
3, according to the signal return mode: manual return and automatic return.
Measuring loop
It is composed of various measuring instruments and their related circuits.
The function is to indicate or record the operating parameters of a device and a system, so that the operator can master the operation of a system.
Analysis of power quality, calculation of economic indicators, understanding of system power flow and other main basis.
Regulating circuit
According to the change of the operating parameters of the primary equipment, the working state of the primary equipment can be adjusted online in real time to meet the operating requirements.
Relay protection and automatic device circuit
Automatically judge the operating status of a device, in the system failure or abnormal operation, automatically jump the circuit breaker (cut the fault) or send abnormal operation signal, the fault or abnormal disappear, quickly put into the circuit breaker, restore the normal operation of the system.
Operating power system
It consists of power supply equipment and power supply network. Dc, AC power supply system. Its main function is to provide working power and operating power for control, protection, signal and other circuits.
Common components in electrical secondary diagrams include push button switches, indicator lights, travel switches/microswitches, combination switches, knife switches, air switches, fuses, thermal relays, time relays, contactors, etc.
Schematic diagram of electrical secondary diagram
Schematic diagram: used to represent the secondary wiring components (instruments, relays, signal devices, automatic devices and control switches and other equipment) electrical connection and working principle of the electrical circuit diagram.
It is customary to divide the schematic diagram into two forms: the generalized schematic diagram and the expanded schematic diagram.
(1) Generalized wiring diagram: all instruments, relays and other equipment in the wiring diagram are represented in the form of a whole;
The connections between AC voltage, current circuit and DC circuit are expressed synthetically in the wiring diagram.
The relevant parts of the primary circuit are also drawn in the wiring diagram, which can clearly show the auxiliary role of the secondary circuit to the primary circuit.
Its disadvantage is that it can not indicate the internal wiring of the components, terminal labels and wire connection methods, etc., and can not be used as construction drawings.
(2) Expansion wiring diagram: It is to draw the wiring circuit of the secondary equipment connection coil and contact separately to form a number of independent circuits.
Its characteristics are: AC current loop. The AC voltage circuit and the DC circuit are divided into several independent parts.
Coils of the same instrument. The coils and contacts of the same element are drawn separately in their respective different circuits, but the same text symbols are used;
There is a corresponding text description on the right side of the figure, indicating the name and purpose of the loop;
Each wire terminal has a unified circuit number.
How to read the split principle wiring diagram
(1) "First once, then twice" :
When there is a primary connection and a secondary connection at the same time in the figure, you should first look at the primary part, find out what equipment and work nature, and then look at the secondary part that plays a monitoring role in the primary part, and what monitoring role it plays.
(2) "AC first, DC later" :
When there are two types of AC and DC circuits in the figure, the AC circuit should be looked at first, and then the DC circuit.
The AC circuit is generally drawn from the secondary winding of the current transformer and the voltage transformer, which directly reflects the operating status of the primary equipment connection. After the AC circuit is understood, the DC circuit is logically inferred according to the electrical capacity of the AC circuit and the change characteristics of these electrical capacity when the system fails. The DC circuit is easy to see.
(3) "First power supply, after wiring" :
Whether AC circuit or DC circuit, the action of the secondary equipment is driven by the power supply, so when looking at the diagram, you should first find the power supply, and then look back along the circuit connection, AC along the closed circuit, DC from the positive power supply along the connection to the negative power supply, and analyze the action of each device.
(4) "coil first, contact later" (special attention)
To analyze the action of the contact, you must first find the relay or device coil, only when the coil is powered on, its corresponding contact will act, and the connection of the contact causes the change of the loop.
In a figure, the coil and its contacts are closely connected, find the contact in the coil, and find the coil in the contact, which is a quick skill to see the picture.
(5) "first up then down" and "first left then right" :
The secondary wiring drawings are drawn from top to bottom and from left to right in accordance with the logical order of the action of the protection device or loop.
The terminal block diagram and the wiring diagram on the back of the screen are also arranged in this way. Therefore, when looking at the drawing, first up and then down, from left to right, in line with the logic of protection action, it is easier to understand the drawing.
(6) The installation drawing should be combined with the development drawing
The installation diagram is generally a layout diagram, wiring diagram and terminal block diagram, which seems to have no logic and basically cannot form a loop, so it should be combined with the principle expansion diagram to see, and the punctuation of the contacts on the drawing is used to determine the position and meaning of the loop.
In order to understand the electrical schematic, you must also memorize the electrical equipment, devices and control components represented by the electrical graphic symbols, on the basis of which you can understand the electrical schematic.