Detailed explanation of power supply and shutdown operations, fault diagnosis and handling of high-voltage switchgear
Function:
The High-Voltage Switchgear has functions such as overhead incoming and outgoing lines, cable incoming and outgoing lines, and busbar connection.
Application:
Mainly suitable for various places such as power plants, substations, power system substations, petrochemicals, metallurgy and steel rolling, light industry and textiles, factories and mines, residential areas, high-rise buildings, etc.
Composition:
The switchgear should meet the relevant requirements of the "AC Metal Enclosed Switchgear" standard, consisting of two main parts: the cabinet body and the circuit breaker. The cabinet body is composed of a shell, electrical components (including insulation parts), various mechanisms, secondary terminals, and wiring.
Five defenses:
1. Prevent load closing: After the vacuum circuit breaker trolley in the high-voltage switchgear is closed at the test position, the trolley circuit breaker cannot enter the working position.
2. Prevent closing with grounding wire: When the grounding knife in the high-voltage switchgear is in the closed position, the circuit breaker of the trolley cannot be closed.
3. To prevent accidental entry into live compartments: When the vacuum circuit breaker inside the high-voltage switchgear is closed, the mechanical grounding knife on the back door of the cabinet is used to lock the cabinet door.
4. Prevent live grounding: When the vacuum circuit breaker in the high-voltage switchgear is closed during operation, the grounding knife cannot be put into operation.
5. Prevent pulling the knife switch under load: The vacuum circuit breaker inside the high-voltage switchgear cannot exit the working position of the trolley circuit breaker when it is in operation and closed.
structural composition
It mainly consists of cabinets, high-voltage Vacuum Circuit Breakers, energy storage mechanisms, carts, grounding switches, and comprehensive protectors.
① Cabinet body
Made by pressing iron plates, it is a closed structure with instrument room, trolley room, cable room, busbar room, etc. The rooms are isolated by iron plates, as shown in Figure 1. The instrument room is equipped with comprehensive protectors, ammeters, voltmeters and other devices; The car compartment is equipped with a car and a high-voltage vacuum circuit breaker; Install three-phase busbars in the busbar room; The cable room is used for external connection of power cables.
② High voltage vacuum circuit breaker
The so-called high-voltage vacuum circuit breaker is a device that installs its main contact in a sealed vacuum chamber. When the contact is turned on or off, its arc does not have gas to support combustion, and it is durable without burning out. At the same time, an insulating material is used as the base to improve the insulation performance of the vacuum switch, so it is called a high-voltage vacuum circuit breaker.
③ Car mechanism
Install the high-voltage vacuum circuit breaker on the trolley and move it with the trolley. When the handle is turned clockwise, the trolley enters the cabinet and inserts the vacuum circuit breaker into the high-voltage circuit; When the handle is shaken counterclockwise, the car exits the cabinet and drives the vacuum circuit breaker to extract the high-voltage circuit, as shown in Figure 2.
④ Energy storage institutions
A small electric motor drives the spring to store energy, and the spring releases kinetic energy to close the vacuum circuit breaker.
⑤ Grounding knife switch
It is a knife switch used for safety interlocking. When the grounding knife switch is closed, the high-voltage cabinet door can only be opened. Otherwise, when the grounding knife switch is not closed, the high-voltage cabinet door cannot be opened, providing safety interlocking protection.
⑥ Integrated protector
It is a microcomputer protector composed of a microprocessor, display screen, buttons, and peripheral circuits. Used to replace the original relay protection circuits for overcurrent, overvoltage, time, etc. Input signals: current transformers, voltage transformers, zero sequence current transformers, and switch signals, etc; The keyboard can be used to set data such as current value, voltage value, quick break time, startup time, etc; The display screen can display real-time data and participate in control, executing protective actions.
(1) According to the main wiring form of the switchgear, it can be divided into bridge type switchgear, single busbar switchgear, double busbar switchgear, single busbar segmented switchgear, double busbar with bypass busbar switchgear, and single busbar segmented with bypass busbar switchgear.
(2) According to the installation method of circuit breakers, they can be divided into fixed switchgear and movable (handcart) switchgear.
(3) According to the cabinet structure, it can be divided into metal enclosed interval switchgear, metal enclosed armored switchgear, and metal enclosed box type fixed switchgear.
(4) According to the installation position of the circuit breaker handcart, it can be divided into floor mounted switchgear and mid mounted switchgear.
(5) According to the different insulation media inside the switchgear, it can be divided into air insulated switchgear and SF6 gas insulated switchgear.
Main technical parameters
1. Rated voltage, rated current, rated frequency, rated power frequency withstand voltage, rated lightning impulse withstand voltage;
2. Rated moderate breaking current, rated peak closing current, rated short-time withstand current, and rated peak withstand current of the circuit breaker;
3. The rated closing peak current, rated short-time withstand current, and rated peak withstand current of the grounding switch;
4. Rated voltage, DC resistance, and power of the opening and closing coils of the operating mechanism, and rated voltage and power of the energy storage motor;
5. Cabinet protection level and corresponding national standard number.
1. Close all rear doors and covers, lock them securely, and only close the rear doors when the grounding switch is in the closed position
2. Insert the grounding switch operating handle into the hexagonal hole on the lower right side of the middle door, rotate counterclockwise to place the grounding switch in the open position, and the interlocking plate at the operating hole will automatically pop back to cover the operating hole, locking the cabinet door.
3. Push the service car up to position it, push the car into the cabinet to position it in the isolation position, manually insert the secondary plug, and close the door of the car compartment.
4. Insert the handle of the circuit breaker handcart into the handle socket, turn the handle clockwise for about 20 turns. If the handle is clearly obstructed and there is a clicking sound, remove the handle. At this time, the handcart is in the working position, and the secondary plug is locked. The circuit breaker handcart's main circuit is connected, and check the relevant signals.
5. The operation is to close the circuit breaker on the dashboard, open the switch to transfer power, and at the same time, the green light on the dashboard is off and the red light is on, indicating successful closing.
Power outage operation procedure
1. Operate the instrument panel to close and open the switch to place the circuit breaker in the open position. At the same time, the red light on the instrument panel will turn off and the green light will turn on, indicating successful opening.
2. Insert the handle of the circuit breaker handcart into the handle socket, rotate the handle clockwise for about 20 turns. If the handle is clearly obstructed and there is a clicking sound, remove the handle. At this time, the handcart is in the test position, and the secondary plug lock is released. Open the handcart compartment door and manually disengage the secondary plug, and the handcart's main circuit is disconnected.
3. Push up the service car to lock it, pull out the handcart to the service car, and drive the service car.
4. Observe the live display or verify if it is not live before continuing with the operation.
5. Insert the operating handle of the grounding switch into the hexagonal hole on the lower right side of the middle door, rotate it clockwise to place the grounding switch in the closed position. After confirming that the grounding switch has been closed, open the lower door of the cabinet for maintenance personnel to enter for repair and maintenance.
Diagnosis and Handling of Closing Fault
Closing faults can be divided into electrical faults and mechanical faults. There are two types of closing methods: manual and electric. Manual failure to close is usually due to mechanical failure. Manual closing is possible, while electric closing is due to an electrical fault.
1. Protection action: Before the switch is powered on, there is a fault protection circuit in the circuit that activates the anti bounce relay. The switch will trip immediately after closing. Even if the switch is still in the closed position, the switch will not close again and jump continuously.
2. Protection failure: The high-voltage cabinet is now equipped with five protection functions, which require that the switch cannot be closed when it is not in the operating or testing position. That is to say, if the position switch is not closed, the electric switch cannot be closed. This type of malfunction is often encountered during the closing process. At this time, the running position light or test position light is not on. Move the switch handcart slightly to close the limit switch to power on. If the offset distance of the limit switch is too large, it should be adjusted. When the position switch cannot be moved outward in the JYN high-voltage cabinet, a V-shaped plate can be installed to ensure the reliable closure of the limit switch.
3. Electrical interlock failure: Some electrical interlocks are set up in high-voltage systems for the reliable operation of the system. For example, in a single busbar segmented system with two incoming power sources, it is required that only two of the three switches, namely the two incoming cabinets and the bus tie cabinet, can be closed. If all three are closed, there is a risk of reverse power transmission. And the short-circuit parameters change, resulting in an increase in short-circuit current during parallel operation. The form of the chain circuit is shown in Figure 4. The interlocking circuit of the incoming cabinet is connected to the normally closed contact of the busbar cabinet, and it is required that the incoming cabinet can be closed in the open state of the busbar cabinet.
The interlocking circuit of the busbar cabinet is connected in series with one normally open and one normally closed of two incoming cabinets, and then connected in parallel. This ensures that the busbar cabinet can only be powered when one of the two incoming cabinets is closed and the other is opened. When the high-voltage cabinet cannot be electrically closed, the first consideration should be whether there is an electrical interlock, and manual closing should not be blindly used. Electrical interlocking faults are generally caused by improper operation that fails to meet the closing requirements. For example, although the incoming cabinet of the busbar is a one on one one off, the handcart inside the circuit breaker is pulled out and the plug is not plugged in. If the interlock circuit malfunctions, a multimeter can be used to check the faulty area.
Using red and green lights to determine auxiliary switch faults is simple and convenient, but not very reliable. You can use a multimeter to check and confirm. The method of repairing the auxiliary switch is to adjust the angle of the fixed flange, adjust the length of the auxiliary switch connecting rod, etc.
4. Control circuit open circuit fault: In the control circuit, damage to the control switch, disconnection of the circuit, etc. all cause the closing coil to be unable to receive power. At this moment, there is no sound of the closing coil moving. There is no voltage at both ends of the measuring coil. The inspection method is to use a multimeter to check the open circuit point.
5. Closing coil fault: The burning of the closing coil is a short circuit fault. At this time, there are phenomena such as odor, smoke, and short melting of the fuse. The closing coil is designed for short-term operation, and the power on time cannot be too long. After a failure to close the circuit, the cause should be promptly investigated and the circuit should not be closed repeatedly. Especially for the closing coil of CD type electromagnetic operating mechanism, it is easy to burn out due to multiple closing cycles caused by high current.