Control system of compensating capacitor tower for transformer test

Control system of compensating capacitor tower for transformer test
Large transformers usually need load and temperature rise tests, and test power generation is often used
Unit power supply. The capacity of the unit is mainly considered according to the active power loss during the load and temperature rise test
The quantity is small. During the test, the input current is mostly inductive reactive current, in order to reduce the output capacity of the power supply
Capacitance compensation is usually used. Compensation capacitor tower is an adjustable capacitor compensation device
In this paper, according to the primary principle design diagram of compensation capacitor tower, according to different test capacitance
The connection mode, capacity, voltage, frequency and other parameters of the disconnector group are used to control each disconnector
In order to meet the requirements of the test, the compensation capacitance is controlled and monitored.


The main control part of the secondary control and protection monitoring system of the capacitor tower adopts programmable controller
Programmable logic controller (PLC), with high reliability, strong anti-interference, easy programming
It is suitable for harsh industrial environment. Due to the use of pneumatic disconnector, 
The opening and closing control and state are connected to the execution and detection part by the air pipe, which improves the overall efficiency
The safety and reliability of the control system. The whole operation interface is simple and easy to use.
1. Working principle
All capacitors in the capacitor tower are switched by pneumatic disconnector
【2】 PLC control part is the core of the whole system. It can accept remote controller

The control command of the computer or local touch screen is output to the pneumatics through the intermediate relay
The magnetic valve controls the switch of the knife switch by controlling the on-off of the electromagnetic valve; Switch status of knife switch
The pneumatic control valve installed on the knife switch is used to control and detect the air pipe, and then the pneumatic pressure is measured
The switch detects whether the gas circuit is on or off, so as to change the switch on / off position state into electrical signal, which is transmitted to the power supply
Input to PLC; According to the input state signal state, PLC judges the closing and opening state of the knife switch,
The status is uploaded to the remote industrial computer and the field touch screen, and displayed in the corresponding screen
As shown in [3].
Monitoring and protection are necessary to ensure the safe operation of the system. Working capacitance
The operation status of tower is directly output from PLC to remote and local controller
At the same time, the capacitor room is equipped with a camera monitoring system to monitor the power on the monitor in real time
The whole process of the system is stored and recorded.
The whole protection system consists of hardware and software. The hardware part is single
Fuse protection outside the capacitor, hardware interlock of some key switches and indication of protective fence
The lamp and safety electrical interlocking system are composed; In the software part, PLC programming is used to form the mutual control of the related switches
Lock and self lock, monitor whether the system current exceeds the limit, and detect whether the air source pressure meets the requirements,
In addition, it keeps locked state in case of pneumatic pressure loss and power failure.
2. Technical parameters微信图片_202009052235146

2.1 power supply
AC power: 220 V, frequency: 50 Hz
2.2 power consumption
PLC cabinet: 120W solenoid valve cabinet: 300W
Test cabinet: 100W industrial computer: 300W
2.3 environmental parameters
Normal working temperature: 0 ~ 40 ℃, limit working temperature: – 10 ~ 50 ℃
2.4 size of control cabinet
Test cabinet size: 2200 (H) * 800 (W) * 600 (T)
Size of PLC control cabinet: 2200 (height) * 1000 (width) * 600 (thickness)
Size of pneumatic control cabinet: 2200 (height) * 1000 (width) * 600 (thickness)
Size of console: 1400 (H) * 1200 (W) * 800 (T)
Cabinet color: computer gray
2.5 communication mode
PLC touch screen: Standard MODBUS PLC industrial computer: TCP / IP or standard MODBUS
(depending on site conditions)
3. Overall introduction of the device
Pneumatic control and protection monitoring system consists of five parts: pneumatic solenoid valve control system
The system consists of three parts: output part, pneumatic switch position detection part, PLC control part, upper configuration part
Video monitoring part. The corresponding device parts are: pneumatic control cabinet, pneumatic detection
Cabinet, PLC control cabinet, remote control computer (upper computer) and video monitoring system.
3.1 pneumatic switch position detection part
It is composed of a pneumatic detection cabinet. Each disconnector has two mechanical control valves which are inspected separately
The opening and closing positions of the switch are measured, and the control position is used to detect the conduction of the trachea; Position detection trachea
The pneumatic pressure switch connected to the pneumatic detection cabinet turns on and off the air pipe (air pressure)
It is converted into electrical signal and output to PLC controller.
3.2 pneumatic solenoid valve control output part
It consists of a pneumatic control cabinet. The electromagnetic valve of main components in the cabinet is controlled by PLC
The control signal of the device controls whether the control air pipe connected with the device is connected or not, so as to realize pneumatic control
Switch in and switch off of disconnector. At the same time, the main gas pipe pressure and power supply condition in the cabinet are detected
In addition, the signal is transmitted to the PLC controller, which can be automatically controlled when the gas pipe loses pressure and the power supply loses power
Move the lock solenoid valve to prevent misoperation.
3.3 PLC control part
There is a PLC control cabinet. There are PLC module and intermediate relay in the cabinet
form. The PLC controller receives the control command from the touch screen or the upper computer, and sends it through the middle
The relay outputs the solenoid valve to the pneumatic control cabinet; At the same time, it receives signals from pneumatic detection cabinet
The position signal of the disconnector is output to the touch screen or the upper computer to realize the status display.
The touch screen is set on the door of PLC control cabinet to realize the local control and the mode control of working state
It will be displayed on the screen.
3.4 upper configuration part
It consists of a set of industrial control computer system and its console in the remote control room. Superior worker
The control computer is the main man-machine dialogue window of the whole control system, which passes through the data line or network
It is connected with PLC system to display system status
Display, accept operator control instructions, complete remote operation, set system working parameters, save
Store and record system operation data, generate data reports, alarm records, etc.
3.5 video monitoring system
It is composed of camera and video monitoring computer. The camera is installed in the capacitor room,
The signal is transmitted to the video monitoring computer in the remote control room to realize the operation of the capacitor room
Real time monitoring of state. The monitoring system has the function of storage, which is convenient to analyze the operation records.
3.6 software functions
Operation interface: the test personnel operate through the computer screen interface, in the above various fields
Under the operation mode, the control signal of the corresponding pneumatic valve is sent out and accepted by the PLC
The upper computer executes the operation after command, outputs to the intermediate relay, controls the solenoid valve, and turns on
Gas path; By closing and opening the pneumatic disconnector, the single-phase / star / triangle transformation and capacity adjustment of the capacitor bank can be achieved. Simulation of control interface during operation
The system diagram, alarm screen and maintenance screen can dynamically display the configuration of switch and capacitor in real time
situation. At the same time, the PLC system will automatically eliminate the wrong instructions, and can achieve the set of each
The protection and interlock function of the two states.
The functions of capacitor switching in and switching off realized by the industrial computer operating system are as follows:
“Single operation of disconnector” mode: used for item by item selection operation of function switch
Operation and maintenance.
1) “Combination operation of disconnector” mode: operator input operation combination
According to the code, the computer displays the corresponding test parameters and switch combination for the operator
Perform the operation after confirmation.
2) “Intelligent operation of disconnector” mode. The operator in the parameter input box
Input test voltage, capacity, phase number, frequency and other parameters, and the recommended group is provided by the computer
The operation can be carried out after the operator’s confirmation.
3) “Disconnector grounding maintenance” mode: During “maintenance” operation, the operation shall be carried out
After 10 minutes, the operator can enter the room, during which the system prompts: “for you and the setting
Please wait ten minutes for the safety of the equipment. In the maintenance state, the “isolation switch list” can be executed
There are two operation modes.
The system detects the position signal of all the pneumatic disconnectors, which does not conform to the operation requirements
Make the request, monitor the system alarm prompt, and do not execute the next operation; system failure
Alarm and display the fault location.
The main disconnector of the device is interlocked with the main disconnector of the test system. system
After switching on, the operation of capacitor disconnector will be forbidden automatically. In case of misoperation, the system will stop automatically
Pop up the “main switch of test system is in closing state, operation of capacitor bank is prohibited”
Fault alarm: the opening and closing of pneumatic disconnector is not in place; High and low air pressure
Police; Over current alarm; The alarm time is recorded and automatically stored in the database
File and diagnostic tips. And can generate the corresponding report or curve.

Post time: Jul-04-2021