Maintenance and common troubleshooting of transformer box
1：The overall structure of a box transformer is mainly divided into three parts: high-voltage switchgear, transformers, and low-voltage distribution equipment. According to system requirements, high voltage switches can be equipped with sulfur hexafluoride or Vacuum Circuit Breakers, ring network switches, load switches with fuses. A measuring device can also be installed on the high-voltage side.
The low-voltage side is generally equipped with a main switch and branch feeder switch, while some only install feeder switches to directly feed low-voltage end users. Compensation capacitors, measuring devices, etc. can also be installed. Distribution Transformers are generally selected as oil immersed or dry-type transformers.The room where High-Voltage Switchgear is located is generally referred to as the high-voltage room, the room where transformers are located is generally referred to as the transformer room, and the room where low-voltage distribution equipment is located is referred to as the low-voltage room. These three rooms are arranged in a "V" shape and a "V" shape in a box transformer.
Box type transformer is a combination of multiple individual devices according to user needs, therefore it has various forms and functions. According to its different structures, it can be divided into American box type transformer and European box type transformer. The commonly used transformer in our country is the European style box transformer.
2） The inspection and maintenance of the transformer box should be carried out regularly according to the inspection and maintenance cycle (no less than once a month), testing the temperature at the cable terminal connection, checking the operation of the equipment, and conducting face testing if necessary. The general inspection items are as follows.
1. Whether the foundation is firm, whether the holes are blocked, and whether there is moisture in the cabinet.
2. Whether the grounding device is complete, the connection is good, and the grounding resistance meets the requirements.
3. Is there any change in the outdoor environment that affects traffic and pedestrian safety.
4. Check the load condition of each feeder line, whether the three-phase load is balanced or overloaded, whether the switch on/off position and instrument indication are correct, and whether the control device is working properly.
5. The dust removal inside the transformer box should be carried out once every year. The surfaces of the high-voltage and low-voltage cabinets and the gas box can be wiped with a damp cloth. The transformer inside the transformer room should be cleaned with air blowing or a vacuum cleaner.
6. Daily maintenance and inspection of the fan. If the fan is not running, use a temperature and humidity controller, adjust it to below the current temperature, and start the fan for inspection.
7. Maintenance and overhaul of high-voltage switches and low-voltage switch electric operating mechanisms
(1) Check the pointer of the pressure gauge to see if it is in the green area. If it enters the red area, perform opening and closing operations. Notify the manufacturer immediately for handling.
(2) The lubrication of mechanical components can be achieved by using universal lithium based grease (butter) for lubrication and conducting opening and closing operation tests.
(3) According to the requirements of routine testing, insulation and leakage current tests are conducted on cables and lightning arresters for routine testing.
8. Routine testing of auxiliary temperature and humidity controllers; Routine testing of smoke alarm devices; Tightening and Inspection of Terminal Blocks: Tightening and Inspection of Standard Components.
9. Terminal block maintenance: Due to thermal expansion and contraction, the terminal block may become loose. An annual inspection should be conducted to re tighten all terminals in the terminal room. Attention: Before re tightening, please confirm that both the primary AC circuit and the secondary control circuit are powered off to avoid electric shock!
10. Precautions for maintaining the transformer box
(1) The box transformer door is equipped with a windproof mechanism, which is a mechanism to ensure that it remains fully open. When closing the box door, be sure to lift the root of the windproof mechanism upwards, and then close the door without pulling or forcefully, to prevent the mechanism or door from deforming and affecting the normal use of the box transformer!
(2) After the local manual operation of the high-voltage load switch is completed, the load switch operating handle should be returned to the handle bracket on the inside of the outer door to avoid loss.
(3) When the backup circuit of the high-voltage ring main unit is temporarily not connected to the cable, the backup circuit should be locked before the ring main unit is powered on, or the cable socket should be sealed with a matching insulation cap to avoid accidents!
(4) The dust cap equipped on the ring main unit when the box transformer leaves the factory cannot replace the insulation cap!
(5) It is not allowed to insert any short-circuit plug into the test hole during operation, otherwise it will cause damage to the voltage sensor.
(6) The low-voltage isolation switch can only be operated when in the unlocked position. Do not forcefully pull or tug!
Correct operation of three box transformer
1. Closing operation
Close the cable room door - disconnect the grounding switch - close the load switch.
2. Opening operation
Separate load switch - close grounding switch - open cable compartment door.
（1） Precautions during operation
(1) When performing the opening and closing operation of the load switch, the switch must be pushed to the final position of opening or closing. Do not release or pull out the operating handle before the switch completes the action, otherwise the spring rebound will harm the operator.
(2) When performing the opening and closing operation of the load switch, the operating handle should be turned outward to prevent injury to the operator during operation.
(3) Before performing the opening and closing operation of the load switch, the electric manual switch knob on the upper left of the corresponding unit panel must be pulled out and rotated 90 ° to fix it in the manual position before manual operation of the load switch can be carried out, otherwise the mechanism may be damaged.
4： Troubleshooting methods for the causes of fault phenomena
（1） The frame circuit breaker cannot be closed
- 1. Control circuit malfunction.
- 2. After the intelligent release is activated, the red button on the panel does not reset.
- 3. Energy storage institutions do not store energy
*Exclusion method
- 1. Use a multimeter to check the open circuit point.
- 2. Identify the cause of the trip, eliminate the fault, and press the reset button.
- 3. Manual or electric energy storage.
（2） Plastic case circuit breaker cannot be closed
- After the mechanism was tripped, it did not reset.
- 2. The circuit breaker has an undervoltage coil and no power supply at the incoming end.
*Exclusion method
- 1. Identify the cause of the trip and troubleshoot before resetting.
- 2. Make the incoming end live, reset the handle, and then close the switch.
（3） The circuit breaker trips when it is closed
- 1. There is a short circuit phenomenon in the outgoing circuit
*Exclusion method
- 1. Do not repeatedly close the switch. The fault must be identified and resolved before closing.
（4） The capacitor cabinet cannot automatically compensate
- 1. The power supply of the control circuit has disappeared.
- 2. The current signal line is not connected correctly.
*Exclusion method
- 1. Check the control circuit and restore the power supply.
- 2. Connect the signal line correctly.