Structural Overview: The core material is made of high-quality cold-rolled silicon steel sheets, and the insulation material is Class III insulation material. The coil adopts a non-encapsulated structure. The transformer's inlet and outlet are bottom-in and bottom-out. Cable holes are opened at the bottom of the enclosure, and there is a device for fixing cables.

Integrity Standard Inspection Method: Inspection Content and Standards

Basic Information:

1. The transformer's nameplate parameters, dimensions, weight, lead direction, etc., meet the technical requirements and relevant national standards;

2. The product manual, inspection certificate, factory test report, packing list, and other accompanying documents are complete.

Appearance Quality:

1. All fasteners are tight, and insulation components are intact;

2. Metal parts are free from rust and damage, and the core has no multiple grounding points;

3. The windings are intact, without deformation, displacement, or damage, with no internal debris, and the surface is smooth and free of cracks;

4. The distance between leads, connecting conductors, and ground meets relevant national standards. The surface of bare conductors is free from damage, burrs, and sharp corners, and the welding is good;

5. The grounding point has clear markings and is equipped with standard nuts and bolts. Fan Unit

1. The fan motor and wiring are well insulated, with an insulation resistance greater than 0.5 megohms, and the overcurrent protection is in good working order;

2. The fan blades are free of cracks and deformation, and rotate without obstruction;

3. During operation, the fan exhibits no abnormal vibration or noise, and the motor does not overheat abnormally.

Temperature Controller

1. Temperature display functions normally, cycling through the display every 2-3 seconds and automatically displaying the temperature value of each phase;

2. Automatically displays the highest temperature value and phase sequence, allows for quick switching and locking of displays, and memorizes the highest temperature value;

3. Controls the fan to start and stop when the temperature exceeds or exceeds the fan start/stop setting, with status indicator lights displaying the status;

4. Activates an over-temperature audible and visual alarm when the temperature exceeds the alarm setting, simultaneously illuminating the trip alarm light, closing the trip output contact, and activating the trip control circuit;

5. Isolates or short-circuits the transformer's PT transformer and leads, illuminates the fault light, closes the alarm output contact, and activates the fault handling circuit;

6. The temperature controller should be unaffected by surrounding electromagnetic interference;

7. The temperature controller is installed in a suitable location for easy observation and maintenance. Protective Devices

1. The installation of the power distribution equipment should meet the design requirements, and the opening of cabinets and mesh doors should not affect each other;

2. The wire connections should be secure, and the phase colors should be clearly and correctly indicated;

3. The phase-to-phase and phase-to-ground distances of energized parts should meet relevant design standards;

4. The grounding parts should be firmly and reliably secured;

5. The fuses of the temperature controller should have sufficient breaking capacity, and dual power supplies can be used if necessary;

6. Cabinets, mesh doors, and barriers should be labeled with equipment names and safety warning signs.

Start-up Acceptance

1. The transformer handover test record is complete;

2. The transformer runs continuously energized for 24 hours without abnormalities;

3. The transformer tap changer meets the operating requirements;

4. All protective devices are engaged, and no-load closing is performed 10 times, the first time for no less than 10 minutes, without abnormalities;

5. The temperature controller is checked, and its temperature display reading matches the actual temperature;

6. The fan starts and stops automatically normally, without abnormal noise or abnormal temperature rise. II. Daily Inspection

* Check the outer surface of the transformer bushings and winding resin insulation for cleanliness, and for any signs of creepage or carbonization.

* Check the temperature monitoring instrument for proper functioning.

* The transformer should be free of unusual odors and noises, and maintain good ventilation.

* Inspect the insulators for cracks and discharge marks.

* The cooling fan should operate normally, and the air inlet filter cloth should be kept clean and well-ventilated.

* Check fasteners, connectors, conductive parts, and other components for rust, corrosion, and for good contact.

* Check the transformer base and outer casing grounding wire for proper grounding.

III. Maintenance

* Tighten the connection bolts of the busbars and leads; promptly address or replace any bolts that show signs of overheating or discoloration.

* Tighten the control circuit terminal connections.

* Check and tighten the grounding wire.

* Clean dust from inside the cabinet and the air inlet filter cloth.

* Replace any cracked or discharge-prone insulating bushings.

* Replace any defective components. IV. After approximately six months of operation, the dry-type transformer should be shut down for the following maintenance:

1. Inspect the coils, core, sealing wires, tap terminals, and fasteners for damage, deformation, discoloration, loosening, signs of overheating, and corrosion. If any abnormalities are found, the cause must be identified and recorded in detail.

2. Remove dust from the transformer. Wipe with a dry cloth; do not use volatile cleaning agents. For hard-to-reach areas, use dry compressed air to blow clean.

3. Check for any localized overheating during operation. Verify that the temperature of each part is normal.

And calibrate the temperature measuring device.

4. Clean the filter cloth inside the transformer's air inlet louvers, allow it to dry, and then reinstall it.

V. After approximately one year of operation, the dry-type transformer should be shut down for the following maintenance:

1. Inspect the coils, core, sealing wires, tap terminals, and fasteners for damage, deformation, discoloration, loosening, signs of overheating, and corrosion. If any abnormalities are found, the cause must be identified and recorded in detail.

2. Remove dust from the transformer. Wipe with a dry cloth; do not use volatile cleaning agents. For hard-to-reach areas, blow clean with dry compressed air.

Disconnect external wiring and measure the insulation resistance to ground of the dry-type transformer coil using a 2500V megohmmeter. The standards are shown in the table below: Voltage Rating: 0.4, 3.0, 6.0, 1035; Humidity: 85%; Temperature: 5, 15, 25, ...5, 15, 5, 15, 5, 15, 5, 15, 5, 15, 5, 15, 5, 15, 5, 15, 5, 15, 5, 15, 5, 15, 5, 15, 5, 15, 5, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 1 VI. Trial Run and Acceptance Before trial run:

1. The transformer body and cooling system, and all accessories, should be installed completely and without defects.

2. There should be no debris left on the transformer.

3. The tap changer or tap switch position should meet operational requirements.

4. The transformer phase and wiring group should meet operational requirements, and the phase color markings should be correct.

5. The grounding lead and its grounding grid connection should meet design requirements, and grounding should be reliable.

6. The temperature measuring device indication should be correct, and the setting value should meet requirements.

7. The fan connection should be correct, and the trial run should be normal.

8. All transformer acceptance tests should be qualified, the protection setting value should meet regulations, and the operation and linkage tests should be correct. Single Unit Trial Run

1. Adjust the parameters of the protection device according to the inrush current situation, disconnect the secondary side wiring, and perform [number] impact closings under rated voltage. After the first energization, run for no less than [number] minutes, and then every [number] minutes thereafter, each run for no less than [number] minutes. The transformer should show no abnormalities.

1. Dry-type transformer: After successful initial impulse closing, run under no-load for 30 minutes. If no abnormalities are observed, gradually increase the load to the rated load and run continuously for 24 hours. If no abnormalities are found, handover can be carried out according to relevant regulations before formal operation. Load testing:

Monitor the sound and temperature of the transformer during operation for any abnormalities.

Monitor and inspect the appearance of the coils, core, and sealing wires for damage, discoloration, dust accumulation, and dirt.

Monitor the functionality of the air-cooling device, tap changer, and temperature measuring device.

Prevent water droplets from falling onto the transformer.

Maintain accurate transformer operation records. VII. Operating Procedures:

Transformer energization operation steps, instructions, and remarks: Pre-energization checks:

Perform a visual inspection:

Cooling fan should be operating normally; Transformer body should be clean, free of dust, foreign objects, cracks, etc.; conductor connections should not be overheated; grounding should be good. Transformer No-Load Energization

Check that the transformer load-side switch is in the open position.

Close the transformer power-side switch to energize the transformer.

To prevent the transformer from being energized under load, which would generate a large inrush current, the transformer must be energized under no-load conditions.

Even with no-load energization, there will be a short-term inrush current of 5-8 times the rated current, which will recover to the no-load rated current value after a transition process. Check the transformer no-load operating parameters. Verify the transformer's no-load current value and whether the three-phase current is balanced. The no-load current is generally 2%-10% of the rated current.

Transformer Under Load

Close the transformer load-side switch. Verify that the transformer load-side voltage is balanced.

Transformer De-energization Operation Procedures

Operating Instructions

Remarks

Disconnect the transformer load-side switch

Reduce the transformer load to the minimum value.

After opening the load-side switch, verify that the load side is de-energized. Record the transformer no-load parameters. Record the transformer no-load current, whether it is balanced, and whether there are any changes compared to previous no-load currents.

Disconnect the transformer power-side switch.

After opening the transformer power-side switch, verify the switchgear indication to confirm that the transformer is indeed de-energized.

VIII. Common Problems and Solutions