Maintenance, Servicing and Overhaul Key Points for Dry-Type Transformers in Electrical Equipment

I. Key Points for Daily Maintenance

Visual Inspection

Visual inspection is the first step during routine patrols. Carefully examine the transformer’s enclosure for any damage or deformation. Enclosure damage not only compromises the transformer’s protective performance but may also expose internal electrical components, increasing safety risks. Additionally, check for dust accumulation, oil stains, or other contaminants on the transformer’s surface. Excessive dust can impair heat dissipation, while oil stains may indicate internal leakage or other faults. Also, ensure the nameplate is clear and legible, as the information on it is essential for understanding the transformer's specifications and operational requirements.

2. Temperature Monitoring

Temperature is a critical indicator of a dry-type transformer’s operating condition. Closely monitor temperature changes using installed temperature sensors or thermometers for real-time tracking. During normal operation, the transformer’s temperature should remain within specified limits. Excessively high temperatures may result from overloading, poor heat dissipation, or internal faults such as short circuits. If abnormal temperature rise is detected, immediate actions should be taken, such as reducing the load or inspecting the cooling system, to prevent damage to winding insulation and extend the transformer’s service life.

3. Cleaning

Regular cleaning of the dry-type transformer is a crucial maintenance task. Use a clean cloth or specialized cleaning tools to gently wipe the transformer’s surface and heat sinks, removing accumulated dust and debris. Pay particular attention to air vents and other openings to ensure they remain unobstructed, maintaining effective ventilation and heat dissipation. During cleaning, avoid using wet cloths or tools containing moisture to prevent water ingress, which could lead to electrical faults.

II. Key Points for Periodic Maintenance

1. Insulation Resistance Testing

Periodic insulation resistance testing is a vital method for assessing the insulation performance of a dry-type transformer. Use an insulation resistance tester to measure the resistance between the high-voltage winding, low-voltage winding, and between windings and the enclosure. The measured values should comply with relevant standards. Low insulation resistance may indicate moisture ingress, aging, or physical damage to the insulation, requiring further investigation and corrective actions such as drying or replacing insulation materials.

2. Tightening of Connection Components

Due to prolonged operation and vibration, connection components of the transformer may become loose. Therefore, it is essential to periodically inspect and tighten bolts, nuts, and other connection parts. Loose connections increase contact resistance, leading to overheating and, in severe cases, fire hazards. When tightening connections, follow specified torque values to avoid damaging components through excessive force.

3. Inspection of Protective Devices

Dry-type transformers are typically equipped with various protective devices, including overcurrent, overvoltage, and temperature protection. Regularly check the operational status of these devices to ensure they function accurately and reliably. Test their response by simulating faults to verify that they can promptly activate and disconnect the circuit. If any protective device is found faulty, repair or replace it immediately to ensure the transformer is effectively protected during abnormal conditions.

III. Key Points for Repair and Overhaul

1. Fault Diagnosis

Accurate fault diagnosis is critical when a dry-type transformer fails. Begin by observing symptoms such as unusual noises, odors, or smoke, and combine these observations with routine operational data and monitoring information for an initial assessment. Use professional diagnostic equipment, such as multimeters and oscilloscopes, to measure and analyze electrical parameters, further pinpointing the location and cause of the fault. For example, if resistance measurements show abnormal values in one phase winding, it may indicate a short circuit or open circuit in that winding.

2. Winding Repair

The windings are the core components of a dry-type transformer, and their repair requires special care. If a short circuit is detected, locate the fault point and repair it. Minor short circuits can be fixed using insulation repair methods; however, severe cases may require complete winding replacement. During repair, maintain the winding’s insulation integrity and avoid damaging the insulation layer during handling.

3. Core Repair

Core faults can also affect the normal operation of a dry-type transformer. Inspect the core for looseness, deformation, or short circuits. Core short circuits can cause severe heating and increase transformer losses. For core short circuits, identify the fault location and address it—such as removing contaminants or repairing insulation at the shorted area.

Maintenance, repair, and overhaul of dry-type transformers are systematic and meticulous tasks. Only by strictly adhering to relevant standards and requirements, and diligently performing daily maintenance, periodic inspections, and timely repairs, can potential issues be identified and resolved promptly. This ensures the safe and stable operation of dry-type transformers, providing reliable support for the dependable power supply of electrical systems.