A comprehensive guide to the maintenance and care of dry-type non-excited tap changers

I. Preface

With the modernization of the power system and the upgrading of urban distribution networks, Dry-Type De-Energized Tap changers (DNOLTC) have been widely used in medium and high voltage transformers and distribution systems. This device can adjust the tap points of the transformer in the event of a power failure, achieving voltage optimization and grid stability. To ensure the long-term reliable operation of the equipment, maintenance and upkeep are particularly important. This article will provide a detailed introduction to the maintenance and care techniques of dry-type non-excited tap changers from aspects such as maintenance principles, routine inspections, cleaning and maintenance, lubrication, and fault detection, offering comprehensive references for operation and maintenance personnel.

Ii. Overview of Dry Non-Excited Tap Changer

Dry-type non-excited tap changer is a kind of switchgear that regulates the tap points of a transformer in the power-off state and has the following characteristics:

Dry insulation structure

Insulated with air or epoxy resin, it is oil-free and environmentally friendly, reducing the risk of fire and pollution.

No excitation operation

Perform tap switching in the event of power failure to prevent arc generation during operation under load and enhance equipment safety.

Compact structure and easy to maintain

The dry structure simplifies the oil circuit and mechanical complexity, has a long maintenance cycle and is easy to operate.

High-reliability contact system

The tap and contact points are made of highly wear-resistant materials to enhance service life and reliability.

Strong environmental adaptability

It can operate safely in industrial plants, urban power distribution and various climatic conditions.

Iii. Basic Principles of Maintenance and Care

Safety first

Maintenance and repair operations must be carried out under power-off and discharge conditions.

Operators must wear insulating gloves, insulating shoes and safety protective equipment.

Regular inspection

Regularly inspect the status of mechanical and electrical components in accordance with the equipment manual and operation and maintenance regulations.

The inspection contents include contact wear, electrical insulation performance and mechanical linkage mechanism.

Clean in time

Dust, dirt or corrosive substances can affect insulation performance and mechanical operation, and must be cleaned regularly.

Reasonable lubrication

The linkage mechanism, gears and moving parts need to be lubricated regularly to ensure smooth mechanical operation.

Use the lubricant recommended by the manufacturer to avoid damaging the insulating material or introducing contamination.

Recording and tracking

Establish maintenance records and operation logs to provide a basis for equipment status assessment and fault detection.

Iv. Routine Inspection Items

1. Mechanical part inspection

The splitter and interlocking mechanism

Check whether the tapping knife is flexible and operates smoothly.

Check whether the linkage mechanism, gears and spring mechanism are in good condition, without looseness or wear.

Fixing bolts and supporting structures

Ensure that the supporting structure is firm and the fixing bolts are tightened reliably.

Avoid loosening of components due to vibration or external force.

2. Inspection of the electrical part

Contact system

Check whether there is any oxidation, ablation or carbonization on the surface of the contact points.

Confirm that the contact pressure is uniform and the contact is reliable.

Insulation performance

Use an insulation resistance tester to test the insulation condition of the tap changer.

Check whether the insulating materials have cracks, aging or contamination.

3. Control and indication system

Check whether the indicator, position indication device and interlocking system are sensitive and accurate.

Test whether the manual operating mechanism and the electric operating mechanism operate properly.

V. Cleaning and Lubrication Skills

1. Cleaning method

Use a dry cloth or lint-free paper to clean the dust and impurities.

For stubborn dirt, you can gently wipe it with an insulating cleaner. Avoid using water-containing or conductive substances.

Regularly inspect the ventilation outlets and dust covers to ensure good air circulation.

2. Lubrication methods

For gears, bearings and linkage mechanisms, the manufacturer recommends using grease or lubricating oil.

When lubricating, it is necessary to avoid contaminating the contacts and insulating materials to prevent a reduction in insulation strength.

The lubrication cycle is adjusted according to the frequency of equipment usage and environmental conditions, generally once every 6 to 12 months.

Vi. Troubleshooting and Handling Skills

1. The operation is not flexible or stuck

Check whether there are any foreign objects obstructing or insufficient lubrication in the mechanical linkage.

Check whether the tap changer and gear meshing are worn. Replace the worn parts if necessary.

2. Poor contact

Check whether the surface of the contacts is oxidized or eroded, and clean or replace the contacts.

Check the contact pressure and ensure that the tap is locked in place.

3. Insulation decline

Check whether the insulating materials are free from contamination or have aged.

Maintain the desiccant or air insulation gap to ensure a dry environment.

4. Abnormal indication or interlock failure

Check whether the indicator is consistent with the actual position of the tap changer.

Adjust or replace the position indicator and interlock mechanism to ensure operational safety.

Vii. Long-term Maintenance Suggestions

Establish equipment files

Record each maintenance, repair and operation situation, and analyze the trend of equipment status.

Environmental monitoring

Keep the operating environment of the equipment dry and well-ventilated, and avoid dust and corrosive gases.

Regularly train the operators

Proficient in manual and electric operation procedures, and enhance maintenance and fault handling capabilities.

Accessories and consumables management

Stock up on commonly used spare parts such as contacts, springs, and linkage gears to ensure timely maintenance of the equipment.

Integration of intelligent monitoring

Temperature sensing, position monitoring and remote alarm systems can be adopted for key equipment to improve maintenance efficiency.

Dry-type non-excited tap changers play a significant role in modern power systems due to their features such as dry insulation, oil-free environmental friendliness, safety and reliability. Standardized maintenance and upkeep not only extend the service life of equipment but also ensure the stability of power supply from the power grid. Through regular mechanical inspections, electrical tests, cleaning and lubrication, as well as troubleshooting, combined with operation training and record management, maintenance personnel can effectively enhance the reliability of equipment operation, providing long-term and stable power support for industrial, urban power distribution and critical infrastructure.