How to maintain a transformer and extend its service life? Sharing long-term operation and maintenance experience.

I am an engineer from Zisheng Electric’s transformer design team, responsible for transformer design, technical product support and on‑site project services. We have taken part in power projects across many countries and regions, ranging from industrial power distribution and new‑energy power generation to grid construction and infrastructure development. During technical discussions with EPC contractors, project owners and power engineering firms, one question frequently comes up: what effective transformer maintenance to extend service life can ensure stable long‑term operation?

This seems like a simple question, yet real‑world project experience shows there is no fixed answer. A well‑manufactured oil‑immersed power transformer running under reasonable conditions with standardized maintenance can operate stably for more than 30 years. However, some units suffer degraded insulation, abnormal temperature rise and accessory aging after only a dozen years of service. Field investigations reveal most failures stem not from manufacturing defects, but from poor long‑term operation management, including missing periodic tests, neglected insulating‑oil conditions, continuous over‑load operation and maintenance plans mismatched with local environments.

I. Main Factors Affecting Transformer Service Life

A transformer is a long-term operating electrical asset, and its service life is influenced by multiple factors working together.

In actual projects, we usually focus on the following key factors:

Influencing Factor	Impact on Transformer	Maintenance Focus
Operating Temperature	Accelerates aging of insulation materials and shortens service life	Control temperature rise, inspect cooling systems, and prevent overheating
Load Level	Increases winding thermal stress and accelerates insulation aging	Monitor load conditions and avoid long-term overload or frequent impact overload
Transformer Oil Condition	Reduces insulation performance, affects heat dissipation, and may generate fault gases	Conduct regular oil analysis, including DGA, dielectric loss testing, moisture content testing, etc.
Environmental Conditions	Sand, dust, salt fog, and high temperatures can cause corrosion, contamination, and reduced cooling efficiency	Apply corrosion protection, perform regular external cleaning, and select equipment suitable for the environment
Power Grid Quality	Overvoltage and harmonics can cause insulation stress and local overheating	Verify protection settings and monitor harmonic impact
Maintenance Management	Directly determines the long-term health condition of the equipment	Establish a regular maintenance plan based on actual operating conditions

Among these factors, temperature and insulation condition are usually the two most critical factors affecting transformer service life.

Especially in large-scale industrial projects, renewable energy projects, and power grid applications, a well-designed operation and maintenance strategy can significantly reduce equipment failure risks.

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II. Regular Inspection of Transformer Insulation Oil Condition

For most oil-immersed transformers, transformer oil performs two critical functions:

First, it provides electrical insulation.

Second, it transfers heat generated by the windings and core to the cooling system.

As operating time increases, the insulating oil is affected by:

• Oxidation
• Moisture ingress
• High-temperature thermal stress
• Internal electrical discharge activity

Eventually, the performance of the oil gradually deteriorates.

If transformer oil testing is not carried out regularly, the following problems may occur:

• Reduced insulation strength
• Increased partial discharge activity
• Abnormal internal temperature rise
• Accelerated aging of solid insulation materials

Main Transformer Oil Testing Items

Test Item	Testing Purpose	Possible Causes of Abnormal Results
Breakdown Voltage Test	Evaluate the insulation capability of transformer oil	Moisture ingress, solid particle contamination
Moisture Content Test	Determine the moisture level in the oil	Seal failure, moisture penetration from the environment
Acid Value Test	Evaluate the oxidation and aging condition of insulating oil	Long-term high-temperature oxidation
Dielectric Loss Test (tanδ)	Assess dielectric loss performance	Oil contamination, moisture, aging, and acidification
Dissolved Gas Analysis (DGA)	Diagnose potential internal transformer faults	Internal overheating, partial discharge, arcing faults, decomposition of solid insulation materials

For large-scale grid projects, renewable energy plants, and industrial facilities, regular oil-immersed transformer maintenance can help identify potential problems at an early stage and prevent unexpected shutdowns.

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III. Controlling Transformer Operating Temperature

During transformer operation, temperature management is extremely important.

Many transformer problems are not caused by insufficient capacity, but by operating conditions exceeding the original design assumptions.

For example, in a Middle East industrial project, the customer initially selected equipment based on standard environmental conditions.

However, after technical review, we identified several challenges:

• Summer ambient temperatures exceeding 50°C
• Long-term continuous operation requirements
• Dust and salt fog exposure at the installation site

If a standard design was used under these conditions, long-term operation could result in excessive temperature rise and accelerated insulation aging.

Therefore, during the design stage, engineers must consider:

• Cooling capacity
• Temperature rise margin
• Protection rating
• Environmental adaptability

For projects in high-temperature regions such as Saudi Arabia and the UAE, transformer selection for hot climates must place special emphasis on cooling performance, corrosion resistance, and long-term operational reliability.

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IV. Avoiding Long-Term Transformer Overloading

Long-term overload operation is one of the major factors affecting transformer service life.

Many industrial projects have sufficient transformer capacity during the initial design stage. However, after several years of operation, actual load demand may exceed the original design conditions due to:

• Production line expansion
• Addition of new electrical equipment
• Changes in actual operating conditions

Long-term overload operation can lead to:

• Increased winding temperature
• Accelerated thermal aging of insulation paper
• Faster oxidation of transformer oil
• Reduced overall equipment service life

For industrial projects, mining projects, and renewable energy applications, proper capacity selection during design and continuous load monitoring during operation are essential parts of transformer maintenance management.

Transformer Load Operation Recommendations

Operating Condition	Load Level	Maintenance Recommendation
Normal Operation	70%–90% of rated capacity	Perform routine periodic inspections
High Load Operation	90%–100% of rated capacity	Strengthen temperature monitoring and shorten oil testing intervals
Short-Term Overload	Above rated capacity	Follow manufacturer recommendations and IEC 60076-7 overload guidelines to control overload magnitude and duration
Long-Term Overload	Continuously exceeding rated capacity	Conduct load analysis, reassess transformer capacity, and consider system upgrades

If a transformer operates under high-load conditions for a long period, a detailed load assessment should be carried out. When necessary, capacity expansion, load redistribution, or operational adjustments should be implemented.

Proper preventive maintenance can effectively reduce the risk of accelerated insulation aging caused by long-term overload operation.

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V. Regular Inspection of Transformer Accessories

Many customers focus on the transformer main body but often overlook the importance of accessories.

In actual operation, however, many transformer failures begin with accessory problems.

For transformer inspection, checking the condition of accessories is a critical part of preventive maintenance.

The main inspection items include:

• Bushings
• Oil level gauges
• Breathers
• Temperature control devices
• Pressure relief devices
• Cooling systems

Main Transformer Accessory Inspection Items

Accessory	Inspection Items	Abnormal Conditions
Bushing	Check for cracks, surface contamination, and discharge marks	Reduced insulation performance, surface flashover
Oil Level Gauge	Monitor oil level changes and check for leakage	Oil leakage, abnormal high or low oil level
Breather	Check silica gel color change condition	Moisture absorption failure, humidity entering the tank
Thermometer / Temperature Control Device	Verify display accuracy and fan linkage function	Temperature indication deviation, incorrect cooling system operation
Radiator	Check dust accumulation, blockage, and fan operating condition	Reduced heat dissipation efficiency, excessive temperature rise
Sealing Components (Flanges, Gaskets)	Check aging, cracks, and deformation	Oil seepage or oil leakage

For oil-immersed transformer maintenance, the condition of accessories directly affects long-term equipment reliability.

Many transformer failures do not occur suddenly. Instead, they gradually develop through a combination of accessory defects, insulation deterioration, and abnormal temperature conditions.

Therefore, establishing a complete accessory inspection system can help identify potential operational risks before they develop into serious failures.

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VI. Developing Maintenance Plans Based on Different Operating Environments

Transformer maintenance cannot follow exactly the same standard everywhere.

Different regions have significantly different environmental conditions.

Especially in overseas projects, transformers often operate under different climate challenges. Therefore, a practical transformer maintenance plan must be developed according to the actual operating environment.

Operating Environment	Main Risks	Maintenance Focus
Desert Areas	High ambient temperature, sand and dust accumulation	Clean radiators regularly, strengthen temperature and cooling system inspections, ensure sealing performance against dust ingress
Coastal Areas	Salt fog corrosion	Inspect anti-corrosion coatings, bushings, terminals, and verify sealing integrity
Tropical Areas	High humidity and condensation	Control moisture content in oil, inspect breathers and sealing components to prevent moisture ingress
Mining Areas	Heavy dust contamination	Regularly clean tanks, radiators, and bushings; inspect external insulation contamination
Industrial Areas	Corrosive gases and industrial dust	Check external insulation and sealing components for corrosion, strengthen oil quality monitoring

For example:

In a Middle East industrial project, the transformer was installed in an environment with high temperatures, dust, and long-term heavy load operation.

During the maintenance planning stage, we recommended:

• Increasing the frequency of radiator cleaning
• Shortening transformer oil testing intervals
• Strengthening temperature monitoring
• Regularly checking sealing performance and external corrosion protection

Through targeted maintenance measures, the operating risk caused by harsh environmental conditions can be significantly reduced, helping the transformer maintain stable performance throughout its service life.

Key Considerations for Saudi Projects

For transformer applications in Saudi Arabia, the main focus areas include:

• High ambient temperature
• Cooling and heat dissipation systems
• Dust protection
• Corrosion resistance

In Middle East regions such as Saudi Arabia and the UAE, summer temperatures are extremely high. When transformers operate continuously under these conditions, special attention must be given to cooling system efficiency, insulation material thermal resistance, and overall equipment protection capability.

Key Considerations for African Mining Projects

Mining projects in Africa mainly focus on:

• Heavy dust contamination
• Load fluctuations
• Continuous operation capability

Most mining projects operate under continuous production conditions. A transformer failure can directly interrupt production activities. Therefore, reliability requirements for transformers in mining applications are significantly higher than those for ordinary grid distribution projects.

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VII. Establishing a Scientific Transformer Maintenance Schedule

Effective maintenance is not about repairing equipment after problems occur. It is about identifying potential risks before failures happen.

For large industrial projects, grid projects, and renewable energy projects, establishing a scientific transformer preventive maintenance plan is essential.

Maintenance Cycle	Maintenance Activities	Purpose
Daily / Weekly Inspection	Monitor operating noise, check temperature, oil level, and external condition	Identify early abnormal signs
Monthly Inspection	Check bushings, breathers, cooling systems, and other accessories	Detect accessory defects and prevent failures
Every 6 Months	Inspect protection systems, temperature control systems, and fan linkage functions	Ensure reliable operation of protection and cooling systems
Annually	Perform transformer oil sampling tests and electrical inspections	Evaluate current equipment health condition
Every 3–5 Years	Conduct comprehensive performance assessment	Evaluate insulation aging condition and remaining service life

Based on accumulated operation and maintenance records, engineers can analyze and determine:

• Overall equipment aging trends
• Existing operational risks
• Whether maintenance, repair, or upgrade actions are required

Scientific maintenance management can reduce unexpected shutdown risks and improve the overall reliability of transformer operation.

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VIII. Improving Maintenance Efficiency Through Online Monitoring

For large-scale applications such as:

• Power grids
• Renewable energy plants
• Data centers
• Industrial production facilities

Transformer online monitoring is becoming increasingly important.

Modern transformer maintenance is gradually moving from traditional manual inspection toward data-driven condition management.

Common monitoring parameters include:

• Winding temperature
• Top oil temperature
• Partial discharge
• Dissolved gases
• Oil dissolved gas analysis (DGA)
• Load variation

Traditional maintenance approach:

Abnormal condition → Shutdown inspection → Fault repair

Online monitoring approach:

Data variation → Early warning → Planned maintenance

This approach can effectively reduce the risk of unplanned downtime and improve equipment operating reliability.

For large renewable energy projects, grid infrastructure, and industrial users, online monitoring has become an important technology for improving long-term transformer reliability.

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IX. Maintenance Focus for Different Transformer Types

Different transformer types have different structures and application environments. Therefore, maintenance priorities also vary.

In actual projects, maintenance strategies should be developed according to equipment type, installation environment, and operating conditions.

1. Oil-Immersed Transformers

Oil-immersed transformers are the most widely used transformers in power systems. They are commonly applied in:

• Power grids
• Industrial power distribution
• Renewable energy projects
• Large infrastructure projects

Key maintenance items include:

• Transformer oil testing
• Oil leakage inspection
• Breather system maintenance
• Temperature rise monitoring
• Insulation condition assessment

Since insulating oil performs both insulation and cooling functions, regular oil-immersed transformer maintenance is essential for extending equipment service life.

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2. Dry-Type Transformers

Dry-type transformers are commonly used in applications requiring higher safety levels and environmental protection, including:

• Commercial buildings
• Data centers
• Industrial facilities
• Metro systems and public infrastructure

Maintenance focuses include:

• Enclosure sealing condition
• Internal operating temperature
• Cable connection status
• Medium-voltage switchgear operating condition
• Moisture and corrosion protection inspection

Especially in desert high-temperature environments and coastal salt-fog areas, dry-type transformers require enhanced protection design and targeted maintenance based on actual site conditions.

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3. Compact Substations

Compact substations are commonly applied in:

• Renewable energy plants
• Industrial parks
• Outdoor distribution projects
• Infrastructure projects

Maintenance focuses include:

• Enclosure sealing
• Internal temperature control
• Cable connections
• Medium-voltage equipment condition
• Moisture and corrosion protection

Especially in desert, high-temperature, and coastal environments, compact substations require enhanced protection measures according to local operating conditions.

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X. About Zisheng Electric

At Zisheng Electric, we focus on transformer design, manufacturing, and power project technical support.

Over the years, we have participated in power projects across different countries and regions, providing EPC contractors, engineering companies, distributors, and project owners with integrated services covering solution design, product selection, manufacturing, factory testing, and delivery support.

Our product portfolio includes:Oil-immersed transformers、Substation transformers、Packaged transformers、Pole-mounted transformers、Dry-type transformers、Other power distribution equipment

Zisheng Electric has obtained 22 utility model patents and 3 software copyrights, is certified under the ISO 9001 Quality Management System, and complies with relevant IEC standards for transformer design and manufacturing.

If you are working on a power transformer project design, technical specification review, or supplier evaluation, please share your project requirements with us.

Our engineering team will provide an initial technical response within 24 hours based on your project parameters.