The Inner Structure of Transformer Oil Tanks: Key Components, Functions, and Design Essentials of Transformer Oil Tank Inner Structure

I. Introduction： Why the Inner Structure of a Transformer Oil Tank Matters

When companies or utilities invest in an oil-immersed power transformer, they often pay attention to the voltage rating, cooling method, brand reputation, and price. However, what truly determines long-term reliability, safety, and lifespan is the inner structure of the transformer oil tank. This “invisible part” of the transformer dramatically affects cooling efficiency, dielectric strength, energy loss, operating noise, and the unit’s ability to withstand short-circuit forces.

A transformer oil tank is not just a steel shell filled with oil. Inside it sits a highly engineered system, including the magnetic core, HV and LV windings, insulation barriers, oil ducts, mechanical support structures, and oil circulation channels. These components work together to ensure that the transformer operates safely under continuous load, fluctuating temperatures, and electrical stress, especially at the points where the primary winding is connected, which are critical for maintaining stable performance and preventing faults.

For potential transformer buyers—industrial users, EPC contractors, utility companies, and distributors—understanding the inner structure helps you identify higher-quality products, evaluate different manufacturers, and avoid hidden risks that may cause overheating, insulation failure, or unexpected downtime.

This blog provides a detailed, user-friendly. You will learn what components are inside, how they work, what materials are used, and what design features you should focus on before purchasing. In particular, it explains the critical points where the primary winding is connected, helping you understand how proper connections impact transformer performance and reliability. By the end, you will have a clear framework for evaluating transformer quality, enabling you to make a confident and informed decision.

II. What Is Inside a Transformer Oil Tank? — A Quick Overview

Before diving into the engineering details, let’s start with a simplified overview. Inside the transformer oil tank, every component has a function directly related to heat management, electrical insulation, or mechanical stability. The following table summarizes the major internal parts and their primary roles:

Table 1: Major Internal Components and Their Functions

This list gives you a surface-level understanding, but in the next sections we will explore each part in depth. For buyers, these internal details are critical because they reveal the true manufacturing quality of a transformer—something that price lists and datasheets cannot show.

III. Core Internal Components of a Transformer Oil Tank

The “heart” of the transformer sits at the center of the oil tank: the magnetic core and windings. Their structural design directly influences energy efficiency, temperature rise, and service life.

1. Magnetic Core

The magnetic core is constructed using laminated silicon steel sheets to minimize eddy current losses. The core is assembled in different shapes—core-type or shell-type—depending on the application and capacity. Inside the oil tank, the core is fully immersed in transformer oil, which keeps the temperature stable and prevents hotspots.

Good manufacturers will use:

• High-grade grain-oriented silicon steel
• Uniform lamination stacking
• Precise cutting and insulation coating
• Optimized step-lap joints to reduce noise and no-load loss

Why it matters for buyers:
A poorly designed core results in higher no-load losses, louder humming, and lower energy efficiency over the transformer’s lifetime. For projects requiring long-term stable operation—such as industrial plants, wind/solar substations, commercial buildings—core quality is one of the most important indicators of a reliable transformer.

2. Transformer Windings (HV & LV)

The windings convert voltage levels, making them one of the most sensitive and critical components inside the oil tank. They are typically made of copper or aluminum, formed into circular or helical shapes, and insulated with paper, enamel, or cast resin.

In an oil-immersed transformer, windings must be carefully designed for:

• Thermal performance: efficient heat transfer into the oil
• Dielectric strength: insulation paper + pressboard support
• Mechanical stability: braces and tie rods prevent deformation
• Short-circuit endurance: high-strength structure avoids collapsing under electromagnetic forces

The windings are positioned either concentrically around the core or arranged in special configurations to optimize cooling and insulation.

Why buyers should care:
Windings are often the first component to fail under overload or short-circuit. High-quality windings significantly extend transformer lifespan and reduce long-term maintenance cost.

3. Transformer Insulating Oil

The insulating oil in the tank performs two essential functions:

• Cooling: oil absorbs heat from the core and windings
• Insulation: oil fills microscopic gaps to prevent electrical discharge

Good transformer oil has:

• High dielectric strength
• Low moisture content
• Strong oxidation resistance
• Good thermal conductivity

Manufacturers may use mineral oil, silicone oil, or natural ester oil depending on the application.

Why it matters for purchasing:
Oil quality outweighs brand marketing. The right oil improves temperature rise performance, enhances insulation life, and lowers operational risk—especially in high-temperature, high-humidity, or high-load environments.

IV. Internal Mechanical Supports and Structural Design

Inside a transformer oil tank, mechanical stability is just as important as electrical insulation. During actual operation, transformers experience continuous thermal expansion, electromagnetic force, short-circuit stress, and vibration. Without a strong internal mechanical support system, the entire structure may deform, causing partial discharge, winding movement, or even catastrophic insulation failure, especially at points where the primary winding is connected to the core and other components.

A well-designed mechanical support structure inside the transformer oil tank typically includes clamping frames, pressboard spacers, epoxy blocks, tie rods, and end rings, all strategically positioned to maintain tight alignment between the core and windings, ensuring the points where the primary winding is connected remain stable under all operating conditions.

1. Clamping Structure & Core Frame

The core clamp keeps the magnetic core firmly compressed to prevent vibration and misalignment. During magnetization, the core naturally vibrates due to alternating flux. If not properly clamped, this vibration will:

• Increase operational noise
• Cause fatigue in mechanical supports
• Loosen lamination sheets
• Lead to long-term insulation damage

High-quality manufacturers use:

• Welded steel frames with anti-vibration spacers
• Epoxy-coated clamping plates
• Precision-machined bolts and tie rods
• High-strength top and bottom beams

For buyers, the clamping structure demonstrates how much attention a manufacturer pays to long-term mechanical reliability—especially for transformers installed in industrial plants or near residential areas where noise control is important.

2. Pressboards, Spacers, and Insulating Blocks

These components serve multiple purposes inside the transformer oil tank:

Electrical Insulation

Pressboards isolate high-voltage components, ensuring safe dielectric distances. Heavy-duty TIV pressboard, laminated phenolic blocks, and diamond dotted paper are commonly used to enhance breakdown resistance.

Oil Channel Formation

Pressboards position windings and create vertical oil ducts, allowing hot oil to rise and cold oil to move downward, maintaining a stable temperature gradient.

Mechanical Reinforcement

They prevent winding deformation under short-circuit forces—an essential factor many buyers overlook.

Why it matters for purchasing:
If the transformer uses low-density or recycled pressboard materials, the entire insulation system becomes vulnerable to moisture absorption, deformation, and thermal degradation. Always check detailed material specifications when evaluating suppliers.

3. Windings Braces, Tie Rods, and End Rings

These mechanical supports give the windings enough structural stiffness to withstand electromechanical stress during faults or overload conditions. Short-circuit forces inside a transformer can exceed several tons, especially in medium and large power distribution transformers.

Good manufacturers will:

• Use high-strength, pre-tensioned tie rods
• Implement multi-point winding bracing
• Add epoxy-coated end rings
• Ensure balanced mechanical pressure around the entire coil

This prevents lateral movement, radial expansion, or axial deformation. Failure to secure the windings properly is one of the main causes of transformer breakdown during short-circuit events.

V. Oil Circulation System Inside the Tank

Cooling performance is one of the most crucial aspects of transformer reliability. Inside the transformer oil tank, the oil circulation system ensures that every component—especially the windings and core—operates within safe temperatures.

Overheating directly accelerates insulation aging. According to the thermal aging rule, every 6–7°C temperature rise above design limits can cut insulation life in half. Therefore, understanding the internal oil circulation layout is essential for choosing a transformer with a longer lifespan and lower maintenance cost.

1. Natural Oil Circulation (ONAN)

Most distribution transformers use ONAN cooling, meaning:

• Oil Natural circulation
• Air Natural cooling

Inside the tank, natural convection occurs:

• Hot oil rises through the internal oil ducts
• Cooler oil sinks and re-enters the winding channels
• Heat dissipates through the external radiator fins

The internal structure must include:

• Vertical oil ducts between windings
• Clear oil channels between core limbs
• Sufficient clearance between windings and core

A poorly designed oil circulation structure will cause:

• Localized hotspots
• Shorter insulation life
• Higher temperature rise under load

For buyers evaluating ONAN transformers, the oil duct design is a key indicator of quality.

2. Forced Oil Circulation (ONAF / ODAF)

In higher-capacity transformers (1MVA+), natural circulation is not enough to dissipate heat. Manufacturers use forced cooling systems such as:

• ONAF: Oil Natural Air Forced
• ODAF: Oil Directed Air Forced

Inside the tank, the oil flow is enhanced using pumps and guided channels. ODAF transformers include specially designed internal oil guide structures that push oil directly through the hottest areas of the windings.

Benefits include:

• Better temperature uniformity
• Higher load capacity
• Longer insulation lifespan
• Lower risk of thermal runaway

ODAF transformers often feature oil distribution headers located at the top and bottom of the tank, ensuring targeted cooling where it is most needed.

3. Components Involved in Oil Circulation

Here is a structured table summarizing the internal components involved in oil circulation inside the tank:

Table 2: Internal Oil Circulation Components and Purposes

4. Why Oil Circulation Design Matters for Buyers

A transformer with well-designed internal oil circulation:

• Operates at lower temperatures
• Maintains insulation strength longer
• Supports higher overload without damage
• Reduces lifetime operation costs

For users who require continuous operation—such as factories, data centers, renewable energy stations, and utility grids—oil circulation design is directly related to total ownership cost (TOC) and long-term reliability.

VI. Insulation System Inside the Transformer Oil Tank

The insulation system inside a transformer oil tank is the core guarantee of electrical safety. It protects the windings, core, and conductive parts from dielectric breakdown caused by high voltage stress, moisture, and thermal aging. A durable insulation system extends the transformer’s service life and reduces the risk of unexpected outages.

For buyers, especially those responsible for industrial power systems, renewable energy projects, or commercial installations, understanding the insulation system helps you evaluate whether a transformer can maintain long-term stability. Poor insulation is the number one cause of transformer failure, making this section essential.

1. Main Insulating Materials Used Internally

Inside the oil tank, the insulation system is composed of multiple layers of materials, each with unique functions.

a. Kraft Insulating Paper

This is the primary insulation for windings. High-quality kraft paper is made from pure cellulose with excellent oil absorption and dielectric strength.

Good kraft paper features:

• High purity
• High mechanical strength
• Good thermal stability
• No contaminants such as metal particles or fibers

b. Pressboard (TIV, laminated pressboard)

Used for spacers, barriers, and support structures.

Pressboard benefits include:

• Forms channels for oil flow
• Ensures electrical clearance
• Provides mechanical support
• Withstands long-term compression and heat

c. Diamond-Dotted Paper (DDP)

Coated with heat-reactive adhesive dots, it enhances winding stability after hot-pressing.

d. Epoxy Resin Blocks and Fiberglass Components

These provide structural reinforcement in high-stress areas.

e. Transformer Oil as Liquid Insulation

Beyond cooling, transformer mineral oil fills microscopic voids between insulation layers, greatly improving dielectric strength.

2. Electrical Clearance and Insulation Distances

The internal layout of the transformer must maintain sufficient insulation distances to prevent electrical discharge. Two types of clearances are used:

a. Oil Clearance

This is the physical distance between live parts separated by transformer oil. Manufacturers must calculate clearances based on:

• Rated voltage
• Operating altitude
• Lightning impulse withstand level
• Switching impulse stress

b. Creepage Distance (along insulation surfaces)

Creepage distance is critical in humid regions or areas with airborne contaminants. Good designs incorporate long creepage paths and smooth insulation surfaces.

3. Moisture Control Inside the Insulation System

Moisture is the enemy of insulation. Even a small amount of water—0.5% in kraft paper—can reduce dielectric strength by up to 70%.

High-quality transformers include:

• Oven-dried coils before tank assembly
• Oil dehydration and degassing treatment
• High-vacuum filling process
• Nitrogen-sealed tank design

Buyers should avoid transformers assembled without vacuum oil filling, as residual moisture may cause partial discharge and premature aging.

4. Insulation Structure for HV and LV Windings

HV windings require thicker insulation, including:

• Multi-layer paper wrapping
• Pressboard cylinders
• Radial ducts between layers
• Axial oil channels

LV windings usually need stronger mechanical support due to higher currents, so manufacturers may use reinforced pressboards and more robust spacers.

Why it matters:
Poor insulation structure leads to internal arcing, a common cause of transformer fires. When evaluating suppliers, require them to provide insulation material specifications and process details.

VII. Safety & Protection Devices Connected to the Inner Structure

Although safety devices are often mounted outside the transformer tank, many of them directly interact with internal structures and play a crucial role in keeping the transformer safe. Their performance directly impacts your system’s reliability, maintenance cost, and fire risk.

1. Buchholz Relay (Gas Relay)

Installed between the main tank and the conservator, this device detects:

• Gas accumulation caused by internal faults
• Oil level drops
• Rapid oil movement during severe failures

A Buchholz relay can predict insulation deterioration early, giving users time to schedule maintenance before a breakdown occurs.

For users operating critical facilities like hospitals, factories, and substations, this is a critical early-warning system.

2. Pressure Relief Device (PRD)

If excessive internal pressure builds up due to short-circuit or arcing faults, the PRD releases pressure instantly to prevent tank rupture.

Key benefits:

• Prevents explosion
• Protects nearby equipment
• Enhances personnel safety

High-quality PRDs include stainless steel springs and corrosion-resistant sealing rings, ensuring long-term reliability.

3. Oil Level Indicator

The oil level is directly related to internal cooling and insulation. A sudden drop may indicate:

• Internal oil leakage
• Moisture ingress
• Thermal overload
• Fault-induced gas generation

Users should regularly inspect oil levels to maintain stable operation.

4. Winding Temperature Indicator (WTI)

This device simulates the hot-spot temperature of windings. Because winding temperature is tightly linked to insulation aging, accurate temperature monitoring helps users:

• Avoid overload
• Extend transformer life
• Improve operational reliability

For transformers on renewable energy systems—where load fluctuates frequently—WTIs are essential.

5. Conservator Tank and Breather Interaction

Although the conservator is external, it interacts with the oil inside the main tank.

The silica-gel breather prevents moisture from entering the oil. A moisture-saturated breather exposes the internal insulation to humidity, accelerating aging.

6. Radiators and Cooling System Components

Radiators are connected to internal oil channels. Proper flow inside the tank ensures:

• Stable temperature rise
• Uniform cooling
• Reduced hotspot risk

Buyers should ensure radiators are made of high-grade steel and are welded or bolted according to international standards.

7. Table: Safety Devices & Their Internal Impact

VIII. Internal Bushings, Leads & Electrical Connections

Inside a transformer oil tank, the bushings and internal leads form the critical pathways that carry electrical current from the windings to the external power system. Their design, insulation quality, and connection stability determine how safely and efficiently electricity flows. For buyers evaluating transformer quality, these internal connections reveal the manufacturer’s engineering strength and process control.

1. Transformer Bushings (HV & LV)

Bushings act as insulated passages that allow high-voltage conductors to enter or exit the tank without electrical breakdown. They must withstand both electrical stress and mechanical forces.

Types of internal bushings

• Oil–Paper Insulated Bushings (OIP) – commonly used for HV
• Resin Impregnated Paper Bushings (RIP) – moisture-resistant
• Porcelain Bushings – used for LV and outdoor connections
• Composite Bushings – lightweight, weather-resistant

High-voltage bushings extend inside the tank where they connect to conductive leads. Their internal surface must remain fully immersed in oil to maintain dielectric performance.

Why bushings matter for buyers

A failure in the HV bushing is one of the costliest transformer failures. Premium bushings from known brands (ABB, Siemens, Weidmann) significantly improve reliability.

2. Internal Leads and Conductors

Internal transformer leads carry large electrical currents; therefore, they must be:

• Made from oxygen-free copper or high-conductivity aluminum
• Insulated using high-grade kraft paper or pressboard tubing
• Routed with mechanical damping to prevent vibration damage

Manufacturers often wrap leads with crepe paper, which expands under oil and improves dielectric stability.

Lead Routing Considerations

Proper routing prevents:

• Excessive bending
• Abrasion against the tank wall
• Partial discharge points
• Damage during transport

For buyers, neat and symmetrical lead arrangement is a strong indicator of high manufacturing quality.

3. Tap Changer Connections

Transformers with on-load or off-circuit tap changers require additional internal conductors.

Off-Circuit Tap Changer (OCTC)

Located inside the tank

• Simple design
• Used mostly in distribution transformers
• Must be operated off-load

On-Load Tap Changer (OLTC)

Often connected through a diverter switch compartment

• Complex internal wiring
• Requires robust insulation
• Generates heat and gas during operation

When purchasing a transformer with OLTC, buyers should confirm:

• Brand of OLTC (e.g., MR, ABB, Huaming)
• Maintenance intervals
• Contact wear materials

4. Internal Grounding System

Every transformer includes a dedicated internal grounding network, ensuring that:

• Tank walls remain at zero potential
• Surge energy is safely diverted
• Fault current does not damage insulation

Copper grounding straps are welded or bolted to the tank, with insulation separators securing them in place.

Neglecting grounding quality can lead to tank potential rise, increasing the risk of electric shock or flashover.

Table: Key Internal Components and Their Importance

IX. Cooling Interfaces and Heat Dissipation Structures

The internal cooling interfaces are carefully engineered to manage heat produced by winding current and core losses. Efficient heat dissipation is essential for long-term transformer performance and directly affects the total cost of ownership (TCO).

1. Radiator Interfaces Inside the Tank

Radiators, attached to the outside of the tank, are fed by internal oil channels. The internal interfaces must be:

• Smooth
• Free from debris
• Designed to prevent air pockets
• Able to maintain steady oil flow

Poor internal radiator interface design leads to uneven temperature rise and hotspots.

2. Oil Guide Plates and Flow Directors

Inside large power transformers, metal plates or oil directors guide oil to the hottest areas.

Benefits of oil guide plates

• Efficient thermal distribution
• Reduced hotspot temperature
• Better long-term insulation life

Buyers choosing 1600 kVA+ transformers should prioritise designs with directional cooling.

3. Top Oil and Bottom Oil Circulation Zones

Inside every transformer, specific temperature zones naturally form:

• Top oil zone: Hot, near HV windings
• Bottom oil zone: Cooler, near LV windings

Internal structures must maintain a stable circulation cycle. Some manufacturers add oil baffles to regulate the flow and stabilise these zones.

4. Cooling Variants and Their Inner Structure Needs

ONAN (Oil Natural Air Natural)

Simple design

• Requires precise internal oil duct layout
• Best for 30–2500 kVA distribution transformers

ONAF (Oil Natural Air Forced)

Adds fans

• Requires larger internal oil paths
• Used for higher capacity

ODAF (Oil Directed Air Forced)

Oil pumps + forced flow

• Requires internal oil header pipes
• Suitable for 10MVA+ power transformers

OFAF / OFWF

Advanced cooling modes

• Internal piping and pump connections
• Used in major substations and grid transformers

5. Internal Heat Dissipation Risks to Watch Out For

If the transformer is poorly designed internally, overheating can lead to:

• Faster insulation aging
• Winding deformation
• Loss of dielectric strength
• Thermal runaway
• Transformer explosion

Buyers should always request a temperature rise test report, especially for medium-voltage applications.

X. Materials & Manufacturing Standards for Oil Tank Inner Structure

High-quality materials and internationally certified manufacturing processes are the foundation of a durable oil tank structure. When you compare transformer suppliers, these internal details often separate true manufacturers from low-cost assemblers.

1. Core Materials

Most manufacturers use:

• Cold Rolled Grain Oriented Silicon Steel (CRGO)
• M4, M5, or grade 23ZDKH silicon steel
• Laser-scribed low-loss steel
• Step-lap joints for reduced losses

Better steel = lower no-load loss = lower electricity cost for users.

2. Copper and Aluminum Conductor Materials

Copper is preferred for higher efficiency.
Buyers should ensure conductors comply with:

• IEC 60228 Class 2
• High-conductivity ≥ 99.9% purity

Aluminum windings must follow ISO/ASTM standards and be fully annealed for flexibility.

3. Pressboard & Paper Standards

Look for materials that comply with:

• IEC 60641
• IEC 60554
• IEC 60317
• ASTM D202
• IEC 60763 (pressboard for electrical purposes)

High-quality pressboards come from suppliers like Weidmann, DuPont, and TIV.

4. Tank Material & Internal Surface Treatment

Transformer tanks must be:

• Made from high-strength Q235/Q345 steel
• Shot-blasted
• Anti-corrosion coated
• Internally cleaned to remove metal particles

Manufacturers with poor surface treatment standards often leave metal debris inside the tank, which can trigger partial discharge or oil contamination.

5. Testing Standards Related to the Inner Structure

Before leaving the factory, a transformer must pass tests including:

• Vacuum oil-filling test
• Pressure leakage test
• Insulation resistance test
• Turns ratio test
• Lightning impulse test
• Temperature rise test

Transformers following IEC 60076 or IEEE C57 standards offer higher long-term reliability.

XI. How Inner Tank Structure Affects Transformer Performance & Lifetime

The inner structure of a transformer oil tank is not just a mechanical container—it directly determines the transformer’s efficiency, temperature stability, insulation strength, and long-term reliability. For buyers planning to invest in distribution or power transformers, understanding how internal design influences performance is essential.

Below is a breakdown of the major performance areas affected by the inner tank structure.

1. Heat Dissipation and Temperature Stability

A well-designed inner oil tank structure ensures:

• Fast and uniform heat transfer
• Stable oil circulation paths
• Reduced hotspot temperatures
• Extended insulation lifespan

Poor oil flow channels or insufficient cooling ducts often lead to:

• Overheating
• Hotspot failures
• Shorter transformer life
• Unexpected downtime

Thermal stability = lower maintenance cost + higher operational safety.

2. Electrical Insulation Performance

Transformer oil and the insulation system must work together. Internal structure affects:

• Oil clearance distances
• Creepage and strike distances
• Dielectric strength under high voltage
• Stability during load fluctuations

If internal bracing is poorly designed, vibrations can damage insulation materials over time.

A strong internal structure keeps the insulation system stable—even during short-circuit forces.

3. Mechanical Strength and Short-Circuit Withstand Capability

During faults, transformers experience extremely high electromagnetic forces.
The internal structure must:

• Hold the core and windings firmly
• Prevent coil deformation
• Minimize displacement under short-circuit stress

Transformers with better bracing and support structures can withstand:

• Short-circuit events
• Transportation vibration
• Long-term mechanical fatigue

This directly contributes to a longer service life.

4. Oil Circulation Efficiency

Oil movement inside the tank is critical for:

• Cooling
• Heat uniformity
• Dissipation of dissolved gases
• Maintaining dielectric strength

Well-engineered oil duct systems ensure:

• Natural convection (ONAN) works efficiently
• Forced oil cooling (OFAF, ODAF) achieves full capacity
• No dead zones or stagnant oil pockets

Smooth oil circulation promotes stable transformer performance, especially under heavy load conditions.

5. Maintenance Requirements and Serviceability

A better internal structure reduces:

• Oil sludge accumulation
• Hotspot formation
• Insulation aging
• Oil contamination risk

High-quality internal design means less maintenance and fewer unexpected failures—ideal for industrial plants, data centers, or continuous operation environments.

XII. Buyer’s Checklist: How to Choose a Transformer With a Reliable Oil Tank Structure

Selecting a transformer goes far beyond checking the power rating or price. The internal oil tank structure determines real-world performance, safety, and lifespan. Use this professional checklist when evaluating a supplier.

1. Core & Winding Quality

• Is the core made of high-grade silicon steel?
• Are windings copper or aluminum?
• Are winding ducts properly designed for cooling?
• Are insulation materials from reputable brands?

Tip: Copper windings and cold-rolled silicon steel improve efficiency and reduce long-term losses.

2. Oil Tank Construction

• Is the tank thickness suitable for your voltage level?
• Is it made from high-quality steel with strong welding?
• Does it include anti-corrosion coatings?
• Are stiffeners reinforced to prevent deformation?

A rigid tank = better pressure stability and longer service life.

3. Oil Circulation & Cooling System

Check for:

• Adequate vertical and horizontal oil ducts
• Smooth oil flow design
• Efficient radiator or cooling fins
• Optional forced-oil cooling (if needed)

More oil ducts = better heat dissipation and lower hotspots.

4. Internal Mechanical Support

Evaluate:

• Bracing strength
• Vibration resistance
• Winding clamping system
• Short-circuit withstand level

Strong support reduces deformation risk during faults.

5. Tap-Changer Quality

Consider:

• Load tap changer (OLTC) or off-circuit tap changer (OCTC)
• Contact material
• Switching reliability
• Maintenance interval

A reliable tap changer ensures stable voltage output.

6. Transformer Oil Type and Quality

Ensure the supplier uses:

• High-purity mineral oil or synthetic insulating oil
• IEC/ASTM certified oil
• Low moisture, low acidity, low gas content

Oil quality directly determines insulation strength.

7. Safety and Monitoring Components

Look for:

• Buchholz relay
• Oil level indicator
• Temperature indicators
• Pressure relief valve
• Gas relay
• Digital monitoring options

These features enhance safety and help detect faults early.

8. Supplier Reliability

Before buying:

• Check certifications (ISO, IEC, CE)
• Review factory capabilities
• Confirm testing procedures
• Request routine test reports and type test reports

A trustworthy supplier ensures stable production quality and timely delivery.

Ready to Choose a Transformer With a Reliable Oil Tank Structure?

A transformer is a long-term investment. A well-designed oil tank structure ensures higher safety, better cooling, and longer service life.

We manufacture oil-immersed transformers, dry-type transformers, HV/LV switchgear, and complete substation solutions with fully optimized internal tank structures and international compliance.

📩 Contact us for a free technical consultation and detailed quotation.
Our engineering team will help you select the most suitable model for your project needs.

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