Description:FIELD OF THE INVENTION

The present invention relates to electrical power distribution systems, specifically to the design and implementation of hybrid distribution transformers (DTRs) that combine features of both oil-filled and dry-type transformers. These hybrid transformers aim to enhance safety, reliability, and efficiency in electricity distribution networks.

Application: The hybrid DTRs are particularly suitable for urban and densely populated areas where safety and space constraints are critical. They are designed to reduce fire hazards, minimize maintenance issues, and provide reliable power supply with reduced failure rates. These transformers can be used by power distribution utilities and consumers seeking efficient, safe, and cost-effective solutions for electricity distribution. The hybrid DTRs are ideal for installations in public spaces, commercial areas, and residential neighborhoods, where enhanced public safety and reduced environmental impact are paramount.

BACKGROUND OF THE INVENTION

In the field of electrical power distribution, conventional oil-filled distribution transformers (DTRs) have been widely used due to their high loading capacity and cost-effectiveness. However, these transformers present significant challenges, particularly in urban and densely populated areas. The primary issues with conventional oil-filled DTRs include the risk of fire hazards due to the presence of mineral insulating oil, frequent maintenance requirements, and a high failure rate due to oil leakage and deterioration.

Distribution transformers are critical components in power distribution networks, converting medium voltage to low voltage for domestic and commercial use. These transformers are often installed in public areas, making safety, reliability, and efficiency paramount concerns. Conventional oil-filled DTRs, while effective, pose significant fire hazards due to the presence of mineral insulating oil. Additionally, maintenance and operational issues such as oil leakage and moisture ingress can lead to transformer failures, increasing operational costs and supply interruptions.
Prior Art Problems
1. Fire Hazards: Conventional oil-filled DTRs are prone to fire incidents due to the flammable nature of mineral insulating oil. This poses a significant risk, especially in densely populated urban areas.
2. Oil Leakage: Oil leakage from bushing seals is a common issue, leading to transformer failures and increased maintenance costs. Approximately 46% of oil-filled DTR failures are attributed to low oil levels.
3. Moisture Ingress: Free-breathing designs in conventional DTRs allow moisture ingress, deteriorating the oil quality and reducing the transformer's lifespan.
4. High Maintenance Costs: Handling and replacing oil-filled components are labor-intensive and costly, leading to higher operational expenses.
5. Large Footprint: Conventional DTRs have a larger footprint, making installation challenging in space-constrained urban environments.
6. Weight: The heavier weight of conventional DTRs complicates transportation and installation processes.
Disadvantages of Prior Art
• Safety Risks: High fire hazard potential due to the presence of flammable oil.
• Frequent Failures: High failure rates due to oil leakage and moisture ingress.
• Maintenance Challenges: Labor-intensive and costly maintenance procedures.
• Space Constraints: Larger footprint limits installation flexibility in urban areas.
• Handling Difficulties: Heavier weight complicates transportation and installation.
Technical Solution of the Present Invention
The present invention introduces a hybrid type distribution transformer (DTR) that combines the benefits of conventional oil-filled and dry type DTRs while addressing their respective drawbacks. Key features of the hybrid DTR include:
1. Reduced Oil Usage: The hybrid DTR uses approximately 600 liters of oil, 20% less than conventional DTRs, with the oil level maintained below the bushings to minimize leakage risks.
2. Dry Type HT Isolator: Incorporation of a dry type high-tension (HT) isolator significantly reduces fire hazards and simplifies maintenance.
3. Non-Free-Breathing Design: The hybrid DTR is designed to be non-free-breathing, reducing moisture ingress and oil deterioration.
4. Compact Footprint: The overall dimensions are reduced by 12%, providing a smaller footprint and easier handling.
5. Pressure Relief Valve (PRV): A PRV is mounted on an elevated platform to manage excess pressure during internal faults.
6. Thermal Upgraded Paper: Use of thermal upgraded paper enhances thermal capacity and maintains lower operating temperatures.
7. Weight Reduction: The hybrid DTR is approximately 5% lighter than conventional models, facilitating easier transportation and installation.
Technical Effect
The technical effects of the present invention include:
• Enhanced Safety: Significant reduction in fire hazards due to the use of a dry type HT isolator and reduced oil quantity.
• Improved Reliability: Lower failure rates due to minimized oil leakage and moisture ingress.
• Cost Efficiency: Reduced maintenance costs and operational expenses due to easier maintenance procedures and lower oil usage.
• Space Efficiency: Smaller footprint allows for flexible installation in space-constrained environments.
• Ease of Handling: Lighter weight simplifies transportation and installation processes.
Need for the Present Invention
The need for the present invention arises from the limitations and risks associated with conventional oil-filled DTRs. Urban electricity distribution networks require transformers that are not only efficient and reliable but also safe and easy to maintain. The hybrid type DTR addresses these needs by offering a solution that combines the best features of oil-filled and dry type transformers, ensuring enhanced safety, reliability, and cost-effectiveness. This innovation is particularly crucial for densely populated urban areas where space constraints and public safety are significant concerns.

OBJECT OF THE INVENTION

The primary object of the invention is to provide a hybrid distribution transformer (DTR) that enhances safety, reliability, and efficiency in power distribution systems.

Another object is to reduce fire hazards by maintaining a lower oil level below the bushings and integrating a dry type high tension (HT) isolator.

A further object is to minimize maintenance issues and failure rates by incorporating an air cell system to prevent moisture ingress and oil deterioration.

An additional object is to improve operational safety with a pressure relief valve (PRV) designed to release excess pressure during internal faults.

Yet another object is to achieve a compact design that reduces the overall footprint by 12%, facilitating easier installation and handling.

Finally, the invention aims to provide a cost-effective solution that maintains similar loading capacity and loss figures as conventional transformers while offering enhanced public safety and reduced environmental impact.

SUMMARY OF THE INVENTION
The following disclosure presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the present invention. It is not intended to identify the key/critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some concept of the invention in a simplified form as a prelude to a more detailed description of the invention presented later.

The invention relates to a hybrid distribution transformer (DTR) designed to improve safety, reliability, and efficiency in electrical power distribution systems. This innovative transformer combines the advantages of both oil-filled and dry-type transformers, addressing the limitations of conventional designs.

The hybrid DTR features a reduced oil level maintained below the bushings, significantly lowering the risk of fire hazards. The integration of a dry type high tension (HT) isolator further enhances safety by eliminating oil-related fire risks within the isolator chamber.

An air cell system is incorporated to prevent moisture ingress and oil deterioration, thereby reducing maintenance requirements and failure rates. This design ensures the transformer is not free breathing, which minimizes the risk of oil degradation.

For enhanced operational safety, the transformer includes a pressure relief valve (PRV) mounted on an elevated platform. This PRV is configured to release excess pressure during internal faults, providing a more efficient pressure relief mechanism compared to conventional explosion vent pipes.

The hybrid DTR is designed with thermally upgraded paper, improving thermal capacity and reducing operating temperatures. This results in a more efficient and reliable performance, with a maximum winding temperature rise of 45°C and a top oil temperature rise of 40°C.

The compact design of the hybrid DTR reduces the overall footprint by 12%, making it easier to install and handle, particularly in urban and densely populated areas. Despite its compact size, the transformer maintains similar loading capacity and loss figures as conventional oil-filled transformers.

Key Features:

1. Reduced Oil Usage: The hybrid DTR uses approximately 600 liters of oil, 20% less than conventional DTRs, with the oil level maintained below the bushings to minimize leakage risks.

2. Enhanced Safety: By incorporating a dry type HT isolator, the design significantly reduces fire hazards. The hybrid DTR has shown a 70% reduction in fire incidents compared to conventional models.

3. Improved Reliability: The failure rate due to oil leakage from bushing seals is reduced by 37%. The hybrid DTR is not free-breathing, reducing moisture ingress and oil deterioration.

4. Compact Design: The overall dimensions are reduced by 12%, providing a smaller footprint and easier handling. The hybrid DTR is also 5% lighter than conventional models.

5. Cost Efficiency: While 10% more expensive than conventional DTRs, it is 30% cheaper than dry type DTRs, offering a cost-effective solution with enhanced features.

6. Pressure Relief: Equipped with a T3 size Pressure Relief Valve (PRV) for better pressure management, unlike the explosion vent pipe in conventional DTRs.

7. Maintenance and Longevity: Easier maintenance due to the absence of oil handling for isolators and studs. The hybrid DTR has a life expectancy of 25-30 years, similar to conventional models.

Benefits:

The hybrid DTR offers reduced maintenance costs, higher network reliability, and improved public safety, making it a valuable innovation for urban electricity distribution systems.

Other aspects, advantages, and salient features of the invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses exemplary embodiments of the invention.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

The above and other aspects, features and advantages of the embodiments of the present disclosure will be more apparent in the following description taken in conjunction with the accompanying drawings, in which:

Figure 1 illustrates schematic of hybrid type distribution transformer (DTR) of the present invention.
Persons skilled in the art will appreciate that elements in the figures are illustrated for simplicity and clarity and may not have been drawn to scale. For example, the dimensions of some of the elements in the figure may be exaggerated relative to other elements to help to improve understanding of various exemplary embodiments of the present disclosure. Throughout the drawings, it should be noted that like reference numbers are used to depict the same or similar elements, features, and structures.

DETAILED DESCRITION OF THE INVENTION

The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of various embodiments of the present disclosure as defined by the claims and their equivalents. It includes various specific details to assist in that understanding, but these are to be regarded as merely exemplary. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the various embodiments described herein can be made without departing from the scope and spirit of the present disclosure. In addition, descriptions of well-known functions and constructions may be omitted for clarity and conciseness.
All terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which various embodiments belong. Further, the meaning of terms or words used in the specification and the claims should not be limited to the literal or commonly employed sense but should be construed in accordance with the spirit of the disclosure to most properly describe the present disclosure.
The terminology used herein is for the purpose of describing particular various embodiments only and is not intended to be limiting of various embodiments. As used herein, the singular forms "a," "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising" used herein specify the presence of stated features, integers, steps, operations, members, components, and/or groups thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, members, components, and/or groups thereof.
The present disclosure will now be described more fully with reference to the accompanying drawings, in which various embodiments of the present disclosure are shown.

DEFINITION OF SOME OF THE TECHNICAL TERMS:
Distribution Transformer (DTR): A transformer that provides the final voltage transformation in the electric power distribution system, stepping down the voltage used in the distribution lines to the level used by the customer.

High Tension (HT) Isolator: A device used to isolate a section of a high voltage circuit for maintenance or safety purposes, ensuring no current flows through the circuit.

Low Tension (LT) Bushings: Insulated devices that allow electrical conductors to pass safely through a grounded barrier, such as a transformer casing, at low voltage levels.

Pressure Relief Valve (PRV): A safety device designed to release excess pressure from a system to prevent equipment failure or explosion.

Air Cell System: A component used in transformers to prevent moisture ingress and maintain consistent internal pressure, reducing the risk of oil deterioration.

Thermally Upgraded Paper: A type of insulation material used in transformers that can withstand higher temperatures, improving the thermal capacity and longevity of the transformer.

Free Breathing Transformer: A transformer design that allows air exchange with the environment, which can lead to moisture ingress and oil degradation.

Explosion Vent Pipe: A safety feature in conventional transformers designed to release pressure in the event of an internal fault, preventing explosions.

Footprint: The physical space occupied by a piece of equipment, such as a transformer, often measured in terms of its dimensions.
The invention pertains to a hybrid distribution transformer (DTR) designed to enhance safety, reliability, and efficiency in power distribution systems. This transformer integrates features from both oil-filled and dry-type transformers, addressing the limitations of conventional designs.

Transformer Tank and Oil Level: The hybrid DTR features a transformer tank that contains a reduced quantity of insulating oil. The oil level is strategically maintained below the bushings, specifically at least 60 mm below the lowest point of the opening for low tension (LT) bushings. This design minimizes the risk of fire hazards by reducing the amount of flammable material within the transformer.

In accordance to an embodiment of the present invention, the transformer tank in the hybrid distribution transformer (DTR) is a critical component designed to house the core, windings, and insulating oil. In the context of the present invention, the tank is engineered to optimize safety and efficiency by incorporating a reduced oil level strategy.

Design and Construction: The transformer tank is constructed from robust materials to withstand environmental and operational stresses. It is designed to be compact, reducing the overall footprint by 12% compared to conventional transformers. This compact design facilitates easier installation and handling, particularly in urban areas where space is limited.

Reduced Oil Level: A key innovation in the hybrid DTR is the strategic reduction of the insulating oil level. The oil is maintained at least 60 mm below the lowest point of the opening for low tension (LT) bushings. This reduction minimizes the amount of flammable material within the transformer, significantly lowering the risk of fire hazards.

Functional Benefits: By reducing the oil level, the transformer not only enhances safety but also decreases the likelihood of oil leakage, which is a common cause of transformer failure. The lower oil volume reduces maintenance requirements and environmental impact, as there is less oil to manage and dispose of.

Integration with Other Components: The reduced oil level works in conjunction with the dry type high tension (HT) isolator to further mitigate fire risks. The design ensures that critical components, such as the HT and LT bushings, are positioned above the oil level, reducing the potential for oil-related failures.

Operational Efficiency: Despite the reduced oil volume, the hybrid DTR maintains similar loading capacity and loss figures as conventional transformers. This is achieved through careful thermal management and the use of thermally upgraded paper in the windings, which compensates for the lower oil volume by enhancing heat dissipation.

Overall, the transformer tank and reduced oil level in the hybrid DTR are integral to the invention's goal of providing a safer, more reliable, and efficient power distribution solution. By addressing the limitations of conventional oil-filled transformers, the hybrid DTR offers a modern approach to transformer design that meets the demands of contemporary power distribution networks.

Dry Type High Tension (HT) Isolator: A key component of the hybrid DTR is the dry type HT isolator. This isolator replaces the traditional oil-filled isolator, eliminating the risk of oil-related fire hazards within the isolator chamber. The dry type isolator is easier to maintain and replace, as it does not require oil handling. In the context of the present invention, the dry type HT isolator replaces traditional oil-filled isolators, offering several advantages.

Design and Construction: The dry type HT isolator is constructed using non-flammable, solid insulation materials. This design eliminates the need for insulating oil, thereby reducing the risk of fire hazards associated with oil-filled components. The isolator is compact and integrates seamlessly with the overall transformer design.

Safety Enhancements: By eliminating oil from the isolator, the hybrid DTR significantly reduces the potential for fire incidents. This is particularly important in urban and densely populated areas where safety is a primary concern. The dry type isolator ensures that the transformer operates safely even under high voltage conditions.

Maintenance and Reliability: The absence of oil in the HT isolator simplifies maintenance procedures. There is no need for oil handling, which reduces the time and cost associated with maintenance tasks. The dry type design also minimizes the risk of oil leakage, a common cause of transformer failure, thereby enhancing the overall reliability of the system.

Integration with Transformer Design: The dry type HT isolator is strategically positioned within the transformer to optimize space and functionality. It works in conjunction with the reduced oil level strategy, ensuring that all critical components are safely isolated from potential oil-related issues.

Operational Efficiency: Despite the absence of oil, the dry type HT isolator maintains high performance levels. It is designed to handle the same electrical loads as conventional isolators, ensuring that the transformer can operate efficiently under various conditions.

Overall, the dry type HT isolator in the hybrid DTR is a key innovation that addresses the limitations of traditional oil-filled transformers. By enhancing safety, reducing maintenance needs, and maintaining operational efficiency, the dry type HT isolator contributes to the invention's goal of providing a modern, reliable, and safe power distribution solution.

Air Cell System: The transformer incorporates an air cell system to prevent moisture ingress and maintain consistent internal pressure. This system reduces the risk of oil deterioration, enhancing the reliability and lifespan of the transformer. The air cell system ensures the transformer is not free breathing, minimizing the risk of oil degradation due to environmental exposure. In traditional transformers, the presence of air in contact with the insulating oil can lead to moisture ingress, which deteriorates the oil quality and increases the risk of failure. The air cell system effectively mitigates these risks.

In the hybrid type DTR, the air cell is a flexible, impermeable membrane that separates the insulating oil from the external atmosphere. This design ensures that the oil does not come into direct contact with air, thereby significantly reducing the chances of moisture ingress and subsequent oil deterioration. The air cell system is not present in conventional DTRs, which are free-breathing and more susceptible to these issues.

By incorporating an air cell, the hybrid DTR maintains a stable internal environment, enhancing the reliability and longevity of the transformer. This system also contributes to the reduced failure rate of the hybrid DTR by minimizing the risk of oil contamination and maintaining optimal insulation properties.

Overall, the air cell system is a key feature that enhances the performance and safety of the hybrid type DTR, making it a more robust and reliable option compared to conventional oil-filled transformers.

Pressure Relief Valve (PRV): In the context of the hybrid type Distribution Transformer (DTR), the Pressure Relief Valve (PRV) is a significant enhancement over conventional systems. For enhanced operational safety, the hybrid DTR includes a pressure relief valve (PRV) mounted on an elevated platform on the main tank top cover. The PRV is configured to release excess pressure during internal faults, providing a more efficient pressure relief mechanism compared to conventional explosion vent pipes. The PRV operates at a pressure of 0.49 kg/cm² and is positioned at a corner away from the core coil assembly (CCA) to ensure effective pressure management.

For the hybrid type DTR, a T3 size PRV of reputed make is installed on an elevated platform on the main tank top cover. This strategic positioning, away from the Core Coil Assembly (CCA), allows the PRV to efficiently release excess pressure during internal faults of high magnitude. This feature is crucial in preventing potential damage or catastrophic failure due to pressure build-up.

In contrast, conventional oil-filled DTRs typically use an explosion vent pipe for pressure relief. However, this method is less efficient compared to the PRV system in the hybrid DTR. The PRV provides a more controlled and reliable means of pressure management, enhancing the overall safety of the transformer.

The inclusion of the PRV in the hybrid DTR not only improves performance but also reduces the risk of fire hazards and operational failures. This makes the hybrid DTR a safer and more dependable choice for electricity distribution systems.

Thermally Upgraded Paper: The windings of the hybrid DTR are insulated with thermally upgraded paper, which improves the thermal capacity and reduces operating temperatures. This results in a more efficient and reliable performance, with a maximum winding temperature rise of 45°C and a top oil temperature rise of 40°C. The thermal design ensures that the transformer can handle high loads without compromising safety or efficiency. This specialized paper is used as insulation for the windings, providing several advantages over conventional insulation materials.

Thermally upgraded paper is treated to withstand higher temperatures without degrading, allowing the transformer to operate efficiently under increased thermal stress. This capability is particularly beneficial in urban environments where transformers may experience higher loading conditions.

The use of thermally upgraded paper in the hybrid DTR contributes to a lower operating temperature, which in turn reduces the risk of insulation failure and extends the transformer's lifespan. The improved thermal capacity also allows the hybrid DTR to maintain performance levels similar to conventional transformers, despite its reduced size and oil content.

Overall, the incorporation of thermally upgraded paper in the hybrid DTR enhances its reliability, efficiency, and safety, making it a superior choice for modern electricity distribution systems.

Compact Design: The compact design of the hybrid type Distribution Transformer (DTR) is a significant advancement that offers multiple benefits over conventional transformers. This design innovation is achieved through several strategic modifications, resulting in a transformer that is both efficient and space-saving.

One of the key features of the compact design is the reduction in overall dimensions. The hybrid DTR is approximately 12% smaller than conventional oil-filled transformers. This reduction is achieved by optimizing the internal components and utilizing advanced materials, such as thermally upgraded paper, which allows for a more efficient layout without compromising performance.

The compact design also includes a reduced oil volume, with the hybrid DTR using about 20% less oil than traditional models. This not only decreases the physical size but also enhances safety by lowering the risk of fire hazards associated with oil leaks.

Additionally, the hybrid DTR's compactness facilitates easier installation and maintenance, particularly in urban areas where space is limited. The lighter weight, approximately 5% less than conventional transformers, further simplifies handling and transportation.

Overall, the compact design of the hybrid DTR provides enhanced flexibility, safety, and efficiency, making it an ideal solution for modern power distribution needs.

Constructional and Functional Linkages: The components of the hybrid DTR are constructionally and functionally linked to optimize performance and safety. The reduced oil level and dry type HT isolator work together to minimize fire hazards. The air cell system and non-free breathing design prevent moisture ingress, reducing maintenance needs. The PRV ensures safe pressure management, while the thermally upgraded paper enhances thermal performance. The compact design allows for efficient use of space without sacrificing capacity or reliability.

Overall, the hybrid DTR offers a cost-effective solution, being 10% more expensive than conventional transformers but 30% less costly than dry-type transformers. It provides enhanced public safety, reduced environmental impact, and improved network reliability, making it an ideal choice for modern power distribution needs.

DESCRIPTION RELATED TO FIGURES:
Figure 1 illustrates the general arrangement of a hybrid type distribution transformer (DTR) with oil level below the bushings and a dry type high-tension (HT) isolator. The figure includes various views and components, each labeled with reference numerals for clarity.
Plan View
• 1. CT Box: The current transformer box is located at the top left of the plan view.
• 2. On/Off PV 2W: The on/off pressure valve is positioned adjacent to the CT box.
• 3. Detachable Flange: Located at the bottom left, this flange allows for easy maintenance and replacement.
• 4. Serial Number Plate: Positioned near the center, this plate displays the transformer's serial number.
• 5. Earthing Terminal: Located at the bottom right, this terminal ensures proper grounding of the transformer.
• 6. Lifting Lug: These are positioned at the corners for lifting and handling the transformer.
• 7. Rating Plate: Displays the transformer's specifications and ratings.
• 8. Drain Valve: Located at the bottom center, this valve allows for draining the oil.
• 9. Oil Level Gauge with Level Marking: Positioned near the drain valve, this gauge indicates the oil level inside the transformer.
• 10. Air Release Plug: Located at the top right, this plug allows for releasing trapped air.
• 11. HV Bushing: High-voltage bushings are positioned at the top right.
• 12. LV Bushing: Low-voltage bushings are located at the bottom right.
Front View
• 13. Thermometer Pocket: Positioned near the top, this pocket holds the thermometer for temperature monitoring.
• 14. PRV (Pressure Relief Valve): Located at the top center, this valve releases excess pressure during internal faults.
• 15. HV Terminal Box: Positioned at the top right, this box houses the high-voltage terminals.
• 16. HV Cable Box: Located adjacent to the HV terminal box, this box manages the high-voltage cables.
• 17. LV Cable Box: Positioned at the bottom right, this box manages the low-voltage cables.
• 18. Tank: The main body of the transformer, housing the core and windings.
• 19. Radiator: Positioned on the sides, these radiators dissipate heat generated during operation.
Side View
• 20. HV Bushing: High-voltage bushings are positioned at the top.
• 21. LV Bushing: Low-voltage bushings are located at the bottom.
• 22. Earthing Terminal: Ensures proper grounding of the transformer.
• 23. Lifting Lug: For lifting and handling the transformer.
• 24. Rating Plate: Displays the transformer's specifications and ratings.
• 25. Drain Valve: Allows for draining the oil.
• 26. Oil Level Gauge with Level Marking: Indicates the oil level inside the transformer.
• 27. Air Release Plug: Allows for releasing trapped air.
• 28. Thermometer Pocket: Holds the thermometer for temperature monitoring.
• 29. PRV (Pressure Relief Valve): Releases excess pressure during internal faults.
• 30. HV Terminal Box: Houses the high-voltage terminals.
• 31. HV Cable Box: Manages the high-voltage cables.
• 32. LV Cable Box: Manages the low-voltage cables.
• 33. Tank: The main body of the transformer, housing the core and windings.
• 34. Radiator: Dissipates heat generated during operation.
Foundation Details
• Section A-A and Section B-B: These sections provide detailed views of the foundation and mounting arrangements for the transformer.
Weight Chart
• Core and Windings: 1440 kg
• Tank and Fittings: 1195 kg
• Oil: 585 kg
• Total Weight: 3220 kg
Electrical Clearance in Air
• Phase to Phase (HV): 130 mm
• Phase to Earth (HV): 80 mm
• Phase to Phase (LV): 45 mm
• Phase to Earth (LV): 20 mm
This detailed description of Figure 1 provides a comprehensive understanding of the hybrid type distribution transformer, highlighting its components and their respective functions.

Advantages of the Hybrid Type Distribution Transformer (DTR):

1. Enhanced Safety: The use of a dry type HT isolator significantly reduces fire hazards, improving public safety.

2. Reduced Failure Rate: Positioning the bushings above the oil level decreases the risk of oil leakage, reducing failure rates by approximately 37%.

3. Compact Design: The transformer has a 12% smaller footprint, allowing for easier installation and more efficient use of space.

4. Lower Maintenance Costs: Easier maintenance and replacement of components without oil handling reduce time and costs.

5. Improved Reliability: The non-free-breathing design minimizes moisture ingress, enhancing the transformer's longevity and performance.

6. Cost Efficiency: While slightly more expensive than conventional DTRs, it is 30% cheaper than dry type DTRs, offering a balanced cost-benefit ratio.

7. Weight Reduction: Being 5% lighter than conventional models, the hybrid DTR is easier to transport and handle.

8. Effective Pressure Management: The inclusion of a pressure relief valve (PRV) provides better pressure management during internal faults.

9. Lower Operating Temperature: The use of thermal upgraded paper enhances thermal capacity, maintaining efficient operation.

10. Environmental Benefits: Reduced oil usage decreases environmental impact and handling risks.

The descriptions and illustrations provided in this document are intended to explain the principles of the invention and its best mode of working. They are not intended to limit the scope of the invention, which is defined by the claims. Variations and modifications to the described embodiments may be made without departing from the scope of the invention. The specific embodiments described in this document are examples of the invention and are not intended to limit the scope of the claims. The claims should be interpreted broadly to cover all equivalent structures and methods that fall within the scope of the invention. The technical specifications and details provided in this document are for illustrative purposes only. Actual implementations of the invention may vary based on specific design requirements, manufacturing processes, and application needs.

Any references to prior art documents, patents, or publications are provided for informational purposes only. The inclusion of such references does not imply that the present invention is limited by or dependent on the prior art.

The inventors and assignees reserve the right to make modifications, improvements, and updates to the invention described in this document. Such modifications and improvements may be made without notice and may not be reflected in this document.
, Claims:WE CLAIM

1. A hybrid distribution transformer (DTR) comprising:

a transformer tank containing a reduced quantity of insulating oil, wherein the oil level is maintained below the bushings to enhance fire safety and reduce maintenance issues;
a dry type high tension (HT) isolator integrated within the transformer to minimize fire hazards associated with oil-filled components;
an air cell system to prevent moisture ingress and oil deterioration, thereby increasing the reliability and lifespan of the transformer;
a pressure relief valve (PRV) mounted on an elevated platform on the main tank top cover, configured to release excess pressure during internal faults, enhancing operational safety;
thermally upgraded paper used in the windings to improve thermal capacity and reduce operating temperature, ensuring efficient performance;
wherein the transformer is designed with a compact footprint, reducing overall dimensions by approximately 12% compared to conventional transformers, facilitating easier installation and handling;
and wherein the transformer is configured to provide similar loading capacity and loss figures as conventional oil-filled transformers, while offering enhanced public safety and reduced failure rates due to oil leakage and fire hazards.

2. The hybrid distribution transformer of claim 1, wherein the oil level is at least 60 mm below the lowest point of the opening for low tension (LT) bushings.

3. The hybrid distribution transformer of claim 1, wherein the quantity of insulating oil is approximately 600 liters.

4. The hybrid distribution transformer of claim 1, further comprising a non-free breathing design to reduce moisture ingress.

5. The hybrid distribution transformer of claim 1, wherein the air cell system is configured to maintain consistent internal pressure.

6. The hybrid distribution transformer of claim 1, wherein the high-tension (HT) and low-tension (LT) bushings are positioned above the oil level, significantly reducing the failure rate due to oil leakage from bushing seals by approximately 37%, thereby enhancing the transformer's reliability and safety.

7. The hybrid distribution transformer of claim 1, wherein the PRV operates at a pressure of 0.49 kg/cm².

8. The hybrid distribution transformer of claim 1, wherein the PRV is positioned at a corner away from the core coil assembly (CCA).

9. The hybrid distribution transformer of claim 1, wherein the thermally upgraded paper reduces the maximum winding temperature rise to 45°C.

10. The hybrid distribution transformer of claim 1, wherein the maximum temperature rise for top oil is limited to 40°C.

11. The hybrid distribution transformer of claim 1, wherein the transformer weight is approximately 2600 kg.

12. The hybrid distribution transformer of claim 1, wherein the transformer reduces fire hazard incidents by 70% compared to conventional transformers.

13. The hybrid distribution transformer of claim 1, wherein the transformer is designed to be 5% lighter than conventional transformers.

14. The hybrid distribution transformer of claim 1, wherein the transformer does not require a conservator.

15. The hybrid distribution transformer of claim 1, wherein the transformer is equipped with a T3 size PRV of reputed make.

16. The hybrid distribution transformer of claim 1, wherein the transformer reduces oil consumption by 20% compared to conventional transformers.

17. The hybrid distribution transformer of claim 1, wherein the transformer is designed to have a maximum total loss at 50% loading of 1225 Watts for 400 kVA.

18. The hybrid distribution transformer of claim 1, wherein the transformer is designed to have a maximum total loss at 100% loading of 3450 Watts for 400 kVA.

19. The hybrid distribution transformer of claim 1, wherein the transformer is configured to prevent oil circuit choked cases.

20. The hybrid distribution transformer of claim 1, wherein the transformer is designed for easy maintenance and replacement of HT and LT studs.

21. The hybrid distribution transformer of claim 1, wherein the transformer provides higher network reliability and lesser supply interruption.

22. The hybrid distribution transformer of claim 1, wherein the transformer is suitable for urban areas with high population density.