Oil-type Transformer

Oil-filled transformers are a vital component of electrical distribution systems. They are used to convert high voltage electricity to lower voltage levels for safe and efficient transmission to homes businesses and industries. These transformers are designed to operate for long periods even under extreme conditions and play a critical role in ensuring the uninterrupted supply of electricity.

One of the most crucial aspects of oil-filled transformers is the type of oil used as their insulating and cooling medium. The choice of oil is essential to enhance the transformer's performance reliability and lifespan. Let's delve into the characteristics and benefits of different types of oils commonly used in transformers.

Mineral oil also known as conventional transformer oil has been widely used for many years due to its excellent electrical insulating properties. It is derived from crude oil and undergoes a refining and purification process to meet industry standards. Mineral oil has a high flash point and is non-toxic making it safe to handle. It also offers good heat transfer and cooling capabilities thereby effectively dissipating the heat generated during transformer operation.

Another type of oil used in transformers is silicone-based oil. Compared to mineral oil silicone oil has a higher flash point lower flammability and superior oxidation stability. It performs well under severe operating conditions such as extreme temperatures and increased moisture levels making it suitable for critical applications.

Vegetable oil is emerging as an environmentally friendly alternative to traditional transformer oils. Made from renewable resources such as soybean rapeseed or coconut oil it is biodegradable and poses minimal risk to the environment in the event of a transformer failure. Vegetable oil also exhibits good dielectric strength and offers enhanced thermal conductivity leading to improved cooling efficiency.

Ester fluids including synthetic ester oils are gaining popularity as well. They are composed of fatty acid esters derived from vegetable or synthetic sources. Ester fluids have excellent fire safety characteristics high biodegradability and low toxicity levels. Additionally they exhibit good dielectric strength and are resistant to moisture ingress thereby enhancing transformer reliability and longevity.

Choosing the right oil type for a transformer depends on several factors including the application load requirements safety regulations and environmental considerations. Manufacturers often conduct extensive testing and analysis to determine the most suitable oil for each particular transformer design and application.

Regular oil testing and maintenance are essential to monitor the oil's condition and ensure that it is performing optimally. Monitoring parameters such as moisture content acidity level dielectric strength and dissolved gas analysis enable early detection of potential issues allowing for timely corrective action.

In conclusion the type of oil used in oil-filled transformers is a critical aspect of their performance and reliability. Whether it is mineral oil silicone-based oil vegetable oil or ester fluids each type offers specific benefits depending on the application requirements. Proper maintenance and monitoring of the oil are key to maximizing the transformer's lifespan and ensuring the continuous supply of electricity.

Standard technical specification for oil type transformers:

1. General Information:

a. Transformer Type: Oil immersed three-phase

b. Rated Power: [Specify the rating of the transformer in kVA]

c. Primary Voltage: [Specify the voltage level for the primary winding in volts]

d. Secondary Voltage: [Specify the voltage level for the secondary winding in volts]

e. Frequency: [Specify the operating frequency in Hertz]

f. Cooling Method: ONAN (Oil Natural Air Natural)

g. Standards: The transformer shall comply with the relevant international standards such as IEC ANSI or NEMA.

2. Construction:

a. Core: Laminated type with high-grade cold-rolled grain-oriented silicon steel

b. Winding Material: Copper or aluminum conductor

c. Insulation: High-quality cellulose-based insulation system with a minimum insulation class of class A (105°C)

d. Tank: Welded steel tank with corrosion-resistant coating designed for oil-tightness

e. Cooling System: Radiators or fans for natural or forced air circulation depending on the rating and cooling requirements

f. Oil Preservation: The transformer shall be subjected to a vacuum treatment and filled with refined mineral oil complying with relevant standards

3. Ratings and Performance:

a. Rated Power Factor: [Specify the rated power factor]

b. Efficiency: The transformer shall have an efficiency of not less than [Specify the minimum efficiency in percentage] at full load

c. Impedance: The impedance shall be specified as a percentage of the rated voltage and current at the rated frequency

4. Electrical Connections:

a. Primary Connections: [Specify the type and arrangement of primary connections]

b. Secondary Connections: [Specify the type and arrangement of secondary connections]

c. Tap Changer: [Specify the type and range of tap changer if applicable]

5. Insulation Levels:

a. Power Frequency Withstand Voltage: [Specify the power frequency withstand voltage level for primary and secondary windings]

b. Impulse Withstand Voltage: [Specify the impulse withstand voltage level for primary and secondary windings]

c. Partial Discharge: The transformer shall be designed to minimize partial discharge levels within acceptable limits

6. Protection and Monitoring:

a. Buchholz Relay: [Specify if the transformer is equipped with a Buchholz relay for detecting internal faults]

b. Temperature Monitoring: The transformer shall be equipped with suitable temperature monitoring devices such as winding temperature indicators (WTI) and oil temperature indicators (OTI)

c. Overcurrent Protection: [Specify the type of overcurrent protection scheme if applicable]

7. Testing and Acceptance:

a. Factory Acceptance Tests: The transformer shall undergo routine tests as per the relevant standards including measurement of impedance insulation resistance ratio tests winding resistance and applied voltage tests

b. Type Tests: The transformer shall also undergo type tests including short circuit withstand test temperature rise test and lightning impulse test as per the relevant standards

8. Documentation:

a. Technical Manuals: The supplier shall provide comprehensive technical manuals containing detailed information about the transformer installation operation maintenance and troubleshooting guidelines

b. Drawings: The supplier shall provide detailed engineering drawings including mechanical electrical and assembly drawings

Note: This is just a sample specification and the actual technical requirements may vary based on project-specific needs and the relevant standards and regulations. It's important to consult with electrical engineers and follow local regulations when preparing technical specifications for oil type transformers.