1 Answer
Dielectric failure of highly purified transformer oil can occur due to several reasons, despite the oil being purified. Here are the main causes:
1. Contamination
- Moisture: Even trace amounts of moisture can significantly reduce the dielectric strength of the oil. Water in the oil reduces its ability to resist electrical breakdown, leading to dielectric failure.
- Dissolved Gases: The presence of dissolved gases like hydrogen, methane, or carbon monoxide (often formed due to overheating or arcing) can lead to a breakdown of the oil's insulating properties.
2. Temperature
- Overheating: Transformer oil operates within a temperature range, and exceeding this range can cause the oil to break down. Higher temperatures can lead to the formation of carbon and other contaminants that degrade the oil's dielectric strength.
- Thermal Aging: Prolonged exposure to high temperatures can cause oil to lose its insulating properties due to oxidation or the breakdown of the chemical composition.
3. Electrical Stress
- Partial Discharges: Small electrical discharges within the oil, known as partial discharges, can create ionized regions that gradually degrade the oil's dielectric properties over time.
- Overvoltage Conditions: If the transformer experiences overvoltage or surges beyond its rated capacity, the dielectric strength of the oil can be exceeded, leading to a breakdown.
4. Chemical Breakdown
- Oxidation: Oil can react with oxygen in the air, especially at high temperatures, leading to the formation of acids, sludge, and other byproducts. This process, called oxidation, reduces the oil's insulating capability.
- Contaminants from the Transformer: Internal components like paper insulation, metal surfaces, and other materials in the transformer can release chemicals or particulate matter that contaminate the oil and degrade its dielectric properties.
5. Inadequate Oil Maintenance
- Insufficient Filtration: If the oil is not regularly filtered or replaced, small particles and contaminants can accumulate, leading to dielectric failure.
- Poorly Sealed Transformer: A poorly sealed transformer may allow air, moisture, or other contaminants to enter, affecting the oil's dielectric properties.
6. Aging of the Oil
- Degradation Over Time: Even highly purified oil ages over time. As the oil ages, its ability to resist electrical breakdown diminishes, and it may need to be replaced or rejuvenated.
7. Presence of Free Carbon
- Carbon Formation: When transformer oil is exposed to arcing or high temperatures, it may form free carbon. This carbon can act as a conductive material, lowering the oil’s dielectric strength and increasing the risk of electrical failure.
In conclusion, dielectric failure in transformer oil often results from a combination of contaminants, electrical stress, temperature variations, and chemical changes. Proper maintenance and regular monitoring of the oil quality can help prevent these issues.
1. Contamination
- Moisture: Even trace amounts of moisture can significantly reduce the dielectric strength of the oil. Water in the oil reduces its ability to resist electrical breakdown, leading to dielectric failure.- Dissolved Gases: The presence of dissolved gases like hydrogen, methane, or carbon monoxide (often formed due to overheating or arcing) can lead to a breakdown of the oil's insulating properties.
2. Temperature
- Overheating: Transformer oil operates within a temperature range, and exceeding this range can cause the oil to break down. Higher temperatures can lead to the formation of carbon and other contaminants that degrade the oil's dielectric strength.- Thermal Aging: Prolonged exposure to high temperatures can cause oil to lose its insulating properties due to oxidation or the breakdown of the chemical composition.
3. Electrical Stress
- Partial Discharges: Small electrical discharges within the oil, known as partial discharges, can create ionized regions that gradually degrade the oil's dielectric properties over time.- Overvoltage Conditions: If the transformer experiences overvoltage or surges beyond its rated capacity, the dielectric strength of the oil can be exceeded, leading to a breakdown.
4. Chemical Breakdown
- Oxidation: Oil can react with oxygen in the air, especially at high temperatures, leading to the formation of acids, sludge, and other byproducts. This process, called oxidation, reduces the oil's insulating capability.- Contaminants from the Transformer: Internal components like paper insulation, metal surfaces, and other materials in the transformer can release chemicals or particulate matter that contaminate the oil and degrade its dielectric properties.
5. Inadequate Oil Maintenance
- Insufficient Filtration: If the oil is not regularly filtered or replaced, small particles and contaminants can accumulate, leading to dielectric failure.- Poorly Sealed Transformer: A poorly sealed transformer may allow air, moisture, or other contaminants to enter, affecting the oil's dielectric properties.
6. Aging of the Oil
- Degradation Over Time: Even highly purified oil ages over time. As the oil ages, its ability to resist electrical breakdown diminishes, and it may need to be replaced or rejuvenated.7. Presence of Free Carbon
- Carbon Formation: When transformer oil is exposed to arcing or high temperatures, it may form free carbon. This carbon can act as a conductive material, lowering the oil’s dielectric strength and increasing the risk of electrical failure.In conclusion, dielectric failure in transformer oil often results from a combination of contaminants, electrical stress, temperature variations, and chemical changes. Proper maintenance and regular monitoring of the oil quality can help prevent these issues.