What are the factors that affect the insulation of transformer oil?
Thermal and mechanical stresses have as a result the oxidation of oil and the degradation of its insulating and cooling properties. Humidity and foreign particles also consist factors contributing to the decrease of oil dielectric strength and its premature failure.
What are the factors affecting the life of transformer?
Main factors affecting the operating life of transformers
- Pay attention to the voltage is too high to accelerate the aging of the transformer.
- Adjust transformer load to achieve the desired life.
- Good maintenance helps you get the most out of your life.
What are the main properties of transformer oil?
The properties (or parameters) of transformer oil are:
- Electrical properties: Specific resistance, dielectric strength, dielectric dissipation factor.
- Chemical properties: Water content, acidity, sludge content.
- Physical properties: Interfacial tension, viscosity, flash point, pour point.
Which factors reduce the breakdown strength of transformer oil?
The considered factors that affect the breakdown voltages are temperature, permittivity, tan δ, viscosity, velocity of the particles. The gap length is considered as 10mm and the factors are optimized around breakdown voltage of 50KV. Generally, oil having breakdown less than 50KV requires oil reconditioning.
What are the agents which contaminate transformer oil?
Contamination commonly found in transformer oil includes water and particulate. The presence of either of these contaminants will reduce the insulating qualities of your transformer oil.
What is the main cause of noise in the transformer?
The main cause of transformer noise is the Magnetostriction Effect. The alternation current that flows through an electrical transformer’s coils has a magnetic effect on its iron core. It causes the core to expand and contract, resulting in a humming sound.
Which loss is independent of frequency?
Copper losses are independent of the frequency and directly proportional to the load current.
What is the power factor of transformer oil?
0.5\%
Modern oil-filled power transformers should have power factors of 0.5\% or less, corrected to 20°C (68°F), for individual windings to ground (CH and CL) and interwinding insulations (CHL). The National Grid transformer specification states that the power factor of the insulation system shall not exceed 0.5\% at 20°C.
What is the most important factor that affects the electrical strength of an insulating oil?
Velocity, impurities, electrodes’ shape and the type of applied voltage are among the factors documented to have a significant effect on breakdown strength. Liquid dielectrics are used as insulating media in high voltage systems as they can easily fill any space and can also be circulated to dissipate heat.
Which of the following affects the breakdown voltage of the transformer oil most *?
In addition, the shape of the electrodes, the size of the electrodes, the distance between the electrodes, and the shape and capacity of the oil cup all have an effect on the breakdown voltage.
What is the breakdown voltage of transformer oil?
It is confirmed that the dielectric breakdown voltage of pure transformer oil is about 10 kV with a gap distance of 1 mm between electrodes.
Why do electrical transformers hum?
The core expands and contracts with the alternating current, which causes a humming sound. As the transformer ages, the layers within the core of the transformer begin to break apart and separate from one another. This causes the vibrations to get louder.
Why does the water content in transformer oil increase with temperature?
But in a loaded transformer, oil becomes hotter, hence the solubility of water in oil increases. As a result, the paper releases water and increase the water content in transformer oil. Thus the temperature of the oil at the time of taking a sample for the test is critical.
What are the properties of insulating transformer oil?
Some specific properties of insulating oil should be considered to determine the serviceability of the oil. The properties (or parameters) of transformer oil are: Electrical properties: Dielectric strength, specific resistance, dielectric dissipation factor. Chemical properties: Water content, acidity, sludge content.
What is the minimum breakdown voltage of transformer oil?
Dry and clean oil gives BDV results, better than the oil with moisture content and other conducting impurities. Minimum breakdown voltage of transformer oil or dielectric strength of transformer oil at which this oil can safely be used in transformer, is considered as 30 KV.
What is the dielectric dissipation factor of transformer oil?
Minimum standard specific resistance of transformer oil at 90 o C is 35 × 10 12 ohm–cm and at 27 o C it is 1500 × 10 12 ohm–cm. Dielectric dissipation factor is also known as loss factor or tan delta of transformer oil. When a insulating materials is placed between live part and grounded part of an electrical equipment, leakage current will flow.
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