What is the breakdown voltage of insulating oil?
Breakdown voltage is also an index to evaluate the electrical performance of insulating oil. It can be used to judge the pollution degree of suspended solids such as water in insulating oil, and check the drying and filtering degree of oil before oil injection.
When an increasing voltage is applied to a clean, dry oil, the electrons are emitted at the negative extremum of the voltage, and when the electrons have enough energy, the oil molecules are micronized and dissociated.
Therefore, the whole dissociation process increases with the increase of voltage. When a certain voltage is reached, a large amount of conductive current will be generated to form an arc. This phenomenon is called breakdown, and the breakdown voltage is called breakdown voltage.
If there is water or solid in the oil, the breakdown voltage will decrease because the conductivity of water and solid is higher than that of oil. The breakdown voltage of oil in operation is a dangerous signal of transformer.
根据国内外变压器油标准，击穿电压一般为40 ~ 50kV，高压一般为60kV以上。
According to the standard of transformer oil at home and abroad, the breakdown voltage is generally 40 ~ 50 kV, and the high voltage is generally more than 60 kV.
What is capacitance?
Dielectric constant, also known as dielectric constant (or relative dielectric constant), refers to the ratio of capacitance of capacitor to vacuum capacitance of the same plate when the insulating oil is filled between and around the two electrodes of capacitor.
Different insulating oils have different dielectric constants, which usually vary with temperature and frequency. In practical application, the smaller the change of dielectric constant of capacitor oil with temperature and frequency, the better.
If the capacitance of the capacitor changes greatly and the sense of safety is lost, corresponding measures should be taken.
What is the dielectric loss coefficient of insulating oil?
The dielectric loss coefficient of the insulating oil is expressed by the tangent value of the dielectric loss angle, which is the angle between the applied AC voltage and the current passing through the insulating oil.
Transformer oil is the insulation medium of transformer or similar equipment. Under the action of electric field change produced by alternating current circuit, only weak capacitive current in medium can be passed theoretically.
It is ahead of the applied voltage phase of 90 C and belongs to reactive current. It only affects the power factor of the equipment and does not produce power loss, but in fact there will be more or less energy in the oil.
A polar molecule that causes an internal charge imbalance, or is caused by an electric field acting as a conductor, producing a resistive conductive current (or leakage current).
In the same phase with current and voltage, there are active current and power loss, which is called dielectric loss of insulating oil, and the ratio of conductive current to capacitive current (Jian), which is called dielectric loss factor.
Insulation loss coefficient is an important index to evaluate the electrical performance of insulating oil, especially the deterioration or pollution of insulating oil has more obvious effect on the change of insulation loss coefficient of insulating oil.
There are few polar substances in the new oil, and the dielectric loss coefficient is generally 0. Between 0001 and 0.001. Operating oil medium loss coefficient is too large to take treatment measures.
What does the change of interfacial tension of transformer oil explain?
(1) The interfacial tension refers to the tension between insulating oil and insoluble water.
(2) The interfacial tension of oil products will be affected by the use of oxidation products and sludge after aging.
(3) The interfacial tension of transformer oil can generally reach 40-50 mN/m. After oil aging, the interfacial tension of transformer oil decreases gradually due to the formation of various polar substances such as organic acids (COOH) and alcohols (OH).