What is the relationship between the oil level of the transformer and the on load voltage regulation

The transformer above 10000kvr is equipped with gas protection when there is a bubble or fault inside the on-load voltage regulation, and the gas relay will send a signal (light gas action) or trip (heavy gas action).

The main role of transformer oil:

1) Insulating effect: Transformer oil has much higher dielectric strength than air. The insulating material is immersed in oil, which not only improves the dielectric strength, but also protects it from moisture.

2) Heat dissipation: The specific heat of transformer oil is large, and it is often used as a coolant. The heat generated during the operation of the transformer makes the oil close to the core and winding expand and rise, and the heat is dissipated through the radiator through the convection up and down of the oil to ensure the normal operation of the transformer.

3) Arc suppression: On the on-load voltage regulating switch of the oil circuit breaker and transformer, the arc will be generated when the contact is switched. Due to the good thermal conductivity of transformer oil, and under the action of high temperature of the arc, a large amount of gas can be contacted, resulting in a large pressure, which improves the arc extinguishing performance of the medium and makes the arc extinguish quickly.

1. The oil leakage of the transformer operation is serious, which will cause the oil level to drop.

2. The transformer is not tightly sealed and damaged, and the oil continues to overflow from the damaged place, which will cause the oil level to drop.

3. When the transformer changes the oil, the dirty oil outside the oil pillow enters the oil tank, which will cause the oil level to rise.

4. The oil in the oil pillow is easy to get wet, and the oil pillow will accumulate water, which will cause the oil level to rise.

Under normal circumstances, the oil level change of the transformer changes with the change of oil temperature. The change of oil temperature directly affects the volume of transformer oil, so that the oil level changes. Factors that affect changes in oil temperature (i.e., oil level) are load, ambient temperature, and the health of the cooling unit.

The oil level of the transformer changes with the change of oil temperature under normal circumstances, because the change of oil temperature directly affects the volume of transformer oil, so that the oil level in the oil standard rises or falls. Factors that affect changes in oil temperature include changes in load, changes in ambient temperature, internal faults, and the operation of cooling devices.

The oil level of the transformer is too low, and it is generally a transformer.

There is oil leakage, or there is gas in the oil tank when the transformer leaves the factory, or there is not enough penetration, and there is a false oil level.

The oil level of the transformer is too low: 1. It will lead to poor local heat dissipation of the transformer, local overheating, and burnout of the transformer after a long time.

2。The dielectric strength is insufficient, and the discharge occurs, resulting in insulation breakdown and burning the transformer.

45 thousand volts and about rated voltage or large volume of 12 thousand volt oil-immersed oil-immersed transformers are installed with oil storage cabinets, the oil volume of the oil storage tank is marked in about a few ways, connecting pipes, pointer oil level gauges, metal bellows. The connecting tube is to choose the principle of the communicator.

In the glass test tube, there is a bright red ball indicating the amount of oil, which is very visual; Some of the analogue oil level gauges immediately indicate the amount of oil remaining in the oil storage tank at the special point of the gauge hand, or match the curve according to different temperatures (usually several, matching the regions with different minimum ambient temperatures).

Calculate the amount of oil remaining in the oil conservator according to the gauge hand; The metal bellows type is marked with the top of the metal bellows to match the normal oil volume of the oil storage cabinet with different water temperature (usually the remaining oil of the oil storage tank is about 12% of its own oil weight).

35kV and above voltage level or 10kV oil-immersed transformer with large capacity are installed with oil storage cabinet, and the oil level indication of the oil storage tank has three ways: connecting pipe, pointer oil level gauge and bellows.

The first article of the national specification GB T6451-1995 "Technical Parameters and Requirements for Three-phase Oil-immersed Power Transformers" clearly stipulates that the structure of the oil conservator of the transformer equipped with the oil conservator shall be easy to clean inside. The volume of the oil conservator should ensure that the oil does not overflow at the ambient temperature of 40 full load, and when -30 is not put into operation, the oil should be visible when the oil level gauge is observed.

1. The connecting pipe adopts the principle of the connecting device, and there is a small red ball in the glass tube to indicate the oil level, which is very intuitive.

2. Some pointer oil level gauges directly mark the position of the pointer to indicate the amount of oil in the oil storage tank, or through different temperature corresponding curves (generally three, corresponding to different minimum ambient temperature areas: such as -30 °, +20 ° and +40 ° on the transformer oil level gauge refer to the normal oil level line of the transformer at an ambient temperature of -30 °, +20 ° and +40 ° respectively. ), according to the position of the pointer, the amount of oil in the oil storage tank is converted.

3. The top of the bellows indicates the normal oil level of the oil storage cabinet corresponding to different oil temperatures.

The curve graph of the oil level temperature of the large power transformer can be known by looking at it again.

According to different situations, there are almost few oil storage cabinets for 10kV oil-immersed transformers with a capacity of 630kva and below, so there is no need to observe the oil level; 35kV and above voltage level or 10kV oil-immersed transformer with larger capacity are installed with oil conservators, and the oil level indication of the oil conservator is probably in the following forms, such as connecting pipes, pointer oil level gauges, and bellows. The connecting pipe is based on the principle of the connecting device, and there is a small red ball in the glass tube to indicate the oil level, which is very intuitiveSome pointer oil level gauges directly mark the position of the pointer to indicate the amount of oil in the oil storage tank, or through different temperature corresponding curves (generally three, corresponding to different areas of the lowest ambient temperature), according to the pointer position to convert the amount of oil in the oil storage tank;The top of the bellows indicates the normal oil level of the oil storage tank corresponding to different oil temperatures (the oil volume of the general oil storage tank is about 10% of the oil weight of the body).

It varies from season to season, with slightly higher in summer and lower in winter.

The transformer oil level will be unstable during the working process, and the transformer oil temperature is abnormal: under normal conditions, the oil temperature is more than 10 degrees Celsius higher than usual or the load remains unchanged and the temperature continues to rise (under the condition that the cooling device is running normally), it can be judged that there is an abnormality inside the transformer. The main ones are:

1. Abnormal temperature caused by internal faults. Its internal faults, such as winding smashing or interlayer short circuit, coil discharge to the enclosure screen, internal lead joint heating, multi-point grounding of the iron core to increase eddy current overheating, seismic pressure gauge zero sequence unbalanced current and other factors cause abnormal transformer temperature and other factors. When these conditions occur, they will also be accompanied by gas or differential protection actions. When the fault is serious, it is also possible to inject oil into the explosion-proof pipe or pressure relief valve, and the transformer should be taken out of service immediately.

2. Abnormal ground temperature caused by abnormal operation of the cooler. The cooler system should be maintained and flushed to improve its cooling effect, due to abnormal operation or failure of the cooler, such as the submersible pump is out of operation, the fan is damaged, the radiator pipe is fouled, the cooling effect is not good, the radiator valve is not opened, the thermometer indication is out of order, and many other factors cause the temperature to rise.

Analysis of abnormal oil level of transformer insulating oil: abnormal oil level and oil leakage phenomenon of transformer during operation are relatively common, and inspections and inspections should be carried out from time to time, which are mainly manifested as: false oil level

The oil mark pipe is clogged;Oil pillow straw device clogged;Explosion-proof pipeline porosity blockage. Low oil level: severe oil leakage from the transformer;The staff failed to replenish the oil in time due to the need for work;The temperature is too low and the oil volume is insufficient, and the pressure gauge or oil pillow capacity is too small to meet the needs of operation.

Through the above points, it is to tell you why the transformer oil level is abnormal, which is more conducive to avoiding some small faults and problems that cannot be solved in time in your usual work.

Except for leaks, it is mainly related to temperature.

1. The oil level of the transformer is too low, which will cause light gas protection action.

2. When there is a serious shortage of oil, the core coil inside the transformer is exposed to air, which is easy to insulate and get wet, and affects the heat dissipation with load, resulting in lead discharge and insulation breakdown accidents.