1. What are the main components of an oil-immersed transformer?
The main components of a transformer include: iron core, windings, oil tank, conservator, breather, explosion vent pipe, radiators, insulating bushings, tap changer, Buchholz relay (gas relay), thermometer, and oil purifier, etc.
2. What is a fully insulated transformer? What is a graded insulation transformer (semi-insulated transformer)?
A graded insulation transformer (also called semi-insulated) is one where the main insulation level of the winding sections near the neutral point is lower than that of the end sections. In contrast, a transformer in which the insulation level is the same at both the line end and neutral end of the windings is called a fully insulated transformer.
3. What is the main function of transformers in power systems?
Transformers are used in power systems to change voltage levels to facilitate efficient power transmission. Step-up transformers raise the voltage to reduce line losses, improve economic efficiency, and enable long-distance transmission. Step-down transformers convert high voltages to the various levels required by users.
4. What hazards do cracks in bushings pose?
Cracks in bushings reduce dielectric strength, which can lead to further insulation damage and eventual complete breakdown. Water entering the cracks may freeze and expand, potentially rupturing the bushing. Therefore, bushing cracks pose a serious threat to the safe operation of transformers.
5. What are the chemical properties of SF6 gas?
Sulfur hexafluoride (SF6) gas is insoluble in water and transformer oil. At high temperatures, it does not react with oxygen, argon, aluminum, or many other substances. However, under electric arcs or corona discharge, SF6 decomposes into lower fluorides. These compounds can damage insulating materials and are highly toxic. SF6 decomposition is closely linked to moisture, so effective moisture-removal measures are required.
6. What is the function of the conservator in a transformer?
When the volume of transformer oil expands or contracts with temperature changes, the conservator stores and supplies oil to keep the main tank completely filled. It also reduces the oil’s contact surface with air, slowing down oil aging. An oil level gauge on the side of the conservator allows monitoring of oil level changes.
7. What is internal overvoltage?
Internal overvoltage occurs during the transition process when switching operations, faults, or other events cause a sudden change in system conditions from one steady state to another. Dangerous overvoltages may appear during this process. These overvoltages result from oscillations and buildup of electromagnetic energy within the system itself, which is why they are called internal overvoltages.
8. What is the function of high-voltage circuit breakers?
High-voltage circuit breakers can interrupt and close normal no-load and load currents in high-voltage circuits. During system faults, they work together with protection devices and automatic systems to rapidly clear fault currents, prevent fault escalation, and ensure safe system operation.