High-voltage wall-through porcelain bushing

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High - voltage wall - through porcelain bushings are very important auxiliary equipment in high - voltage transformers. The following is a detailed introduction for you: ### Structural Characteristics

- **Porcelain Sleeve**: As the main insulating component, it is usually made of high - strength electrical porcelain, has good insulation performance and mechanical strength, and can withstand high voltage and external mechanical stress. The shape of the porcelain sleeve is generally a hollow cylinder with a smooth surface to prevent the concentration of electric field and the occurrence of creeping discharge.

- **Conductor**: The conductor passing through the center of the porcelain sleeve is the current transmission channel, and is generally made of metal materials with good electrical conductivity such as copper or aluminum. The surface of the conductor usually undergoes special treatment, such as silver plating, to reduce the contact resistance and improve the electrical conductivity.

- **Flange**: Located at both ends of the porcelain sleeve, it is used to fix the porcelain sleeve and connect the transformer oil tank and the external circuit. The flange is generally made of metal materials, has sufficient strength and sealing performance to ensure that the insulating oil inside the transformer will not leak, and at the same time ensure good electrical connection.

### Working Principle - The main function of the high - voltage wall - through porcelain bushing is to lead the high - voltage lead inside the transformer out of the oil tank and connect it with the external high - voltage line, while ensuring the insulation performance and safe operation inside the transformer.

- During operation, the insulating medium (such as air, insulating oil, etc.) inside the porcelain sleeve can effectively isolate the high - voltage conductor from the surrounding environment and prevent the occurrence of current leakage and short - circuit accidents. - The umbrella - skirt structure on the surface of the porcelain sleeve can increase the creepage distance, improve the insulation performance, and prevent the surface discharge phenomenon in a humid or dirty environment.

### Main Parameters - **Rated Voltage**: It refers to the maximum effective value of the voltage at which the porcelain bushing can operate stably for a long time. There are usually different levels such as 10 kV, 35 kV, 110 kV, and 220 kV. The selection of its value depends on the rated voltage of the transformer and the voltage level of the power system where it is located.

- **Rated Current**: It represents the maximum effective value of the current that the porcelain bushing can pass through for a long time under normal working conditions. It determines the conductive capacity of the porcelain bushing and the capacity of the matching transformer.

- **Creepage Distance**: It refers to the shortest path between two conductive parts measured along the insulating surface or between the conductive part and the equipment protection interface. The size of the creepage distance directly affects the insulation performance of the porcelain bushing. Generally speaking, the higher the rated voltage, the longer the required creepage distance.

Application Scenarios - Widely used in substations, power plants and power supply systems of industrial enterprises of various voltage levels, it is an important bridge connecting transformers and external power grids.

- In indoor substations, high - voltage wall - through porcelain bushings can be installed on walls or switch cabinets to connect transformers with indoor high - voltage buses or cables; in outdoor substations, porcelain bushings are usually installed on the outgoing line bushing box of the transformer and connected with overhead transmission lines.

### Selection Points - **Voltage Level Matching**: High - voltage wall - through porcelain bushings of the corresponding voltage level must be selected according to the rated voltage of the transformer to ensure that they can withstand the operating voltage of the system and avoid accidents such as insulation breakdown.

- **Current Capacity Adaptation**: The rated current of the porcelain bushing should not be less than the rated current of the transformer to meet the current transmission requirements during the normal operation of the transformer and prevent overheating damage caused by overload.

- **Consideration of Environmental Conditions**: If the operating environment is relatively harsh, such as humid, dusty, and salty - foggy, porcelain bushings with better insulation performance and anti - pollution flashover ability should be selected, or corresponding protective measures should be taken.

- **Mechanical Strength Requirements**: For porcelain bushings installed outdoors or those that may be subjected to relatively large mechanical stress, it is necessary to consider whether their mechanical strength can meet the requirements to prevent damage under the action of wind load, earthquake and other external forces.