What are the measures to reduce partial discharge in transformers?
1. Dust control
Foreign objects and dust are very important factors in causing partial discharge. The test results indicate that the diameter is ф one point five μ Under the action of an electric field, metal particles of m can generate discharges much greater than 500pC. Both metallic and non-metallic powders generate a concentrated electric field, which reduces the initial discharge voltage and breakdown voltage of the insulator. Therefore, it is very important to keep the environment and body clean during the manufacturing process of transformers, and dust must be strictly controlled. Strictly control the extent to which products are affected by dust during the production process, and establish a sealed and dustproof workshop.
2. Centralized processing of insulation parts
It contains metal dust, which is very important because once the insulation sheet adheres to the metal dust, it is difficult to completely remove it. Therefore, it is necessary to concentrate processing in the isolation workshop and set up an area that must be isolated from other dust producing areas.
3. Strictly control the machining burrs of silicon steel plates!
The transformer core parts are formed by longitudinal and transverse cutting. These cutting cuts have varying degrees of burrs. Burrs not only cause short circuits between chips, but also increase losses and increase the thickness of the iron core. More importantly, when the iron core is inserted into the magnetic yoke or subjected to vibration during operation, burrs may fall on the body and discharge may occur. Even if the burrs fall to the bottom of the box, they can be arranged in an orderly manner under the influence of an electric field, causing ground potential discharge. Therefore, the core burrs should be as small as possible. The core burrs of 110KV products should not exceed 0.03mm.
4. Lead wire, cold pressed terminal
The use of lead cold pressed terminals is an effective measure to reduce partial discharge. When using phosphorus copper welding, a large amount of spatter welding slag will be formed, which is easy to spread to the body and insulation parts. In addition, the source boundary area must be separated by submerged asbestos wires so that water can enter the insulation layer. If the moisture is not completely removed after the insulation winding, it will increase the partial discharge of the transformer.
5. Edge of rounded component
The purpose of rounding the edges of parts is to improve the field power distribution and increase the discharge starting voltage. Therefore, metal structural components such as clamps, pull plates, pads and bracket edges, pressure plates and outlet edges, the wall of the box riser, and the magnetic shielding cover inside the box wall in the iron core must be rounded Prevent the generation of iron filings due to friction. For example, the contact part between the lifting hole of the clamp and the hanging rope or hook should be circular.
6. Product environment and body coating during the final assembly process
After vacuum drying of the hull, it should be classified before packaging. The larger the product, the more complex the structure, and the longer the completion time. When the valve stem is compressed and the fasteners are tightened, the valve stem is exposed to air, during which moisture absorption and dust dispersion occur. Therefore, the vehicle body should be cleaned in dust-proof areas such as when completed (or exposed to air). If the time exceeds 8 hours, it must be dried again. After the hull is completed, the vacuum and fuel tank filling stages begin. Due to the fact that stem insulation materials absorb moisture during the stem trimming stage, it is necessary to dehumidify the stem. This is an important measure to ensure the insulation strength of high-voltage products. The method used is to vacuum the product. Determine the vacuum cleaning time based on the body,
7. Vacuum lubrication
The purpose of vacuum oiling is to inject transformer oil into the vacuum, eliminate dead corners in the insulation structure of the product by vacuuming the transformer, completely empty the air, and then completely absorb the transformer body. After oil injection, wait at least 72 hours before testing the transformer, as the permeability of the insulation material is related to the thickness of the insulation material, the temperature of the insulation oil, and the immersion time. The higher the penetration level, the less likely it is to ejaculate, so please ensure that sufficient absorption time has passed.
8. Sealing of fuel tanks and components
The quality of the sealing structure directly affects the leakage of the transformer. If there is a leakage point, water will inevitably enter the interior of the transformer, causing moisture absorption in the transformer oil and other insulation components, which is one of the factors of partial discharge. Therefore, it must meet reasonable sealing values.
The ZC-254B four channel partial discharge detector is suitable for AC and DC partial discharge detection and positioning of transformers, reactors, generators, transformers, bushings, GIS, lightning arresters, high-voltage switches, switchgear, and other high-voltage electrical equipment. Widely used in high-voltage electrical equipment manufacturers, power electronics high-tech enterprises, power supply companies across the country, and power science research institutes and other units.
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