One is the cause of partial discharge

Due to the insulator and metal body in baoding dry type transformer often have some sharp angles and burrs, the charge will be concentrated on the sharp Angle or burr under the action of the electric field intensity, resulting in the transformer partial discharge high electric field intensity. The charging capacity is concentrated at a sharp Angle, leading to discharge.

In the case of vacuum casting epoxy resin casting insulation baoding dry type transformer, if the process control is not good, there will be bubbles inside and partial discharge will occur. In epoxy insulators, there are usually small air gaps, which are usually the dielectric constants of the bubbles. It is much lower than the insulator, which makes the bubble in the insulator bear much higher electric field intensity than the neighboring insulation material, and easy to reach the breakdown degree, so that the bubble first discharge.

If electrical connections between conductors are not well connected to each other, discharges may occur, the most serious of the metal suspension potentials.

Air humidity is too large, the insulation strength of the conversion part is not enough, or the transformer insulation is damaged during installation; The idling time of transformer is too long, the moisture content of insulation material exceeds bid, whole is affected by damp, also can affect partial discharge.

The insulation structure of baoding dry-type transformer is too high in the design of interlayer or turns, such as the unreasonable design of insulation structure; If not the required fake material, select the quality of the insulation material; The level of winding and drying and casting process is not in place; Assembly technology level is not well assembled, such as the production of high and low voltage leads have burr or distance will affect the local discharge increase.

The other is the danger of partial discharge

There are multiple types of firings within the bureau. One of them is a pattern of partial discharge occurring on an insulating surface. If the energy is high, leaving a small discharge on the surface of the insulator can affect the life of the test transformer. The other type is a high intensity discharge on a cavitation or sharp electrode, and a concentrated partial discharge at several points is a corrosive discharge. This discharge can be deep into the insulation board layer and deep, and eventually lead to breakdown. Partial discharge is the main cause of insulation aging and breakdown. Short term discharge will not cause damage to the dielectric of the whole channel, and the electrolysis of discharge accelerates the oxidation of insulation and corrodes insulation, thus reducing the service life of the test transformer. The degree of damage depends on discharge performance and failure mechanism of discharge insulation. For example, the dry type transformer discharge seriously exceeds the standard, its service life generally occurs in the internal insulation aging and breakdown burns within 3 to 5 years. Partial discharge of all China baoding dry type transformers must be strictly controlled.

Dry transformer partial discharge control

The main insulation material of baoding dry type transformer is epoxy resin, which is safe and reliable. It is widely used in power systems up to 35kV. There are many factors affecting partial discharge of dry type transformer. The main factors are raw material selection, product structure design and winding casting process. Through long-term design adjustment, process improvement, material selection and production practice, the following control measures are proposed for our company.

1. Winding structure design

1 main insulation distance. When designing transformer windings, high insulation between high and low voltage coils, phase of high voltage coils and grounding of high voltage coils should be ensured and taken into account. If conditions permit, the larger insulation distance will be. Moreover, the insulation of the inner wall of the high-voltage coil can be appropriately increased to effectively reduce the external field strength.

If the high voltage winding is wrapped with segmented copper foil, the interlayer voltage is equal to the interturn voltage. Generally, the voltage between the coils of 10-20 volts and segmented electromagnetic wire structure can reach 400-800 volts, and the number of segments is as large as possible. For example, the number of 35kV dry transformers can be 16-18 or more. And, of course, this leads to a very nice winding process. Annoying lock.

3 shielding control, using effective high and low basic education shielding layer can produce sharp Angle, burr and air gap on the shielding layer, can effectively eliminate tip and air gap discharge, reduce partial discharge, and should be reliably connected between high pressure shielding and high pressure outlet end, low pressure shielding and clamping. Shielding process should be clean, shielding layer should be smooth, no damage, no tip.

2. Coil winding, mold clamping and vacuum casting process control

The coil of baoding dry type transformer is the most critical. If the transformer is in good condition, the coil will fail first. The effect of vacuum casting on partial discharge is also very important. Even if the tiny pores affect the partial discharge of the transformer, the coil manufacturing and casting process must be strictly controlled.

Familiar with drawing and process when winding coils. You cannot change the number of revolutions between layers and the amount of insulation between layers! Material must be cleaned when winding.

When welding the terminal of the welding lead, please pay attention to the high temperature to destroy the insulation of the coil, and the welding wire must be sharpened with sharp burrs. Ensure that there is sufficient insulation between all leads to fill epoxy resin and keep the assembly process clean. The assembled molding coil is dried in strict accordance with the drying process.

3 epoxy resin composition and degassing, the process should be in strict accordance with the process rules, such as material proportion, temperature and degassing time, the whole process should closely follow the viscosity, vacuum, temperature and bubble phenomenon, from time to time to observe the temperature and vacuum degree of mixed irrigation. The temperature of the coil (die) is controlled within the specified process range. During pouring, the speed should not be too fast and bubbles should not form. During dynamic pouring, attention should be paid to the time from the completion of pouring to the completion of pouring. The viscosity of the resin is too high.

3. Selection and control of raw materials

The choice of electromagnetic wire can use enameled wire insulated flat copper or round copper wire design; Solenoid wire requires suppliers to use special deburring and testing equipment in production to minimize burrs.

2 epoxy resin material selection, different epoxy resin, their characteristics are different, on the product partial discharge and comprehensive performance of the impact is also very big, should choose a small viscosity, good toughness, high insulation strength resin. Resin model, technical department should develop the corresponding process specification.

Insulation control in coils. The quality of interlayer insulation in dry transformers is directly related to local discharge. Therefore, long-term stable suppliers should be selected to provide raw materials, because the transformer will not find any problems in the short term after the replacement of new materials.

Baoding zhongyi electric material manufacturing co., LTD. Is a professional transformer manufacturer in baoding transformer factory. It has professional production equipment, lifting equipment, tooling and testing equipment.

Main products: baoding dry type transformer, baoding box type transformer, baoding oil immersed transformer, baoding high and low voltage complete sets of equipment, etc. I companies to follow "detail decides success or failure, honesty molded the future" of the enterprise purpose, adhere to "quality measuring market, seek development by innovation, to management for efficiency" business philosophy, to make my company's products are widely used in power plant, chemical, construction, mining, metallurgy, rail transportation and other industries, to meet the needs of various users, my company rely on superior product quality, thoughtful service, won the trust of our customers.