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Views: 0 Author: Site Editor Publish Time: 2022-06-23 Origin: Site
The oil-immersed transformer is widely used equipment for power transmission and transformation in the power grid. Its price is expensive and its reliability directly determines the normal operation of the power grid. The heating of the Oil-immersed transformer during operation is an important reason for the gradual aging of its insulation system. From the perspective of power equipment renewal, the increase in the service time of the transformer will greatly reduce the cost of funds. The winding coil and iron core are the heat sources, while the transformer’s excessive internal temperature leads to a loss of the service life of the transformer. The transformer oil-paper insulation system is most affected by temperature changes, and the transformer hot-spot temperature reaches above the limit value. The deterioration of the insulation paper may lead to the failure of the insulation system. If monitoring and maintenance are not carried out in time, serious accidents will eventually occur. So what is the reason for the damage to the Oil-immersed transformer? Here are some answers.
This is the content list:
l The selected wire size and hardness are unreasonable
l Limitations in the core material, process efficiency, etc.
l Failure to achieve effective support for distribution transformer windings by pads and braces
l Due to the asymmetry of the tapping of the high and low voltage windings
l The influence of temperature on the thermal stability of winding short-circuit is not fully considered in the check calculation
l Neglect to check the short-circuit resistance after the closing of distribution transformers
In the design process of the power distribution transformer, the electromagnetic force damage caused by the rapid increase of the Oil-immersed transformerwinding short circuit is not fully considered the interlayer insulation fails.
Because some distribution transformer cores are made of amorphous alloy materials, affected by the material process, the Oil-immersed transformer winding can only be made into a rectangular or oval shape. Compared with the circular winding, the stability is poor, and it is easy to lose after a short circuit. Stable deformation occurs, and there is a lack of effective assessment and calculation methods.
Due to the influence of the processing technology, the end pads and struts of the Oil-immersed transformer windings are not effectively compressed and wound during the processing process, resulting in the lack of effective support for the windings during short-circuit impact, and instability is prone to occur.
The tap of the outer layer of the high-voltage winding of the power distribution transformer increases the lateral unbalanced ampere-turn of the winding, and the magnetic leakage is larger. This factor is greatly affected by the process and reduces the stability of the Oil-immersed transformer winding.
After the power distribution transformer is short-circuited, the windings are under adiabatic conditions, and the temperature of the Oil-immersed transformer windings rises sharply. According to GB1094.5, the maximum allowable temperature of the copper windings is 250 °C. At this time, the short-circuit resistance of the windings is greatly reduced. When the transformer windings are hot When the temperature is lower than 98°C, the aging coefficient will be reduced by half for every 6K decrease in temperature, and the life of the transformer will be doubled. When reclosing, the winding temperature can easily exceed 250℃, resulting in deformation and damage.
Reclosing means that after the short-circuit fault is not eliminated in time, after the initial short-circuit shock, the power distribution transformer will suffer a higher-intensity shock again in a short period. The secondary shock is affected by factors such as iron core remanence, short-circuit phase angle, etc. The current is greater than the initial short-circuit current, and the temperature of the winding will rise sharply in a short period, so the Oil-immersed transformer short-circuit accident is very likely to occur after reclosing.
The above is the relevant content about the causes of damage to the Oil-immersed transformer. If you are interested in an Oil-immersed transformer, please contact us. Our website is www.sntoom.com.
