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Research on Ventilation of Distribution Transformer Room 2

2. Countermeasures for transformer temperature rise and heat dissipation

In view of the above-mentioned reasons of transformer temperature rise and heat dissipation, we recommend the following measures to achieve the purpose of enhancing transformer heat dissipation and reducing transformer temperature rise.

Note that the ventilation area during the design of the transformer room refers to the effective ventilation area. The coefficient conversion between the window area and the effective ventilation area should be carried out during the civil design of the transformer room. (Grid or metal mesh cover: an increase of about 15%; with a grid plus shutter cover, an increase of about 50-70%.

It is recommended to increase the distance between the door of the transformer room and the rat-proof baffle>0.2㎝ to increase the area of the air inlet of the transformer room. It is also possible to open a few more air inlet windows outside the transformer room door and below the wall about 40 cm from the ground to increase the area of the air inlet.

Try to install the transformer between the air inlet and the air outlet to enhance the ventilation effect of the transformer.

Install large-capacity transformers on the ground, and use fences or screens for safety protection to prevent personnel from touching the live parts of the transformer. In this way, the transformer is placed in a lower temperature area in the room, which enhances the heat dissipation effect of the transformer.

The installation position of the exhaust fan should be far away from the air outlet above the transformer room, and ensure that the air convection path between the exhaust fan and the air inlet effectively passes through the transformer to increase the heat dissipation effect of the transformer.

The hundred pages above the door of the transformer room are cancelled to increase the effective convection in the room.

Use low-loss transformers as much as possible, or use a transformer with a wide heat sink with better heat dissipation effect.

Properly qualified production units can install large industrial fans and even air conditioners in the transformer room to achieve the effect of increasing the heat dissipation and cooling of the transformer room.

3. The area and volume of ventilation windows in the transformer room

High transformer room temperature may be one of the above-mentioned reasons. However, after analysis, we believe that the main reason is concentrated on poor ventilation, and poor ventilation has a great relationship with the area of ventilation. Therefore, the area and ventilation volume of the ventilation window in the transformer room are calculated and analyzed below.

According to the outlet temperature of the transformer room at 45°C and 40°C, the area of the inlet and outlet windows of the transformer room is calculated using the formula of "Building Electrical Equipment Installation and Debugging Technology", and compared with the area of the inlet and outlet windows in the national standard figure 88D264, and the result is obtained As follows: Since this calculation uses the parameters of the new S11 transformer, its loss is small. When the temperature difference between the inlet and outlet air temperature of the transformer room is 5℃, 10℃, 15℃, the area of the wind window calculated by this calculation is slightly smaller than the area of the national standard in 88D264 , In line with normal conditions.

The following is based on the above calculation results to calculate the ventilation requirements of the transformer room at different temperature differences.

(1) According to the formula (3-1) of the "Concise Ventilation Design Manual", G1 = 3600Q/[(tp-tj)Cb] to calculate the ventilation weight per hour.

(2) Divide the calculation result of the above formula by the density of air, and convert the weight of ventilation per hour into the volume of ventilation per hour, that is, G2 = G1/r, check Table 1-3 of the "Concise Ventilation Design Manual", dry air Density under pressure of 100kPa; density r = 1.11kg/m3 when dry air temperature is 35℃; density r = 1.092kg/m3 at 40℃; density r =1.056 kg/m3 at 50℃; at 45℃ The density can be substituted into the formula according to r = (1.092 + 1.056)/2 = 1.074 kg/m3. The data of natural ventilation of transformers of different capacities at different temperature differences can be obtained.

4, exhaust fan selection and configuration

From the calculation results, when the temperature difference between the inlet and outlet air of the transformer room is 15℃, the transformer of 1600kVA and below, the temperature difference between the inlet and outlet is 10℃, the transformer of 1000kVA and below, and the temperature difference between the inlet and outlet is 5℃, the transformer of 630kVA and below is installed in the transformer room. The area required for natural entry and exit of the wind window is relatively easy to meet, and there is no difficulty.

Add mechanical exhaust in the transformer room where it is difficult to get in and out of the windshield naturally. Mechanical exhaust volume G4 = G2×(1-k), G4 mechanical exhaust volume, G2 total exhaust volume, k is the ratio of the natural inlet and outlet windows of the transformer room to the total area. The maximum ratio of the inlet and outlet window area in the standard drawing is 1:1.5. The addition of mechanical exhaust only compensates for the exhaust air volume, and the area of the inlet window is not compensated. Therefore, the area ratio of the inlet and outlet windows can be 1:2, and the mechanical exhaust volume can be calculated. .

The ventilation of the transformer room is jointly completed by using louvers with inlet and outlet wind and mechanical exhaust. In summer and when the transformer load is full, the exhaust fan needs to be put into operation. When the inlet air temperature is 25°C and below or the transformer oil surface temperature is 90°C and below, the exhaust fan can be stopped. The fan chooses DGF type fan and is installed at the highest point on one or both side walls of the transformer room. The outdoor nozzle is perpendicular to the outer wall. The outdoor nozzle is equipped with a stainless steel mesh with a hole not larger than 10×10mm2. Calculations show that different numbers of exhaust fans are used for transformers of different capacities at different temperature differences to meet the needs of ventilation and heat dissipation.

5 Conclusion

The temperature rise and heat dissipation of the transformer are related to many factors, which are more complicated. We must clearly analyze the main reasons for the temperature rise, find a solution, and try our best to increase the heat dissipation to reduce the temperature rise, so as to reduce the loss of the transformer and increase the transformer. In terms of natural convection ventilation, we must pay more attention to effective ventilation area and effective convection channels to improve the effect of natural convection ventilation. When natural ventilation cannot be satisfied, we must adopt forced ventilation , When using mechanical ventilation, attention should be paid to the installation location of the exhaust fan and the amount of ventilation required at different temperature differences to achieve the purpose of forced ventilation to dissipate heat and reduce temperature.