Discussion on ventilation of the hottest transform

2022-09-21
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Discussion on ventilation of transformer room

Abstract: some inappropriate practices and differences in specifications in people's design, coupled with the thousands of differences in ready-made transformer rooms, cause poor ventilation effect of transformer room. By looking for the problems existing in natural ventilation and forced ventilation, find out some solutions for ventilation and heat dissipation and the selection of exhaust air volume

key words: effective area of ventilation louver in transformer room forced ventilation exhaust volume with the progress of society and the continuous improvement of electrification, the phenomenon of insufficient capacity or overheating of transformer appears more and more frequently in power capacity, distribution and transformation equipment. It is incumbent on the power system to give full play to the existing equipment, reduce the failure rate of equipment, and supply power with high quality, stability, continuity and reliability. According to the investigation and statistics of transformer faults in a district substation; There were 79 transformer faults, including 53 faults caused by high transformer temperature, accounting for 67.09% of the total faults. Therefore, it is of great significance to discuss the temperature, ventilation mode and ventilation volume of the transformer room and correctly design the ventilation system of the transformer room to reduce the failure rate of the indoor distribution transformer. 1. The reason why the transformer room temperature is high is that the area of the ventilation window of the transformer room in the national standard figure 88d264 (hereinafter referred to as the national standard figure) is designed according to the conditions that the calculated temperature of the transformer room in summer ventilation is not more than +35 ℃ (calculated temperature of the inlet air), the outlet air temperature is 45 ℃, and the temperature difference between the inlet and outlet air is not more than 15 ℃. According to the regulations of the transformer manufacturer, the ambient air temperature of the transformer in normal use shall not exceed +40 ℃. The ventilation condition in the national standard drawing is 5 ℃ higher than the normal ambient temperature specified by the manufacturer. The transformer room designed according to the size of the transformer room in the national standard drawing does not meet the requirements of the transformer for the surrounding air temperature. The highest temperature in summer is also the time of the maximum electrical load. The air temperature around the transformer is high, the load is large, and the temperature rise of the transformer itself is too high, so the failure of the transformer is difficult to avoid. In the national standard drawing 88d264, the area of the ventilation window in the transformer room is given as the effective area, and the effective area coefficient of the ventilation window is less than 1. Some designs do not pay attention to the difference between the area and the effective area. During the design, conditions are proposed to the civil engineering according to the area required in the standard drawing, and the area of the ventilation window in the transformer room is discounted again. The area of ventilation window does not meet the requirements of transformer operation. Clause 9 of article 6.0.1 of GB stipulates that "the indoor passage of power distribution device shall be unobstructed, no threshold shall be set, and there shall be no pipeline irrelevant to the power distribution device". In some areas, in order to prevent the entry of small rodents, a 0.6m-high rat gate, namely the threshold, is set at the gate of the transformer room. The upper and lower shutters of the transformer room door are screened, and a large area of the air inlet shutter at the lower part of the transformer room door is just blocked, which makes the effective area of the air inlet window of the transformer room smaller and the ventilation effect worse. The size of the transformer room in the new substation is limited by the column spacing of the whole building. Some transformer rooms are too deep. The transformer is located far away from the air inlet and outlet louvers on the substation wall, which reduces the ventilation effect around the transformer. When the newly-built transformer room is part of the built standard plant, the design height of some transformer rooms is limited to a certain extent. For 1600KVA and 2000 KVA transformer rooms, bench layout is still required in some areas, and the ventilation effect is poor. In order to improve the distance between the incoming and outgoing terminals of the transformer to the ground, the transformer is installed on the steel platform. The indoor temperature of the transformer varies with the height from the ground. The higher the height from the ground, the higher the temperature. The transformer is installed on the steel platform and is in a higher position from the ground, making the transformer in a disadvantageous position of higher indoor temperature. Although an exhaust fan has been added next to the air outlet louver of the transformer room for forced ventilation, the efficiency of the exhaust fan has not been brought into full play due to the short circuit between the air flow of the exhaust fan and the air flow of the air outlet louver. The running loss of the transformer heats the indoor air, and the rise of the hot air forms a flow airflow channel with the inlet and outlet louvers. The larger the height difference of the inlet and outlet louvers, the higher the air flow speed, and the better the ventilation effect. Air inlet and outlet louvers are set at the lower part of the transformer room door and the wall surface of the top of the transformer room, but some transformer rooms also set louvers at the upper half of the transformer door, that is, in the middle of the upper and lower air inlet and outlet louvers, which reduces the ventilation effect of the louvers. The load supplied by the transformer increases year by year, and the transformer is overloaded, and the capacity of the transformer has not been increased in time. Fortunately, with the progress of science and technology and the improvement of transformer design and manufacturing technology, the loss of the transformer is decreasing, and the overload capacity is increasing, which alleviates the problems caused by the high temperature rise in some transformer rooms. However, some transformers still have the quality problem of high loss. 2. Countermeasures for transformer temperature rise and heat dissipation in view of the above reasons for transformer temperature rise and heat dissipation, we suggest the following measures to enhance transformer heat dissipation and reduce transformer temperature rise. Note that the ventilation area in the design of transformer room refers to the effective ventilation area. The coefficient conversion between window area and effective ventilation area should be carried out in the civil design of transformer room. (grid or metal cover: the increment is about 15%; the increment of grid plus louver cover is about 50 ~ 70%. It is recommended to increase the distance between the louver door of the transformer room and the rat guard plate by 0.2 cm to increase the area of the air inlet of the transformer room. You can also open several more air inlet windows outside the transformer room door and under the wall about 40cm close to the ground to increase the area of the air inlet. Try to install the transformer between the air inlet and the air outlet It is very important for customers to better understand the strength of the company. The large capacity transformer shall be installed on the ground and fenced or covered for safety protection to prevent personnel from touching the live parts of the transformer. In this way, the transformer is placed in the area with lower indoor temperature, which enhances the thermal effect of the transformer walking in the direction of opening. 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, so as to increase the heat dissipation effect of the transformer. Cancel the hundred pages above the door of the transformer room to increase the effective convection in the room. Try to use a transformer with low loss, or a transformer with good heat dissipation effect by using bandwidth fins. Qualified production units can install large industrial fans or even air conditioners in the transformer room to increase

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