Supporting facilities for rural Hermetically Sealed Oil Filled distribution transformers
Both developed and developing countries will have a gap between the rich and the poor, and there will be a large number of rural areas that are underdeveloped. Timely is a rural area, and the demand for electricity is also gradually increasing. In order to meet the electricity demand in rural areas and ensure stable power supply, it is necessary to prepare complete supporting facilities for rural Hermetically Sealed Oil Filled distribution transformers.
1.Fuse
Fuse should be installed on the high and low voltage sides of the distribution transformer. The vertical distance of the bottom of the high-voltage side fuse to the ground is not less than 4.5m, and the horizontal distance of each phase fuse is not less than 0.5m. In order to facilitate the operation and the fuse tube can be smoothly dropped after the fuse is blown, the drop fuse The axis should be at an angle of 15% to 30% from the vertical. The vertical distance of the bottom of the low-voltage side fuse to the ground is not less than 3.5m, and the horizontal distance of each phase fuse is not less than 0.2m.
The selection of the drop fuse switch fuse is selected according to the principle of “the fuse inside the distribution transformer or the high and low voltage outlet tubes can be quickly blown”. The fuse blow time must be less than or equal to 0.1s. If the distribution transformer capacity is below 100kVoA, the rated current of the high-voltage side fuse is selected 2 to 3 times of the rated current of the Satons transformer capacity; if the capacity is above 100kVoA, the rated current of the high-voltage fuse is 1.5~2 times of the rated current of the transformer capacity. . The low-voltage side fuse of the transformer is selected according to the rated current of the low-voltage side.
2. Arrester
Most of the external factors affecting the operation of Hermetically Sealed Oil Filled transformers come from lightning accidents. Therefore, the rural Hermetically Sealed Oil Filled distribution transformers should be equipped with lightning protection devices. The metal oxide surge arresters with no gaps and synthetic insulation jackets should be selected. The power frequency voltage withstand capability is strong, the sealing performance is good, and the protection characteristics are stable.
The high-voltage side arrester should be installed between the high-voltage fuse and the transformer, and as close as possible to the distribution transformer, but must be kept more than 0.5m from the transformer end cover, which not only reduces the influence of the down-conducting inductance on the transformer during lightning strikes, but also avoids The whole line is blacked out for maintenance and repair of the arrester, and it can also prevent the lightning arrester from damaging the transformer bushing. In addition, in order to prevent the low-voltage inverse wave and the low-voltage side lightning wave from invading, a low-voltage arrester should be installed in the low-voltage side distribution box, thereby protecting the distribution transformer and its total metering device.
3. Grounding device
In the current rural network transformation, rural small-capacity transformers are distributed. The lightning-damping 10kV distribution transformers are often subjected to lightning strikes. Because the grounding resistance is too large, the specified values are not met, and the lightning current cannot be quickly discharged into the earth, causing the arresters themselves to be disabled. The voltage is too high, or a high voltage drop occurs on the grounding resistance, causing the transformer to burn. Therefore, the grounding resistance of the grounding device must comply with the regulations. For 10kV distribution transformers: the grounding resistance should be no more than 10Ω for the capacity of 100kVoA and below; the grounding resistance should not exceed 4Ω for the capacity above 100kVoA. After the grounding device is finished, the grounding resistance test should be carried out. After passing the test, the earth can be backfilled. At the same time, the Hermetically Sealed Oil Filled transformer jacket must be well grounded, and the grounding of the casing should be tightened with bolts. It is not allowed to be welded directly for repair.
The underground part of the grounding device is composed of a horizontal grounding body and a vertical grounding body. The horizontal grounding body generally adopts four 40mm×4mm flat steels with a length of 5m, and the vertical grounding body adopts five 50mm×50mm×5mm lengths of 2.5m. The angle steel is welded to the horizontal ground every 5m.
The horizontal grounding body is buried deep in the soil by 0.6 to 0.8 m, and the vertical grounding body is driven into the ground on the basis of the horizontal grounding body. The grounding lead wire adopts 40mm×4mm flat steel. For the convenience of inspection and electricity safety, the transformer used for on-column installation should be located at the position of the channel under the rural distribution transformer.
ZTELEC introduced international advanced transformer technology in 2008, built a dust-free automation workshop, and adopted scientific management to ensure the quality of rural Hermetically Sealed Oil Filled distribution transformers.
1.Fuse
Fuse should be installed on the high and low voltage sides of the distribution transformer. The vertical distance of the bottom of the high-voltage side fuse to the ground is not less than 4.5m, and the horizontal distance of each phase fuse is not less than 0.5m. In order to facilitate the operation and the fuse tube can be smoothly dropped after the fuse is blown, the drop fuse The axis should be at an angle of 15% to 30% from the vertical. The vertical distance of the bottom of the low-voltage side fuse to the ground is not less than 3.5m, and the horizontal distance of each phase fuse is not less than 0.2m.
The selection of the drop fuse switch fuse is selected according to the principle of “the fuse inside the distribution transformer or the high and low voltage outlet tubes can be quickly blown”. The fuse blow time must be less than or equal to 0.1s. If the distribution transformer capacity is below 100kVoA, the rated current of the high-voltage side fuse is selected 2 to 3 times of the rated current of the Satons transformer capacity; if the capacity is above 100kVoA, the rated current of the high-voltage fuse is 1.5~2 times of the rated current of the transformer capacity. . The low-voltage side fuse of the transformer is selected according to the rated current of the low-voltage side.
2. Arrester
Most of the external factors affecting the operation of Hermetically Sealed Oil Filled transformers come from lightning accidents. Therefore, the rural Hermetically Sealed Oil Filled distribution transformers should be equipped with lightning protection devices. The metal oxide surge arresters with no gaps and synthetic insulation jackets should be selected. The power frequency voltage withstand capability is strong, the sealing performance is good, and the protection characteristics are stable.
The high-voltage side arrester should be installed between the high-voltage fuse and the transformer, and as close as possible to the distribution transformer, but must be kept more than 0.5m from the transformer end cover, which not only reduces the influence of the down-conducting inductance on the transformer during lightning strikes, but also avoids The whole line is blacked out for maintenance and repair of the arrester, and it can also prevent the lightning arrester from damaging the transformer bushing. In addition, in order to prevent the low-voltage inverse wave and the low-voltage side lightning wave from invading, a low-voltage arrester should be installed in the low-voltage side distribution box, thereby protecting the distribution transformer and its total metering device.
3. Grounding device
In the current rural network transformation, rural small-capacity transformers are distributed. The lightning-damping 10kV distribution transformers are often subjected to lightning strikes. Because the grounding resistance is too large, the specified values are not met, and the lightning current cannot be quickly discharged into the earth, causing the arresters themselves to be disabled. The voltage is too high, or a high voltage drop occurs on the grounding resistance, causing the transformer to burn. Therefore, the grounding resistance of the grounding device must comply with the regulations. For 10kV distribution transformers: the grounding resistance should be no more than 10Ω for the capacity of 100kVoA and below; the grounding resistance should not exceed 4Ω for the capacity above 100kVoA. After the grounding device is finished, the grounding resistance test should be carried out. After passing the test, the earth can be backfilled. At the same time, the Hermetically Sealed Oil Filled transformer jacket must be well grounded, and the grounding of the casing should be tightened with bolts. It is not allowed to be welded directly for repair.
The underground part of the grounding device is composed of a horizontal grounding body and a vertical grounding body. The horizontal grounding body generally adopts four 40mm×4mm flat steels with a length of 5m, and the vertical grounding body adopts five 50mm×50mm×5mm lengths of 2.5m. The angle steel is welded to the horizontal ground every 5m.
The horizontal grounding body is buried deep in the soil by 0.6 to 0.8 m, and the vertical grounding body is driven into the ground on the basis of the horizontal grounding body. The grounding lead wire adopts 40mm×4mm flat steel. For the convenience of inspection and electricity safety, the transformer used for on-column installation should be located at the position of the channel under the rural distribution transformer.
ZTELEC introduced international advanced transformer technology in 2008, built a dust-free automation workshop, and adopted scientific management to ensure the quality of rural Hermetically Sealed Oil Filled distribution transformers.