High Voltage Test Transformer Protection
High-voltage test transformers should pay special attention to their fire safety measures.
1. The fire separation distance should not be less than 5m between a high-voltage test transformer with an oil volume of more than 2500kg and oil-filled electrical equipment with an oil volume of 600kg-2500kg.
2. When the fire separation distance between two adjacent high-voltage test transformers does not meet the requirements, a fire partition wall or a fire water curtain shall be installed on the top of the fire partition wall. Only fire partition walls or fire water curtains may be set between single-phase high-voltage test transformers.
3. When the distance between the outer wall of the factory building and the outer edge of the outdoor high-voltage test transformer is less than that specified in the specification table, the outer wall should use a firewall. The distance between the wall and the outer edge of the transformer should not be less than 0.8m.
4. When the outer wall of the factory building is within 5m from the outer edge of the high-voltage test transformer, no doors, windows and holes should be opened below the horizontal line of the total thickness of the transformer plus 3m and within the range of plus 3m on both sides of the outer edge; The fire resistance rating of the upper doors and fixed windows shall not be lower than 0.9h.
5. When the oil volume of a high-voltage test transformer and other oil-filled electrical equipment is more than 1000Kg, an oil storage pit and a public oil collection pool should be set up.
6. The high-voltage test transformer shall be equipped with a fixed fire extinguishing system such as water spray according to the current relevant specifications. The oil-immersed factory transformer should be installed in a separate room, and the door of the room should be a class B fire door that opens outwards, and directly leads to the outside of the house or corridor, and should not open to other rooms.
According to the number of phases of a single transformer, it can be divided into three-phase transformers and single-phase transformers. In a three-phase power system, a three-phase transformer is generally used. When the capacity is too large and is limited by transportation conditions, three single-phase transformers can also be used to form a transformer group in a three-phase power system.
According to the number of windings, it can be divided into two-winding transformers and three-winding transformers. The usual transformers are double-winding transformers, that is, there are two windings on the iron core, one is the primary winding and the other is the secondary winding. The three-winding transformer is a transformer with a larger capacity (over 5600 kVA), which is used to connect three different voltage transmission lines. In special cases, there are also transformers with more windings.
According to the structure, it can be divided into iron core transformers and iron shell transformers. If the winding is wrapped around the iron core, it is an iron core transformer; if the iron core is wrapped around the winding, it is an iron shell transformer. The two are only slightly different in structure, and there is no essential difference in principle. Power transformers are iron core type.
According to the insulation and cooling conditions, it can be divided into high-voltage test transformers and dry-type transformers. To enhance insulation and cooling conditions, both the core and windings of the transformer are immersed together in a tank filled with transformer oil. In special cases, such as street lamps and mine lighting, dry-type transformers are also used.
In addition, there are various special transformers for special purposes. For example, high-voltage transformers for testing, transformers for electric furnaces, transformers for welding and transformers used in thyristor lines, voltage transformers and current transformers for measuring instruments.
During the operation of the high-voltage test transformer, the heat of the winding and iron core is first transferred to the oil, and then to the cooling medium through the oil. The cooling methods of high-voltage test transformers can be divided into the following types according to the size of the capacity:
1. Natural oil circulation and natural cooling (oil-immersed self-cooling)
2. Natural oil circulation air cooling (oil-immersed air cooling)
3. Forced oil circulating water cooling
4. Forced oil circulation air cooling
