Explosion proof measures and technical requirement

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Explosion proof measures and technical requirements for oil filled electrical equipment

in addition to the electrical part, oil filled electrical equipment also includes: shell and observation window, oil level indicator, oil drain hole, exhaust hole and other components. The shell (oil tank) of oil filled electrical equipment that needs to bear 4000 vehicles is used to protect the electrical components in the shell and transformer oil. It is generally made of non combustible materials (such as metal materials) and has a certain mechanical strength. The shell shall be able to effectively prevent external dust and moisture from invading the shell. Therefore, the enclosure should have a certain degree of protection, and its degree of protection is IP43. The oil level indicator on the shell is our pleasure to observe the oil level inside the equipment. The oil level inside the equipment directly affects the safe operation of electrical equipment. The oil level indicator is equipped with a maximum oil level mark and a minimum oil level mark. The maximum allowable oil level is the highest position that the oil level in the housing can reach. If the oil level exceeds this height, the oil will flow out. If the oil level in the shell is lower than the allowable minimum oil level, the electrical components installed in the shell that generate sparks and arcs during operation will expose the oil level, and the generated arcs and sparks cannot be isolated by the oil in the shell, which may ignite explosive mixtures above the oil level or outside the shell, which is very dangerous. Therefore, the minimum oil level marked by the oil level indicator is very important, and it is also a component that needs to be observed frequently in use. The oil level indicator mainly includes observation window, transparent parts and other structures. The observation window is set at a position that is not vulnerable to the impact of external force by 2 slightly pinching the two ends of the elastic paper shaft to remove the paper shaft. The structure should be firm and have a replaceable oil seal structure. The observation window is equipped with transparent parts, which must be made of glass or other transparent materials resistant to mechanical, thermal, chemical and other effects. Transparent parts must have the performance of not damaging, deforming and reducing transparency under the long-term action of transformer oil. In order to ensure the safe operation of the equipment, the shell shall be equipped with oil drain holes and exhaust holes. The oil drain hole and the exhaust hole are respectively used to discharge the excess oil and the gas released by the oil in the housing. The oil drain hole should be closed with bolts and have a good sealing effect on oil. The exhaust hole shall be provided with good dust and water-proof measures, and the protection grade is IP41. In order to prevent the loss of mineral oil in the equipment shell, sealing parts, such as gaskets and sealing rings, should be added on the shell where sealing is required. All seals shall be made of oil resistant materials. In order to realize explosion-proof of oil filled electrical equipment, the parts and components that generate sparks, arcs and dangerous temperatures during normal operation must be immersed below the oil level, and the immersion depth should not be less than 25mm, so as not to ignite the explosive gas mixture above the oil level and outside the shell. However, live parts that do not produce sparks, arcs or dangerous temperatures during normal operation can be immersed in oil or not. For live parts that are not immersed in oil, the electrical clearance and creepage distance shall comply with the values specified in the table. In order to ensure the safe operation of oil filled electrical equipment, for electrical equipment with a rated voltage of more than 1kV, all wire products passing through the oil surface are widely used in products widely used in nuclear power, petrochemical, chemical fertilizer, aviation and other fields, and good insulation should be added. The length of the insulation layer of the conductor is greater than 10mm above the maximum oil level and below the minimum oil level. The insulation structure and arrangement of the conductor shall be able to avoid any discharge on the oil surface, and also prevent the loss of oil in the shell caused by capillary or siphon. The insulating materials used for electrical components, cables and wires in contact with oil or oil gas in the shell must be oil resistant. The mineral oil used in the shell must be non combustible insulating oil. Under the rated operation state, the limit temperature of oil is not higher than +60 ℃ for t1~t5 group equipment; For T6 group equipment, not higher than 40 ℃. In any case, the allowable temperature of oil shall not exceed 100 ℃. The maximum surface temperature of oil and parts in contact with explosive gas mixture shall meet the specified value. Common oil filled electrical equipment include circuit breakers, controllers, load switches, starters and transformers. For switches and controllers, their allowable power-off capacity is generally not more than 75% of their safe on-off capacity. In order to ensure the safe operation of oil filled electrical equipment, the heating elements, main circuit starters, regulators and controllers under the oil immersion surface should be equipped with automatic protection devices. When the oil temperature in the shell exceeds +100 ℃, or the maximum surface temperature of the oil exceeds the value specified in the table, the protection device will automatically cut off the power supply. For non airtight oil filled transformers, oil expanders should be equipped. When the oil temperature rises, the oil level in the shell rises. When the maximum oil level is exceeded, the excess oil can be shunted into the oil expander without oil outflow. The transformer shall also be equipped with protective devices. When there is an internal fault in the transformer or its oil temperature exceeds the specified allowable value, the transformer can automatically cut off the power supply to ensure its safety

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