The transformer is a device that uses the principle of electromagnetic induction to convert AC energy into another type of electrical energy with different voltage and current parameters. Its internal insulation liners and brackets mostly use organic combustible materials such as paper, cotton yarn, cloth, wood, and a large amount of insulating oil, such as a transformer of 1000 kilowatts, about 0.012 cubic meters of wood, 40 kilograms of paper material, and insulating oil 1 Ton. Therefore, its fire hazard is flammable. Once a severe overload or short circuit occurs inside the transformer, the flammable insulating material and insulating oil will be affected by high temperature or arc, decompose and burn, and generate a large amount of gas, which will increase the pressure inside the transformer. As a result, the shell burst, a lot of fuel injection, and the burning oil flow further expands the fire hazard and causes a large area of ​​blackouts, affecting normal production and life. The causes of fire and explosion in transformers in operation are as follows:
(I) Insulation Damage 1. Coil Insulation Aging When the transformer is overloaded for a long time, it will cause the coil to heat up, gradually aging the insulation, causing a short circuit between the turns, a short circuit between the phases, or a short circuit to the ground, causing the transformer to burn and explode. Therefore, before the transformer is installed and operated, the insulation strength test shall be conducted and no overload shall be allowed during the operation.
2. Poor oil quality, too little oil The transformer insulation oil is inadvertently stored, transported, or operated and maintained so that the moisture, impurities, or other oils are mixed into the oil and the insulation strength is greatly reduced. A short circuit occurs when the dielectric strength drops to a certain value. Therefore, the insulating oil with a longer storage time must be tested before it is put into operation, such as moisture, impurities, viscosity, breakdown strength, dielectric loss angle, and dielectric constant. During operation, the oil quality should also be tested regularly. When problems are found, appropriate measures should be taken in time.
3. Insulation aging of iron core Damage to the insulation between silicon steel sheets, or damage to the bolt sleeve of the iron core, causing the iron core to generate a large eddy current, causing heat to increase the temperature, and will also accelerate the aging of the insulation.
The transformer core should be tested periodically for its dielectric strength (test methods and requirements are the same as those for the coil). When it is found that the insulation strength is lower than the standard, the bolt sleeve must be replaced or the core must be insulated.
4. Inadvertent maintenance, damage to the insulation When the core is inspected and repaired, the insulation of the coil and the porcelain casing are inadvertently damaged. If the porcelain casing is damaged, if it continues to operate, the flashover will be slight and the short circuit will occur. Therefore, special care should be taken when overhauling to prevent damage to the insulation. After the inspection is over, special personnel should check the tools (to prevent accidents from causing accidents in the tank), inspect the components, test the insulation, etc., and confirm that they are intact and safe and reliable before they can be put into operation. In addition, it is necessary to pay attention to the safety distance of the lead wire during overhaul to prevent flashover caused by insufficient distance and cause accidents.
(2) Poor contact of wires The joints inside the coil, the connection points between the coils and the contacts leading to the high and low voltage porcelain bushings and the contacts on the tap changer will cause local overheating if the contact is bad, or damage the insulation of the coils and cause a short circuit or Broken circuit.
(I) Insulation Damage 1. Coil Insulation Aging When the transformer is overloaded for a long time, it will cause the coil to heat up, gradually aging the insulation, causing a short circuit between the turns, a short circuit between the phases, or a short circuit to the ground, causing the transformer to burn and explode. Therefore, before the transformer is installed and operated, the insulation strength test shall be conducted and no overload shall be allowed during the operation.
2. Poor oil quality, too little oil The transformer insulation oil is inadvertently stored, transported, or operated and maintained so that the moisture, impurities, or other oils are mixed into the oil and the insulation strength is greatly reduced. A short circuit occurs when the dielectric strength drops to a certain value. Therefore, the insulating oil with a longer storage time must be tested before it is put into operation, such as moisture, impurities, viscosity, breakdown strength, dielectric loss angle, and dielectric constant. During operation, the oil quality should also be tested regularly. When problems are found, appropriate measures should be taken in time.
3. Insulation aging of iron core Damage to the insulation between silicon steel sheets, or damage to the bolt sleeve of the iron core, causing the iron core to generate a large eddy current, causing heat to increase the temperature, and will also accelerate the aging of the insulation.
The transformer core should be tested periodically for its dielectric strength (test methods and requirements are the same as those for the coil). When it is found that the insulation strength is lower than the standard, the bolt sleeve must be replaced or the core must be insulated.
4. Inadvertent maintenance, damage to the insulation When the core is inspected and repaired, the insulation of the coil and the porcelain casing are inadvertently damaged. If the porcelain casing is damaged, if it continues to operate, the flashover will be slight and the short circuit will occur. Therefore, special care should be taken when overhauling to prevent damage to the insulation. After the inspection is over, special personnel should check the tools (to prevent accidents from causing accidents in the tank), inspect the components, test the insulation, etc., and confirm that they are intact and safe and reliable before they can be put into operation. In addition, it is necessary to pay attention to the safety distance of the lead wire during overhaul to prevent flashover caused by insufficient distance and cause accidents.
(2) Poor contact of wires The joints inside the coil, the connection points between the coils and the contacts leading to the high and low voltage porcelain bushings and the contacts on the tap changer will cause local overheating if the contact is bad, or damage the insulation of the coils and cause a short circuit or Broken circuit.
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