Handling Fires in Dry-Type Transformers
1. Fires Caused by Insulation Aging (Fire faults in dry-type transformers are relatively common during operation)
Statistical analysis shows that 50% of burnt dry-type transformers are caused by insulation aging leading to breakdown. During operation, dry-type transformers must withstand the heat generated by the applied electric field, no-load losses, and load losses, as well as the influence of the environment (such as air temperature) on the insulation. The insulation material ages under the influence of electric field strength, heat, and other factors, gradually leading to insulation breakdown, i.e., the complete loss of electrical properties.
Insulation aging can be divided into:
(1) Initial breakdown. Initial breakdown may be caused by manufacturing errors or weaknesses in the insulation.
(2) Sudden breakdown. Sudden breakdown is determined by the inherent properties of the product.
(3) Aging breakdown. Aging breakdown is the result of insulation aging over time. 9. Hazards of Transformer Fire
1. Internal short circuits or grounding faults within the transformer, fires in nearby cables, and external short circuits or discharges causing fires or explosions can all lead to transformer fires.
2. Transformer fires can cause severe damage to the transformer, forcing the unit to shut down. In severe cases, it can result in a complete power outage, both internally and externally.
3. A transformer fire may cause an explosion, injuring surrounding personnel and facilities. The toxic fumes produced can pollute the factory air, causing poisoning, asphyxiation, and other personal injury accidents.
2. Extinguishing Dry-Type Transformer Fires
Upon early detection of a fire, personnel should immediately report to the shift supervisor. On-site personnel should first disconnect the power supply, stop the cooler, and quickly use fire extinguishing equipment. Once a transformer catches fire, it should be immediately isolated from the system. If isolation is not possible, dry-type fire extinguishers or carbon dioxide fire extinguishers should be used.
1. If the transformer has not tripped:
Immediately open all switches on both sides of the transformer. If this endangers the safe operation of adjacent equipment, immediately stop the operation of adjacent equipment.
2. Shut down the cooling system.
3. Check if the fire deluge valve is functioning properly. If not, try to inject fire water, or use fire extinguishers as needed. Dry-type fire extinguishers should be used.
3. Inspection of Dry-Type Transformers:
1. Check for abnormal sounds and vibrations.
2. Check for discoloration caused by localized overheating, corrosion from harmful gases, or other factors that result in surface corrosion, electrical creep, and carbonization.
3. Check if the transformer’s air-cooling system is operating normally.
4. High- and low-voltage connections should not overheat. Cable heads should not have leakage or creepage.
5. The temperature rise of the windings should be monitored according to the insulation material grade used in the transformer. The temperature rise should not exceed the specified value.
6. Support insulators should be free of cracks and discharge marks.
7. Check if the winding clamps are loose. 8. Indoor ventilation should be ensured. The iron core air duct should be free of dust and debris blockage, and the iron core should be free of rust or corrosion.