Fire hazard and preventive measures for 6 hydro-generator units Zhang Xiaozhong has been through the 122-year history of hydropower construction since the construction of the first hydropower station in France in 1878. The use of hydroelectric power generation does not lose water, does not pollute the environment, and is flexible in operation, efficient, and low in production cost. Therefore, many countries in the world give priority to the development of hydropower resources. As the core equipment of hydropower stations, hydropower generating units have always been valued by design and manufacturing units and operating units at home and abroad.

The composition and working principle of a hydro-generator unit The hydro-generator is mainly composed of two parts, one is a rotor that can rotate at a speed, and the other is a stationary stator with a winding placed on the iron core. The rotor is located in the cavity at the center of the stator, has a fixed air gap with the stator, and is provided with a magnetic pole capable of generating a magnetic field on the rotor.

When the water flow impacts the rotation of the rotor, mechanical energy is generated. The magnetic pole of the rotor rotates with the rotor at a high speed, and the magnetic field generates relative motion with the stator winding. The magnetic field cuts the conductors of the stator windings, creating an induced potential that converts the machine into electrical energy.

2 The fire hazard of the hydro-generator unit is damaged by the insulation of the stator winding, causing the winding to the ground or the winding of the winding. The short-circuit arc can blow the copper wire and can fuse the copper wire and the iron core. High humidity can cause the burning of insulating materials.

If the generator cooling device fails or the wire joint is poorly welded, etc., the stator or rotor windings will be overheated and the aging of the windings and the inter-winding joints will melt, and may progress to an arc fire.

3 Fire-fighting safety measures for hydro-generator units According to the size and importance of the type of generator set, for the short-circuit accidents that may occur, the relay protection Zhang Xiaozhong and the Yichang City Public Security Fire Brigade should be installed.

Protect the automatic device.

When the stator windings are short-circuited between phases, the protection device shall act to disconnect the generator circuit breaker and the automatic fire-extinguishing magnetic device, and at the same time act in the event of an accident.

When the stator winding over-current over-voltage and de-magnetization protection action, the generator breaker and the automatic de-excitation device should be disconnected. However, for units that are not equipped with permanent magnets, they should also operate in the event of an accident.

When the stator winding grounding and overload of the capacitor current less than 5 people and the excitation circuit point are grounded, the protection device can act on the signal with time limit.

For generators above 80, the phase-to-phase short circuit between the stator winding and its lead wire should be protected, and the longitudinal differential protection should be installed.

The single-phase ground fault of the stator winding of the generator can be signaled by a single-phase grounding device mounted on the busbar.

The overcurrent of the generator stator winding is caused by an external short circuit, and the overvoltage protection of the composite voltage including the negative sequence voltage and the line voltage or the low voltage start may be employed.

The stator winding of the generator should be equipped with overvoltage protection. The setting value can be 1.5 times rated voltage, and the action time limit can be 0.58.

4 Fighting measures for generator fires At present, domestic and foreign departments use water-oxygenated carbon to extinguish hydro-generator fires. The water fire extinguishing economy is reliable and safe, and the shortcoming is that it needs to be effectively baked during the recovery and use of the equipment to meet the qualified insulation standards. Extinguishing with carbon oxide requires a good sealing structure for the generator, and the initial investment is large. After the fire extinguishing, the carbon oxide must be discharged for maintenance. Only a few hydropower stations are used in China. Therefore, most of the hydroelectric generating units in China use water fire extinguishing methods, especially the use of water spray fire extinguishing, so that the fire extinguishing effect is better and more reliable.

The generator automatic water spray fire extinguishing system consists of water source water filter electrical cabinet mechanical cabinet water distribution network spray head alarm and so on. According to the accident adjustment and analysis, it is found that the burning part of the unit is usually at the end of the stator coil. Therefore, the fire ring and the nozzle are respectively arranged at the upper and lower ends of the stator coil. In the hood of a hydro-generator with a single unit capacity of 125 and above, an automatic fire alarm system shall be provided. The electrical connection shall be shielded cable, and the fire detector shall be of anti-frequency electromagnetic field type. When a fire occurs, the fire alarm signal is sent to the electric control cabinet of the generator automatic water spray fire extinguishing system and the central control room of the unit operation control unit. The automatic water spray fire extinguishing system has a fully automatic semi-automatic manual operation mode, and the operation mode can be arbitrarily converted by the operation personnel as needed. The generator automatic water spray fire extinguishing equipment is arranged in the turbine layer of each unit, and the mechanical cabinet is arranged beside the side of the main plant turbine layer. The amount of water mist sprayed on the circumference of the upper and lower ends of the generator stator should not be less than 10! The operating personnel of the heating and air intake generators of the hydro-generator should strictly follow the requirements of the generator operating regulations, and strengthen the inspection and strict operation system when on duty. The maintenance personnel should improve the process level and maintenance quality. When the oil head of the low head turning turbine is repaired, it is necessary to prevent the oil leakage on the blade. Before the inspection, the oil trace on the parts should be removed first. The used waste cotton yarn or rag should be placed in the designated iron drum and disposed of in time. When the generator is in a fire, in order to quickly control the delay of the fire, the generator and the system should be quickly dismantled and immediately extinguished with a fixed fire extinguishing device.

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