In the operation of power equipment, internal gas pollution in generators is a significant risk that impacts equipment performance and lifespan. This is especially true for enclosed generators, where the accumulation of combustible gases like hydrogen and methane mixed with lubricating oil vapor not only reduces the insulation performance of the windings but also poses a risk of combustion.
1. Analysis of Gas Pollution Causes
The main sources of gas generation during the operation of the generator include: hydrocarbons (C₃H₈, C₄H₁₀, etc.) produced by the high-temperature decomposition of lubricating oil, pyrolysis products of insulating materials (CO₂, H₂S), and leakage gases from the hydrogen cooling system. Experimental data indicates that when the gas concentration reaches 25% of the Lower Explosion Limit (LEL), the treatment procedure should be initiated.
2. Gas Purification Technology System
Dynamic Circulating Displacement Method
During generator shutdown, nitrogen or dry air is used for forced displacement. The specific operation involves injecting inert gas (purity ≥99.5%) through the bottom intake valve and connecting the top exhaust valve to a gas analyzer. The displacement pressure is maintained at 0.05-0.1 MPa, and the gas components are monitored every 15 minutes until the combustible gas concentration is reduced to below 50 ppm. This method is suitable for emergency hazard removal, but care should be taken to avoid damaging the sealing system due to negative pressure.
Adsorption Filtration System
A three-stage composite filter is added to the cooling air duct: the first stage is an activated carbon layer (200-300 mesh) that adsorbs large organic molecules; the second stage is a silica gel layer to control humidity (RH ≤ 30%); the third stage is a molecular sieve (13X type) to capture residual gases. In an application case of a 600MW unit, this solution reduced gas pollution by 83%, and the filter replacement cycle reached 8,000 hours.
Vacuum Degassing Process
For gases dissolved in the lubricating oil, a three-stage vacuum degassing device is used for treatment. By applying a gradient pressure reduction (0.08 MPa → 0.03 MPa → 0.01 MPa) with a constant temperature of 60°C, the dissolved gases are fully released. Key parameter control: the oil’s kinematic viscosity must be maintained in the range of 28-32 mm²/s to prevent excessive degassing, which could result in a reduction of lubrication performance.
3. Preventive Maintenance Strategy
- Establish a gas chromatography online monitoring system, setting warning thresholds for H₂ concentration >1% and total hydrocarbons >0.5%.
- Perform sealing gap detection every 2,000 hours of operation, controlling the radial gap within 0.15-0.20 mm.
- Use low-volatile synthetic lubricating oil (ISO VG32 grade) with a flash point >220°C.
- Optimize the cooling system design to maintain hydrogen purity >97% and dew point humidity < -25°C.
Engineering practices show that by implementing the above comprehensive control solutions, the internal gas pollution index of the generator can be reduced by more than 90%, the winding temperature rise can be lowered by 8-12°C, significantly improving the reliability of equipment operation. For different models, the technical parameters should be adjusted according to the actual structural characteristics, and it is recommended that the treatment operations be carried out under the guidance of professional engineers.