In hydrogen-cooled generators, what is the function of maintaining hydrogen pressure above atmospheric pressure, and what is the risk if this pressure is not maintained?

In hydrogen-cooled generators, the function of maintaining hydrogen pressure above atmospheric pressure is primarily to prevent air from leaking into the generator casing. Hydrogen has a much higher thermal conductivity than air, making it a superior coolant for removing heat generated by the generator's windings. Maintaining a positive pressure differential ensures that any leakage that occurs is hydrogen escaping into the surrounding environment, rather than air entering the generator. The risk if this pressure is not maintained, and air leaks into the generator, is a significant reduction in cooling efficiency. Air mixed with hydrogen reduces the overall thermal conductivity of the cooling gas, leading to higher winding temperatures. This can damage the insulation on the windings, shortening the generator's lifespan and potentially leading to catastrophic failure. Furthermore, the presence of oxygen from air creates an explosive mixture with hydrogen, posing a significant safety hazard. The mixture of hydrogen and air becomes flammable within certain concentration ranges. Therefore, maintaining a positive hydrogen pressure is crucial for both cooling performance and safety.