| In large power plant, wet steam in turbine and water in turbine oil and wet hydrogen in hydrogen-cooled generator will decrease safety and economic of turbine generating unit.The last several stage of condensing steam turbine, the presence of wet steam leads to problems of blade erosion and losses in turbine efficiency.High level water ratio in turbine oil would introduce the oil demulsibility reduced, and then the lubrication performance and stable thick oil film can't be formed. The abnormal wear of journal and bear, burned liner and stick to liner would occur.High wetness in hydrogen of hydrogen-cooled generator would introduce corrosion of generator stator insulation and metal structures. Even cause major accident such as grounding and inter phase short circuit.So the accurate measurement of steam wetness and water ratio and wetness in hydrogen is a important research direction which can provide guiding for safe and economic operation of unit.Wetness measurement by the method of microwave resonant cavity perturbation is studied in the paper. Research is focused on detection technique and experimental study for turbine exhaust wetness and water ration in turbine oil and wetness in hydrogen of hydrogen-cooled generator.The dielectric characteristics of turbine exhaust and turbine oil with water and wet hydrogen is studiedThe expression of relationship between aquifer medium effective permittivity and medium wetness is derived. A method of wetness measurement based on microwave resonator perturbation is presented. The measurement method principle is described, and the coincided resonator type and working mode for different wetness is determined, and the relationship between frequency offset in resonator with chosen working mode and medium wetness is derived.Key problems of this measurement technology in the microwave resonant cavity perturbation method implementation and measurement device development are studied. When designing the microwave resonator perturbation, the working frequency is determined based on the relationship between different wave length and water dielectric constant and the resonator proper size according to the working wave length.As the sensor of measurement device, the resonator is the key parts of measuring device, its construction and electromagnetic property is important to measuring accuracy, the resonator construction is optimum designed by ANSOFT HFSS, and the high frequency electromagnetic characteristic of the resonator is analyses.On-line turbine exhaust wetness measurement system is designed and installed on the 200mw unit in Baoding power plant.The design condition of sampling device is numerical simulated, and the sampling location and measurement method is determined. The experimental system of turbine oil is designed and put up which provide experimental platform for studying the relationship between resonator temperature and frequency offset, and the relationship between water ratio in turbine oil and frequency offsetUsing the self-building experimental system, the curve between resonator temperature and frequency offset is obtained by experience. The correlation formulas are obtained by smooth curve fitting. The water ratio in turbine oil and frequency offset has been experimentally investigated. The main factors are analyzed. Electrical properties of turbine oil with water have been experimentally investigated. Industrial test for turbine exhausts wetness on-line measurement system provided a stable result. In the experimental operating conditions, frequency offset kept a stable population in 100 kHz according to the vacuum state in field. The experience shows the moisture content measurement is feasible. |
PDF Full Text Request