Foreword Shanghai is the largest fixed-point base for the development and production of complete sets of equipment for nuclear power plants in China. During the "10th Five-Year Plan" period, Shanghai will develop a 1000MW nuclear power unit, in which the rated voltage of the stator of the generator will reach 27kV, which is close to the critical value of the stator voltage of large steam turbine generators. The key technology that affects the reliability of the generator under such high voltage. One is the anti-corona problem at the end of the stator. In order to cooperate with Shanghai Turbine Generator Co., Ltd. to develop the task of 1000MW steam turbine generator, we made a preliminary exploration on the anti-corona material and anti-corona structure of the stator end. Engaged in the research and teaching of insulation materials and insulation technology Uel: 1 non-linear semi-conductive anti-corona material stator end anti-halation layer has a paint model and a strap type. In this study, the anti-corona layer of the paint film was used, and the nonlinear semi-conductive material such as silicon carbide and zinc oxide was added to the modified alkyd resin paint, and the resistance adjusting materials such as carbon black and graphite were adjusted, and the nonlinear coefficient of the paint film was adjusted. And resistivity to achieve the purpose of optimizing the anti-halation layer structure. In the external screen anti-halation treatment of the stator end of the generator, the silicon carbide non-linear resistor is used to improve the electric field at the slot, so the relationship between the resistivity and the electric field strength is more intuitive: when measuring the silicon carbide powder When resistivity is expressed in terms of volume resistivity: when measuring a silicon carbide semiconductive paint film, the resistivity is expressed as surface resistivity: therefore, from the above equations, the value of resistivity at different electric field strengths can be tested. And plot the relationship between electric field strength and resistivity based on the obtained data. Then, the curve is straight-line fitted, and the intercept of the obtained straight line on the vertical axis (the longitudinal axis is the resistivity) is within the resistivity value when the electric field strength is zero, and the absolute value of the straight line slope is the nonlinear coefficient P. The reason why the electric resistivity at the time of the electric field strength is zero is obtained for the convenience of comparison, because in general, each manufacturer uses the electric resistivity at the zero value to perform the comparative calculation of the electric field distribution at the end. Due to the presence of the lacquer base, the nonlinear semiconducting properties of the SiC film are not the same as those of the SiC powder. In addition, during the testing of the film, the four silicon carbide powders are better at the high field strength. Non-linear characteristics, but in the environment of alkyd resin, there is no good semi-conducting nonlinearity. 3 Silicon carbide paint consisting of silicon carbide micropowder and alkyd resin base alone. No low resistance is measured. Yu and larger nonlinear coefficients. Therefore, it needs to be modified. The main method is to add a substance with a lower resistivity. They are generally colloidal graphite and conductive carbon black, here. We only give the test results of the silicon carbide paint film prepared by colloidal graphite. The test calculation results are listed in Table 1. The 1st body 3rt carbonization ft泫 hire number linear resistance slaughter P, The addition of carbon black reduces the linear resistivity, but also changes the nonlinear coefficient of the SiC film. We believe that due to the different particle sizes of the silicon carbide micropowder, after the carbon black is added, a large amount of carbon black particles are filled between the silicon carbide fine powder; and it is generally considered that the carbon black itself is a linear conductive substance. In addition, the carbon black is easy to float and has a great influence on the test results. The composition of the paint film is listed in Table 2, and the test results of the paint film are listed in Table 3. Table 2 Composition of silicon carbide paint film No. Silicon carbide type Paint-based carbon black Table 3 Non-linear semi-conductive twisting test of silicon carbide paint film U number number linear resistance slaughter ((1) Nonlinear coefficient (cm/kV) Table 4 gives Some data on the zinc oxide paint film is the same as the silicon carbide paint film prepared with colloidal graphite, and only the relevant parameters of the paint film are listed here. The same paint base, zinc oxide paint film can exhibit nonlinear semi-conducting properties, and silicon carbide paint film can not be tested because the resistivity is too high, so only the silicon carbide paint film can be modified; Good nonlinear semiconducting properties of zinc oxide. Table 4: Zinc Oxide Paint Film Nonlinear Semiconducting Characteristics No. Linear Resistivity Ps Nonlinearity Factor 3 While exploring the use of low resistivity materials to modify the nonlinear semiconducting properties of silicon carbide paint films. We have combined some of these materials together as part of a silicon carbide film. Since the results are not the same every time the brushing is applied, the results obtained are not completely satisfactory, which is why the domestic manufacturer generally adopts the anti-halation process of the secondary curing or semi-curing molding. Although the one-time curing molding process or the semi-curing molding process is more complicated than the painting process, the process stability is good. Therefore, under the current domestic technical level conditions, one-time assimilation molding process or semi-curing molding process can effectively prevent electricity. The occurrence of halo. Table 5 Composition of Silicon Carbide Paint Film Sample No. Nonlinear Material Carbon Black Paint Based Silicon Carbide Zinc Oxide The composition of the paint film is listed in Table 5. The test results are listed in Table 6. It should be noted that we only use here. The lacquer base labeled DC was tried and the effect was not satisfactory. Table 6 Test results of nonlinear semi-conductivity. Sample No. Linear resistivity p(n) Nonlinear coefficient P It can be seen that as the amount of zinc oxide increases, the nonlinear coefficient becomes larger, which is not practical. The main reason for the analysis is in the paint base and painting process. Many domestic manufacturers use epoxy resin as the base of anti-corona paint. From the relevant data, the linear resistivity and nonlinear coefficient of silicon carbide paint film and the origin, batch, paint base type, painting process and test conditions of silicon carbide The test environment has a relationship, which is why the root cause of the silicon carbide anti-corona film test specification has not been available until now. 2 Anti-halation structure We input the test data into the “large generator silicon carbide anti-corona coating calculation software†to calculate whether the paint film is suitable, and use high resistance and medium resistance paint to obtain A graph of voltage, electric field strength, and loss distribution. Electric field strength: maximum field strength is not greater than 9.lkV / loss: maximum loss is not greater than 0. Use "large generator silicon carbide anti-halation coating calculation software", and input test data, you can get. The calculation of the high resistance and the medium resistance is shown in Table 7. As shown in Fig. 4, we can see that the prepared silicon carbide paint film base can meet the anti-corona requirement of the stator end of the 27 kV turbo generator. However, from Table 38, we also found out. The calculation software 希S in the resistance film 7 table 7 optimized processing input data corresponding to the group linear resistivity P (n) nonlinear coefficient P (cnkV) length (C pattern number in the high resistance of the resistance high resistance medium resistance high resistance Table 8 Calculation Results List Graphic No. Linear Resistivity Nonlinear Coefficient P(cm/kV) Brushing Length (cm) Maximum Loss Medium Resistance High Resistance Medium Resistance High Resistance Diagram: Medium resistance section length: 1. High resistance section length: Maximum field strength of 1:15 medium resistance section: Maximum field strength of 2.56 high resistance section: Maximum loss of 5.21 medium resistance section: 0.539 High resistance section Maximum loss: 0.543 Group 14 optimization curve: Medium resistance section length: 11.H high Block length: 18> Maximum field strength of the middle resistance section: Maximum field strength of the high resistance section: 4.11 Maximum loss of the high resistance section of the middle resistance section: Maximum loss of the high resistance section of the medium resistance section: 5:H is an optimization curve of 27 grouping: Medium resistance section length: 111K high resistance section length lf). 2 The maximum field strength of the middle resistance section: 2.W The maximum field strength of the high resistance section: 4.07 The maximum loss of the resistance section: The maximum loss of the high resistance section: 0. The linear resistivity of S24 can be lower. For example, in 3, 4, the linear resistivity of the medium-resistance paint film is close to the lower limit of the input data; for the high-resistance paint film, the nonlinear coefficient is expected to be larger. The calculation of the nonlinear coefficient of some high-resistance paint films is also very close to the upper limit. 3 Conclusions (1) The anti-corona material added with silicon carbide, zinc oxide and conductive carbon black can adjust the nonlinear coefficient and resistivity to the required range of the optimization curve of 5; (2) adopt high and medium resistance two-stage defense The halo structure can basically meet the requirements of the 27kV voltage level and simplify the process. In order to make the anti-halation performance better, a three-stage structure can be adopted, but the process and materials are more complicated.
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