| In recent years,the demand for electricity in daily production and life has been increasing with the economic strength of our country,a large number of high-voltage substations,transmission lines,and converter stations have been put into operation in various provinces of our country,the electromagnetic environment is extremely complicated.At the same time,with the continuous improvement of people's awareness of safety and environmental protection,the problem of electromagnetic radiation generated by electric power facilities has caused a new panic in society,especially for the operators who maintain and repair in the power supply enterprise,it is very important to establish a scientific and reasonable system to evaluate the occupational health hazards of electromagnetic environment in power supply places.In this paper,a comprehensive evaluation model of health hazards in power frequency electromagnetic field for power supply enterprises is established based on multilevel fuzzy analysis method.Taking 220 kV substation as an example,we analyzed the general equipment data,measured electromagnetic field strength data of multiple substations and residence time data of operators in different areas in a comprehensive way.According to the measured data,a small number of exposure value of electric field strength in 220 kV substation exceed the International Commission on Non-Ionizing Radiation Protection(ICNIRP)requirements for 5kV/m public exposure limits and 10 kV/m occupational exposure limits and 5kV/m occupational exposure limits requirements of China National Health Standard,the magnetic induction intensity is also higher than the ICNIRP requirements for 100?T public exposure limits and 500?T occupational exposure limits and 22?T public exposure limit and 78?T occupational exposure limit set by the “National Standard Opinion” of China.However,operators rarely contact these areas,so it can't indicate that substations have great occupational health hazards.This paper uses the established comprehensive evaluation model to verify it and the result shows that the intensity of the electromagnetic field in the four different regions of the 220 kV type substation is "extremely low" grade,and the operators contact level of 220 kV type substation in electromagnetic field is also "extremely low",the occupational health hazard to the operators is minimal.The traditional methods only consider whether the intensity of electromagnetic field exceeds the limits of domestic and foreign,The model in this study not only model not only evaluates the electromagnetic field strength,but also takes the time of the workers to contact the electromagnetic field as an evaluation factor,analyzes from electromagnetic environment and operator contact time,makes objective weight division to different levels of index,it can break through the limitations and subjectivity of traditional methods,it also can avoid the hysteresis and harmfulness of medical evaluation and make a more objective judgment on whether the electromagnetic field of supply enterprise contact will cause health hazards to the operators.This paper also establishes a prediction model of electromagnetic field intensity based on 2-12-2 structure BP neural network to solve problems that encountered in the process of establishing the evaluation model of some operation areas represented by transmission lines,such as the intensity of electromagnetic field is not easy to measure and the cost of measurement is high.Taking 220 kv typical transmission lines and 500 kv typical transmission lines as examples,simulating and predicting their electromagnetic field strength through the Transmission line height and the horizontal distance between the operator and the center line,the comparison of the predicted results with the actual values shows that the model has a high degree of accuracy.The BP neural network has the ability of nonlinear mapping and self-learning,and the calculation process is simple,to a certain extent,the prediction model of electromagnetic field intensity based on BP neural network can solve the problem that the electromagnetic field strength is not easy to measure and the measurement cost is high,it also has guiding significance for the research of the evaluation of electromagnetic environment. |
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