Research On Simulation And Analogy Feasibility Of Environmental Impact Assessment Of Electric Power Transmission And Conversion Project

As the stratagem of "Electric Power Transmission from West to East" is executed and the Three Gorges Project is in the period of harvest in our country, the contribution of Electric Power Transmission and Conversion Projects stepped into a new era, more and more attention that people paid on Electromagnetic and environmental dissensions triggered by Electric Power Transmission and Conversion Projects increasingly. At present, as the development of Environment Impact Assessment (EIA) of Electric Power Transmission and Conversion Projects, HJ/T24-1998 couldn't fit the Electric Power Transmission and Conversion Projects those are under or above 500kV voltage class. especially for the simulation and analogy of the transformer substations or transmission lines, In practical Environmental Impact Assessment, simulation and analogy objects without feasibility are chosen randomly or unregulated, which leads to the result that the actual measurement values are quite different from the predicted values in EIA reports.Based on dozens of actual measurement values and experience of EIA of Electric Power Transmission and Conversion Projects in recent years in our country, and sufficient research on HJ/T24-1998 and (will replaced the former), and combined the relative research, this dissertation concludes main factors an conditions and their comparatively importance that should be considered when choosing object or transmission lines for simulation and analogy in EIA of Electric Power Transmission and Conversion Projects, and the feasibility of simulation and analogy that HJ/T24-1998 states, and finally indicates how to enhance the feasibility of simulation and analogy and veracity of environmental impact prediction combined the practical conditions of the projects.The conditions of simulation and analogy that HJ/T24-1998 states are not clear and comprehensive enough, besides the consistency of voltage class and similarity of transformer capability, more factors or conditions should be considered for the analogy of electromagnetic environment as follows:(1) Similarity of scale Because of the critical influence on electromagnetic environment of transformer substations, confirming how many transmission lines in which period of construction is more important than transformer capability when choosing an analogy object.(2) Similarity of overall layoutWhen other conditions are same, outdoor transformer substations have more effect on surrounding electromagnetic environment than indoor ones, and the difference of overall layout will lead to the difference of distributing of transmission lines and electric equipments, which will lead to the difference of distributing of electromagnetic environment, therefore the similarity of overall layout is more important than transformer capability when choosing an analogy object.(3) Similarity of running conditionThe analogy would be more persuasive and credible if the running condition of transformer substations, including transformer working condition, load of transmission lines, line voltage, line current, is cleared.(4) Veracious and rational monitoringThe influence on the surrounding electromagnetic environment could be revealed exactly only if transformer substations were monitored and measured in veracious and rational way according to the relative regulations, so if the monitoring or the measuring is veracious and rational or not, is the critical condition for the analogy.The factors such as transformer style, surrounding environment, and overall layout effect more on noise environment than other factors, so following conditions should be considered for the analogy of transformer substations noise environment:(1) Similarity of transformer capability and styleThe transformer capacity should not be smaller than the objective one for an analogy of noise environment of transformer substations, meanwhile, the transformer style should be similar and the working condition of the cooling fan (if there is one).(2) Similarity of surrounding environmentThe influence on the noise environment of transformer substations is constrained by the surrounding (background) noise to much extent, so the similarity of surrounding environment is quite necessary when analyzing the influence on the noise environment of transformer substations.(3) Similarity of overall layoutThe intensity and distributing of noise source would be different because of the screening and reducing effect between outdoor and indoor transformer substations, so the similarity of overall layout will make the analogy more persuasive and credible.(4) analogy of the noise source combined modal predictionIf comparability conditions could not available simultaneously, we can analyzed the intensity of noise source, not the bindery noise, and calculate the contribution intensity according to the reducing modal, and finally combined the background noise is also an effective way to analyze the noise influence of transformer substations. The simulation and analogy for the electromagnetic environment of transmission lines that HJ/T24-1998 states are constrained by some more factors or conditions should be considered by conditions as follows:(1) The feasibility of theoretical calculationThe field intensity that calculated in theory is only appropriate for the middle part of the lines, besides the calculation result could only demonstrate the non-aberration field, not the intensity and the distributing of the electric or magnetic field inside or outside the houses right under the transmission lines.(2) Indetermination of the relative factorsMany relative factors such as tower style, line style and arrangement, actual running current and line height from the ground could be determined in the period of feasibility research, so the veracity of the theoretical calculation cannot be assured. The same situation is occurred for the simulation and analogy because of the relative factors is not easily available.(3) Restriction of monitoring and measuring environmentPreconditions such as tower style, line style and arrangement, and line height from the ground is the comparative conditions in theory, however in practice the landform or environment conditions is not usually appropriate for monitoring and measuring, so it is a good choice to combined the theoretical calculation and analogy, the monitoring data of the analogy could prove the result of the theoretical calculation, meanwhile the theoretical calculation couls demonstrate the actual running intensity on different conditions.