Calculation Of Three-dimensional Power Frequency Electromagnetic Field Under UHV Transmission Lines And Analysis Of The Influence Factor

With the strengthening of environmental awareness, the environmental problemscaused by the power transmission projects, which gradually aroused widespreadconcern in society. After the power transmission project put into operation, itselectromagnetic phenomena became a major environmental problem. According tothe frequency range from low to high, electromagnetic environment problems aredivided into the power frequency electric field, power frequency magnetic field andradio interference and corona noise. At present, people use the2-D model to calculatethe power frequency electromagnetic field around the transmission lines. Namely,assuming the transmission lines between the spans are contour, people seldomconsider the sag of transmission lines influences on the electromagnetic field, whichleads to impossible to accurately assess the spatial distribution of power frequencyelectromagnetic fields. In order to accurately calculate the power frequencyelectromagnetic field around the transmission lines, and analyze the key factors andprovide reliable technical data for assessing electromagnetic environment aroundtransmission lines, people use the3-D calculation and analyze the factors affectingpower frequency electromagnetic field around the transmission lines.According to the mechanical characteristics of the transmission lines in the caseof wind, ice, and other conditions, deducing the catenary’s equation. On the basis,combining the charge simulation method with the moment method to calculate the3-D power frequency electric field. The results show that there are some largedifferences between the2-D model and the3-D model. However, the results obtainedby using the3-D coincide with the measured results. Analyzing that the arrangementof wires, tower height, distance of wires, phase sequence, span and meteorologicalconditions (temperature, ice thickness, and wind speed) influence on power frequencyelectric field, and discussing the shielding effect that shielded wire on powerfrequency electric field. Previously, people usually use simulation current method to calculate powerfrequency magnetic field around the transmission lines. In simulation current method,the implied condition is that the induced current in lightning conductors have noeffect on power frequency magnetic field. As a matter of fact, the small inducedcurrent flow through the lightning conductors. Ignoring the current will bringcalculation error. In response to these deficiencies, using the circuit combination tocalculate the3-D power frequency magnetic field around transmission lines. Theresult shows that there are some large differences between the3-D model and the2-Dmodel. Analogously, analyzing the affecting factors,such as, the arrangement of wires,tower height, and distance of wires, phase sequence and meteorological conditions:temperature, ice thickness and wind speed.