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Research on Soil Resistivity Measurement and Distribution Characteristics of Electric Field in EHV Transmission Corridor

Author: SuJie
Tutor: WuGuangNing
School: Southwest Jiaotong University
Course: Proceedings of the
Keywords: Soil resistivity High frequency diffuser Transmission lines Frequency electric field Curve integral
CLC: TM862
Type: Master's thesis
Year: 2011
Downloads: 59
Quote: 0
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Abstract

Power system grounding techniques is to ensure the safety of persons and equipment, and maintenance of the system is safe and reliable operation of one of the important measures. In recent years, with the rapid expansion of grid capacity, short-circuit current into the earth rise sharply, the large number of inputs of various monitoring equipment, plus lightning hazards, more and more stringent requirements for grounding. The soil resistivity measurement is the first step of grounding design to reflect the flow characteristics of the grounding in the bulk of the earth when the fault current and the lightning current is released, and the fault current, and the lightning current equivalent high frequency, so in order to ground the accuracy of the design have to study the response of the soil in the high-frequency current role. On the other hand, due to China's UHV transmission project construction is booming and people electromagnetic environment enhanced safety awareness, the design of the transmission line is about electromagnetic indicators of control within the safety limit is an important issue before the designer, and the workers frequency electric field intensity electromagnetic environment is a measure of the safety of one of the key indicators. Firstly, based on the principle of controlled source audio magnetotelluric (CSAMT) study flow characteristics of the soil high frequency scattered, shallow low resistivity soil depth of penetration of the high-frequency current, high resistance soil depth of penetration of the low-frequency current; were soil resistivity 100Ω · m and 300Ω · m of circumstances by CDEGS software to achieve a simulation of CSAMT soil resistivity and Schlumberger method in the frequency range of 10Hz ~ 105Hz measurement. The results showed that: the the CSAMT Method measuring soil resistivity is more accurate, more reliable, especially in the high-band measurement results are stable, can be fully reflect the bulk flow of the soil high frequency characteristics. Transmission line frequency electric field, the first derivation of a file from the inside contour flying the transmission line catenary equation, the equation shows that the the Sag shape only loads its lowest point by the wire unit length units interface stress decision The distance from the lowest point of sag and suspension regardless of the point of the height difference. Catenary model for the establishment of a three-dimensional space based on this two-conductor transmission line, the method of images and the potential coefficient wears solving a transmission wire surface the equivalent charge the three-dimensional curve integration method, further promotion of multi-conductor transmission line sub conductor Surface equivalent general method for solving the charge. Space electric field intensity vector integral scalar decomposition AC transmission getting off work frequency field strength of each component rms the synthetic field strength RMS solving method and the field strength of the instantaneous value of the time-domain expressions. Meter and three-dimensional wire sag frequency electric field mathematical model based on the design parameters of a 500kV EHV transmission lines to establish, with Matlab numerical integration method based on three-dimensional curves, calculated the wire surface equivalent to the real part of the charge and the imaginary part of the charge distribution function, which calculated qualify under ground and ground height of 1.5m at the field intensity distribution from the central file and with the two-dimensional model to calculate the results of the accuracy and validity of the comparison, prove that the model and algorithm. Analysis of the three-dimensional field strength variation of each component and its horizontal and vertical distribution characteristics results show that: the X-axis component in the file from the central ground field strength is zero, the field strength from the Y, Z axis component of the decision, wherein the Z-axis component share larger proportion with the horizontal distance of the mobile field strength decreases gradually increase the proportion of its X-axis component, but the Z-axis component of any decision field strength; distance on both sides of the file from the central phase conductor outside of approximately 3m location field strength reaches a maximum and then decreases gradually toward the both sides of the tower at the tower location to reach the minimum (ignore tower field strength caused distortion effects) phase at a distance on both sides of the wire outside of about 10m position subsequent field decreases rapidly. Model compared to the two-dimensional, three-dimensional model can be more fully reflect the variation of each component and its lateral line end strong, vertical distribution characteristics.

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