Research On Dispersion Characteristics Of Spiral Grounding Module And Its Application In Tower Grounding Device

The safe and effective grounding of the power system is a crucial part to ensure the safe and stable operation of power equipment.The grounding design of the existing grounding device often has problems such as low resistance reduction efficiency,limited construction conditions,and uneven distribution of surface potential.In order to improve the lightning protection performance of the transmission line and the safe operation of the power system,a spiral grounding device is used in the grounding device in this paper.Using the CDESG grounding calculation software,the principle analysis of the self-scattering characteristics of the spiral grounding device was carried out.By comparing the module with ordinary vertical grounding body and thin tubular grounding module,the applicability and advantages of this module in power system grounding are discussed,so as to effectively solve the grounding problems in different application scenarios.Due to the limitation of environmental conditions,it is often difficult to reduce the impact grounding resistance of the grounding device of the high-voltage transmission line tower in mountainous areas with a high probability of being struck by lightning.This paper makes full use of the vertical space of the tower foundation,and adopts the method of laying the spiral grounding device along the surface of the tower foundation pile to the bottom of the foundation pile,which can dissipate the impulse current to a greater extent and reduce the difficulty of laying horizontal rays.The principle of impulse grounding resistance and its realization method in CDEGS software simulation calculation are studied,and the reliability of the calculation method is verified.Establish a grounding model considering the nonlinear ionization of soil under lightning current impact,and study the impact characteristics of the spiral grounding device under different lightning current amplitudes and soil resistivity,so as to optimize the selection of the spiral structure.Taking the typical four-corner radial grounding device of a 110kV transmission tower as a prototype,the length of the required epitaxial rays before and after the external application of the helical device to the tower foundation under double-layer soil is compared and calculated.The application effect of the external application of the spiral grounding device on the tower foundation is analyzed.For urban transmission steel pipe towers in densely populated areas,in addition to grounding resistance,the check and design of safety indicators such as step voltage and touch voltage need to attract the attention of relevant departments.Based on the safe current allowed by the human body,this paper calculates the maximum allowable value of each safety index under the condition of power frequency short circuit and lightning strike.Taking the two typical designs of the existing 220kV urban transmission steel pipe tower grounding device as prototypes,the actual value of the safety index of the grounding device under the typical design is calculated by using CDEGS software.Combined with the actual situation,it is considered that the power frequency step voltage exceeding the standard is the key problem of the safety of the grounding device at present.A method of replacing part of the vertical grounding electrode with a spiral grounding module is proposed to balance the step voltage,and the optimal design of the spiral grounding module is carried out.Two typical designs of the grounding device of the urban transmission steel pipe tower are given and the design methods of the spiral grounding module are combined,and the safe grounding design scheme of the transmission steel pipe tower is obtained,which provides a method reference for the safety design of the urban transmission tower grounding.