输电线路杆塔接地系统的研究

发布时间：2018-06-06 14:23

本文选题：接地电阻 + 杆塔接地装置　；参考：《西安科技大学》2017年硕士论文

【摘要】：电网运行表明,良好的接地保护装置是电力系统安全运行的基础。目前,我国的输电网络正朝着更高的电压等级和更大的输送容量方向发展,因此,通过输电线路杆塔接地装置入地的故障电流也变得很高。以前输电线路电压等级不高且大多数杆塔位于高山或者人流很小的地方,所以考虑较多的还是避雷线的防雷及保护问题,对杆塔接地系统周围的电位分布、地电位涌升及散流问题考虑的较少。伴随着“坚强智能电网”的发展和更高电压等级输电线路的出现,输电线路杆塔数量在人流量较大的地区正在增加,当一些地区的杆塔接地系统附近发生单相接地故障或者其它类型故障时,杆塔周围出现的跨步电压已经超出了安全值。所以,在输电线路设计、建设和运行维护的过程中,除了考虑输电杆塔的防雷因素外,还需要对输电线路杆塔周围散流和分流因素进行考虑,并对特殊区域的常用杆塔接地装置进行选择。过去,一般认为杆塔接地系统分流并不多,但很多实地测量表明,杆塔接地装置所占分流部分比重很大。文中首先对常用杆塔接地装置的现状进行分析,找出降低杆塔接地装置接地电阻的方法。由于杆塔周围的接触电压、跨步电压和地电位升与杆塔故障入地电流有关,而较小的杆塔接地电阻阻值,可以提高杆塔接地装置的入地电流下泄能力,因此,可以从常用杆塔接地装置中选择出工频接地电阻和冲击接地电阻较小的杆塔接地装置。结合现场试验,可选择出更合适的杆塔接地装置形状。同时,随着杆塔档距、档数和接地电阻阻值的变化,可以得到三者对杆塔分流系数的影响关系。本文对输电线路杆塔接地系统做了实验研究,实验结果表明:材料总体积固定时,接地体半径越小,工频接地电阻也就越小;在30KHz以内,接地装置在高频冲击下电感效应远大于阻抗效应;土壤电阻率越大,冲击特性所反映的相应接地阻抗均明显增大;当杆塔接地电阻越小时,电网分流系数越大;根据杆塔接地电阻、档距和档数的变化,模拟分析出分流系数的数值变化,当杆塔接地电阻大于15欧姆时,分流系数基本不再变化;接地装置的分流系数的大小与档距和档数变化成正比,且当档距和档数变化越大时,分流系数变化也越大。当杆塔的档数在15档以上,档距大于400米时,分流系数基本维持在一个稳定值。杆塔档距、档数和杆塔接地电阻由于在一定程度上相对地改变了地线和接地网的分流能力,因此对接地网分流系数有较大影响。
[Abstract]:Power grid operation shows that good grounding protection is the basis for safe operation of power system. At present, the transmission network of our country is developing towards the direction of higher voltage level and larger transmission capacity, therefore, the fault current entering the ground through the transmission line tower grounding device is also becoming very high. In the past, the voltage level of transmission lines was not high and most of the towers were located in high mountains or places where the flow of people was very small, so the lightning protection and protection of the lightning protection lines were considered more, and the potential distribution around the grounding system of the towers was also considered. The problems of ground potential surge and dispersion are less considered. With the development of the "strong smart grid" and the emergence of higher voltage transmission lines, the number of transmission line towers is increasing in areas with large human flow. When a single-phase grounding fault or other type of fault occurs near the grounding system of the tower in some areas, the step voltage around the tower has exceeded the safety value. Therefore, in the course of the design, construction and operation and maintenance of transmission lines, in addition to the lightning protection factors of transmission towers, it is also necessary to consider the diffusing and diffusing factors around transmission line towers. The common earthing device of pole tower in special area is selected. In the past, it was generally believed that there were not many diversions in the earthing system, but many field measurements showed that the earthing device of the tower accounted for a large proportion of the shunt. In this paper, firstly, the current situation of common grounding devices is analyzed, and the method to reduce the grounding resistance of tower earthing devices is found out. Because of the contact voltage around the tower, the step voltage and the ground potential rise are related to the grounding current of the tower fault, and the smaller resistance value of the tower grounding can improve the discharge ability of the earthing current of the tower grounding device. It is possible to select the earthing device with less grounding resistance and impulse earthing resistance from common grounding devices. Combined with field test, a more suitable shape of pole tower earthing device can be selected. At the same time, with the change of the distance, number and resistance of the tower, the influence of the three factors on the shunt coefficient of the tower can be obtained. The experimental results show that the smaller the radius of the grounding body, the smaller the grounding resistance of power frequency, and the smaller the grounding resistance is within 30KHz, when the total volume of the material is fixed, the grounding system of transmission line tower is studied experimentally. The inductance effect of grounding device under high frequency impact is much greater than impedance effect; the larger the soil resistivity, the larger the corresponding grounding impedance reflected by the impact characteristics, and the larger the shunt coefficient of power network is when the grounding resistance of tower is smaller. According to the change of tower grounding resistance, distance and number, the numerical variation of shunt coefficient is analyzed. When the grounding resistance of tower is more than 15 ohms, the shunt coefficient will not change. The magnitude of the shunt coefficient of the earthing device is directly proportional to the variation of the distance and the number of files, and the greater the variation of the distance and the number of files is, the greater the variation of the shunt coefficient is. When the tower has more than 15 stalls and a distance of more than 400 meters, the shunt coefficient is maintained at a stable value. Due to the relative variation of the distribution capacity of ground wire and grounding grid to some extent the distribution coefficient of ground grid is greatly affected by the distance between tower and tower the number of stations and the grounding resistance of tower.
【学位授予单位】：西安科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM75;TM862

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