接地装置冲击接地电阻测试方法

雷击是影响电力系统安全运行的重要因素,接地装置是雷电防护的主要设施,其性能需要定期检测,但目前缺乏有效的测试方法。实地埋设了小型接地装置,通过实测,研究了三极法、圆环回流法等测试方法的优缺点,并从理论上分析了圆环回流法产生误差的原因。通过测量和仿真计算,提出了使用均流圆环的冲击接地电阻三极法测试方法,给出了均流圆环尺寸与接地装置形状的关系。研究表明,使用围绕被测接地装置的圆环作为回流极进行冲击接地电阻测试得到的结果偏小,在已有三极法的基础上增设独立的均流圆环后可以使得接地装置周围的电流分布更加均匀。在实际测量中,对大多数形式接地装置,均流环半径应不小于接地装置对角线的长度。

Measurement Method of Impulse Grounding Impedance of Grounding Device

Lightning is an important factor affecting safe operation of power system.Grounding device is the main facility of lightning protection.Its performance needs to be tested regularly.But at present there is no effective test method.In this paper,a small grounding device is embedded on-site.The advantages and disadvantages of three-pole method and the method using ring as current-return electrode are studied.The causes of measuring error of the method using ring as current-return electrode are analyzed theoretically.By means of measurement and simulation,a three-pole method using an additional ring as current-sharing ring is proposed,and the relationship between ring size and the shape of grounding device is given.The study shows that the measured grounding impedance with ring around the measured grounding device as current return pole is relatively small.In the three-pole method,application of a separate ring surrounding the grounding device under test can make the current distribution near the grounding device more even.In practice,no matter what kind of grounding device,the radius of the current-sharing ring shall not be less than the diagonal distance of the grounding device.