多功能接地电阻测量装置设计

Multi-functional grounding resistance measuring equipment

为解决接地网及其他谐波对接地网接地电阻测量的影响,提高测量精度,采用正弦脉宽调制SPWM(Sinusoidal Pulse-Width Modulation)、数字频率合成DDFS(Direct Digital Frequency Synthesis)及微处理器控制技术,研制出了多功能接地电阻测量装置。该装置基于变频测量原理控制电源按设定的频率点输出交流信号,并经电流极注入接地网(频率范围30～70 Hz),在对电压极、电流极的测量值进行数字滤波及离散傅里叶变换DFT(Discrete Fourier Transform)后,依据获得的电压、电流同相分量计算出接地网接地阻抗及阻性分量。型式试验及现场测量结果表明,该装置操作方便、性能稳定,有效地消除了工频干扰以及谐波干扰,测量数据准确可靠,符合《接地装置特性参数测量导则》对接地网接地电阻测量的要求,适合接地网接地阻抗、土壤电阻率、导通电阻的测量。

A multi-functional grounding resistance measuring equipment based on SPWM（Sinusoidal Pulse -Width Modulation）, DDFS（Direct Digital Frequency Synthesis） and microprocessor control technology is developed to reduce the influences of grounding grids and harmonics and improve measurement precision. Based on variable-frequency measurement principle, it injects AC signal with preset frequency （30-70 Hz） into grounding grids via current probe and calculates the grounding impedance and resistance based on the co -phase components of voltage and current, which are deduced from the sampled values of voltage probe and current probe after digital filtering and DFT（Discrete Fourier Transform）. Type test and field operation show that the equipment is convenient in operation and stable in performance, effectively eliminating the power-frequency and harmonic interferences. Its measurements are correct and precise, satisfying the needs of Measure Guide for Characteristic Parameter of Grounding Sets. It is applicable for measuring the grounding resistance, soiling resistivity and connection resistance.