Design Of Apparatus For Measuring Grounding Impedance Based On The Impulse Current

The measurement of grounding resistance is of great importance for stable operation of power system, and for safety of electronic equipment and person.At present, many measurement methods and measurement apparatus are used to measure ground resistance under industrial frequency. However, many tests show that characteristics of grounding device under the impulse current are nonlinear time-varying which are very different from characteristics under the industrial frequency current. The grounding grid, especially in large grounding grid, the inductive component can not be neglected; in the role of the impulse current containing high frequency components, such as the lightning current, the inductance effect significantly and even played a major role. Therefore, the traditional measurem -ent methods of grounding resistance of grounding grids can not reflect the situation, we should focus on the research of the grounding impedance in the conditions of impulse current.Based on the above, we propose that impulse current with sharp wave head and large amplitude as the test current to simulate lightening current is injected into grounding systems, the data acquisition device collects the current and voltage signals of grounding systems respectively, which are transformed from time-domain to frequency-domain, then impulse grounding impedance, resistance and inductance component can be calculated.Finally, we carried out a field test measurement to grounding grid in power plant of Pangzhihua steel plant using impulse grounding impedance measurement device, and combined with theoretical analysis of the impact of characteristics of the grounding grid. It is proved that impulse grounding impedance measured is real and effective, and the apparatus is applicable to practical engineering survey.