Designing Of Measuring System For Ground Impedance Of Earth Screen

As the development as the power system, the expansion of electrical network scale, and the application of various microcomputer monitoring aids, the requirement of grounding is more and more strict. And one of the most important standards of grounding is the value of the earth screen.But the results of many measuring methods for ground resistance were ground resistance under industrial frequency, and those methods could rise accuracy of measurement or reduce the noise when measuring. Even the frequency-changing method and different frequency method could only compute the ground resistance under industrial frequency.After the long time observation at electric power plant in many places, however, we found that the most current earth screen received was lightning current, and the lightning current is an instant unipolar pulse with steep wave front, and contents plentiful frequencies. The process was different when lightning current flowed into earth screen compares to conventional measuring signal.Under the impulse current circumstances, ground resistance was still working, but the reactive resistance could not be ignored, even it is the most important component. So, the concept of ground resistance under industrial frequency was not working when referred to impulse current. We should study the earth screen's impedance under the impulse current.So, we made the experiments on earth screen with impulse current based on the concept of impulse grounding impedance and the advantages of conventional methods, and we worked out the results of resistance and inductance by optimized arithmetic. After analyzed the data from the scene, we confirmed that this system deserved popularization.