Study Of Method On Grounding Resistance Measurement With Short Leads And Measurement Equipment

Grounding resistance is a main technical parameter of power plant and substation grounding system. The change of grounding resistance relates the safe operation of the power system directly. But how to measure grounding resistance of large grounding grid simply and exactly is a difficult problem to electric power staff all the time.The effect of grounding resistance is summed up in this thesis, and three interference factors soil resistance, grounding grid area and vertical ground rods is analyzed.The existing measurement theory and technology of ground resistance are listed of the advantages and disadvantages of each one. The paper analyzes the measurement method with short electrode wire of grounding grid resistance, and discusses the distance between current-electrode and grounding grid. The placement of voltage-electrode with different two-layer soil mode is deduce, which is carried out by MATLAB simulating software. By using the simulation software CDEGS, the paper simulates the grounding potential in and out of the grounding grid with different two-layer soil model, and compares the measurement of short electrode wire method with the real grounding resistance, then verifies the placement of voltage-electrode selected reasonable. The position of voltage-electrode along with the soil reflection factor and the soil level thickness change rule is analyzed by drawing picture.A three rods short current wire compensation method combination of frequency-changing power measurement is discussed, and the new intelligent measurement device of the grounding grid substation grounding resistance is preliminary designed. The device using short electrode wire compensation method and the frequency-changing power supply, can greatly reduce the wire length of current and voltage fuse for small current, can eliminate the power frequency disturbance effectively, and hence enhance the accuracy of the measurement. Data-processing DSP chip used as the core of this device controls the external components and the data analysis and treatment. The influence of impedance between down-leads is eliminated from the measurement results.