Grounding impedance reduction

Effect of Electrode Shapes on Grounding Impedance Reduction... 

Reduction of Grounding Impedance Effect of Electrode Shape... 

There are a number of publications that discuss the reduction of grounding impedances. In recent years it has become common to install digital circuits not only in power system control equipment but also in buildings and home appliances. Thus, it becomes more important to reduce the grounding impedances to guarantee reliable operation of the digital circuits for both steady and transient states as observed in References 47, 48, 49 and 50. From the above, KEPCO carried out a series of field tests to measure the grounding impedances. 

This section shows field test results of transient and steady-state responses on grounding electrodes with various shapes, that is, a vertical rod, a rectangular plate, a circular plate, etc. [29]. The field tests were carried out in different seasons over a period of 3 years to obtain reliable results. Then, NEA simulations were carried out using VSTL [39] that is based on an FDTD method. A comparison with the measured results is first made to confirm the accuracy of the VSTL. Then, the VSTL is applied to investigate the reduction of the grounding impedances with various electrodes. 

Figures 7,40 and 7.41 show FDTD simulation results corresponding to the measured results in Figures 7.37 and 7.38. The simulation results of peak and steady-state voltages are given in Table 7.6. In the simulation, the soil resistivity is set at 150 Qm and the relative permittivity is 10. It can be observed in the table and figures that the simulation results agree reasonably well with the measured results. Thus, it is possible to investigate the effect of electrode shapes on the reduction of grounding impedances.

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