Inventor
Associate Professor Dr. Normiza Binti Mohamad NorDescription of Invention
Earthing systems are installed to allow any high fault currents to be effectively discharged to the ground. Grounding systems are normally assessed at low voltage, low frequency currents, using earth tester, to obtain for dc resistance value, RDC. However, under high impulse currents such as lightning, switching or temporary overvoltages (TOV), the performance of grounding systems is found to be different that that RDC. It has been shown in many studies that the resistance of earthing systems become ‘non-linear’ under high impulse conditions. The nonlinearity of the resistance of earthing systems is found to be attributed by ionization, or local discharges in soil in the area where the electric field gradient exceeds the critical electric field. The earth resistance can be lower than that earth resistance measured at steady-state, RDC. On the other hand, under high impulse conditions, the inductive component can become significantly dominant due to extended ground electrodes, wires, or strips and the steep impulse front wave, which can increase the impedance of the earthing systems. From these non-linear characterization and inductive components of earthing systems under high impulse conditions, which are different than that measured at steady-state, it is therefore important to assess the practical grounding systems under high impulse conditions. So far, there is no specific standard per say can be found in discussing and outlining all important aspects of measurements and testing of earthing systems by field measurements under high impulse conditions. This invention is to provide the experimental arrangement (test set up) and equipment for testing practical grounding systems under high impulse conditions.