Investigation of the Transient Behaviour of Earthing Systems Subjected to High Impulse Currents - Dissertation Example

The effect of the transient voltages and currents on the earthing systems has a great influence on the performance and evaluation of the substation equipment against lightning overvoltage. While the characteristics of the earthing system under steady-state depends on the electrode design and soil prosperities alone, the characteristics of the earthing system under impulse currents depends on the magnitude and shape of the impulse current. The experimental setup for the impulse tests on earthing systems has been designed with an impulse generator, voltage and current transducers and different types of earthing systems.

The impulse tests with impulse voltages ranging from 500 V to 4 kV have been carried out and the impulse resistances have been calculated. The calculated resistances have been compared with the measured resistances and the error is found to be negligible. The simulation of the analytical data has been carried out with the aid of LT SPICE for the 2, 3 and 4-rod bed earthing systems. The simulated waveforms and the experimental waveforms have been compared and it has been proved that they are close to each other.

Thus the measured values have been validated by the simulated values.Most of the practical electrical systems are not perfectly shielded or isolated from other systems and the environment. The systems may be connected externally with each other through communication cables, power supplies and pipes that carry gas or water. Thus any electrical disturbance in the vicinity of the system leads to potential difference and transient energy transfer between the system and the environment. These electrical disturbances may cause damage to the systems and injury to people in that vicinity.

To avoid these risks, there has to be a grounding system. A safe and good earthing system is expected to dissipate the excess or unexpected currents into the ground and guarantee the continued operation of the equipment even under fault conditions.