Influence of the nature of impulse current propagation in soils on transient impedance characteristics

The reported methods dealing with calculation of transient impedance of an earth electrode assume that the lightning current diffuses into the conducting soil. From the results of recent indoor and outdoor experiments it is shown that the above mechanism is not always operative and that the nature of current propagation in the soil is related to soil characteristics and parameters of the impulse current generator. The response of the soil has been investigated with different types of soils with different resistivities. The differing mechanisms of current propagation in dry and wet soil are indicated; it is shown that a lower impedance results in the former case