
492 Power System Transients
dependent on σ, ε, and μ. When the separation distance becomes large, cur-
rents in the soil concentrate at ground level, and thus, the propagation veloc-
ity converges to the light velocity in free space.
7.4.2 Theoretical Analysis of Transient Response
A model circuit of a grounding electrode composed of a RC parallel circuit
and a distributed-parameter line is illustrated in Figure 7.26a [28]. The imped-
ance ωL being far greater than the resistance R of the distributed line in gen-
eral, the model circuit of Figure 7.26a is simplied as Figure 7.26b where L
0
is
the series inductance of the distributed line and L′ is ...