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Thus, at the end of the process, the result should be an optimized grounding system. To
evaluate this, the electrical parameters of the grounding system will be initially estimated,
taking into account its own structural parameters, such as number of stems, distance
between them and their depths.
Once the electrical parameters of the grounding system are known, the characteristic
impedance of the grounding can then be calculated. This characteristic impedance is a value
that allows relating the propagation of voltage induced by the distribution system to the
propagation by the grounding system. To relate both modes of propagation, it is necessary
to consider the electrical data of the feeder.
Once the parameters to model the distribution system at high frequencies are known, as
well as the characteristic impedance of the grounding system, it is then possible to conduct
simulations to verify impulsive voltage in the system.
To illustrate this evaluation procedure, a feeder in which the grounding system is not
optimally implemented will be considered. This feeder belongs to the substation BIR of EDP
Bandeirante. The induced voltage in the distribution system was calculated by assuming
standard data for the lightning. The temporal behavior of the induced voltages is presented
in Figure 16.
time (s)
Fig. 16. Behavior of induced voltages for a non-optimized grounding system.
Fig. 16 shows that the peak value of induced voltage to a non-optimized grounding system
was above 140 kV (in module). These magnitudes can be compared with those obtained
when considering an optimized grounding system.
