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Figure 6.36: EPR and injected current for the tower base earth impedance
measurement. Tower leg four disconnected.
Figure 6.38 shows the EPR and injected current characteristics for the earth
tower base impedance measurement before and after tower leg four was disconnected.
The RMS of the injected current and applied voltage, shown in Figure 6.38(a,b),
indicate that the injected current magnitude decreased and the EPR increases slightly
when leg four was disconnected about 70 seconds into the test.
Figure 6.38(c) shows a 3% THD for the injected current with that value jumping
to 7.5% due to the switching operation and then settling to around 4.3%. The THD of
the applied voltage is rather constant at 0.3% throughout the 10-minute test, with a jump
to 1.6% due to the switching out of leg four.
A reduction in the average power can be seen in Figure 6.38(e), around 70
seconds into the test, again due to disconnecting out of leg four. The accumulated
energy also shows a small reduction in its rate of increase which is attributed to the
disconnecting out of leg four.
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