D. Status of Ferroresonance detection tools
Ferroresonance detection tools register status of parameters
continuously. At the beginning of Ferroresonance (in the time
of 0.1 s), all orders of harmonics are presented in waveforms
of parameters. The magnitudes of 2
th
-15
th
orders in current
waveform of HV side are 10-60 % respectively. Maximum
value of T.H.D becomes 248, 260, and 192 % for 3 phases
respectively. Frequency varies irregularly from 55 to 74.5 Hz
for 0.3 s. Consequently, a continuous harmonic spectrum (Fig.
6e) and non-periodic characteristic (irregular frequency
variation) is the evidence of existing chaotic mode of Ferro-
resonance. In the time of 0.3 s, harmonics are changed to new
values. Waveforms of harmonic orders follow power
oscillation in the network. T.H.D value of current varies from
90 to 165 %. In addition, frequency varies irregularly from 60
to 83 Hz. Nevertheless, it is considered that chaotic mode of
Ferroresonance is presented again with values different from
previous state.