Page 538 - Decision Making Applications in Modern Power Systems

496 Decision Making Applications in Modern Power Systems

FIGURE 18.12 Performance of WPE_BDT-3 and -4 modules for detection/classification of
phase-A1 to ground fault during PS: (A) Three phase instantaneous currents of circuit-I (B)
Three phase instantaneous currents of circuit-II (C) Three phase instantaneous voltages at
sending-end bus (D) Fault detection using WPE_BDT-3 module (E) Fault classification
using WPE_BDT-4 module. PS, Power swing; WPE_BDT, wavelet packet energy and bagged
decision tree.

3.053 seconds. From Fig. 18.12 and test results in Table 18.11, the efficacy
of the proposed scheme has been confirmed for variation of the source
impedance.

18.5.4.4 Performance during variation in sampling frequency
It is imperative to test the impact of variation in sampling frequency on the
proposed scheme. In this regard, different type of case studies have been per-
formed with variation in sampling frequency at 1.2, 5, 10, and 20 kHz, and
the test results are summarized in Table 18.12 by assuming fault parameters
L f 5 25 km, R f 5 10 Ω, φ 5 90degrees. The results from Table 18.12 show
f
that the proposed WPE_BDT modules are not affected by variation in the
sampling frequency.

18.5.4.5 Performance during current transformer saturation and
capacitor coupling voltage transformer transient
While measuring high fault currents at the relaying point, it is imperative to
consider the effect of measuring CT saturation due to large DC offset current
component in the faulty signal which may lead to an error in measurements
and creates overreach problem as well. In order to assess the influence of CT