Page 529 - Decision Making Applications in Modern Power Systems

488 Decision Making Applications in Modern Power Systems

FIGURE 18.7 Performance of proposed WPE_BDT-2 module in case of a stable power swing.
(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) Three stepped MHO
relay characteristics (E) Output of WPE_BDT-2 module during stable PS. WPE_BDT, Wavelet
packet energy and bagged decision tree.

depicted in Fig. 18.7A C, respectively, and Fig. 18.7D the performance of
the three-stepped MHO relay characteristic with double blinder PS detection
technique in R X plane, and Fig. 18.7E shows the output of proposed
WPE_BDT-2 module output, which remains at zero level confirming the sys-
tem state in stable PS. Furthermore, an unstable PS is initiated and illustrated
in Fig. 18.8, when the same fault is cleared after 9-cycles from the fault incep-
tion at 1.18 seconds (PS has been initiated). From Fig. 18.8A C,itcan be
appreciated from the high swing rate of the voltage and current waveforms,
that it is an unstable PS condition. Therefore the impedance seen by the MHO
relay enters in its third zone in Fig. 18.8D, and correspondingly, the output of
WPE_BDT-2 module in Fig. 18.8E rises up to high (1) level at 1.243 seconds,
confirming it to be an unstable PS.

18.5.3 Detection of faults during power swing condition

The conventional distance relays fail to detect the fault during PS owing to
blocking through PS blinders. However, if fault during PS remains unde-
tected, it may damage the equipment and create a severe economic loss. It is
very important to detect the fault during the PS condition to prevent malo-
peration of distance relaying scheme, thereby neutralizing the PSB function.
In the proposed protection scheme, WPE_BDT-3 module is used for detec-
tion of shunt faults during the PS has been trained and tested for different
combinations of training and testing datasets using cross-validation