Surge Impedance Relay

Optimizing solution of fault location using single terminal quantities

“…Modulus maxima (MM) of dyadic wavelet transform (WT) are more useful in this case. These MM denote WT component's local extremum and indicate the exact time points of the sharp changes of waveform [7,17] as in Figure 6. Fault location can be simply calculated with the following formula [17] :…”

“…Transient traveling waves generated by fault possess abundant information, which has been made use of successfully to develop directional elements [7] . In fault location, the velocity of traveling wave is a constant for a given transmission line.…”

Fast isolation of faults in transmission systems using current transients

“…Alternative to using power frequency phasor based techniques, high frequency components of the voltage and current signals can also be used to develop protection schemes [1][2][3][4][5][7][8][9]. Transient based techniques can be very fast and immune to power swings and CT saturation.…”

“…Majority of the transient based protection schemes use traveling waves formed after a fault and their reflections by the fault to estimate the distance to a fault [1][2][3][4][5]9]. However, traveling wave methods have their own limitations.…”

“…Several solutions have been proposed for this problem. Surge impedance relay proposed in [5] determines fault direction by using the ratio of initial voltage and current traveling waves under multiple frequency bands. Surge impedance relay utilizes wavelet transform to extract traveling waves.…”