Intelligent Power Swing Detection Scheme to Prevent False Relay Tripping Using S-Transform

Abstract

Distance relay design is equipped with out-of-step tripping scheme to ensure correct distance relay operation during power swing. The out-of-step condition is a consequence result from unstable power swing. It requires proper detection of power swing to initiate a tripping signal followed by separation of unstable part from the entire power system. The distinguishing process of unstable swing from stable swing poses a challenging task. This paper presents an intelligent approach to detect power swing based on S-Transform signal processing tool. The proposed scheme is based on the use of S-Transform feature of active power at the distance relay measurement point. It is demonstrated that the proposed scheme is able to detect and discriminate the unstable swing from stable swing occurring in the system. To ascertain validity of the proposed scheme, simulations were carried out with the IEEE 39 bus system and its performance has been compared with the wavelet transform–based power swing detection scheme.

Adaptive Distance Protection to Prevent False Relay Tripping during Power Swing

“…Initially, the relay continuously monitoring the measured voltage and measured current. Once the measured voltage or measured current enters the fault detection area, the relay shall distinguish between a fault and power swing by using the indicator proposed by authors in [8] and [9].…”

“…Power Swing Indicator. The developed power swing detection technique proposed by author in [8] is based on the use of S-Transform feature of active power at the distance relay point. The detection process starts with retrieving the active power at distance relay point, followed by S-Transform processing to produce the S-matrix.…”

“…• For measured current and voltage that between two setting values, x3 = (I trip -I>) + 1 (7) where I trip = measured current that enters the tripping region I> = minimum current pickup I>> = over-current pickup As aforementioned in [8], the minimum current pickup, I> is equal to 0.5 times the nominated current, I N and the over-current pickup is equal to 2.5 times the nominated current, I N . Thus, the new adaptive tripping relay setting function can be expressed as,…”

Performance of power swing blocking methods in UPFC-compensated line

“…Time frequency transforms are other solutions for this issue. Wavelet transform and S‐transform are presented in Dubey and Samantaray and Mohamad and Abidin, respectively, to detect power swing, but they require high sampling rate, a requirement of most time‐frequency transforms. Another method based on adaptive neuro‐fuzzy inference system and support vector machine have been proposed in Chothani et al These methods require many simulations in different conditions for training process and even retraining in other power system.…”

Adaptive concentric power swing blocker

“…Application of time frequency transforms is another solution. Wavelet transform and S-transform are presented in [8] and [9] respectively, to detect power swing but they require high sampling rate, which is a requirement of most Time-Frequency transforms. Another method based on adaptive neuro-fuzzy system is proposed in [10].…”