Fault Position Identification And New Principle Of Protection For Series Compensated Transmission Lines With SSSC

Static Synchronous Series Compensator(SSSC)is a new-series compensatorcomponent of FACTS family With the continuous development and application ofstatic synchronous series compensator,the complication of its structure and controlbecomes a challenge to the conventional extra--high--VOltage transmission lineprotection,which w-e have to study further Based on the analysis of the principleofSSSC,the influence of SSSC onthe measured impedances ofdistance protectionand the operation characteristic of the impedance relay is studied Results show-that SSSC may make the impedance relay over--reaching or under--reaching w-henSSSC is included in fauIt loop Then the wavelet packet entropy is improved toenhance its sensitivity in fault detection,which is used to analyze the transient faultcurrent in the relaying point ofthe series compensated line with SSSC The resuRsshow-that the wavelet packet entropy w-hen the fault point is before SSSC is muchhigher than that w-hen the fault point is behind SSSC According to thischaracteristic,the scheme of identifying fault position for series compensated linesis put forward,on the basis of which measured impedance of distance protection isadjusted When the wavelet packet entropy at the relaying point is lower than theset wavelet packet entropy,the fault point is behind SSSC and the actual t:auItimpedance is the original measured impedance minus additional impedance On thecontrary,the actual impedance is just the impedance Simulation results show-thatthe adjustion scheme can eliminate the influence of SSSC on distance protectioneffectively SO that the impedance relay can operate correctly As the wavelet packetentropy in both ends of the line is obviously different w-hen the internal or externalfauIt occurs,according to the characteristic that the differences of wavelet packetentropy in both ends of line w-hen the internal fauIt occurs is much higher than thatw-hen the external occurs,a scheme of two-end transient protection for the seriescompensated lines with SSSC is proposed The simulation show-s that it canefficiently distinguish the internal and external fault...