A technique is presented for rapid measurement of the distance to a fault using fault initiated travelling waves. The measurement uses the time it takes a given surge to travel from the relaying point to the fault and back. A correlation technique is used to recognise the surge returning from the fault and distinguish it from other surges present on the system. For a three phase transmission line, the modal components describing the incident wave are delayed and cross-correlated against the respective components reflected by the fault. Maximum output occurs when the delay corresponds to twice the fault distance.

Distance Protection Based on Travelling Waves

This paper proposes a new noncommunication protection technique for transmission line protection. The technique relies on firstly the detection of fault generated high frequency current transient signals. A specially designed multi-channel filter unit is then applied to the captured signals to extract desired bands of high frequency signals. Comparison between the spectral energies of different bands of the filter outputs determines whether a fault is internal or external to the protected zone. In addition to the saving in costs through negating the need for a communication link, the technique also retains many advantages of the 'transient based protection' technology, such as insensitivity to fault type, fault position, fault path resistance and fault inception angle. It is also not affected by CT saturation, the power frequency short-circuit level at the terminating busbar or the precise configuration of the source side networks.

A new non-communication protection technique for transmission lines

The authors examine some problem areas and suggest techniques to improve the proposed distance protection based on travelling waves outlined by P.A. Crossley and P.G. McLaren (1983). A composite correlation output is used to recognize the reflection from the fault and distinguish it from other reflections from points behind the fault. The correlator output magnitude is also used to achieve UHS (ultra high speed) fault detection for close-up faults. Effects of fault inception angle are compensated. Fault-resistance effects and external faults are also examined. >

Travelling wave distance protection-problem areas and solutions

This paper describes a fundamental approach for detecting the direction to a power system fault within the first milliseconds following the fault inception. The method is based on a combined evaluation of the voltage and current deviations generated by the fault occurrence. Design considerations and test results based on numerical simulations and on a transient network analyser are presented. The method solves several problems occurring in conventional relaying and is suitable for use in ultra high speed protection systems which employ a fast telecommunication channel between the ends of the protected network

A Fundamental Concept for High Speed Relaying

The power swing caused by various disturbances will affect distance relay behavior and may result in relay misoperation. This paper provides a fast detection scheme for symmetrical fault during power swing for distance relay, which is based on extracting the high-frequency component energy of forward and backward traveling waves induced by faults. The multiresolution analysis based on wavelet transform has the ability to decompose the analyzed signals into different frequency bands. The selection of mother wavelet and the number of levels of wavelet transform are carefully studied. The fault can be identified by feature extracting from the d1 component of Daubechies-8 (Db8) wavelet transform. The proposed approach is verified by using the IEEE reference model implemented by using the Alternate Transients Program and the test results have been presented in this paper. This proposed method can be used for distance relay operation blocking or monitoring.

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Fast Distance Relay Scheme for Detecting Symmetrical Fault During Power Swing

A new protective relay that solves many of the problems associated with the protection of EHV and future UHV systems is described. Based on a traveling wave approach the relay system operates at ultra high speed and can detect and determine the direction to a fault in a few milliseconds. The relay operating principle, design and application are presented as well as results from computer simulation studies and laboratory tests. The first relay system was installed in the USA in Bonneville Power Administration's 500 kV system and represents a substantial contribution to present efforts to shorten fault clearing times as a method to improve system stability and power transfer capability.

M. Chamia

Papers

Ultra High Speed Relay for EHV/UHV Transmission Lines -- Development, Design and Application