A CORRELATIONMETHOD FOR TRANSMISSIONLINE PROTECTION

Most methodsfor determiningthe fault locationon a power transmission line known A method of transmission line protec- todayare based on the fundamentalsinusoidal tion based on a distributed parametermodel voltageand current signal components.Conseof the line is outlined. It is shown that quently,the undesired transientsignalcomthe fault distanceappears as a time delay ponents must be suppressed prior to evalubetween two quantities associated with the ating the voltageand current waveforms.In travelling waves at the measurement site.The4E conventionalelectromechanicaldevices, for time delay can be extractedfrom the funda- example,the DC-transient can be compensated mental voltageand current waveforms in the to a certain extent by the use of an inducpresence of superimposedline transientsby K tive lumpedparameterline replicawhile the means of a correlation technique.The pro- > highfrequency oscillationsare normallyof posedmethodhas been tested by numerical'< littleconcern due to the inertiaof mechanisimulationsand by means of a real-time cal parts. In solid state relaysthe problem analog-typecomputeron a model transmissionN of high frequencytransientscan be solved by line and the resultswere found to be satis- providing adequatebut time consuming filterfactory.The feasabilityof a digitalcomput- N ing. Since the late 1960's,when computer er implementationis brieflydiscussed. relayinghas come to the attentionof protec! tion engineers, a number of computer-oriented