LINE MONITORING AND FAULT LOCATION USING SPREAD-SPECTRUM ON POWER-LINE CARRIER

Signals transmitted over the power line carrier system are used to loc ate faults and other impedance mismatches on EHV power lines. The comp atibility and sensitivity performance requirements for doing this are summarised. Conventional remote sensing waveshapes are reviewed and di rect-sequence spread-spectrum modulation is proposed for this applicat ion. Optimal signal processing techniques are outlined and frequency d omain correlation techniques are detailed, Prototype hardware has been constructed and on-line results are presented for a 225km 330kV line, Line reflections were identified within an accuracy of 1.6km even tho ugh the channel bandwidth was limited to 50kHz by external constraints . It is shown that accuracy is dependent on channel bandwidth, signal- to-noise ratio and waveform energy. It is suggested that a further inc rease in accuracy is possible by referencing the received signal to kn own impedance discontinuities such as the transpositions, Fault locati on accuracy down to one span should be possible using this technique, which will work on both energised and de-energised lines.