NONUNIT PROTECTION TECHNIQUE FOR EHV TRANSMISSION-SYSTEMS BASED ON FAULT-GENERATED NOISE .1. SIGNAL MEASUREMENT

The paper describes the basis of a protection technique for transmission lines which utilises the high-frequency (HF) components of fault-generated noise caused by arcing faults. The approach involves signal measurement in an arrangement which uses conventionally connected power-line communication-signal traps and capacitor voltage transformers (CVTs). The line traps confine the HF components to within the protected zone and the associated HF signals are then captured by specially designed coupling devices via the high-voltage capacitor of the CVT. The paper presents some interesting results relating to faults on a typical 400 kV vertical-construction transmission line. In particular, the effect on the HF signals of, for example, fault type, fault inception angle and fault resistance, is highlighted.