High Voltage Technology
The Transient Earth Detector (TED) is a device for detecting and locating insulation breakdown faults on wood pole overhead lines. It comprises two parts: a passive low-cost detector that clips around the earth wire on earthed poles, and a battery-powered hand held reader that is carried by a linesman that can be used to interrogate the detector to see if it has witnessed one or more fault occurrences.
Most faults that result in the overhead line protection tripping will occur on earthed poles where there is a clear return path for the fault current. Such faults include cracked insulators, damaged bushing or arcing horns, faulty surge arresters, internal breakdown within transformers, flashovers etc. By their nature, these faults are often intermittent and occur during adverse weather conditions/unsociable hours which means they are difficult and costly to locate. In addition, the reoccurring sequence of supply interruptions leads to significant annoyance to customers. The detector works by detecting the momentary transient earth current produced by the fault and recording it in an internal counter. The Reader, when placed near the detector, allows the contents of the detector’s counter to be displayed and, if required, re-set. By fitting a detector to each earthed pole (either routinely as part of a foot patrol, or specifically in the case of known troublesome lines) defective poles will be readily identifiable from the ground after a fault event, even whilst the line is energised