Precision location system for high resistance cable faults - operates with synchronised trigger, time-shifted display unit and laser generator

摘要

The fault location system consists of a high-voltage DC source which charges up a capacitor via its internal resistance. A CRT display and trigger unit triggers a laser generator. The generator causes the capacitor to discharge via a choke and spark-gap. One of the spark gap electrodes is connected to the near end of the cable under test and, via a capacitor, to the vertical input of the display/trigger unit. The capacitor is able to recharge between trigger pulses. The reflected energy from the breakdown point on the faulty cable appears at the end of the cable and is displayed on the oscilloscope with a time delay. The time-shift unit is operated so that a narrower time range is selected so that an accurate display of the measured location of the fault is obtained by means of the synchronisation method employed. The test gear is suitable for the location of high-resistance, intermittent cable faults.