The Navigator-LM Short-Circuit Indicator is an electronic device which is designed for medium-voltage utility overhead lines. It consists of a housing made from black UVstable polyamide material with a stainless steel clamping mechanism, a transparent cap, a display unit with light emitting diodes, and an electronic circuit. The Short-Circuit Indicator is powered by replaceable long -life lithium batteries which have a life expectancy of 15-20 years. The display unit is provided with an integrated battery control. When the battery capacity decreases from a total indicating time of 400 hours to a residual time of 50 hours, the indicator will signal this condition via a flashing yellow indicator light for up to 6 months. The Short-Circuit Indicator is installed on and removed from overhead lines with a hot stick. The display unit provides excellent visibility from all sides.
The Navigator -LM is provided with a load-dependent-self-adjustment of the trip current, i.e. the indicator continuously samples the load current on the overhead line and electronically sets a corresponding trip point for a fault according to the load current. The maximum load current is kept in a 72 hour high load memory so that the indicator is most favourably adapted to the network to be monitored even if low load is present.
The Navigator-LM allows for differentiating between two subsequent short-circuit detections. The detection of the first short-circuit results in an equally flashing LED, whereas upon detecting a second short-circuit (e.g. after ARC) the LED is switched to double flashing.
