The Sigma 2.0 is a phase-selective short-circuit indicator and is used to detect, display and remotely signal short-circuit currents in medium-voltage networks. The current is measured via three single-phase current sensors. By using these sensors, a subsequent upgrade to a higher generation of indicators is possible at any time without changing the sensors. Two excitation criteria can be selected for short-circuit excitation. On the one hand, excitation takes place via a fixed response value and the duration of the set response time delay, and on the other hand via self-adjustment and a defined factor depending on the operating current. If the current of the selected response criterion – fixed response value or self-adjustment – is exceeded, the LED of the relevant phase flashes and the remote signaling contact is activated. If a second excitation occurs within the reset time, e.g. due to automatic reclosing, this is signaled by a double flashing display and the remote signalling contact is activated again. For testing and commissioning purposes, the current response values can be reduced to 10 A without changing the DIP switch settings.

The Sigma 2.0 AC/DC variant offers an auxiliary voltage connection. If the auxiliary voltage fails in the event of a fault, the LED display can be operated with capacitor support for up to 8 hours.