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6. SETTINGS
Settings are defined using selectable DIP switches. A diagram of the DIP switch array is shown in Figure 6.1 below.
Figure 6.1: Sigma 3 Dip Switch Array
6.1 Trip Relay Operating Modes
The trip relay operating settings can be set with DIP switch 1. The Sigma 3 can be set for a shunt trip operating mode
(not failsafe) or an undervoltage trip operating mode (failsafe) operation with the trip relay operating mode dip switch.
See Table 6.1 for configuration details.
6.1.1 Shunt Trip Mode
In the shunt trip mode (not failsafe), the trip relay remains de-energized (no trip) when control voltage is applied to the
Sigma monitor relay and the system is operating normally. The trip relay is energized (trip) when the measured values
of the ground fault current or NGR Resistance exceed the threshold settings for the time specified.
The trip relay will energize (trip) after a fault is qualified and will remain energized (tripped) until the Sigma monitor relay
is reset whether or not the fault that caused the trip remains present on the system. The trip relay will be de-energized
(no-trip) if the control voltage is removed.
When control voltage is applied the trip relay will at first be de-energized (no-trip) and the Sigma monitor relay will start
operating normally. If the trip memory option is OFF the trip relay will remain de-energized (no-trip). However, if the trip
memory option is ON and a trip state is stored in the non-volatile memory, the trip relay will energize (trip) approximate-
ly 1 second after control voltage is applied and will remain energized (tripped), regardless of whether a fault is present
on the system.
The trip relay will de-energize (no-trip) if the Sigma monitor relay is reset through a local or remote reset. When reset,
the Sigma monitor relay will resume monitoring of the system and, if a fault remains on the system, will detect the fault
and will re-trip, energizing the trip relay.
6.1.2 Failsafe (Undervoltage Trip) Mode
When programmed for the FAILSAFE (UNDERVOLTAGE TRIP) MODE and the Sigma 3 is operating normally, the trip
relay energizes approximately 1 second after control voltage is applied. The trip relay de-energizes (trips) under any of
the following conditions:
- The measured values of the ground fault current or NGR resistance exceed the threshold settings for the
time specified
- The Sigma 3 is reset
- Control voltage is removed
