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To protect against loss of polarization voltage, the system includes adjustable fuse-failure logic. This logic
allows to either block the operation of the units or to convert the directional units into non-directional. The
selection is done through a setting. The fuse failure function operates on two different conditions (OR logic):
- Operation of undervoltage detectors (adjusted at 3.5 volts)
- Activation of a digital input connected to the voltage MCB.
• Phase over and under voltage:
• Under voltage:
• Over voltage:
The three-phase under and overvoltage units operate under conditions of under or over voltage (depending
on the unit) in any of the three phases. Both units are adjusted and operate on phase-to-phase voltage
values, calculated from the phase-to-ground voltages applied to the unit.
•
Ground overvoltage:
•
High Setting:
•
Low Setting:
There are two ground overvoltage units. The SMOR7000 model has a dedicated open-delta input. In all
other models the voltage is calculated from the phase to ground inputs.
•
Underfrequency :
•
Overfrequency:
The under and over frequency units are measured on one phase (phase B).
27P
59P
59 NH
59 NL
81U
81O
GEK-105593C
8
2.1.3. VOLTAGE UNITS
2.1.4. FREQUENCY UNITS
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