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Voltage Check
Voltages are checked and closing of the circuit breaker is permitted only when the following
conditions are fulfilled.
- Voltage is higher than the set value Vov (live condition) on one end of the circuit breaker and
lower than the set value Vuv (dead condition) on the other end.
- Voltages are dead on both ends.
The synchronism check zone is shown in Figure 2.5.5 (a) and in Figure 2.5.5 (b), A, C and D are
voltage check zones and B is a synchronism check zone.
2.6.4
Metering and Counter Function
The GRD150 measures current and demand values of phase currents, phase and phase-to-phase
voltages, residual current, residual voltage, symmetrical component currents and voltages,
frequency, power factor, active and reactive power, and energy. The measurement data shown
below is displayed on the LCD of the relay front panel or on the local or remote PC.
Current
The following quantities are measured and updated every second.
- Magnitude and phase angle of phase current (I a , I b , I c )
- Magnitude and phase angle of zero sequence current from residual circuit (I e )
- Magnitude and phase angle of zero sequence current from core balance CT (Ise) for model 200
and 400 series
- Magnitude and phase angle of symmetrical component current (I 1 , I 2 , I 0 )
- Magnitude and phase angle of phase voltage (V a , V b , V c )
- Magnitude and phase angle of phase-to-phase voltage (V ab , V bc , V ca )
- Magnitude and phase angle of zero sequence voltage which is measured directly in the form of
the system residual voltage (Ve) for model 100 and 300 series
- Magnitude and phase angle of voltage for synchronism check (V s ) for model 300 and 400 series
- Magnitude and phase angle of symmetrical component voltage (V 1 , V 2 , V 0 )
- Active power (P)
- Reactive power (Q)
- Active energy (Wh)
- Reactive energy (varh)
- Power factor (PF)
- Frequency (f)
- Frequency rate-of-change (Hz/s)
- Percentage of thermal capacity (THM%)
Demand
- Maximum, minimum and average of phase voltage (V a , V b , V c : max, min, av)
- Maximum, minimum and average of phase-to-phase voltage (V ab , V bc , V ca : max, min, av)
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