-Uo (Polarizing quantity)
Backward
area
Forward
area
Io (Operating quantity)
Zero torque line
Minimum
operate current
Maximum torque line
forward direction (RCA = 0˚)
Correction angleCorrection angle
Forward
area
Backward
area
Figure 308: Definition of correction angle
The polarity of the polarizing quantity can be changed (rotated by 180°)
by setting
Pol reversal
to "True" or by switching the polarity of the
residual voltage measurement wires.
Residual power calculation
The Residual power calculation module calculates the magnitude of residual power
3UoIoCosφ. Angle φ is the angle between the operating quantity and polarizing
quantity, compensated with a characteristic angle. The angle value is received from
the Directional calculation module. The Directional calculation module enables the
residual power calculation only if the minimum signal levels for both operating
quantity and polarizing quantity are exceeded. However, if the angle calculation is
not valid, the calculated residual power is zero. Residual power (RES_POWER) is
calculated continuously and it is available in the monitored data view. The power
is given in relation to nominal power calculated as Pn = Un × In, where Un and In
are obtained from the entered voltage transformer and current transformer ratios
entered.
Level detector
Level detector compares the magnitudes of the measured operating quantity
(residual current Io), polarizing quantity (residual voltage Uo) and calculated
residual power to the set
Current start value
(×In),
Voltage start value
(×Un) and
Power start value
(×Pn) respectively. When all three quantities exceed the limits,
Level detector enables the Timer module.
As nominal power is the result of the multiplication of the nominal current and the
nominal voltage Pn = Un × In, the calculation of the setting value for
Power start
value
(×Pn) depends on whether Io and Uo are measured or calculated from the
phase quantities.
Protection functions
1MRS759142 F
534 REX640
Technical Manual
To Next Page
Loading...
