ABB RELION Series, Technical Manual

Page: 371 / 804

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,
and depend on the
Io signal Sel and Uo signal Sel settings.
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.
When calculating the setting values for Level detector, it must be considered that the
nominal values for current, voltage and power depend on whether the residual
quantities are measured from a dedicated measurement channel or calculated from
phase quantities, as defined in the
Io signal Sel and Uo signal Sel settings.
For residual current Io, if "Measured Io" is selected, the nominal values for primary
and secondary are obtained from the current transformer ratio entered for residual
current channel
Configuration/Analog inputs/Current (Io, CT) . If "Calculated Io"
is selected, the nominal values for primary and secondary are obtained from the
current transformer ratio entered for phase current channels
Configuration/Analog
inputs/Current (3I, CT) .
For residual voltage Uo, if "Measured Uo" is selected, the nominal values for primary
and secondary are obtained from the voltage transformer ratio entered for residual
voltage channel
Configuration/Analog inputs/Voltage (Uo, VT) . If "Calculated
Uo" is selected, the nominal values for primary and secondary are obtained from the
voltage transformer ratio entered for phase voltage channels
Configuration/Analog
inputs/Voltage (3U, VT) .
Calculated Uo requires that all three phase-to-earth voltages are
connected to the protection relay. Uo cannot be calculated from the
phase-to-phase voltages.
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.
Table 377: Measured and calculated Io and Uo
Measured Io Calculated Io
Measured Uo Pn = (Uo, VT) × (Io, CT) Pn = (Uo, VT) × (3I, CT)
Calculated Uo Pn = (3U, VT) × (Io, CT) Pn = (3U, VT) × (3I, CT)
Example 1. Io is measured with cable core CT (100/1A) and Uo is measured from
open delta-connected VTs (20/sqrt(3) kV:100/sqrt(3) V:100/3 V). In this case,
1MRS758755 A
Section 4
Protection functions
REC615 and RER615 365
Technical Manual