ABB RER620 Technical Manual page 275

1MAC309294-MB F
RER620
Technical Manual
Table 279: Recommended Characteristic angle setting for different network
Type of network
Compensated network
Solidly earthed network
Isolated network
The Characteristic angle setting is adjusted to the operation according to the method of
neutral point earthing so that in an isolated network the Characteristic angle = -90° and in
a compensated network = 0°. In addition, the Characteristic angle can be changed via the
control signal RCA_CTL, in which case the alternatives are -90° and 0°. The operation of
the RCA_CTL depends on the Characteristic angle setting.
The Peterson coil or the earthing resistor may be temporarily out of operation. To keep the
protection scheme selective, it is necessary to update the Characteristic angle accordingly.
This is done with an auxiliary input in the relay which receives a signal from an auxiliary
switch of the disconnector of the Peterson coil in compensated networks or of the earthing
resistor in earthed network as a result the Characteristic angle is set automatically to suit
the earthing method. The table below shows the Characteristic angle control for
RCA_CTL condition.
Table 280: Characteristic angle control for RCA_CTL condition
Characteristic angle Setting
-90°
0°.
Low level blocking
For reliable operation, signals levels should be greater than minimum level. If they are not
greater than minimum level, Timer is blocked.
In "Neg. seq. volt." polarization selection using Pol signal Sel, if the amplitude of the
negative sequence current is greater than Min operate current value and negative sequence
voltage amplitude is greater than Min operate voltage value then enable signal is sent to
the Timer.
In "Measured VG" or "Calculated VN" polarization selection using Pol signal Sel, if the
amplitude of the residual current is greater than the Min operate current value and residual
voltage amplitude is greater than the Min operate voltage value then enable signal is sent
to the Timer.
Timer
Once activated the internal operate timer is started. The timer characteristic is according
to Definite Time (DT). When the Timer has reached the value of Release delay time, the
RELEASE output is activated. If a drop-off situation happens, that is, if operating current
moves out of the operating sector or signal amplitudes become below the minimum levels,
before the Release delay time is exceeded, the timer reset state is activated. If drop off
continues for more than Reset delay time the Timer is deactivated.
Characteristic angle recommended
0 ˚
+60 ˚
-90 ˚
RCA_CTL=FALSE
Characteristic angle
= -90°
Characteristic angle
= 0°.
Section 4
Protection functions
RCA_CTL=TRUE
Characteristic angle
= 0°.
Characteristic angle
= -90°
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