a negative value if operating signal IG or IN leads the polarizing quantity
–VG or –VN, respectively.
Table 229:
Recommended Characteristic angle setting for different network
Type of network
Characteristic angle recommended
Compensated network
0°
Solidly grounded network
+60°
Isolated network
-90°
The
Characteristic angle
setting is adjusted to the operation according to the method of
neutral-point grounding, so that in an isolated network
Characteristic angle
is -90° and in
a compensated network 0°. In addition,
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
input depends on the
Characteristic angle
setting.
The Peterson coil or the grounding resistor may be temporarily out of operation. To keep
the protection scheme selective, it is necessary to update the
Characteristic angle
settings
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 grounding resistor in grounded network as a result the
Characteristic angle
is set
automatically to suit the grounding method.
Table 230:
Characteristic angle control for the
RCA_CTL
condition
Characteristic angle Setting
RCA_CTL
=FALSE
RCA_CTL
=TRUE
-90°
Characteristic angle =-90°
Characteristic angle = 0°
0°
Characteristic angle = 0°
Characteristic angle =-90°
Low-level blocking
For a reliable operation, signal levels should be greater than the minimum level. If they are
not greater than the minimum level, Timer is blocked.
In the "Neg. seq. volt." polarization selection using
Pol signal Sel
, if the amplitude of the
negative-sequence current is greater than the
Min trip current
value and the negative-
sequence voltage amplitude is greater than the
Min trip voltage
value, the enabling signal
is sent to Timer.
In the "Measured VG" or "Calculated VN" polarization selection using
Pol signal Sel
, if
the amplitude of the residual current is greater than the
Min trip current
value and residual
voltage amplitude is greater than the
Min trip voltage
value, the enabling signal is sent to
Timer.
Section 4
1MRS240050-IB C
Protection functions
292
REF615R
Technical Manual
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