ABB 615 Series ANSI, Technical Manual

Page: 297 / 713

Section 4
1MAC050144-MB C
Protection functions
290 615 series ANSI
Technical Manual
Table 285: Recommended Characteristic angle setting for different network
The Characteristic angle setting is adjusted to the operation according to the method of
neutral point grounding 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 grounding 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 grounding resistor in grounded network as a result the
Characteristic angle is set
automatically to suit the grounding method. The table below shows the Characteristic
angle control for RCA_CTL condition.
Table 286: Characteristic angle control for RCA_CTL condition
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 trip current value and negative sequence
voltage amplitude is greater than Min trip 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 trip current value and residual
voltage amplitude is greater than the Min trip 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.
Type of network Characteristic angle recommended
Compensated network 0 ˚
Solidly grounded network +60 ˚
Isolated network -90 ˚
Characteristic angle Setting RCA_CTL=FALSE RCA_CTL=TRUE
-90°
Characteristic angle
= -90°
Characteristic angle
= 0°.
0°. Characteristic angle = 0°. Characteristic angle = -90°