Timer
Once activated, the timer activates the
START
output. The time characteristic is
according to DT. When the operation timer has reached the value set with the
Operate delay time setting, the
OPERATE
output is activated. If the fault disappears
before the module operates, the reset timer is activated. If the reset timer reaches
the value set with the
Reset delay time setting, the operation timer resets and
the
START
output is deactivated. The timer calculates the start duration value
START_DUR, which indicates the percentage ratio of the start situation and the
set operation time. The value is available in the monitored data view.
Blocking logic
There are three operation modes in the blocking function. The operation modes
are controlled by the
BLOCK
input and the global setting in Configuration >
System > Blocking mode which selects the blocking mode. The
BLOCK
input can be
controlled by a binary input, a horizontal communication input or an internal signal
of the protection relay's program. The influence of the
BLOCK
signal activation is
preselected with the global setting
Blocking mode.
The
Blocking mode setting has three blocking methods. In the "Freeze timers"
mode, the operate timer is frozen to the prevailing value, but the
OPERATE
output
is not deactivated when blocking is activated. In the "Block all" mode, the whole
function is blocked and the timers are reset. In the "Block OPERATE output" mode,
the function operates normally but the
OPERATE
output is not activated.
4.2.4.5
Neutral admittance characteristics
The applied characteristic should always be set to cover the total admittance of
the protected feeder with a suitable margin. However, more detailed setting value
selection principles depend on the characteristic in question.
The settings defining the admittance characteristics are given in primary
milliSiemens.
The forward and reverse boundary settings should be set so that the forward
setting is always larger than the reverse setting and that there is space between
them.
Overadmittance characteristic
The overadmittance criterion is enabled with the setting
Operation mode set to
"Yo". The characteristic is a circle with the radius defined with the
Circle radius
setting. For the sake of application flexibility, the midpoint of the circle can be
moved away from the origin with the
Circle conductance and Circle susceptance
settings. Default values for
Circle conductance and Circle susceptance are 0.0 mS,
that is, the characteristic is an origin-centered circle.
Operation is achieved when the measured admittance moves outside the circle.
The overadmittance criterion is typically applied in unearthed networks, but it can
also be used in compensated networks, especially if the circle is set off from the
origin.
Protection functions
1MRS757644 H
442
620 series
Technical Manual
