The
Absolute hysteresis
setting can be used for preventing unnecessary oscillations if the
input signal is slightly above or below the
Pickup value
setting. After leaving the
hysteresis area, the pickup condition has to be fulfilled again and it is not sufficient for the
signal to only return to the hysteresis area. If the
ENA_ADD
input is activated, the
threshold value of the internal comparator is the sum of the
Pickup value Add
and
Pickup
value
settings. The resulting threshold value for the comparator can be increased or
decreased depending on the sign and value of the
Pickup value Add
setting.
Timer
Once activated, the timer activates the
PICKUP
output. The time characteristic is
according to DT. When the operation timer has reached the value set by
Trip delay time
,
the
TRIP
output is activated. If the pickup condition disappears before the module trips,
the reset timer is activated. If the reset timer reaches the value set by
Reset delay time
, the
operation timer resets and the
PICKUP
output is deactivated.
The timer calculates the pickup duration value PICKUP_DUR, which indicates the ratio
of the pickup situation and the set trip 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
operation timer is frozen to the prevailing value, but the
TRIP
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 TRIP output" mode, the function operates normally but the
TRIP
output is not activated.
4.11.5
Application
The function block can be used for any general analog signal protection, either
underprotection or overprotection. The setting range is wide, allowing various protection
schemes for the function. Thus, the absolute hysteresis can be set to a value that suits the
application.
The temperature protection using the RTD sensors can be done using the function block.
The measured temperature can be fed from the RTD sensor to the function input that
detects too high temperatures in the motor bearings or windings, for example. When the
ENA_ADD
input is enabled, the threshold value of the internal comparator is the sum of the
Section 4
1MAC059074-MB A
Protection functions
764
615 series ANSI
Technical Manual
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