Application - ABB 615 series Technical Manual

Section 4
Protection functions
4.11.5
764
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.

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
1MAC059074-MB A
615 series ANSI
Technical Manual