ABB Relion 670 series - Built-in overvoltage protection steps; Built-in undervoltage protection steps; Logic diagram

time than the set time delay the undercurrent step will set its trip signal to one. Reset of
the pickup and trip signal can be instantaneous or time delay in accordance with the
setting.
10.1.2.5 Built-in overvoltage protection steps
Two overvoltage protection steps are available. They are absolutely identical and
therefore only one will be explained here.
Overvoltage step simply compares the magnitude of the measured voltage quantity (see
table
298) with the set pickup level. The overvoltage step will pickup if the magnitude
of the measured voltage quantity is bigger than this set level. Reset ratio is settable,
with default value of 0.99.
The pickup signal will start definite time delay or inverse (IDMT) time delay in
accordance with the end user setting. If the pickup signal has value one for longer time
than the set time delay, the overvoltage step will set its trip signal to one. Reset of the
pickup and trip signal can be instantaneous or time delay in accordance with the end
user setting.
10.1.2.6 Built-in undervoltage protection steps
Two undervoltage protection steps are available. They are absolutely identical and
therefore only one will be explained here.
Undervoltage step simply compares the magnitude of the measured voltage quantity
(see table
298) with the set pickup level. The undervoltage step will pickup if the
magnitude of the measured voltage quantity is smaller than this set level. Reset ratio is
settable, with default value of 1.01.
The pickup signal will start definite time delay or inverse (IDMT) time delay in
accordance with the end user setting. If the pickup signal has value one for longer time
than the set time delay, the undervoltage step will set its trip signal to one. Reset of the
pickup and trip signal can be instantaneous or time delay in accordance with the end
user setting.
10.1.2.7 Logic diagram
The simplified internal logics, for CVGAPC function are shown in the following figures.
1MRK505222-UUS C Section 10
Multipurpose protection
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Technical reference manual