ABB RER620, Техническое руководство

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Section 4
Protection functions
RER620 199
Technical Manual
The level detector contains a low-level blocking functionality for cases where one of the
measured voltages is below the desired level. This feature is useful when unnecessary
pickups and trips are wanted to avoid during, for example, an autoreclose sequence. The
low-level blocking is activated by default (
Enable block value is set to “True”) and the
blocking level can be set with the Voltage block value setting.
Phase selection logic
If the fault criteria are fulfilled in the level detector, the phase selection logic detects the
phase or phases in which the fault level is detected. If the number of faulty phases match
with the set
Num of pickup phases , the phase selection logic activates the timer.
Timer
Once activated, the timer activates the
PICKUP(START)
output. Depending on the value
of the set Operating curve type , the time characteristics are selected according to DT or
IDMT.
When the operation timer has reached the value set by Trip delay time in the DT mode or
the maximum value defined by the IDMT, the
TRIP (OPERATE)
output is activated.
When the user-programmable IDMT curve is selected, the trip time characteristics are
defined by the parameters
Curve parameter A , Curve parameter B , Curve parameter C ,
Curve parameter D and Curve parameter E .
If a drop-off situation occurs, that is, a fault suddenly disappears before the trip delay is
exceeded, the reset state is activated. The behavior in the drop-off situation depends on the
selected trip time characteristics. If the DT characteristics are selected, the reset timer runs
until the set
Reset delay time value is exceeded. If the drop-off situation exceeds the set
Reset delay time , the timer is reset and the
PICKUP
output is deactivated.
When the IDMT trip time curve is selected, the functionality of the timer in the drop-off
state depends on the combination of the
Type of reset curve and Reset delay time settings.
For a detailed description of the voltage IDMT curves, see the General
function block features section in this manual.