The time set for
Delay acts in this kind of scheme as a backup which does not rely on the
communication channel. Thus when the Receive input is being used, the setting for Delay must
be longer than the setting for
tWait:
Delay > t
Wait
Response after decay of the memorized voltage
The voltage measured by the protection can quickly decay to almost zero for a close fault and
make determining direction unreliable. For this reason, the function includes a voltage
memory feature and for the first 200 milliseconds after the incidence of an overcurrent, the
voltage measured immediately before the fault is used as reference to determine fault
direction.
After this time, the last valid direction is used for an adjustable period.
MemDirMode provides facility for setting how the protection must respond after this time or
in the event that the circuit-breaker is closed onto a fault and no voltage could be memorized
beforehand. The two possible settings are the protection can trip or it can block.
Time during which the memorized direction is valid
The
MemDuration setting determines how long the last valid direction measurement shall be
used. The setting should be as short as possible (200 ms) when the function is being used as
backup for a distance function in an HV power system, because an actually measured voltage
is only available during this time and therefore it is only possible to detect a reversal of
direction during this time. For longer settings, the last valid power direction is used instead of
the actually memorized voltage.
5.6
Definite time over- and undervoltage protection 59/27
(OVDT)
5.6.1
Mode of operation
GUID-F6B02B2E-018D-461C-B3B6-4D6EE83D2E82 v1
Standard voltage applications (overvoltage and undervoltage function)
5.6.2
Features
GUID-DCE098A7-D900-43B1-A3F8-4C2F1CC68D9B v1
•
Insensitive to DC component
•
Insensitive to harmonics
•
Single or three-phase voltage measurement
•
Maximum value, respectively minimum value detection in the three-phase mode
5.6.3
Inputs and outputs
5.6.3.1
CT/VT inputs
GUID-200D6EFF-67E4-44C5-9699-9B30B2E6D32A v1
•
Voltage
5.6.3.2
Binary inputs
GUID-41F14722-531C-4106-8B7E-A60E806F41C3 v1
•
Blocking
1MRK 505 406-UEN B
Section 5
Bay protection functions
Bay protection functions REB500
111
Technical manual
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