ABB Relion 670 Series Applications Manual page 387

1MRK 511 401-UUS F
Setting
RevActPartBk(aut
omatically reset)
CmdErrBk
(manually reset)
Table continues on next page
Bay control REC670
Application manual
Values (Range) Description
Alarm The risk of voltage instability increases as
Auto Block transmission lines become more heavily loaded in an
attempt to maximize the efficient use of existing
generation and transmission facilities. In the same
time lack of reactive power may move the operation
point of the power network to the lower part of the P-
V-curve (unstable part). Under these conditions, when
the voltage starts to drop, it might happen that an
VRAISE command can give reversed result that is, a
lower busbar voltage. Tap changer operation under
voltage instability conditions makes it more difficult
for the power system to recover. Therefore, it might
be desirable to block TR1ATCC (90) or TR8ATCC (90)
temporarily.
Requirements for this blocking are:
•
•
•
If all three requirements are fulfilled, TR1ATCC (90) or
TR8ATCC (90) automatic control will be blocked for
raise commands for a period of time given by the
setting parameter
REVACBLK will be set. The reversed action feature can
be turned off/on with the setting parameter
OperationRA .
Alarm Typical operating time for a tap changer mechanism is
Auto Block around 3-8 seconds. Therefore, the function should
Auto&Man Block wait for a position change before a new command is
issued. The command error signal, CMDERRAL on the
TCMYLTC or TCLYLTC (84) function block, will be set if
the tap changer position does not change one step in
the correct direction within the time given by the
setting
function block. The tap changer module TCMYLTC or
TCLYLTC (84) will then indicate the error until a
successful command has been carried out or it has
been reset by changing control mode of TR1ATCC (90)
or TR8ATCC (90) function to Manual and then back to
Automatic. The outputs CMDERRAL on TCMYLTC or
TCLYLTC (84) and TOTBLK or AUTOBLK on TR1ATCC
(90) or TR8ATCC (90) will be activated depending on
the actual parameter setting.
This error condition can be reset by the input
RESETERR on TCMYLTC (84) function block, or
alternatively by changing control mode of TR1ATCC
(90) or TR8ATCC (90) function to Manual and then
back to Automatic.
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The load current must exceed the set value
RevActLim
After an VRAISE command, the measured busbar
voltage shall have a lower value than its previous
value
The second requirement has to be fulfilled for
two consecutive VRAISE commands
tRevAct and the output signal
tTCTimeout in TCMYLTC or TCLYLTC (84)
Section 14
Control
381