ABB REC670 Applications Manual page 411

1MRK 511 401-UEN A
Bay control REC670 2.2 IEC
Application manual
Setting Values (Range)
RevActPartBk(auto Alarm
matically reset) Auto Block
CmdErrBk Alarm
(manually reset) Auto Block
Auto&Man Block
TapChgBk Alarm
(manually reset Auto Block
Auto&Man Block
Table continues on next page
Description
The risk of voltage instability increases as 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 URAISE 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 or
TR8ATCC temporarily.
Requirements for this blocking are:
• The load current must exceed the set value
RevActLim
• After an URAISE command, the measured busbar
voltage shall have a lower value than its previous
value
• The second requirement has to be fulfilled for two
consecutive URAISE commands
If all three requirements are fulfilled, TR1ATCC or
TR8ATCC automatic control will be blocked for raise
commands for a period of time given by the setting
tRevAct and the output signal REVACBLK will
parameter
be set. The reversed action feature can be turned off/on
OperationRA .
with the setting parameter
Typical operating time for a tap changer mechanism is
around 3-8 seconds. Therefore, the function should wait
for a position change before a new command is issued.
The command error signal, CMDERRAL on the
TCMYLTC or TCLYLTC 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
tTCTimeout in TCMYLTC or TCLYLTC function block.
The tap changer module TCMYLTC or TCLYLTC will then
indicate the error until a successful command has been
carried out or it has been reset by changing control mode
of TR1ATCC or TR8ATCC function to Manual and then
back to Automatic. The outputs CMDERRAL on
TCMYLTC or TCLYLTC and TOTBLK or AUTOBLK on
TR1ATCC or TR8ATCC will be activated depending on
the actual parameter setting.
This error condition can be reset by the input RESETERR
on TCMYLTC function block, or alternatively by changing
control mode of TR1ATCC or TR8ATCC function to
Manual and then back to Automatic.
If the input TCINPROG of TCMYLTC or TCLYLTC
function block is connected to the tap changer
mechanism, then this blocking condition will be active if
the TCINPROG input has not reset when the
timer has timed out. The output TCERRAL will be
activated depending on the actual parameter setting. In
correct operation the TCINPROG shall appear during the
URAISE/ULOWER output pulse and disappear before the
tTCTimeout time has elapsed.
This error condition can be reset by the input RESETERR
on TCMYLTC function block, or alternatively by changing
control mode of TR1ATCC or TR8ATCC function to
Manual and then back to Automatic.
Section 14
Control
tTCTimeout
405