ABB REG670 Applications Manual page 578

Section 15
Control
572
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
Generator protection REG670 2.2 IEC and Injection equipment REX060, REX061, REX062
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
with the setting parameter OperationRA .
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
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
tTCTimeout timer has timed out. The
not reset when 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.
1MRK 502 071-UEN -
tTCTimeout in
Application manual