Setting Values (Range) Description
RevActPartBk(auto
matically reset)
Alarm
Auto Block
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
parameter
tRevAct
and the output signal REVACBLK will
be set. The reversed action feature can be turned off/on
with the setting parameter
OperationRA
.
CmdErrBk
(manually reset)
Alarm
Auto Block
Auto&Man Block
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.
TapChgBk
(manually reset
Alarm
Auto Block
Auto&Man Block
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
tTCTimeout
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.
Table continues on next page
1MRK 506 375-UEN A Section 12
Control
Railway application RER670 2.2 IEC 313
Application manual
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