ABB RET650 Applications Manual page 227

1MRK 504 169-UEN A
Transformer protection RET650 2.2 IEC
Application manual
single transformer", except that horizontal communication messages are still sent
and received, but the received messages are ignored. TR8ATCC is at the same time
also automatically excluded from the parallel group.
Disabling of blockings in special situations
When the Automatic voltage control for tap changer TR1ATCC for single control
and TR8ATCC for parallel control, function block is connected to read back
information (tap position value and tap changer in progress signal) it may
sometimes be difficult to find timing data to be set in TR1ATCC or TR8ATCC for
proper operation. Especially at commissioning of for example, older transformers
the sensors can be worn and the contacts maybe bouncing etc. Before the right
timing data is set it may then happen that TR1ATCC or TR8ATCC becomes totally
blocked or blocked in auto mode because of incorrect settings. In this situation, it is
recommended to temporarily set these types of blockings to alarm instead until the
commissioning of all main items are working as expected.
Tap Changer position measurement and monitoring
Tap changer extreme positions
This feature supervises the extreme positions of the tap changer according to the
settings LowVoltTap and HighVoltTap. When the tap changer reaches its lowest/
highest position, the corresponding ULOWER/URAISE command is prevented in
both automatic and manual mode.
Monitoring of tap changer operation
The Tap changer control and supervision, 6 binary inputs TCMYLTC or 32 binary
inputs TCLYLTC output signal URAISE or ULOWER is set high when TR1ATCC
or TR8ATCC function has reached a decision to operate the tap changer. These
outputs from TCMYLTC and TCLYLTC function blocks shall be connected to a
binary output module, BOM in order to give the commands to the tap changer
mechanism. The length of the output pulse can be set via TCMYLTC or TCLYLTC
setting parameter tPulseDur. When an URAISE/ULOWER command is given, a
timer ( set by setting tTCTimeout ) (settable in PST/local HMI) is also started, and
the idea is then that this timer shall have a setting that covers, with some margin, a
normal tap changer operation.
Usually the tap changer mechanism can give a signal, "Tap change in progress",
during the time that it is carrying through an operation. This signal from the tap
changer mechanism can be connected via a BIM module to TCMYLTC or
TCLYLTC input TCINPROG, and it can then be used by TCMYLTC or TCLYLTC
function in three ways, which is explained below with the help of figure 81.
Section 11
Control
SEMOD159053-329 v4
SEMOD159053-337 v1
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