ABB RET670 Applications Manual page 659

1MRK504116-UUS C
Application manual
Of these alternatives, the first and the last require communication between the function
control blocks of the different transformers, whereas the middle alternative does not
require any communication.
The voltage control includes many extra features such as possibility to avoid
simultaneous tapping of parallel transformers, hot stand by regulation of a transformer
within a parallel group, with a LV CB open, compensation for a possible capacitor
bank on the LV side bay of a transformer, extensive tap changer monitoring including
contact wear and hunting detection, monitoring of the power flow in the transformer so
that for example, the voltage control can be blocked if the power reverses and so on.
The voltage control function is built up by two function blocks which both are logical
nodes in IEC 61850-8-1:
• Automatic voltage control for tap changer, TR1ATCC (90) for single control and
TR8ATCC (90) for parallel control.
• Tap changer control and supervision, 6 binary inputs, TCMYLTC (84) and 32
binary inputs, TCLYLTC (84)
Automatic voltage control for tap changer, TR1ATCC (90) or TR8ATCC (90) is a
function designed to automatically maintain the voltage at the LV-side side of a power
transformer within given limits around a set target voltage. A raise or lower command
is generated whenever the measured voltage, for a given period of time, deviates from
the set target value by more than the preset deadband value (degree of insensitivity). A
time delay (inverse or definite time) is set to avoid unnecessary operation during
shorter voltage deviations from the target value, and in order to coordinate with other
automatic voltage controllers in the system.
TCMYLTC and TCLYLTC (84)are an interface between the Automatic voltage
control for tap changer, TR1ATCC (90) or TR8ATCC (90) and the transformer load
tap changer itself. More specifically this means that it gives command-pulses to a
power transformer motor driven load tap changer and that it receives information from
the load tap changer regarding tap position, progress of given commands, and so on.
TCMYLTC and TCLYLTC (84) also serve the purpose of giving information about
tap position to the transformer differential protection.
Control location local/remote
The tap changer can be operated from the front of the IED or from a remote place
alternatively. On the IED front there is a local remote switch that can be used to select
the operator place. For this functionality the Apparatus control function blocks Bay
control (QCBAY), Local remote (LOCREM) and Local remote control
(LOCREMCTRL) are used.
Information about the control location is given to TR1ATCC (90) or TR8ATCC (90)
function through connection of the Permitted Source to Operate (PSTO) output of the
Section 3
IED application
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