• With the master-follower method
• W
ith the reverse reactance method
• With the circulating current method
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 for single control and
TR8ATCC for parallel control.
• Tap changer control and supervision, 6 binary inputs, TCMYLTC and 32
binary inputs, TCLYLTC
Automatic voltage control for tap changer, TR1ATCC or TR8ATCC 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 are an interface between the Automatic voltage control
for tap changer, TR1ATCC or TR8ATCC 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 also serve the purpose of giving information about tap
position to the transformer differential protection.
Control location local/remote
SEMOD159053-30 v3
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.
1MRK 506 375-UEN A Section 12
Control
Railway application RER670 2.2 IEC 289
Application manual
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