14.4.2
Functionality
M5864-3 v11
Tap changer control and supervision, 6 binary inputs TCMYLTC (84) as well as Tap changer control
and supervision, 32 binary inputs TCLYLTC (84) are is used for control of power transformers with
a on-load tap changer. The functions provide automatic regulation of the voltage on the secondary
side of transformers or alternatively on a load point further out in the network.
Control of a single transformer, as well as control of up to eight transformers in parallel is
possible. For parallel control of power transformers, three alternative methods are available, the
master-follower method, the circulating current method and the reverse reactance method. The
first two methods require exchange of information between the parallel transformers and this is
provided for within IEC 61850-8-1.
Voltage control includes many extra features such as possibility of to avoid simultaneous tapping
of parallel transformers, hot stand by regulation of a transformer in a group which regulates it to a
correct tap position even though the LV CB is 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 etc.
14.4.3
Automatic voltage control for tap changer TR1ATCC (90) and
TR8ATCC (90)
SEMOD158820-1 v2
SEMOD158823-5 v4
The Automatic voltage control for tap changer TR1ATCC (90) for single control and TR8ATCC (90)
for parallel control function controls the voltage on the LV side of a transformer either
automatically or manually. The automatic control can be either for a single transformer, or for a
group of parallel transformers.
14.4.3.1
Operation principle
SEMOD158880-5 v4
The LV-side of the transformer is used as the voltage measuring point. If necessary, the LV side
current is used as load current to calculate the line-voltage drop to the regulation point. This
current is also used when parallel control with the circulating current method is used.
In addition, all three-phase currents from the HV-winding (usually the winding where the tap
changer is situated) are used by the Automatic voltage control for tap changer TR1ATCC (90) for
single control and TR8ATCC (90) for parallel control function for over current blocking.
The setting
MeasMode is a selection of single-phase, or phase-phase, or positive sequence
quantity. It is to be used for voltage and current measurement on the LV-side. The involved phases
are also selected. Thus, single-phases as well as phase-phase or three-phase feeding on the LV-
side is possible but it is commonly selected for current and voltage.
The analog input signals are normally common for other functions in the IED for example,
protection functions.
The LV-busbar voltage is designated V
B
, load current I
L
and for load point voltage
V
L
will be used in the text to follow.
1MRK 502 066-UUS B
Section 14
Control
869
Technical manual
Summary of Contents for Relion 670 series
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