Tap Changer Position Inputs - ABB RELION REX640 Technical Manual

Section 9
Control functions
9.10.5.2
1542
transformer. If the phase voltages are measured, the voltage U_AB is calculated
internally in the protection relay.
The currents from the secondary side of the power transformer (I_x, where x is A, B
or C) have several uses.
• The highest phase current value is used for overcurrent blocking.
• The currents from the secondary side of the power transformer are used for LDC
(average of the connected inputs).
• The currents from the secondary side of the power transformer are used for
calculating the circulating current in the NRP and MCC operation modes.
Both voltage U_AB and the phase currents from the secondary side are always
measured using the value of the filtered fundamental frequency component (DFT).
Hence, the harmonics are always suppressed. Moreover, the measured voltage value
is continuously average-filtered with the eight-value-long sliding window. The phase-
compensated voltage U_A is always used in calculations, although it is not connected.
This averaged value, the parameter U
magnitude can be read from the monitored data U_MEAS.
Similarly, the magnitude of the phase current of the own transformer, I_x, and the
phase angle difference between the internally phase-compensated voltage U_A and
phase current I_x are also average-filtered by the same fixed-length window. The
phase angle value can be read from the monitored data ANGL_UA_IA. These
currents and phase angle differences are used solely in circulating current
calculations.
The angle difference is used in
There are minimum limits for the voltage and current magnitudes, so the magnitude
and phase angle difference values diverge from zero. The voltage magnitude must
exceed three percent of U

Tap changer position inputs

The position value of the tap changer can be brought to OL5ATCC as a resistance
value, an mA signal or a binary-coded signal. More information on how the resistance
value, the mA signal or a binary-coded interface are implemented can be found in
TPOSYLTC in this manual.
The indicated tap changer position of the own transformer is internally connected to
the TAP_POS input, and the tap changer positions of the parallel transformers are fed
to inputs TRx_DAT via data combiner function blocks OLGAPC. This also defines
the connection identity so that follower 1 is connected to TR1_DAT, follower 2 is
connected to TR2_DAT and follower 3 is connected to TR3_DAT. The own
transformer position can be read from the input TAP_POS. The follower tap changer
positions can be read from the input data TR_TAP_POS of OLGAPCx.
in Equation
m
Equation 341
and the current I_A must exceed two percent of I
n
1MRS759142 C
345, is used for control, and its
and Equation 343.
Technical Manual
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REX640