ABB RELION REX640, Техническое руководство, Страница: 1703 / 1960

Band
width
voltage
U
ΔU
step
t
bandwidth limit
hysteresis limit
U
m
, measured voltage
U
p
, control voltage
T1
s
ta
rt
T1
re
se
t
T1
s
ta
rt
Lowe
r
T1
Figure 916: Voltage-regulating function. A control pulse to lower the voltage is
issued after the elapsed T1.
If the measured voltage is outside the hysteresis when the delay counter T1 reaches
its setting value, the raising or lowering output relay is activated. This activates
either output pulse
RAISE_OWN
or
LOWER_OWN
, and the motor drive of the tap
changer operates. The status of these outputs can be read from the output data
RAISE_OWN
or
LOWER_OWN
.
If the measured voltage falls or rises within the hysteresis limits during the
operating time, the delay counter is reset.
The pulse length can be defined with the
LTC pulse time setting. The default value is
1.5 seconds.
A short delay, same as the typical tap changer operating time, is active before the
start of the next operating timer. For OL5ATCC, the delay is set to 6 seconds. If one
tap changer operation is not enough to regulate the transformer voltage within the
hysteresis limits, a second adjustable delay T2 (
Control delay time 2), usually with
a shorter time setting than T1, starts. This delay is used for the control commands
within the same sequence until the recovery of voltage occurs. The delays T1 and
T2 can be selected either with definite or inverse time characteristics. In the inverse
time mode, the operate time depends on the difference between the control voltage
and the measured voltage as shown in
Equation 384
. The bigger the difference in
the voltage, the shorter the operating time. More information on the inverse time
operation can be found in the
Chapter 9.10.5.8 Timer characteristics
.
Regulation equation
The simple regulating principle is often complemented by additional features to
take the voltage drop of lines into account (line drop compensation), coordinate the
regulation of parallel transformers and change the voltage level according to the
loading state of the network. The control voltage U
p
is calculated according to the
equation
U U U U U
p s z ci rsv
=
+ + −
(Equation 373)
1MRS759142 F Control functions
REX640
Technical Manual
1703