ABB RER670 - Page 302

1. Automatic load voltage adjustment, proportional to the load current.
2. Constant load voltage adjustment with four dif
ferent preset values.
In the first case the voltage adjustment is dependent on the load and maximum
voltage adjustment should be obtained at rated load of the transformer.
In the second case, a voltage adjustment of the set point voltage can be made in
four discrete steps (positive or negative) activated with binary signals connected to
TR1ATCC or TR8ATCC function block inputs LVA1, LVA2, LVA3 and LVA4. The
corresponding voltage adjustment factors are given as setting parameters
LVAConst1, LVAConst2, LVAConst3 and LVAConst4. The inputs are activated with
a pulse, and the latest activation of anyone of the four inputs is valid. Activation of
the input LVARESET in TR1ATCC or TR8ATCC block, brings the voltage setpoint
back to USet.
With these factors, TR1ATCC or TR8ATCC adjusts the value of the set voltage
USet according to the following formula:
2
L
a ci
I
Usetadjust Uset S S
I Base
= + × +
IECEQUATION1978 V1 EN-US (Equation 70)
U
set, adjust
Adjusted set voltage in per unit
USet Original set voltage: Base quality is U
n2
S
a
Automatic load voltage adjustment factor, setting
VRAuto
I
L
Load current
I2Base Rated current, LV winding
S
ci
Constant load voltage adjust. factor for active input
i (corresponding to
LVAConst1, LVAConst2, LVAConst3 and LVAConst4 )
It shall be noted that the adjustment factor is negative in order to decrease the load
voltage and positive in order to increase the load voltage. After this calculation
U
set, adjust
will be used by TR1ATCC or TR8A
TCC for voltage regulation instead of
the original value USet. The calculated set point voltage U
Set, adjust
is shown on the
local HMI as a service value under Main menu/Test/Function status/Control/
TransformerVoltageControl(ATCC,90)/TR1ATCC:x/TR8ATCC:x.
Automatic control of parallel transformers
SEMOD159053-135 v5
Control of parallel transformers means control of two or more power transformers
connected to the same busbar on the LV side and in most cases also on the HV
side. Special measures must be taken in order to avoid a runaway situation where
the tap changers on the parallel transformers gradually diverge and end up in
opposite end positions.
Three alternative methods can be used for parallel control with the Automatic
voltage control for tap changer, single/parallel control TR8ATCC:
Section 12 1MRK 506 375-UEN A
Control
296 Railway application RER670 2.2 IEC
Application manual