ABB Relion 670 Series Applications Manual page 404

Section 15
Control
~
IEC06000487 V2 EN-US
Figure 206: Vector diagram for line voltage drop compensation
The calculated load voltage U
Test/Function status/Control/TransformerVoltageControl(ATCC,90)/TR1ATCC:x/
TR8ATCC:x.
Load voltage adjustment
Due to the fact that most loads are proportional to the square of the voltage, it is possible to
provide a way to shed part of the load by decreasing the supply voltage a couple of percent.
During high load conditions, the voltage drop might be considerable and there might be
reasons to increase the supply voltage to keep up the power quality and customer
satisfaction.
It is possible to do this voltage adjustment in two different ways in Automatic voltage control
for tap changer, single control TR1ATCCand parallel control TR8ATCC:
1. Automatic load voltage adjustment, proportional to the load current.
2. Constant load voltage adjustment with four different 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 TR1ATCCor TR8ATCC
function block inputs LVA1, LVA2, LVA3 and LVA4. The corresponding voltage adjustment
factors are given as setting parameters
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 TR1ATCCor TR8ATCC block, brings the voltage
setpoint back to
With these factors, TR1ATCCor TR8ATCC adjusts the value of the set voltage
the following formula:
Usetadjust
IECEQUATION1978 V1 EN-US
U
set, adjust
USet
S
a
Table continues on next page
398
U
B
U
B
jX I
U
L L
L
R I
L L
is shown on the local HMI as value ULOAD under Main menu/
L
USet .
I
L
= + × +
Uset S S
a ci
I Base 2
Adjusted set voltage in per unit
Original set voltage: Base quality is U
Automatic load voltage adjustment factor, setting
© Copyright 2017 Hitachi Power Grids. All rights reserved
X
R
L
L
Re
IEC06000487-2-en.vsd
LVAConst1 , LVAConst2 , LVAConst3 and LVAConst4 .
n2
VRAuto
1MRK 511 401-UEN Rev. K
SEMOD159053-118 v7
USet according to
(Equation 187)
Bay control REC670
Application manual