ABB REG670 - Page 557

L
o
a
d
T
a
p
C
h
a
n
g
e
r
raise,lower
signals/alarms
position
BOM
MIM
IED
IL1,IL2,IL3
TRM
3ph or ph-ph or 1ph Current
High Voltage Side
(Load Current) IL
Low Voltage Side
Line Impedance R+jX
U
B
(Busbar Voltage)
Load Center
UL (Load Point Voltage)
IEC10000044-2-en.vsd
BIM
3ph or ph-ph or 1ph Voltage
IEC10000044 V2 EN
Figure 281: Signal flow for a single transformer with voltage control
On the HV side, the three-phase current is normally required in order to feed the three-
phase over current protection that blocks the load tap changer in case of over-current
above harmful levels.
The voltage measurement on the LV-side can be made single phase-earth. However,
it shall be remembered that this can only be used in solidly earthed systems, as the
measured phase-earth voltage can increase with as much as a factor √3 in case of earth
faults in a non-solidly earthed system.
The analog input signals are normally common with other functions in the IED for
example, protection functions.
The LV-busbar voltage is designated U
B
, the load current I
L
and load
point voltage U
L
.
Automatic voltage control for a single transformer
Automatic voltage control for tap changer, single control TR1ATCC measures the
magnitude of the busbar voltage U
B
. If no other additional features are enabled (line
voltage drop compensation), this voltage is further used for voltage regulation.
1MRK 502 071-UEN - Section 15
Control
Generator protection REG670 2.2 IEC and Injection equipment REX060, REX061, REX062 551
Application manual