ABB REG670 Applications Manual page 557

1MRK 502 071-UEN -
Generator protection REG670 2.2 IEC and Injection equipment REX060, REX061, REX062
Application manual
High Voltage Side
(Load Current) I
L
Low Voltage Side
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
point voltage U
Automatic voltage control for a single transformer
Automatic voltage control for tap changer, single control TR1ATCC measures the
magnitude of the busbar voltage U
voltage drop compensation), this voltage is further used for voltage regulation.
I ,I ,I
L1 L2 L3
p r
a e
g
T
signals/alarms
n
d
a
a
h
o
position
C
L
3ph or ph-ph or 1ph Current
3ph or ph-ph or 1ph Voltage
Line Impedance R+jX
Load Center
.
L
. If no other additional features are enabled (line
B
Section 15
IED
raise,lower
BOM
BIM
MIM
TRM
U (Busbar Voltage)
B
UL (Load Point Voltage)
IEC10000044-2-en.vsd
, the load current I
B
Control
and load
L
551