ABB Relion 670 Series Applications Manual page 342

Section 13
Control
High Voltage Side
(Load Current) I
Low Voltage Side
ANSI10000044 V1 EN-US
Figure 163: 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-ground. However, it shall be
remembered that this can only be used in solidly grounded systems, as the measured phase-
ground voltage can increase with as much as a factor √3 in case of ground faults in a non-solidly
grounded system.
The analog input signals are normally common with other functions in the IED for example,
protection functions.
Automatic voltage control for a single transformer
Automatic voltage control for tap changer, single control TR1ATCC (90) measures the magnitude
of the busbar voltage V
compensation), this voltage is further used for voltage regulation.
336
I ,I ,I
A B C
L
3ph or ph-ph or 1ph Currents
3ph or ph-ph or 1ph Voltages
Line Impedance R+jX
Load Center
The LV-busbar voltage is designated V
V .
L
. If no other additional features are enabled (line voltage drop
B
raise,lower
signals/alarms
position
VB (Busbar Voltage)
VL (Load Point Voltage)
ANSI10000044-1-en.vsd
, the load current I
B
1MRK 511 358-UUS A
IED
BOM
BIM
MIM
TRM
and load point voltage
L
SEMOD159053-73 v6
Application manual