ANSI10000044-1-en.vsd
L
o
a
d
T
a
p
C
h
a
n
g
e
r
raise,lower
signals/alarms
position
MIM
BOM
IED
TRM
3ph or ph-ph or 1ph Currents
High Voltage Side
Low Voltage Side
Line Impedance R+jX
Load Center
3ph or ph-ph or 1ph Voltages
IA,IB,IC
(Load Current) IL
VL (Load Point Voltage)
VB (Busbar Voltage)
BIM
ANSI10000044 V1 EN-US
Figure 169: 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.
The LV-busbar voltage is designated V
B
, the load current I
L
and load
point voltage V
L
.
1MRK 511 401-UUS A Section 14
Control
Bay control REC670 2.2 ANSI 411
Application manual
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