GE 889 Instruction Manual page 209

CHAPTER 4: SETPOINTS
NOTE:
NOTE
889 GENERATOR PROTECTION SYSTEM – INSTRUCTION MANUAL
The angle of Winding 1 is always 0°, and this setpoint is omitted from the Winding 1 setup
menu.
The 889 supports all standard two-winding transformer types, and a variety of non-
standard applications, where the selection of winding connection type and selected
lagging angle with respect to Winding 1 are not described in the table of standard
transformer types.
Figure 4-20: Menu for transformer windings setup
..\Transformer\Winding 2
Item Name
Rated MVA
Nominal Ph Ph Voltage
Connection
Angle With Respect To W1
Grounding
W 2
As shown in the menu for transformer windings setup, the 30° lag of the Delta winding
currents, will result in a 0° phase shift applied to Delta currents (Delta –phase reference),
and a 30° phase angle correction (phase shift) applied to the winding 1 currents (Wye
winding). These angle corrections are described in the table as Phase shift.
In general, zero sequence removal is necessary if zero sequence can flow into and out of
one transformer winding but not the other windings. Transformer windings that are
grounded inside the zone of protection allow zero sequence current flow in that winding,
and therefore it is from these windings that zero sequence removal is necessary.
The 889 performs this phase angle compensation and zero sequence removal
automatically, based on the settings entered for the transformer. All CTs are connected
Wye (polarity markings pointing away from the transformer). All currents are phase and
zero sequence compensated internally before the calculation of differential and restraint
quantities.
The phase reference winding (w
to it. The phase reference winding is chosen to be the delta (non-wye) winding with the
lowest winding index, if one exists. For a transformer that has no delta windings, the first
"wye" winding is chosen.
Value
5.000
13.800
Wye
0 °
Not Within Zone
) is the winding which will have a phase shift of 0° applied
f
SYSTEM
Unit
MVA
kV
4–79