GE 745 Instruction Manual page 131

CHAPTER 5: SETPOINTS
WARNING
745 TRANSFORMER PROTECTION SYSTEM – INSTRUCTION MANUAL
• FREQUENCY TRACKING: In situations where the AC signals contain significant amount
of sub-harmonic components, it may be necessary to disable frequency tracking.
• PHASE SEQUENCE: Enter the phase sequence of the power system. Systems with an
ACB phase sequence require special considerations. See Phase Shifts on Three-phase
Transformers on page 5–8 for details.
• TRANSFORMER TYPE: Enter the transformer connection from the table of transformer
types. Phase correction and zero-sequence removal are performed automatically as
required.
If is entered as "2W External Correction" or "3W External Correction"
TRANSFORMER TYPE
with a delta/wye power transformer, the
must be divided by on the delta current transformer side to compensate the current
3
magnitude. With this correction, the 745 will properly compare line to neutral currents on
all sides of the power transformer.
For example, for a two-winding delta/wye power transformer with wye-connected current
transformers on the delta side of the power transformer (25000:5 ratio), and delta-
connected current transformers on the wye side of the transformer (4000:5 ratio), set:
TRANSFORMER TYPE: "2W External Connection"
WINDING 1 PHASE CT
WINDING 2 PHASE CT
• LOAD LOSS AT RATED LOAD: Enter the load loss at rated load. This value is used for
calculation of harmonic derating factor, and in the Insulating Aging function. This is an
auto-ranging setpoint dependent on the
ranges in the following table
Setting
MINIMUM TAP
POSITION VOLTAGE
VOLTAGE
INCREMENT PER TAP
LOAD LOSS AT
RATED LOAD
NO LOAD LOSS
• LOW VOLTAGE WINDING RATING: Enter the low voltage winding rating. This selection
affects the ranges of
WINDING 1(3) NOM ø-ø VOLTAGE
MINIMUM TAP POSITION VOLTAGE
table above.
• RATED WINDING TEMP RISE: Determines the type of insulation; for use in the
computation of insulation aging.
• NO-LOAD LOSS: From the transformer data. It is required for insulation aging
calculations This is an auto-ranging setpoint dependent on the
value; see ranges in the above table.
WINDING RATING
• TYPE OF COOLING: From Transformer data; required for insulation aging calculations.
• RATED TOP OIL RISE OVER AMBIENT: Required for insulation aging calculations
• XFMR THRML CAPACITY: Required for insulation aging calculations. Obtain from
transformer manufacturer
WINDING 1(3) PHASE CT PRIMARY
PRIMARY: "25000:5"
PRIMARY: (4000 / 3 ):5 or "2309:5"
LOW VOLTAGE WINDING RATING
Low voltage winding rating
above 5 kV 1 kV to 5 kV
0.1 to 2000.0 kV 0.01 to 200.00 kV
in steps of 0.1 in steps of 0.01
0.01 to 20.00 kV 0.001 to 2.000 kV
in steps of 0.01 in steps of 0.001
1 to 20000 kW 0.1 to 2000.0 kW
in steps of 0.1 in steps of 0.01
0.1 to 2000.0 kW 0.01 to 200.00 kW
in steps of 1 in steps of 0.1
, and VOLTAGE INCREMENT PER TAP
S2 SYSTEM SETUP
setting values
value; see
below 1 kV
0.001 to 20.000 kV
in steps of 0.001
0.0001 to 0.2000 kV
in steps of 0.0001
0.01 to 200.00 kW
in steps of 0.001
0.001 to 20.000 kW in
steps of 0.01
,
WINDING 1(3) RATED LOAD
as shown in the
LOW VOLTAGE
,
5–35