GE T60 Instruction Manual page 316

SYSTEM SETUP
The T60 is provided with this optional feature, specified as an option at the time of ordering. Using the order
code for your device, see the order codes in chapter 2 for details.
The settings specific to each winding are shown in the table.
Transformer differential protection uses the following calculated quantities (per phase): fundamental, second harmonic,
and fifth harmonic differential current phasors, and restraint current phasors. This information is extracted from the
current transformers (CTs) connected to the relay by correcting the magnitude and phase relationships of the currents for
each winding, so as to obtain zero (or near zero) differential currents under normal operating conditions. Traditionally,
these corrections were accomplished by interposing CTs and tapped relay windings with some combination of CT
connections.
The T60 simplifies these configuration issues. All CTs at the transformer are connected wye (polarity markings pointing
away from the transformer). User-entered settings in the relay characterizing the transformer being protected and allow
the relay to automatically perform all necessary magnitude, phase angle, and zero-sequence compensation.
5
This section describes the algorithms in the relay that perform this compensation and produce the required calculated
quantities for transformer differential protection, by means of the following example of a delta-wye (Δ-Y) connected power
transformer with the following data:
Table 5-17: Example of delta-wye connected power transformer data
Data
Voltage Phasor Diagram
Phase Shift
Grounding
Rated MVA
Nominal φ-φ Voltage
CT Connection
CT Ratio
Auxiliary Cooling
The abbreviated nomenclature for applicable relay settings is as follows:
Rotation =
SETTINGS  SYSTEM SETUP  POWER SYSTEM  PHASE ROTATION
w =
SETTINGS  SYSTEM SETUP  TRANSFORMER  GENERAL  NUMBER OF WINDINGS
total
Compensation =
SETTINGS  SYSTEM SETUP  TRANSFORMER  GENERAL  PHASE COMPENSATION
Source [w] =
SETTINGS  SYSTEM SETUP  TRANSFORMER  WINDING w  WINDING w SOURCE
P [w] =
SETTINGS  SYSTEM SETUP  TRANSFORMER  WINDING w  WINDING w RATED MVA
rated
V [w] =
SETTINGS  SYSTEM SETUP  TRANSFORMER  WINDING w  WINDING w NOM F-F VOLTAGE
nominal
Connection [w] =
SETTINGS  SYSTEM SETUP  TRANSFORMER  WINDING w  WINDING w CONNECTION
5-134
WINDING 1

CONNECTION: Wye
WINDING 1 GROUNDING:

Not within zone
WINDING ~ ANGLE WRT

WINDING 1: 0.0°
WINDING 1 RESISTANCE

3φ: 10.0000 ohms
Winding 1
Δ
(delta) connection
0°
In-zone grounding bank
100/133/166 MVA
220 kV
Wye
500/5
Two stages of forced air
Range: Wye, Delta, Zig-zag
Range: Not within zone, Within zone
Range: –359.9 to 0.0° in steps of 0.1, ('~' > 1)
(shown when viewed Winding is not Winding 1)
Range: 0.0001 to 100.0000 ohms in steps of 0.0001
Winding 2
Y (wye) connection
30° lag (i.e. phases of wye winding lag
corresponding phases of delta winding by 30°)
Ungrounded
100/133/166 MVA
69 kV
Wye
1500/5
Two stages of forced air
T60 TRANSFORMER PROTECTION SYSTEM – INSTRUCTION MANUAL
CHAPTER 5: SETTINGS