5-150 T35 TRANSFORMER PROTECTION SYSTEM – INSTRUCTION MANUAL
SYSTEM SETUP CHAPTER 5: SETTINGS
5
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 T35 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.
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 5-18: Example of delta-wye connected power transformer data
The abbreviated nomenclature for applicable relay settings is as follows:
Rotation =
SETTINGS SYSTEM SETUP POWER SYSTEM PHASE ROTATION
w
total
= SETTINGS SYSTEM SETUP TRANSFORMER GENERAL NUMBER OF WINDINGS
Compensation = SETTINGS SYSTEM SETUP TRANSFORMER GENERAL PHASE COMPENSATION
Source [w] = SETTINGS SYSTEM SETUP TRANSFORMER WINDING w WINDING w SOURCE
P
rated
[w] = SETTINGS SYSTEM SETUP TRANSFORMER WINDING w WINDING w RATED MVA
V
nominal
[w] = SETTINGS SYSTEM SETUP TRANSFORMER WINDING w WINDING w NOM F-F VOLTAGE
Connection [w] = SETTINGS SYSTEM SETUP TRANSFORMER WINDING w WINDING w CONNECTION
WINDING 1
CONNECTION: Wye
Range: Wye, Delta, Zig-zag
WINDING 1 GROUNDING:
Not within zone
Range: Not within zone, Within zone
WINDING ~ ANGLE WRT
WINDING 1: 0.0°
Range: –359.9 to 0.0° in steps of 0.1, (‘~’ > 1)
(shown when viewed Winding is not Winding 1)
WINDING 1 RESISTANCE
3φ: 10.0000 ohms
Range: 0.0001 to 100.0000 ohms in steps of 0.0001
The T35 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.
Data Winding 1
Δ (delta) connection
Winding 2
Y (wye) connection
Voltage Phasor Diagram
Phase Shift 0° 30° lag (i.e. phases of wye winding lag
corresponding phases of delta winding by 30°)
Grounding In-zone grounding bank Ungrounded
Rated MVA 100/133/166 MVA 100/133/166 MVA
Nominal φ-φ Voltage 220 kV 69 kV
CT Connection Wye Wye
CT Ratio 500/5 1500/5
Auxiliary Cooling Two stages of forced air Two stages of forced air
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