T35 TRANSFORMER PROTECTION SYSTEM – INSTRUCTION MANUAL 8-1
T35 Transformer Protection System
Chapter 8: Commissioning
Commissioni ng
8.1 Differential characteristic test
8.1.1 Description
8.1.1.1 Overview
The following commissioning tests are organized in two parts: general procedures for testing points of the differential-
restraint characteristics, and examples of the percent differential element response, based on different transformer
configurations and fault current distribution. The following tests can be performed by using either 2 or 3 individually
adjustable currents, and do not require additional specialized equipment.
Preparation
1. Select a 0° or 180° transformer phase shift and identical winding connection type into the relay.
2. Select the “Not Within Zone” setting value for each winding grounding setting.
3. Select and set the CT ratios for each winding.
4. Calculate the magnitude compensation factors M[1] and M[2] for each winding.
5. Enable the Transformer Percent Differential element, and enter the required test settings to shape the differential
restraint characteristic.
6. Connect the relay test set to inject x current (I
x
) into the Winding 1 Phase A CT input, and y current (I
Y
) into the Winding
2 Phase A CT input.
Testing
The tests of the differential restraint characteristic verify the minimum pickup point, the intersection point of Breakpoint 1
and Slope 1, and the intersection point of Breakpoint 2 and Slope 2.
For simplicity, enter the following settings for each winding:
SYSTEM SETUP TRANSFORMER WINDING 1(4) WINDING 1(4) CONNECTION: “Wye”
SYSTEM SETUP TRANSFORMER WINDING 1(4) WINDING 1(4) GROUNDING: “Not Within Zone”
SYSTEM SETUP TRANSFORMER WINDING 2(4) WINDING 2(4) ANGLE WRT WINDING 1: “0°”
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