GE P643 User Manual

6.3 CLO Implementation 161
6.4 Application Notes 163
6.4.1 CLI Setting Guidelines 163
6.4.2 CLO Setting Guidelines 163
Chapter 8 Restricted Earth Fault Protection 165
1 Chapter Overview 167
2 REF Protection Principles 168
2.1 Resistance-Earthed Star Windings 169
2.2 Solidly-Earthed Star Windings 169
2.3 Through Fault Stability 170
2.4 Restricted Earth Fault Types 170
2.4.1 Low Impedance REF Principle 170
2.4.2 High Impedance REF Principle 171
3 Restricted Earth Fault Protection Implementation 173
3.1 Enabling REF Protection 173
3.2 Selecting the Current Inputs 173
3.3 Low Impedance REF 174
3.3.1 Setting the Bias Characteristic 174
3.3.2 Delayed Bias 175
3.3.3 Transient Bias 175
3.3.4 Restricted Earth Fault Logic 175
3.4 High Impedance REF 175
3.4.1 High Impedance REF Calculation Principles 176
4 Second Harmonic Blocking 177
4.1 REF 2nd harmonic Blocking Logic 177
5 Application Notes 178
5.1 Star Winding Resistance Earthed 178
5.2 Low Impedance REF Protection Application 179
5.2.1 Setting Guidelines for Biased Operation 179
5.2.2 Low Impedance REF Scaling Factor 179
5.2.3 Parameter Calculations 179
5.2.4 Dual CB Application with Different Phase CT Ratios 180
5.2.5 Dual CB Application with Same Phase CT Ratios 181
5.2.6 CT Requirements - Low Impedance REF 181
5.3 High Impedance REF Protection Application 183
5.3.1 High Impedance REF Operating Modes 183
5.3.2 Setting Guidelines for High Impedance Operation 185
5.3.3 Use of Metrosil Non-linear Resistors 187
5.3.4 CT Requirements - High Impedance REF 189
Chapter 9 Current Protection Functions 191
1 Chapter Overview 193
2 Overcurrent Protection Principles 194
2.1 IDMT Characteristics 194
2.1.1 IEC 60255 IDMT Curves 195
2.1.2 European Standards 196
2.1.3 North American Standards 198
2.1.4 Differences Between the North american and European Standards 199
2.2 Principles of Implementation 199
2.2.1 Timer Hold Facility 200
2.3 Magnetising Inrush Restraint 200
3 Phase Overcurrent Protection 202
3.1 Phase Overcurrent Protection for Power Transformers 202
3.2 Phase Overcurrent Protection Implementation 202
3.3 Selecting the Current Inputs 203
P64x Contents
P64x-TM-EN-1.3 v

GE P643 Specifications

General

Brand	GE
Model	P643
Category	Relays
Language	English