15.3 Second Harmonic Blocking Logic (SEF Input) 151
15.4 Application Notes 151
15.4.1 Setting Guidelines 151
16 Load Blinders 152
16.1 Load Blinder Implementation 152
16.2 Load Blinder Logic 153
17 Neutral Admittance Protection 156
17.1 Neutral Admittance Operation 156
17.2 Conductance Operation 156
17.3 Susceptance Operation 157
18 Busbar Protection 159
18.1 Buswire Supervision 160
Chapter 7 Restricted Earth Fault Protection 161
1 Chapter Overview 163
2 REF Protection Principles 164
2.1 Resistance-Earthed Star Windings 165
2.2 Solidly-Earthed Star Windings 165
2.3 Through Fault Stability 166
2.4 Restricted Earth Fault Types 166
2.4.1 Low Impedance REF Principle 167
2.4.2 High Impedance REF Principle 168
3 Restricted Earth Fault Protection Implementation 171
3.1 Restricted Earth Fault Protection Implementation 171
3.2 Low Impedance REF 171
3.2.1 Setting the Bias Characteristic 171
3.2.2 Delayed Bias 172
3.2.3 Transient Bias 172
3.3 High Impedance REF 172
3.3.1 High Impedance REF Calculation Principles 173
4 Application Notes 174
4.1 Star Winding Resistance Earthed 174
4.2 Low Impedance REF Protection Application 175
4.2.1 Setting Guidelines for Biased Operation 175
4.2.2 Low Impedance REF Scaling Factor 175
4.2.3 Parameter Calculations 176
4.3 High Impedance REF Protection Application 177
4.3.1 High Impedance REF Operating Modes 177
4.3.2 Setting Guidelines for High Impedance Operation 178
Chapter 8 CB Fail Protection 181
1 Chapter Overview 183
2 Circuit Breaker Fail Protection 184
3 Circuit Breaker Fail Implementation 185
3.1 Circuit Breaker Fail Timers 185
3.2 Zero Crossing Detection 185
4 Circuit Breaker Fail Logic 187
5 Undercurrent and ZCD Logic for CB Fail 190
6 CB Fail SEF Protection Logic 191
7 CB Fail Non Current Protection Logic 192
8 Circuit Breaker Mapping 193
9 Application Notes 194
9.1 Reset Mechanisms for CB Fail Timers 194
9.2 Setting Guidelines (CB fail Timer) 194
9.3 Setting Guidelines (Undercurrent) 195
P14x Contents
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