Siemens 7SG12 DAD-N - Table of Contents

7SG12 DAD N Applications Guide
Contents
1. Introduction .......................................................................................................................................................... 3
2. Differential Protection........................................................................................................................................... 3
3. High Impedance Differential Protection................................................................................................................ 3
3.1 Stabilising Resistor ............................................................................................................................................ 4
3.2 Non-Linear Resistor ....................................................................................................................................... 6
3.3 Fault Setting................................................................................................................................................... 7
3.4 Check Zone.................................................................................................................................................... 7
4. Current Transformer Requirements ..................................................................................................................... 9
5. Current Transformer Location .............................................................................................................................. 9
5.1 CTs overlapping the Circuit Breaker .............................................................................................................. 9
5.2 CTs on the circuit side of the Circuit Breaker ............................................................................................... 10
5.3 CTs on the Busbar side of the Circuit Breaker ............................................................................................. 10
5.4 Bus Section and Bus Couplers .................................................................................................................... 10
6. CT Supervision .................................................................................................................................................. 11
Figures
Figure 1 – Current Differential Protection................................................................................................................. 3
Figure 2 – Simple 4 CT Protection ........................................................................................................................... 4
Figure 3 – Current Distribution with one CT totally saturated................................................................................... 4
Figure 4 – Stabilising Resistor ................................................................................................................................. 4
Figure 5 – Measuring Lead Resistance ................................................................................................................... 5
Figure 6 – Non-Linear Resistor ................................................................................................................................6
Figure 7 – Shunt Resistor ........................................................................................................................................ 7
Figure 8 – Check Zone Relay .................................................................................................................................. 8
Figure 9 – CTs Overlapping the CB ......................................................................................................................... 9
Figure 10 – CTs on other side of CB...................................................................................................................... 10
Figure 11 – CTs on Busbar side of CB .................................................................................................................. 10
Figure 12 – CTs on Bus Section and Bus Coupler................................................................................................. 10
Figure 13 – DAD-N Connection Diagram............................................................................................................... 12
Figure 14 – Typical High Impedance Protection Components ............................................................................... 13
Figure 15 – High Impedance Protection of Auto-transformer................................................................................. 14
Figure 16 – High Impedance Protection of Motor, Generator or Reactors ............................................................. 15
Figure 17 – DAD-N-101 Differential Protection Elements ...................................................................................... 16
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