©2015 Siemens Protection Devices Limited
Chapter 7 Page 5 of 64
List of Figures
Figure 2-1 Procedure for calculating Overall Differential Protection Settings ........................................ 9
Figure 2-2: 87BD Characteristic ........................................................................................................ 12
Fig. 2-3: Differential Highset Characteristic ........................................................................................ 14
Fig. 2-4 New Transformer Application ............................................................................................... 15
Figure 2-5: AC Connections - Example 1 ........................................................................................... 15
Figure 2-6 ICT Settings – Example 1 ................................................................................................. 16
Figure 2-7: Relay Currents - Star Winding Internal Earth ................................................................... 18
Figure 2-8: Relay Currents - Star Winding Internal Phase Fault ......................................................... 19
Figure 2-9: Relay Currents - Delta Winding Internal Earth Fault ......................................................... 20
Figure 2-10: Relay Currents - Delta Winding Internal Phase Fault ..................................................... 20
Figure 2-11 Relay Replacement ........................................................................................................ 22
Figure 2-12: AC Connections - Example 2 ......................................................................................... 22
Figure 2-13 Summary of ICT Settings ............................................................................................... 23
Figure 2-14 IEC NI Curve with Time Multiplier and Follower DTL Applied .......................................... 26
Figure 2-15
IEC NI Curve with Minimum Operate Time Setting Applied ............................................ 26
Figure 2-16 Overcurrent Reset Characteristics .................................................................................. 27
Figure 2-17: REF Protection Applied to a Delta/Star Transformer ...................................................... 28
Figure 2-18: AC Connections: REF ................................................................................................... 28
Figure 2-19 Thermal Overload Settings ............................................................................................. 34
Figure 2-20 NVD Application ............................................................................................................. 36
Figure 2-21 NVD Protection Connections .......................................................................................... 36
Figure 2-22 Load Shedding Scheme Using Under-Frequency Elements ............................................ 37
Figure 3-1 CT Requirements ............................................................................................................. 40
Figure 4-1 Example Use of Quick Logic............................................................................................. 41
Figure 5-1 - Circuit Breaker Fail......................................................................................................... 45
Figure 5-2 - Single Stage Circuit Breaker Fail Timing......................................................................... 45
Figure 5-3 - Two Stage Circuit Breaker Fail Timing ............................................................................ 46
Figure 5-4:
Trip Circuit Supervision Scheme 1 (H5) ......................................................................... 47
Figure 5-5:
Trip Circuit Supervision Scheme 2 (H6) ......................................................................... 48
Figure 5-6:
Trip Circuit Supervision Scheme 3 (H7) ......................................................................... 48
Figure 5-7
Close Circuit Supervision Scheme ................................................................................. 49
Figure 6-1: Relay Currents – External Earth Fault with In Zone Earthing Transformer ........................ 51
Figure 6-2: Relay Currents – External Earth Fault with In Zone Earthing Transformer ........................ 52
Figure 6-3 7SR24 Applied to Yd Transformer with an In Zone Earthing Transformer.......................... 52
Figure 6-4: Protection of Star/Star Transformer with Tertiary ............................................................. 53
Figure 6-5 – AC Connections: Yd9, 90
0
Transformer – Non-standard Secondary
Connections .................................................................................................................. 54
Fig. 6-6 AC Connections: Yd9, 90
0
Transformer – Standard Secondary Connections ........................ 55
Fig. 6-7 Dyn11 Transformer with Reverse Phase Notation ................................................................. 56
Fig. 6-8: AC Connections for Auto-Transformer Overall Protection .................................................... 57
Fig. 6-9: AC Connections for Auto-Transformer Overall and REF Protection ...................................... 57
Fig. 6-10 AC Connections for Reactor and Connections Protection ................................................... 58
Figure 7-1
Example Use of Alternative Settings Groups.................................................................. 59
Figure 7-2 Example of Transformer Alarm and Trip Wiring ................................................................ 60
Figure 7-3 – Binary Input Configurations Providing Compliance with EATS 48-4 Classes
ESI 1 and ESI 2 ............................................................................................................. 62
List of Tables
Summary of Contents for 7SR242 Duobias
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