7SR11 & 7SR12 Applications Guide
©2017 Siemens Protection Devices Limited Chapter 7 Page 3 of 48
Contents
Section 1: Common Functions ................................................................................................................................. 5
1.1 Multiple Settings Groups ......................................................................................................................... 5
1.2 Binary Inputs ........................................................................................................................................... 6
1.2.1 Alarm and Tripping Inputs ......................................................................................................... 6
1.2.2 AC Rejection ............................................................................................................................. 6
1.2.3 Use of Binary Inputs in control and tripping circuits .................................................................. 8
1.2.4 Capacitance Discharge Current in Centre Tapped Battery Installations ................................... 8
1.3 Binary Outputs ...................................................................................................................................... 10
1.4 LEDs ..................................................................................................................................................... 10
Section 2: Protection Functions ............................................................................................................................. 11
2.1 Time delayed overcurrent (51/51G/51N) ............................................................................................... 11
2.1.1 Selection of Overcurrent Characteristics ................................................................................. 12
2.1.2 Reset Delay ............................................................................................................................ 13
2.2 Voltage dependent overcurrent (51V) ................................................................................................... 14
2.3 Cold Load Settings (51c)....................................................................................................................... 14
2.4 Arc Flash Detection (50AFD) ................................................................................................................ 15
2.5 Instantaneous Overcurrent (50/50G/50N) ............................................................................................. 16
2.5.1 Blocked Overcurrent Protection Schemes .............................................................................. 16
2.6 Sensitive Earth-fault Protection (50SEF)............................................................................................... 18
2.7 Directional Protection (67) ..................................................................................................................... 19
2.7.1 2 Out of 3 Logic ....................................................................................................................... 21
2.8 Directional Earth-Fault (50/51G, 50/51N, 50/51SEF) ............................................................................ 22
2.8.1 Compensated Coil Earthing Networks .................................................................................... 22
2.8.2 Isolated Networks ................................................................................................................... 25
2.8.3 Minimum Polarising Voltage.................................................................................................... 25
2.9 High Impedance Restricted Earth Fault Protection (64H) ..................................................................... 26
2.10 Negative Phase Sequence Overcurrent (46NPS) ................................................................................. 27
2.11 Undercurrent (37) .................................................................................................................................. 28
2.12 Thermal Overload (49) .......................................................................................................................... 28
2.13 Under/Over Voltage Protection (27/59) ................................................................................................. 29
2.14 Neutral Overvoltage (59N) .................................................................................................................... 30
2.14.1 Application with Capacitor Cone Units .................................................................................... 31
2.14.2 Derived NVD Voltage .............................................................................................................. 31
2.15 Negative Phase Sequence Overvoltage (47) ........................................................................................ 31
2.16 Under/Over Frequency (81) .................................................................................................................. 31
2.17 Power (32) ............................................................................................................................................ 33
2.18 Sensitive Power (32S)........................................................................................................................... 33
2.19 Power Factor (55) ................................................................................................................................. 33
Section 3: CT Requirements .................................................................................................................................. 34
3.1 CT Requirements for Overcurrent and Earth Fault Protection .............................................................. 34
3.1.1 Overcurrent Protection CTs .................................................................................................... 34
3.1.2 Earth Fault Protection CTs ...................................................................................................... 34
3.2 CT Requirements for High Impedance Restricted Earth Fault Protection ............................................. 34
Section 4: Control Functions .................................................................................................................................. 35
4.1 Auto-reclose Applications ...................................................................................................................... 35
4.1.1 Auto-Reclose Example 1, typical complex distribution network sequence .............................. 36
4.1.2 Auto-Reclose Example 2, simple multishot sequence ............................................................ 37
4.1.3 Auto-Reclose Example 3, simple single shot sequence .......................................................... 38
4.1.4 Auto-Reclose Example 4 (Use of Quicklogic with AR) ............................................................ 39
4.2 Quick Logic Applications ....................................................................................................................... 40
4.2.1 Auto-Changeover Scheme Example ....................................................................................... 40
Section 5: Supervision Functions ........................................................................................................................... 41
5.1 Circuit-Breaker Fail (50BF) ................................................................................................................... 41
5.1.1 Settings Guidelines ................................................................................................................. 41
5.2 Current Transformer Supervision .......................................................................................................... 43
5.3 Voltage Transformer Supervision (60VTS) ........................................................................................... 44
5.4 Trip/Close Circuit Supervision (74T/CCS) ............................................................................................ 45
5.4.1 Trip Circuit Supervision Connections ...................................................................................... 45
5.4.2 Close Circuit Supervision Connections ................................................................................... 47
5.5 Inrush Detector (81HBL2) ..................................................................................................................... 47
5.6 Broken Conductor / Load Imbalance (46BC) ........................................................................................ 47
5.6.1 Broken Conductor example..................................................................................................... 48
5.7 Circuit-Breaker Maintenance ................................................................................................................. 48
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