7SR11 & 7SR12 Description Of Operation
©2017 Siemens Protection Devices Limited Chapter 1 Page 3 of 88
Contents
Section 1: Introduction ............................................................................................................................................. 8
Section 2: Hardware Description ............................................................................................................................ 18
2.1 General ................................................................................................................................................. 18
2.2 Case...................................................................................................................................................... 19
2.3 Front Cover ........................................................................................................................................... 20
2.4 Power Supply Unit (PSU) ...................................................................................................................... 21
2.5 Operator Interface/ Fascia .................................................................................................................... 22
2.6 Current Inputs ....................................................................................................................................... 25
2.7 Voltage Inputs ....................................................................................................................................... 25
2.8 Binary Inputs ......................................................................................................................................... 25
2.9 Binary Outputs (Output Relays) ............................................................................................................ 26
2.10 Virtual Input/Outputs ............................................................................................................................. 27
2.11 Self Monitoring ...................................................................................................................................... 28
2.11.1 Protection Healthy/Defective ................................................................................................... 30
Section 3: Protection Functions ............................................................................................................................. 31
3.1 Current Protection: Phase Overcurrent (67, 51, 50) .............................................................................. 31
3.1.1 Directional Control of Overcurrent Protection (67) – 7SR12 ................................................... 31
3.1.2 Instantaneous Overcurrent Protection (50) ............................................................................. 32
3.1.3 Time Delayed Overcurrent Protection (51).............................................................................. 33
3.1.4 Current Protection: Voltage Controlled Overcurrent (51V) - 7SR12 ........................................ 35
3.2 Current Protection: Derived Earth Fault (67N, 51N, 50N) ..................................................................... 36
3.2.1 Directional Control of Derived Earth Fault Protection (67N) – 7SR12 ..................................... 36
3.2.2 Instantaneous Derived Earth Fault Protection (50N) ............................................................... 37
3.2.3 Time Delayed Derived Earth Fault Protection (51N) ............................................................... 37
3.3 Current Protection: Measured Earth Fault (67G, 51G, 50G) ................................................................. 39
3.3.1 Directional Control of Measured Earth Fault Protection (67G) – 7SR12 ................................. 39
3.3.2 Instantaneous Measured Earth Fault Protection (50G) ........................................................... 40
3.3.3 Time Delayed Measured Earth Fault Protection (51G) ........................................................... 41
3.4 Current Protection: Sensitive Earth Fault (67SEF, 51SEF, 50SEF) ...................................................... 42
3.4.1 Directional Control of Sensitive Earth Fault Protection (67SEF) – 7SR12 .............................. 42
3.4.2 Instantaneous Sensitive Earth Fault Protection (50SEF) ........................................................ 43
3.4.3 Time Delayed Sensitive Earth Fault Protection (51SEF) ........................................................ 45
3.5 Current Protection: High Impedance Restricted Earth Fault - (64H) ..................................................... 47
3.6 Current Protection: Cold Load (51c) ..................................................................................................... 47
3.7 Current Protection: Negative Phase Sequence Overcurrent - (46NPS) ................................................ 48
3.8 Current Protection: Under-Current (37) ................................................................................................. 49
3.9 Current Protection: Thermal Overload (49) ........................................................................................... 50
3.10 Current Protection: Line Check 50LC, 50G LC and 50SEF LC – Only software option ‘C’ ................... 51
3.11 Current Protection: Arc Flash Detector (50 AFD) .................................................................................. 53
3.12 Voltage Protection: Phase Under/Over Voltage (27/59) – 7SR12 ......................................................... 54
3.13 Voltage Protection: Negative Phase Sequence Overvoltage (47) – 7SR12 .......................................... 55
3.14 Voltage Protection: Neutral Overvoltage (59N) – 7SR12 ...................................................................... 55
3.15 Voltage Protection: Under/Over Frequency (81) – 7SR12 .................................................................... 57
3.16 Power Protection: Power (32) – 7SR12 ................................................................................................ 58
3.17 Power Protection: Sensitive Power (32S) – 7SR12 .............................................................................. 59
3.18 Power Protection: Power Factor (55) – 7SR12 ..................................................................................... 60
Section 4: Control & Logic Functions ..................................................................................................................... 61
4.1 Auto-Reclose (79) Optional Function .................................................................................................... 61
4.1.1 Overview ................................................................................................................................. 61
4.1.2 Auto Reclose sequences ........................................................................................................ 62
4.1.3 Autoreclose Prot’n Menu ......................................................................................................... 63
4.1.4 Autoreclose Config Menu ........................................................................................................ 63
4.1.5 P/F Shots sub-menu ............................................................................................................... 65
4.1.6 E/F Shots sub-menu ............................................................................................................... 65
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