7SR11 & 7SR12 Description Of Operation
©2012 Siemens Protection Devices Limited Chapter 1 Page 2 of 76
Contents
Section 1: Introduction ............................................................................................................................................. 7
1.1 Current Transformer Circuits................................................................................................................... 7
1.2 External Resistors................................................................................................................................... 7
1.3 Front Cover ............................................................................................................................................. 7
Section 2: Hardware Description............................................................................................................................ 15
2.1 General ................................................................................................................................................. 15
2.2 Case...................................................................................................................................................... 15
2.3 Front Cover ........................................................................................................................................... 16
2.4 Power Supply Unit (PSU)...................................................................................................................... 17
2.5 Operator Interface/ Fascia .................................................................................................................... 18
2.6 Current Inputs ....................................................................................................................................... 21
2.7 Voltage Inputs ....................................................................................................................................... 21
2.8 Binary Inputs ......................................................................................................................................... 21
2.9 Binary Outputs (Output Relays) ............................................................................................................ 22
2.10 Virtual Input/Outputs ............................................................................................................................. 23
2.11 Self Monitoring ...................................................................................................................................... 24
2.11.1 Protection Healthy/Defective................................................................................................... 24
Section 3: Protection Functions ............................................................................................................................. 26
3.1 Current Protection: Phase Overcurrent (67, 51, 50).............................................................................. 26
3.1.1 Directional Control of Overcurrent Protection (67) – 7SR12 ................................................... 26
3.1.2 Instantaneous Overcurrent Protection (50) ............................................................................. 27
3.1.3 Time Delayed Overcurrent Protection (51).............................................................................. 28
3.1.4 Current Protection: Voltage Controlled Overcurrent (51V) - 7SR12........................................ 30
3.2 Current Protection: Derived Earth Fault (67N, 51N, 50N) ..................................................................... 31
3.2.1 Directional Control of Derived Earth Fault Protection (67N) – 7SR12..................................... 31
3.2.2 Instantaneous Derived Earth Fault Protection (50N)............................................................... 32
3.2.3 Time Delayed Derived Earth Fault Protection (51N) ............................................................... 32
3.3 Current Protection: Measured Earth Fault (67G, 51G, 50G) ................................................................. 34
3.3.1 Directional Control of Measured Earth Fault Protection (67G) – 7SR12 ................................. 34
3.3.2 Instantaneous Measured Earth Fault Protection (50G)........................................................... 35
3.3.3 Time Delayed Measured Earth Fault Protection (51G) ........................................................... 36
3.4 Current Protection: Sensitive Earth Fault (67SEF, 51SEF, 50SEF)...................................................... 37
3.4.1 Directional Control of Sensitive Earth Fault Protection (67SEF) – 7SR12 .............................. 37
3.4.2 Instantaneous Sensitive Earth Fault Protection (50SEF) ........................................................ 38
3.4.3 Time Delayed Sensitive Earth Fault Protection (51SEF) ........................................................ 40
3.5 Current Protection: High Impedance Restricted Earth Fault - (64H) ..................................................... 42
3.6 Current Protection: Cold Load (51c) ..................................................................................................... 42
3.7 Current Protection: Negative Phase Sequence Overcurrent - (46NPS) ................................................ 43
3.8 Current Protection: Under-Current (37)................................................................................................. 44
3.9 Current Protection: Thermal Overload (49) ........................................................................................... 45
3.10 Current Protection: Line Check 50LC, 50G LC and 50SEF LC – Only software option ‘C’ ................... 46
3.11 Voltage Protection: Phase Under/Over Voltage (27/59) – 7SR12......................................................... 47
3.12 Voltage Protection: Negative Phase Sequence Overvoltage (47) – 7SR12 .......................................... 49
3.13 Voltage Protection: Neutral Overvoltage (59N) – 7SR12 ...................................................................... 49
3.14 Voltage Protection: Under/Over Frequency (81) – 7SR12 .................................................................... 50
Section 4: Control & Logic Functions ..................................................................................................................... 52
4.1 Auto-Reclose (79) Optional Function .................................................................................................... 52
4.1.1 Overview................................................................................................................................. 52
4.1.2 Auto Reclose sequences ........................................................................................................ 53
4.1.3 Autoreclose Prot’n Menu......................................................................................................... 54
4.1.4 Autoreclose Config Menu........................................................................................................ 54
4.1.5 P/F Shots sub-menu ............................................................................................................... 56
4.1.6 E/F Shots sub-menu ............................................................................................................... 56
4.1.7 SEF Shots sub-menu.............................................................................................................. 56
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