7SR18 Description Of Operation
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Contents
Document Release History ................................................................................................................................. 2
Software Revision History .................................................................................................................................. 2
Section 1: Introduction ....................................................................................................................................... 8
1.1 CURRENT TRANSFORMER CIRCUITS ........................................................................................................ 8
1.2 EXTERN AL RESISTORS .......................................................................................................................... 8
1.3 FIBRE OPTIC COMMUNICATION ............................................................................................................... 8
1.4 FRONT COVER ..................................................................................................................................... 8
Section 2: Hardware Description ...................................................................................................................... 16
2.1 General ........................................................................................................................................... 16
2.2 Case ............................................................................................................................................... 17
2.3 Front Cover ..................................................................................................................................... 18
2.4 Power Supply Unit (PSU) ................................................................................................................. 19
2.5 Operator Interface/ Fascia................................................................................................................ 19
2.6 Current Inputs.................................................................................................................................. 23
2.7 Voltage Inputs ................................................................................................................................. 23
2.8 Binary Inputs ................................................................................................................................... 23
2.9 Binary Outputs (Output Contacts) ..................................................................................................... 24
2.10 Virtual Input/Output Connections ...................................................................................................... 25
2.11 Self Monitoring ................................................................................................................................ 26
2.11.1 Protection Healthy/Defective ............................................................................................... 27
Section 3: Protection Functions ........................................................................................................................ 28
3.1 Differential Protection ....................................................................................................................... 28
3.1.1 Overall Biased Differential (87L-n) ...................................................................................... 28
3.1.2 Differential Highset (87HS-n) .............................................................................................. 30
3.1.3 Protection Communication Signalling Supervision ............................................................... 31
3.2 Inter-Trip Elements .......................................................................................................................... 31
3.2.1 Internal Inter-Trip Elements (87R-n) .................................................................................... 31
3.2.2 External Inter-Trip Elements (85S-n, 85R-n) ........................................................................ 31
3.3 Current Protection: Phase Overcurrent (67, 50, 51) ........................................................................... 32
3.3.1 Directional Control of Overcurrent Protection (67) ................................................................ 32
3.3.2 Instantaneous Overcurrent Protection (50) .......................................................................... 33
3.3.3 Time Delayed Overcurrent Protection (51) .......................................................................... 35
3.3.4 Voltage Controlled Overcurrent (51V) ................................................................................. 37
3.4 Current Protection: Derived Earth Fault (67N, 51N, 50N)................................................................... 38
3.4.1 Directional Control of Derived Easrth Fault Protection (67N) ................................................ 38
3.4.2 Instantaneous Derived Earth Fault Protection (50N) ............................................................ 39
3.4.3 Time Delayed Derived Earth Fault Protection (51N) ............................................................. 40
3.5 Current Protection: Measured Earth Fault (67G, 51G, 50G)............................................................... 41
3.5.1 Directional Control of Measured Earth Fault Protection (67G) .............................................. 41
3.5.2 Instantaneous Measured Earth Fault Protection (50G) ......................................................... 42
3.5.3 Time Delayed Measured Earth Fault Protection (51G) ......................................................... 43
3.6 Current Protection: Cold Load (51c) ................................................................................................. 44
3.7 Current Protection: Negative Phase Sequence Overcurrent - (46NPS) .............................................. 45
3.8 Current Protection: Under-Current (37 & 37G) .................................................................................. 46
3.9 Current Protection: Thermal Overload (49) ....................................................................................... 47
3.10 Current Protection: Line Check 50LC, 50G LC .................................................................................. 48
Section 4: Control & Logic Functions ................................................................................................................ 49
4.1 Auto-Reclose (79) ............................................................................................................................ 49
4.1.1 Overview............................................................................................................................ 49
4.1.2 Auto Reclose sequences .................................................................................................... 51
4.2 Autoreclose Prot’n Menu .................................................................................................................. 52
4.3 Autoreclose Config Menu ................................................................................................................. 52
4.4 P/F Shots Sub-Menu........................................................................................................................ 54
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