Table Of Contents; Contents - Siemens 7SR21 Manual

Contents

Document Release History....................................................................................................................1
Software Revision History.....................................................................................................................1
Contents ..................................................................................................................................................2
Section 1: Common Functions .............................................................................................................4
1.1 Multiple Settings Groups...........................................................................................................4
1.2 Binary Inputs .............................................................................................................................5
1.3 Binary Outputs ..........................................................................................................................8
1.4 LEDs .........................................................................................................................................8
Section 2: Protection Functions .........................................................................................................10
2.1 Time delayed overcurrent (51/51G/51N) ................................................................................10
2.1.1 Selection of Overcurrent Characteristics ...................................................................11
2.1.2 Reset Delay................................................................................................................12
2.2 Voltage dependent overcurrent (51V).....................................................................................13
2.3 Cold Load Settings (51c) ........................................................................................................13
2.4 Instantaneous Overcurrent (50/50G/50N) ..............................................................................14
2.4.1 Blocked Overcurrent Protection Schemes .................................................................14
2.5 Sensitive Earth-fault Protection (50SEF) ................................................................................16
2.6 Directional Protection (67) ......................................................................................................17
2.7 Directional Earth-Fault (50/51G, 50/51N, 51/51SEF) .............................................................20
2.8 High Impedance Restricted Earth Fault Protection (64H) ......................................................21
2.9 Negative Phase Sequence Overcurrent (46NPS) ..................................................................23
2.10 Undercurrent (37)....................................................................................................................23
2.11 Thermal Overload (49)............................................................................................................23
2.12 Under/Over Voltage Protection (27/59) ..................................................................................24
2.13 Neutral Overvoltage (59N) ......................................................................................................25
2.13.1 Application with Capacitor Cone Units.......................................................................26
2.13.2 Derived NVD Voltage .................................................................................................26
2.14 Negative Phase Sequence Overvoltage (47) .........................................................................26
2.15 Under/Over Frequency (81) ....................................................................................................27
Section 3: CT Requirements ...............................................................................................................28
3.1 CT Requirements for Overcurrent and Earth Fault Protection ...............................................28
3.1.1 Overcurrent Protection CTs .......................................................................................28
3.1.2 Earth Fault Protection CTs.........................................................................................28
3.2 CT Requirements for High Impedance Restricted Earth Fault Protection ..............................28
Section 4: Control Functions ..............................................................................................................29
4.1 Auto-reclose Applications .......................................................................................................29
4.1.1 Auto-Reclose Example 1............................................................................................30
4.1.2 Auto-Reclose Example 2 (Use of Quicklogic with AR) ..............................................31
4.2 Quick Logic Applications.........................................................................................................32
4.2.1 Auto-Changeover Scheme Example..........................................................................32
Section 5: Supervision Functions ......................................................................................................33
5.1 Circuit-Breaker Fail (50BF) .....................................................................................................33
5.1.1 Settings Guidelines ....................................................................................................33
©2010 Siemens Protection Devices Limited
7SR21 & 7SR22 Argus Applications Guide
Chapter 7 Page 2 of 39