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
1.2.4
1.3 Binary Outputs ...................................................................................................................................... 10
1.4 LEDs ..................................................................................................................................................... 10
Section 2: Protection Functions ............................................................................................................................. 11
2.1.1
2.1.2
Reset Delay ............................................................................................................................ 13
2.3 Cold Load Settings (51c)....................................................................................................................... 14
2.5.1
2.7.1
2 Out of 3 Logic ....................................................................................................................... 21
2.8.1
2.8.2
Isolated Networks ................................................................................................................... 25
2.8.3
2.11 Undercurrent (37) .................................................................................................................................. 28
2.12 Thermal Overload (49) .......................................................................................................................... 28
2.14 Neutral Overvoltage (59N) .................................................................................................................... 30
2.14.1
2.14.2
Derived NVD Voltage .............................................................................................................. 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
3.1.1
Overcurrent Protection CTs .................................................................................................... 34
3.1.2
Earth Fault Protection CTs ...................................................................................................... 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
4.1.3
4.1.4
4.2 Quick Logic Applications ....................................................................................................................... 40
4.2.1
5.1.1
Settings Guidelines ................................................................................................................. 41
5.4.1
5.4.2
5.5 Inrush Detector (81HBL2) ..................................................................................................................... 47
5.6.1
Broken Conductor example..................................................................................................... 48
©2017 Siemens Protection Devices Limited
7SR11 & 7SR12 Applications Guide
Chapter 7 Page 3 of 48