Siemens 7UT51 Instruction Manual page 5

7UT51 v3
5.4 Trip Characteristic....................................................................................................................................... 71
5.4.1 Trip Characteristic Settings......................................................................................................................... 72
5.5 Through-Fault Restraint.............................................................................................................................. 74
5.6 Blocking by Frequency Variance ................................................................................................................ 74
5.7 Time Delays................................................................................................................................................ 75
5.8 Events and Actions ..................................................................................................................................... 75
6 Bus Differential Protection (87B) ................................................................................................. 79
6.1 Method of Operation ................................................................................................................................... 79
6.2 Describing the Protected Bus .....................................................................................................................79
6.2.1 Type of Protected Object ............................................................................................................................79
6.2.2 System Frequency......................................................................................................................................80
6.2.3 Rated Nominal Current ............................................................................................................................... 80
6.2.4 Normal Operational Status ......................................................................................................................... 80
6.3 Describing the CT Scheme......................................................................................................................... 81
6.3.1 Nominal Primary Rating of CTs .................................................................................................................. 81
6.3.2 Nominal Secondary Rating of CTs..............................................................................................................81
6.3.3 Orientation of CTs ....................................................................................................................................... 81
6.4 Trip Characteristic....................................................................................................................................... 83
6.4.1 Trip Characteristic Settings......................................................................................................................... 84
6.5 Through-Fault Restraint.............................................................................................................................. 85
6.6 CT Circuit Monitoring .................................................................................................................................. 86
6.7 Time Delays................................................................................................................................................ 86
6.8 Events and Actions ..................................................................................................................................... 86
7 Ground Differential Protection (87N) ........................................................................................... 91
7.1 Calculated Quantities .................................................................................................................................92
7.2 Trip Decision ...............................................................................................................................................93
7.3 Second Harmonic Restraint........................................................................................................................ 94
7.4 Normal Operational Status ......................................................................................................................... 95
7.5 Pickup Level and Limit Angle .....................................................................................................................95
7.6 Harmonic Restraint ..................................................................................................................................... 96
7.7 Time Delays................................................................................................................................................ 96
7.8 Events and Actions ..................................................................................................................................... 96
8 Time Overcurrent Protection (50HS and 50/51) .......................................................................... 99
8.1 Method of Operation ................................................................................................................................... 99
8.2 Normal Operational Status ......................................................................................................................... 99
8.3 High-Set Element (50HS) ......................................................................................................................... 100
8.4 Overcurrent Element (50 or 51) ................................................................................................................ 100
8.4.1 Definite Time Element (50) ....................................................................................................................... 101
PRIM-2330C
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