Siemens 7SR21 Manual page 4

List of Figures
Figure 2-1 Directional Phase Fault Boundary System Angles ............................................................15
Figure 2-2 Phase Overcurrent.............................................................................................................16
Figure 2-3 Voltage Controlled Overcurrent .........................................................................................19
Figure 2-4 Cold Load...........................................................................................................................21
Figure 2-5 Cold Load Logic diagram...................................................................................................22
Figure 2-6 Directional Earth Fault Boundary System Angles..............................................................24
Figure 2-7 Derived Earth Fault ............................................................................................................25
Figure 2-8 Measured Earth Fault ........................................................................................................29
Figure 2-9 Sensitive Earth Fault..........................................................................................................33
Figure 2-10 Restricted Earth Fault ........................................................................................................37
Figure 2-11 Negative Phase Sequence Overcurrent ............................................................................39
Figure 2-12 Undercurrent ......................................................................................................................42
Figure 2-13 Thermal Overload ..............................................................................................................44
Figure 2-14 Phase Under/Over Voltage................................................................................................46
Figure 2-15 Vx Under/Over Voltage......................................................................................................49
Figure 2-16 NPS Overvoltage ...............................................................................................................51
Figure 2-17 Neutral Overvoltage ...........................................................................................................53
Figure 2-18 Under/Over Frequency ......................................................................................................55
Figure 3-1 CB Fail ...............................................................................................................................57
Figure 3-2 Voltage Transformer Supervision ......................................................................................59
Figure 3-3 Current Transformer Supervision ......................................................................................61
Figure 3-4 Broken Conductor ..............................................................................................................63
Figure 3-5 Trip Circuit Supervision......................................................................................................65
Figure 3-6 Magnetising Inrush Detector..............................................................................................66
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7SR21 & 7SR22 Argus Commissioning and Maintenance
Chapter 6 Page 4 of 69