When we use positive-sequence memory voltage polarization, the mho characteristics expand
all the way back to the source. The relay impedance setting Z
r
defines the maximum reach
point. Figures 2.5, 2.6, and 2.7 show the impedance plane characteristics for several fault
types. The forward-reaching mho circles extend from the source impedance Z
s
, forward to
the relay impedance setting Z
r
.
Table 2.7 shows the voltage and current combinations used to operate and polarize the six
mho elements.
Figure 2.5: Phase-Phase Element Response for a Three-Phase Forward Fault
Figure 2.6: Phase-Phase Element Response for a Phase-Phase Forward Fault
Date Code 920508
Specifications
SEL-221F, -1 Instruction Manual
2-33
Summary of Contents for SEL-221F
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Page 110: ...Example Event Report 2 4 12 Event Reporting SEL 221F 1 Instruction Manual Date Code 930830 ...
Page 158: ...SETTINGS SHEET FOR SEL 221F RELAY PAGE 2 OF 6 DATE Date Code 921110 ...
Page 160: ...SETTINGS SHEET PAGE 4 OF 6 FOR SEL 221F RELAY DATE Date Code 930601 ...
Page 161: ...SETTINGS SHEET PAGE 5 OF 6 FOR SEL 221F RELAY DATE Date Code 961208 ...
Page 229: ...SEL 200 Series Relay Main Board Troubleshooting Test Points and Jumper Locations ...