ii Maintenance and Testing Date Code 20011026
SEL-321/321-1 Instruction Manual
Phase Distance Element Supervisory Conditions .......................................................7-32
Phase-to-Phase Nondirectional Overcurrent Element, 50PPn ............................7-32
Negative-Sequence Directional Element.............................................................7-32
Loss-of-Potential Logic....................................................................................... 7-32
Single-Pole Open Logic ......................................................................................7-32
Load-Encroachment Logic ..................................................................................7-32
Out-of-Step Blocking Logic................................................................................7-33
Phase Distance Element Test Using Three Voltage Sources and One Current
Source..................................................................................................................7-33
Ground Mho Distance Elements......................................................................................... 7-38
Ground Distance Element Supervisory Conditions ....................................................7-39
Phase and Ground Nondirectional Overcurrent Elements, 50Ln and 50Gn .......7-39
Loss-of-Potential Logic....................................................................................... 7-39
Single-Pole Open Logic ......................................................................................7-39
Three-Pole Open Logic .......................................................................................7-39
Ground Distance Element Disable Inputs ...........................................................7-40
Ground Mho Distance Element Test Using Three Voltage Sources and One
Current Source.....................................................................................................7-40
Ground Quadrilateral Distance Element Reactive Reach Test Using Three
Voltage Sources and One Current Source...........................................................7-45
Ground Quadrilateral Distance Element Resistive Reach Test Using Three
Voltage Sources and One Current Source...........................................................7-49
Troubleshooting Test Results .....................................................................................................7-54
Relay Troubleshooting................................................................................................................7-55
Inspection Procedure...........................................................................................................7-55
Troubleshooting Procedure.................................................................................................7-55
All Front Panel LEDs Dark.........................................................................................7-55
Cannot See Characters on Relay LCD Screen ............................................................7-56
Relay Does Not Respond to Commands From Device Connected to Serial Port.......7-56
Tripping Output Relay Remains Closed Following Fault ..........................................7-56
No Prompting Message Issued to Terminal upon Power-Up......................................7-56
System Does Not Respond to Faults...........................................................................7-57
Terminal Displays Meaningless Characters................................................................ 7-57
Relay Calibration........................................................................................................................7-57
Firmware Upgrades.....................................................................................................................7-57
Firmware Upgrade Instructions ..........................................................................................7-57
Factory Assistance......................................................................................................................7-60
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