Schweitzer Engineering Laboratories SEL-351 - Page 76

ii Overcurrent, Voltage, Synchronism Check, Frequency, and Power Elements Date Code 20001006
SEL-351 Instruction Manual
Settings Ranges.......................................................................................................3-25
Accuracy.................................................................................................................3-25
Residual Ground Time-Overcurrent Element....................................................................3-25
Settings Ranges.......................................................................................................3-26
Accuracy.................................................................................................................3-27
Negative-Sequence Time-Overcurrent Element ................................................................3-27
Settings Ranges.......................................................................................................3-28
Accuracy.................................................................................................................3-28
Voltage Elements....................................................................................................................3-29
Voltage Values................................................................................................................3-29
Voltage Element Settings.................................................................................................3-29
Accuracy.................................................................................................................3-36
Voltage Element Operation..............................................................................................3-36
Undervoltage Element Operation Example ...............................................................3-37
Overvoltage Element Operation Example .................................................................3-37
Voltage Elements Used in POTT Logic ...........................................................................3-37
Synchronism Check Elements .................................................................................................3-38
Voltage Input VS Connected with a Different CT Configuration than the Reference
Phase or Beyond a Delta-Wye Transformer..............................................................3-38
Synchronism Check Elements Settings.............................................................................3-39
Setting SYNCP...............................................................................................................3-40
Accuracy.................................................................................................................3-40
Synchronism Check Elements Voltage Inputs...................................................................3-42
System Frequencies Determined from Voltages V
A
(or V
AB
for Delta) and V
S
...........3-43
System Rotation Can Affect Setting SYNCP ....................................................3-43
Synchronism Check Elements Operation..........................................................................3-44
Voltage Window......................................................................................................3-44
Other Uses for Voltage Window Elements ........................................................3-44
Block Synchronism Check Conditions......................................................................3-44
Slip Frequency Calculator........................................................................................3-45
Angle Difference Calculator.....................................................................................3-45
Voltages V
P
and V
S
are “Static” .......................................................................3-45
Voltages V
P
and V
S
are “Slipping” ...................................................................3-46
Angle Difference Example (Voltages V
p
and V
s
are “Slipping”) ........................3-46
Synchronism Check Element Outputs.......................................................................3-49
Voltages V
P
and V
S
are “Static” or Setting TCLOSD = 0.00.............................3-49
Voltages V
P
and V
S
are “Slipping” and Setting TCLOSD ≠ 0.00 ......................3-49
Synchronism Check Applications for Automatic Reclosing and Manual Closing...............3-51
Frequency Elements................................................................................................................3-51
Frequency Element Settings.............................................................................................3-51
Accuracy.................................................................................................................3-53
Create Over- and Underfrequency Elements .............................................................3-53
Overfrequency Element ....................................................................................3-54
Underfrequency Element ..................................................................................3-54
Frequency Element Operation..........................................................................................3-54
Overfrequency Element Operation............................................................................3-54
Underfrequency Element Operation..........................................................................3-55
Frequency Element Voltage Control.........................................................................3-55
Other Uses for Undervoltage Element 27B81....................................................3-55
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