Allen-Bradley Rockwell Automation 857 User Manual page 5

Earth Fault Protection I
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Input Signal Selection .................................................... 3-31
Intermittent Earth Fault Detection .................................. 3-31
Four or Six Independent Undirectional Earth Fault
Overcurrent Stages ................................................... 3-31
Inverse Operation Time (I
Inverse Time Limitation ................................................. 3-32
Setting Groups ................................................................ 3-32
Recorded Values of the Latest Eight Faults ................... 3-35
Intermittent Transient Earth Fault Protection I
Direction Algorithm ....................................................... 3-36
I Pick-up Sensitivity ...................................................... 3-36
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Co-ordination with U
Co-ordination with Normal Directional Earth Fault
Protection based on Fundamental Frequency Signals ... 3-36
Auto Reclosing ............................................................... 3-37
Intermittent Time ........................................................... 3-37
Operation Time Setting and Actual Operation Time ..... 3-37
Setting Groups ................................................................ 3-38
Recorded Values of the Latest Eight Faults ................... 3-39
Capacitor Bank Unbalance Protection .................................. 3-40
Compensation Method ................................................... 3-41
Compensation and Location ........................................... 3-41
Zero Sequence Voltage Protection U
Measuring the Residual Voltage .................................... 3-44
Two Independent Stages ................................................ 3-44
Setting Groups ................................................................ 3-44
Recorded Values of the Latest Eight Faults ................... 3-45
Thermal Overload Protection T> (49) .................................. 3-46
Thermal Model ............................................................... 3-46
Time Constant for Cooling Situation ............................. 3-47
Heat Capacitance, Service Factor and Ambient Temp. ... 3-47
Example of a Behavior in the Thermal Model ............... 3-48
Initial Temperature Rise After Restart ........................... 3-48
Alarm Function .............................................................. 3-48
Overvoltage Protection U> (59) ........................................... 3-50
Three Independent Stages .............................................. 3-51
Configurable Release Delay ........................................... 3-51
Configurable Hysteresis ................................................. 3-51
Setting Groups ................................................................ 3-51
Recorded Values of the Latest Eight Faults ................... 3-52
Undervoltage Protection U< (27) ......................................... 3-53
Blocking during VT Fuse Failure ................................... 3-53
Self Blocking at Very Low Voltage ............................... 3-53
Three Independent Stages .............................................. 3-54
Setting Groups ................................................................ 3-54
Recorded Values of the Latest Eight Faults ................... 3-55
Reverse Power and Underpower Protection P< (32) ............ 3-56
> (50N/51N) ................................... 3-30
> stage only) ........................ 3-32
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> (67NT) .... 3-35
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> back-up Protection ................... 3-36
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> (59N) ...................... 3-44
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857-UM001A-EN-P - July 2009
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