ABB RET650 Technical Manual page 9

Technical manual
Restrained and unrestrained limits of the differential
protection................................................................................94
Fundamental frequency negative sequence differential
currents.................................................................................. 96
Internal/external fault discriminator........................................ 98
Unrestrained, and sensitive negative sequence protections 101
Instantaneous differential currents....................................... 103
Harmonic and waveform block criteria................................. 103
Switch onto fault feature.......................................................104
Logic diagram.......................................................................105
Technical data........................................................................... 110
Restricted earth-fault protection, low impedance REFPDIF .......... 110
Identification.............................................................................. 110
Functionality.............................................................................. 111
Function block........................................................................... 111
Signals.......................................................................................111
Settings......................................................................................112
Monitored data...........................................................................112
Operation principle.................................................................... 113
Fundamental principles of the restricted earth-fault
protection..............................................................................113
Operate and restrain characteristic...................................... 115
Calculation of differential current and bias current............... 116
Detection of external earth faults..........................................117
Algorithm of the restricted earth-fault protection.................. 118
Technical data........................................................................... 119
1Ph High impedance differential protection HZPDIF .....................119
Identification.............................................................................. 119
Introduction................................................................................120
Function block........................................................................... 120
Signals.......................................................................................120
Settings......................................................................................121
Monitored data...........................................................................121
Operation principle.................................................................... 121
Logic diagram.......................................................................121
Technical data........................................................................... 122
Section 7 Impedance protection...................................................123
Power swing detection ZMRPSB ...................................................123
Identification.............................................................................. 123
Functionality.............................................................................. 123
Function block........................................................................... 123
Signals.......................................................................................124
Settings......................................................................................124
Table of contents
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