ABB REB670 Applications Manual page 9

Application manual
Differential protection..................................................................104
Zone selection (CT switching).................................................... 107
Auxiliary contact requirement and evaluation.............................107
Minimum contact requirements.................................................. 108
Auxiliary contact evaluation logic................................................108
Zone selection features.............................................................. 111
CT disconnection for bus section and bus coupler current
transformer cores....................................................................... 113
End fault protection.....................................................................117
Zone interconnection (Load transfer)......................................... 120
Tripping circuit arrangement.......................................................125
Trip arrangement with one-phase version.................................. 126
Centralized trip unit.....................................................................127
Decentralized trip arrangement.................................................. 127
Mechanical lock-out function...................................................... 128
Contact reinforcement with heavy duty relays............................128
Trip circuit supervision for busbar protection..............................129
Different busbar arrangements........................................................129
General.......................................................................................129
Single busbar arrangements...................................................... 129
Single busbar arrangements with sectionalizer.......................... 130
Single busbar arrangements with bus-section breaker.............. 131
H-type busbar arrangements......................................................132
Double circuit breaker busbar arrangement............................... 134
Breaker-and-a-half busbar arrangements.................................. 136
Double busbar single breaker arrangement............................... 138
Double busbar arrangements with two bus-section breakers
and two bus-coupler breakers.................................................... 144
Double busbar-single breaker with transfer bus arrangements..145
Combined busbar arrangements................................................ 147
Summation principle........................................................................ 149
Introduction.................................................................................149
Auxiliary summation CTs............................................................152
Possible ASCT connections for REB670....................................154
Main CT ratio mismatch correction.............................................155
Primary pick-up levels for summation type differential
protection ...................................................................................155
SLCE 8/ASCT characteristics for end-connection......................158
SLCE 8/ASCT characteristics for series-connection.................. 159
Section 7 Current protection..............................................................161
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