GE B90 - Page 7

TABLE OF CONTENTS
B90 LOW IMPEDANCE BUS DIFFERENTIAL SYSTEM – INSTRUCTION MANUAL vii
7 COMMANDS AND
TARGETS
7.1 Commands menu................................................................................................... 7-1
7.1.1 Virtual inputs........................................................................................................................... 7-2
7.1.2 Clear records .......................................................................................................................... 7-2
7.1.3 Set date and time................................................................................................................. 7-2
7.1.4 Relay maintenance.............................................................................................................. 7-3
7.1.5 Security ..................................................................................................................................... 7-4
7.2 Targets menu.......................................................................................................... 7-4
7.2.1 Target messages .................................................................................................................. 7-5
7.2.2 Relay self-tests ...................................................................................................................... 7-5
8 APPLICATION OF
SETTINGS
8.1 Overview.................................................................................................................. 8-1
8.1.1 Introduction............................................................................................................................. 8-1
8.1.2 Sample busbar and data.................................................................................................. 8-1
8.2 Zoning and dynamic bus replica ......................................................................... 8-3
8.2.1 North bus zone ...................................................................................................................... 8-3
8.2.2 South bus zone...................................................................................................................... 8-4
8.3 Biased characteristic breakpoints...................................................................... 8-5
8.3.1 Description .............................................................................................................................. 8-5
8.3.2 High breakpoint .................................................................................................................... 8-5
8.3.3 Low breakpoint...................................................................................................................... 8-6
8.4 Slopes and high set threshold ............................................................................. 8-6
8.4.1 Description .............................................................................................................................. 8-6
8.4.2 External faults on C-1......................................................................................................... 8-7
8.4.3 External faults on C-2......................................................................................................... 8-9
8.4.4 External faults on C-3......................................................................................................... 8-9
8.4.5 External faults on C-4.......................................................................................................8-10
8.4.6 External faults on C-5.......................................................................................................8-10
8.5 Bus differential settings...................................................................................... 8-10
8.5.1 Description ............................................................................................................................8-10
8.6 Enhancing relay performance...........................................................................8-11
8.6.1 Using setting groups.........................................................................................................8-11
9 THEORY OF
OPERATION
9.1 Introduction ............................................................................................................ 9-1
9.1.1 Bus differential protection................................................................................................9-1
9.2 Dynamic bus replica.............................................................................................. 9-3
9.2.1 Dynamic bus replica mechanism ................................................................................. 9-3
9.2.2 CT ratio matching................................................................................................................. 9-3
9.3 Differential principle.............................................................................................. 9-3
9.3.1 Biased differential characteristic.................................................................................. 9-3
9.3.2 Differential and restraining currents........................................................................... 9-4
9.3.3 Enhanced security ............................................................................................................... 9-5
9.4 Directional principle.............................................................................................. 9-6
9.4.1 Current directional protection........................................................................................ 9-6
9.5 Saturation detector ............................................................................................... 9-7
9.5.1 CT saturation detection..................................................................................................... 9-7
9.6 Output logic and examples .................................................................................. 9-9
9.6.1 Output logic............................................................................................................................. 9-9
9.6.2 Internal and external fault example..........................................................................9-10
10 MAINTENANCE 10.1 Monitoring............................................................................................................. 10-1
10.1.1 Devices with Site Targets................................................................................................10-1
10.1.2 Data with Modbus Analyzer ..........................................................................................10-1