ABB REB670 - Page 127

related disconnectors. In addition, in two-zone busbar differential protections, a setting
parameter is also introduced to determine, together with the binary inputs, how the bay
CT current shall be connected to the differential zones.
The philosophy is to allow every CT input to be individually controlled by a setting
parameter
. This parameter called ZoneSel can be individually configured for every CT
input. This parameter, for every bay, can be set to only one of the following five
alternatives:
1. FIXEDtoZA
2. FIXEDtoZB
3. FIXEDtoZA&-ZB
4. CtrlIncludes
5. CtrlExcludes
If for a particular CT input setting parameter ZoneSel is set to FIXEDtoZA, then this
CT input will be only included to the differential zone A. This setting is typically used
for simple single zone application such as: single busbar staions, breaker-and-a-half
stations or double breaker stations.
If for a particular CT input setting parameter ZoneSel is set to FIXEDtoZB, then this
CT input will be only included to the differential zone B. This setting is typically used
for applications such as: breaker-and-a-half stations or double breaker stations.
If for a particular CT input setting parameter ZoneSel is set to FIXEDtoZA&-ZB, then
this CT input will be included to the differential zone A, but its inverted current value
will be as well included to the differential zone B. This setting is typically used for bus
coupler or bus section bays when only one current transformer is available see Figure
47.
If for a particular CT input setting parameter ZoneSel is set to Ctrl_Includes, then this
CT input will be:
• included to the dif
ferential zone A when input signal CTRLZA on corresponding
bay block is given logical value one and it will be excluded from the differential
zone A when input signal CTRLZA on corresponding bay block is given logical
value zero.
• included to the differential zone B when input signal CTRLZB on corresponding
bay block is given logical value one and it will be excluded from the differential
zone B when input signal CTRLZB on corresponding bay block is given logical
value zero.
This setting is typically used for feeder bays in double busbar stations in order to form
proper busbar disconnector replica. It is especially suitable both when normally open
1MRK 505 370-UUS A Section 6
Differential protection
Busbar protection REB670 2.2 ANSI 121
Application manual