ABB Relion 670 Series Applications Manual page 116

Section 6
Differential protection
This situation only means that for this particular bay its busbar disconnectors are closed and therefore
zone interconnection switching is happening in the station.
When zone switching feature is activated inside the IED, each individual bay current will behave in the
predetermined way. In six-zone busbar differential protection, it is internally determined how a bay CT
should behave during zone interconnection, depending the bay is a feeder or a bus coupler or section
bay. In two-zone busbar differential protections, it is determined by the end user with a settable setting
ZoneSwitching. This parameter, for every bay, can be set to only one of the following three alternatives
• ForceOut
• ForceIn
• Conditionally
If for a particular CT input setting parameter ZoneSwitching is set to ForceOut, then this CT input will be
disconnected from both the differential zones, regardless of any other set value or active binary input,
while zone switching feature is active within the IED. This setting is typically used for bus coupler bay in
double busbar stations.
If for a particular CT input setting parameter ZoneSwitching is set to ForceIn, then this CT input will be
connected to both the differential zones, regardless of any other set value or active binary input, while
zone switching feature is active within the IED. This setting is typically used for all feeders bay in a
station with two single zone interconnected by a sectionalizing disconnector.
If for a particular CT input setting parameter ZoneSwitching is set to Conditionally, then this CT input will
be connected to both the differential zones only if it was included to any of the two zones for 2ms before
the zone switching feature was activated. This setting is typically used for all feeders bay in double
busbar stations. With this setting all feeder bays, which were not connected to any of the two zones
before the zone interconnection activation (that is, out for scheduled maintenance), will not either be
included during zone interconnection.
This practically means that for double busbar station, when zone switching feature is active, all feeder
bays will be connected to both differential zones, while bus coupler CT will be disconnected from both
zones. In this way simple but effective solution is formed. It is as well important to notice that all
necessary changes in the individual bay tripping arrangements will be automatically performed within the
internal logic.
A dedicated binary signal will be immediately activated in the internal logic when zone interconnection
feature is activated. If this feature is active longer than the pre-set time separate alarm binary signal is
activated, in order to alarm the station personnel about such operating conditions. ZoneInterconnection
feature can be disabled by a parameter setting for substation arrangements where it is not required that
is, single busbar stations, breaker-and-a-half stations and so on.
6.1.3.9 Tripping arrangements
Tripping circuit arrangement
The contact outputs are of medium duty type. It is possible to use them to directly trip the individual bay
circuit breakers. This solution is suitable for all types of station arrangements. The internal zone selection
logic provides individual bay trip signals in the internal software and no external relay for this purpose are
required. This arrangement insures correct trip signal distribution to all circuit breakers in case of busbar
protection operation or individual bay breaker failure protection operation. Breaker failure protection can
be internal or external to the IED.
110
© 2017 - 2021 Hitachi Power Grids. All rights reserved
1MRK 505 370-UUS Rev. K
M12116-3 v3
Busbar protection REB670
Application manual