ABB RELION REB670, Applications Manual

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sometimes interlocked while both busbar disconnectors within one of the feeder
bays are closed.
• opening of the feeder bay busbar disconnector originally closed. The load is now
transferred from one to other bus.
• opening of bus coupler or bus section bay CB.
The zone interconnection has to be taken into consideration for the busbar differential
protection scheme, as each two busbar zones are interconnected together via two
disconnectors. The primary current split between busbars is then not known and the
two separate measuring zones cannot be maintained.
In conventional, analog busbar protection systems the solutions have been to, by
extensive zone switching IEDs. For example, in two-zone applications, it leads to
disconnect one zone (normally zone B, and connect all feeders to other zone (normally
zone A). At the same time the current from the bus-coupler bay, which just circulates
between zones, must be disconnected from the measuring differential zone.
Similar situation regarding to busbar protection can occur between any busbar sections
interconnected via sectionalizing disconnector, see Figure
55 for an example. When
each sectionalizer is closed, two separate protection zones becomes the one and busbar
protection must be able to dynamically handle this.
Due to the numerical design the IED can manage this situation in an elegant and simple
way. Internal feature called Zone Interconnection will be used to handle both
situations. This feature can be activated either externally via binary input or derived
internally by built-in logic. Especially in two-zone busbar protections, to internally
activate such feature, the setting
ZoneSel shall be also considered. Consequently, the
zone interconnection will be activated internally only when the following conditions
are met:
• bays have parameter ZoneSel set to either CtrlInclude or CtrlExcludes
• internal zone selection logic concludes that this particular bay shall be
simultaneously connected to multiple internal differential zones
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
1MRK 505 370-UUS A
Section 6
Differential protection
Busbar protection REB670 2.2 ANSI 131
Application manual