ABB Relion 670 Series Applications Manual page 115

1MRK 505 370-UUS Rev. K
some time after feeder CB opening (that is, after 400 ms). This measure will ensure fast busbar
protection tripping for faults within end fault region in that feeder bay, while feeder CB is open.
However, it shall be noted that in order to utilize end fault protection feeder circuit breaker status and its
closing command must be connected to the binary inputs of busbar protection scheme in order to be
available for zone selection logic.
End fault protection logic can be easily done with the help of graphical configuration tool. One stage (that
th
is, 4 stage) from optionally available overcurrent protection can be used as dedicated end fault
protection for feeders with CT on the line side of the CB.
End fault protection is here explained for simple single busbar station. However the same principles are
applicable to almost all other station layouts. Moreover, under certain circumstances, for stations with a
transfer bus more extensive logic for end fault protection implementation might be required.
6.1.3.8 Zone interconnection (Load transfer)
In multiple busbar stations, with or without transfer bus, it is common requirement to use the possibility of
zone interconnection loading current in any feeder bay from one busbar to the other(s). The sequence of
operation during zone interconnection is normally as the following:
• bus coupler or bus section bay is closed (that is, CB and both disconnectors).
• feeder bay busbar disconnector to the busbar not already in service is then closed. The switchgear
interlocking system shall allow this only when the bus coupler breaker is already closed. Depending
on the thermal capacity of the feeder busbar disconnectors (189 and 289) the opening of the bus
coupler circuit breaker is 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
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
Busbar protection REB670
Application manual
55 for an example. When each sectionalizer is closed, two
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Section 6
Differential protection
M12114-3 v4
109