Zone Selection Features - ABB REB670 Applications Manual

1MRK 505 337-UUS -
6.1.3.8
Application manual
ZA
ZB
189 289
152
989
189G
en06000086_ansi.vsd
ANSI06000086 V1 EN
Figure 42: Feeder bay layout when line disconnector position might be required for
busbar protection
Such feeder set-up can be often found in GIS stations where cable CTs are used for busbar
protection. If in such feeder the line disconnector 989 is open and then immediately the
grounding switch 189G is closed before the busbar disconnectors 189G & 289 are open
there is a danger to get current unbalance into the zone differential measurement under
following circumstances:
• In case of parallel lines zero sequence mutual coupling can induce zero sequence
current into the grounded line especially during externalground-faults.
• In case of cable feeder the stored energy in the cable will be discharged through the
grounding switch at the moment of its closing.
In order to avoid such problems for busbar protection the status of line disconnector can
be monitored by busbar protection and CT measurement can be disconnected from both
differential zones as soon line disconnector is open. Similar functionality can be obtained
by instead monitoring the position of feeder breaker 152. In such case the breaker closing
signal shall be connected to busbar protection as well.

Zone selection features

The IED offers an extremely effective solution for stations where zone selection (that is,
CT switching) is required. This is possible due to the software facility, which gives full
and easy control over all CT inputs connected to the IED. 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:
Section 6
Differential protection
111