8 STUB BUS DIFFERENTIAL PROTECTION
This product can provide stub-bus protection associated with the differential protection.
If y
ou wish to use this feature you must ensure that the current differential protection is enabled. You will need to
map one of the opto-isolated inputs to the DDB Stub Bus Enabled using the programmable scheme logic and you
will need to enable the feature by setting Ph Diff Stub Bus in the CURRENT DIFF column to Enabled.
When the stub bus protection is enabled and activated by energisation of the opto-isolated input, the differential
protection is disabled. No differential trip signals will be issued by the affected terminal. No differential intertrip
signals will be issued, or acted upon by the affected terminal. No permissive intertrip signals will be issued, or
acted upon by the affected terminal. Intertripping signals mapped via IM64 will be acted upon, and the affected
terminal remains active to protect the isolated stub bus.
For products having two sets of CT inputs, the stub bus protection takes the two sets of current inputs and uses
them as inputs to the phase differential current protection. The values are compared against the dual slope
characteristics to determine whether tripping should occur or not.
For products having a single set of CT inputs, an additional setting (Ph Is1 StubBus) is provided. In these
applications, if the stub-bus feature is enabled and activated, the protection will trip if the measured current
exceeds the Ph Is1 StubBus setting.
Tripping due to the operation of the stub-bus protection is always three-phase.
The principle is outlined in the figure below:
V02614
To busbar 1
P54x
To busbar 2
P543/5
Communication channel
Protected line
End X
End Y
CT
X1
CT
X2
CT
Y
Figure 44: Stub Bus protection
Not
e:
Models having distance protection feature a phase segregated stub bus protection associated with the distance protection
elements. Where applicable these are described along with the distance elements.
Chapter 6 - Current Differential Protection P54A/B/C/E
114 P54xMED-TM-EN-1
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