12 STUB BUS DIFFERENTIAL PROTECTIONThis product can provide stub-bus protection associated with the differential protection.If you wish to use this feature you must ensure that the current differential protection is enabled. You will need tomap one of the opto-isolated inputs to the DDB Stub Bus Enabled using the programmable scheme logic and youwill 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 differentialprotection is disabled. No differential trip signals will be issued by the affected terminal. No differential intertripsignals will be issued, or acted upon by the affected terminal. No permissive intertrip signals will be issued, oracted upon by the affected terminal. Intertripping signals mapped via IM64 will be acted upon, and the affectedterminal 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 usesthem as inputs to the phase differential current protection. The values are compared against the dual slopecharacteristics 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 theseapplications, if the stub-bus feature is enabled and activated, the protection will trip if the measured currentexceeds 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:V02614To busbar 1P54xTo busbar 2P543/5Communication channelProtected lineEnd XEnd YCTX1CTX2CTYFigure 47: Stub Bus protectionNote:Models having distance protection feature a phase segregated stub bus protection associated with the distance protectionelements. Where applicable these are described along with the distance elements.Chapter 6 - Current Differential Protection P543i/P545i124 P54x1i-TM-EN-1
