Unit controller 3BSE015088R1

Unit controller 3BSE015088R1

Unit controller 3BSE015088R1

The directional function (ZDSRDIR) which is able to cope with the condition at voltage reversal, shall be used in all IEDs with conventional distance protection (ZMCPDIS,ZMCAPDIS). This function is necessary in the protection on compensated lines as well as all non-compensated lines connected to this busbar (adjacent lines).

All protections that can be exposed to voltage reversal must have the special directional function, including the protections on busbar where the voltage can be reversed by series compensated lines not terminated to this busbar. The directional function is controlled by faulty phase criteria. These criteria must identify all forward and reverse faults that can cause voltage reversal. Setting of the corresponding reach of the impedance measuring elements is separate for reactive and resistive reach and independent of each other for phase-to-earth and for phase-tophase measurement.

It is also necessary to consider the minimum load impedance limiting conditions: Setting of zone 1 A voltage reversal can cause an artificial internal fault (voltage zero) on faulty line as well as on the adjacent lines. This artificial fault always have a resistive component, this is however small and can mostly not be used to prevent tripping of a healthy adjacent line. An independent tripping zone 1 facing a bus which can be exposed to voltage reversal have to be set with reduced reach with respect to this false fault.

When the fault can move and pass the bus, the zone 1 in this station must be blocked. Protection further out in the net must be set with respect to this apparent fault as the protection at the bus. Different settings of the reach for the zone (ZMCPDIS) characteristic in forward and reverse direction makes it possible to optimize the settings in order to maximize dependability and security for independent zone1.