• Evolving fault where the fault during the dead-time spreads to another phase. Theother two phases must then be tripped and a three phase dead-time and autorecloseinitiated• Permanent fault• Fault during three phase dead-time• Auto-reclose out of service or CB not ready for an auto-reclosing cyclePrepare three phase tripping is then used to switch the tripping to three phase. This signalis generated by the auto-recloser and connected to the trip function block and alsoconnected outside the IED through IO when a common auto-recloser is provided for twosub-systems. An alternative signal Prepare 1 Phase trippingis also provided and can beused as an alternative when the autorecloser is shared with another subsystem. Thisprovides a fail safe connection so that even a failure in the IED with the auto-recloser willmean that the other sub-system will start a three-phase trip.A permanent fault will cause the line protection to trip again when it recloses in an attemptto clear the fault.The auto-reclosing function allows a number of parameters to be adjusted.Examples:• number of auto-reclosing shots• auto-reclosing program• auto-reclosing open times (dead time) for each shot.11.3.2.1 Auto-reclosing operation Disabled and EnabledOperation of the automatic reclosing can be set OFF and ON by a setting parameter andby external control. Parameter Operation = Disabled, or Enabled sets the function OFFand ON. In setting Operation=ExternalCtrl= Disabled and Enabled control is made byinput signal pulses, for example, from the control system or from the binary input (andother systems).When the function is set Enabled and operative (other conditions such as CB closed andCB Ready are also fulfilled), the output SETON is activated (high) when the function isready to accept a reclosing start.11.3.2.2 Initiate auto-reclosing and conditions for initiation of a reclosing cycleThe usual way to start a reclosing cycle, or sequence, is to start it at tripping by lineprotection by applying a signal to the input PICKUP. Starting signals can be either,General Trip signals or, only the conditions for Differential, Distance protection Zone 11MRK 506 334-UUS A Section 11Control321Application manual
