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79 - Auto recloser


Automatic reclosing is a well-established method for the restoration of service in a power system after a transient line fault. The majority of line faults are flashover arcs, which are transient by nature [1]. The 79 Auto Recloser is used to resolve most of the outages by simple close breaker operation.

Icons and diagrams

Model overview

When a fault is detected, the breaker trips. Automatic reclosing is usually started by the line protection and in particular by instantaneous tripping of protection scheme. The recloser then waits for a predetermined time before reclosing the breaker. If all is well, that’s the finish of the process, but if the fault persists the breaker trips again and, after an extra delay, the controller recloses it for a second time and checks again for the continuing presence of the fault. If the fault remains present after this second recloses, the breaker trips once more.  If the fault persists; this scheme permanently opens the circuit breaker and issues the Lock Out output.

When the power line is switched off by the operation of line protection and line breakers, the arc de-ionizes and recovers its ability to withstand voltage at a somewhat variable rate. Thus, a certain open interval (or dead) time with a de-energized line is necessary. Line service can then be resumed by automatic reclosing of the line breakers. The open interval time selected should be long enough to ensure a high probability of arc de-ionization and successful reclosing [1].

The reclaim time is the time the function takes from issue of the reclosing command, until the new or next reclosing attempt is issued. The reclaim timer is started when the CB closing command is given [2]. The CB closing command, output CB_Close is given as a pulse with a duration set by parameter CB_Close_Pulsewidth.


The below figure shows the control panel of the 79-AR relay model.

The following parameters are tunable:

Parameter tab of 79-AR Relay

NameUnitDescriptionSample value
Operation-79-Recloser enable/disable-
Number of reclosure shots


Number of reclosure attempts. Max number of reclosing shots is 3.2
79OI1 Open Interval


Open Interval time for shot 15.0
79OI2 Open Interval


Open Interval time for shot 25.0
79OI3 Open Interval


Open Interval time for shot 35.0
Reclaim time


Duration of reclaim time2.0
CB_Close pulse width


Duration of the circuit breaker closing pulse0.5

Input and output signals
The module has 5 inputs and 2 outputs:

79-AR Relay I/O

I/O NameType (Unit)Description



Input triggers the reclosing function



Position of CB contacts. 1-> Close; 0-> Open



CB must be ready for reclosing operation. 1-> Ready; 0-> Not ready



Synchronism-check condition fulfilled.



Resets the AR to initial conditions. The function reset with the rising edge of the reset signal.



Closing command for CB



Lock Out command for CB


[1] REL-670 Application Manual - ABB

[2] REL-670 Technical Manual - ABB

[3] SEL-651 Recloser Control, Instruction Manual - SEL

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