Technically, whenever any transient faults causing the trip of the circuit breaker, mainly for Over head lines occur, most of utilities prefer to reclose the breaker or they try to reclose for number of times, before coming to the conclusion that the fault is permanent.
You must know which kind of faults you need to consider for transient faults. Not all faults are transient. Ph-Gd, O/C or Multi-phase faults generally account for Transient faults. These AR initiation can be other source too. Energized by user-defined precondition to start AR. As per Siemens Relays, Non-directional faults/Directional/Other/via BI is possible. But it is important that fault occurs. Unless relay sees a fault and breaker trips due to that fault, AR sequence will not start.
- AR and Synch Check goes hand in hand. So when you configure any protection, enable 79 (for auto-reclose)and 25(for synch check).
- So, to first know what is AR and then what is synch check to understand AR sequence.
- it is also important to know Power System Data, V, f, VT connection, Vsynch connection, etc.
- Always set the AutoReclose function.
- Use Inbuilt function for checking how auto reclose works by initiating Overcurrent fault.
- Check then how the sequence is initiated.
Source:
1. Siemens Manual for Line Relay 7SA522/
http://siemens.siprotec.de/download_neu/index_e.htm
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