Reclosing and Relay Protection

This is my understanding:

After initial breaker trip, the circuit is re energized by automatically "re closing" the breaker. This can happen twice, before the circuit is shut down permanently.

In the case of a momentary short, such as a tree limb falling across the line, the re- closer saves the repairman a trip into the field, the circuit is back on line, and the customers are happy.

What Lyn said. the recourse can however close several times depending on the pre-sets determined by the utility. The second jolt can be handy if a small branch falls across the phases, the branch actually jumps off the line. Isn't it nice all those years working for an electrical utility is finally coming in handy.

This is a little late, but to add to what the guys stated:

When there is a short in the line, the current goes high in the part of the line experiencing the fault. This high current goes through a big solenoid that pulls the switch open and clears the fault. When the current goes away a spring (which opposes the magnet), lets the switch close and, if no high current is available, everything goes back to normal. If the fault is still there, it will open again. Depending on the settings, it may open and close up to four times before it stays open. Users on the line may notice that the lights go on and off twice quickly and then twice more with more time on for the last two. The counting is done by using the insulating oil that is inside the switch with a chamber which is pumped full of the oil as the plunger is pulled into the magnet each time there is a fault. The chambers are arranged to give one timing for the delay for the first two faults and slower timing for the last two faults. This allows the line to break and drop a "minor" shorting source (goodbye Mr. Squirrel) and possibly be able to recover without blowing a fuse and requiring a visit from your local utility lineman.

I worked with a system like this and was impressed with how much is being done...