Circuit Breaker Open/Close Time

Closing time is always faster because no load is being interrupted, when opening the electrical arc slows the process slightly...

When it comes to breakers, relays and switches, faster is better.

I've no concerns as long as the breaker works within it's parameters.

The faster the better!

60 milliseconds of closing time is rather slow in my opinion ... are you sure of this figure? Perhaps some details of how it is measured and which event to which event is it measured ... etc may be interesting for many people on CR4...

The 80 msec specification is the design or "nominal" closing time. 5 cycles (US) closing time is reasonable for an oil breaker, but somewhat slow for an air or SF6 breaker. The actual closing time should be no longer than the design value. As others have said, shorter is usually better. A longer closing time may lead to reduced life of the arcing contacts.

If the breaker closes too fast, it may over-stress the moving contact arms. If you have concerns about fast closing speed, you should inspect and verify proper operation of whatever type of buffer system is used by the breaker.

The "closing time" is probably a maximum over ambient temperature range and specified [close coil] voltage range[e.g. 90 - 130V DC] and differences between individual breakers.

A DC supply would usually have a "float charged" battery, which would put it "on-charge", say 125-130 V, in normal use. This would make the close time shorter than at 90V or 110V supply. Getting 60ms versus 80 ms specification looks OK.

The better auto-synchronizers [ASUs], which can make a close with a 2 second slip cycle, have adjustment for "breaker closing time" by 20 millisecond intervals.

Note that for 2 seconds = 2000 millisecond slip cycle, 20 ms is equivalent to 20/2000 = 1/100 cycle, that is 360/100 = 3.6 degrees angle.

Since the usual specification for an ASU is less than about 6 degrees phase error, 20 ms change of breaker close time [ = 3.6 degrees] is a big fraction of the allowable error for 2 second slip.

In such a critical case, the commissioning would measure the actual breaker close time (several times) before choosing the ASU "breaker close time" setting.

A breaker with abnormal closing time fluctuation would be rejected. The closing time with float voltage would usually be chosen, since this is normal supply condition.