So, we all know that an arc flash study, and all the PPE requirements and safe work practices that follow are based on a very big assumption, clearing times.

These clearing times are difficult to verify, if you test your breakers you have to open them, rack them out, then test them, so by the time you record the data the breaker has been cycled a few times, that dried grease has been broken loose, those tired springs got a little workout, etc...

So what about first trip testing? Anyone do it? I have, and the results are often scary. Let's say you are an engineer at a facility, you did an arc flash study, you based your labels on a 60mS clearing time but find out from testing first trip it is really 300mS?? (Those are pretty realistic numbers by the way).

Now what?

Testing is not the same as maintained, and I think a lot of places will overlook that one. Proper maintenence means checking adjustments, lubrication (Not spray lubes, that makes things worse), and refirbsment per OEM recomendations. First trip timing tells the real life condition of your breakers, at least the part that is meaningful for arc flash studies.

Wouldn't it be great if there was an easy, inexpensive way to gather first trip data on something like your iPhone????

So what about first trip testing? Anyone do it? I have, and the results are often scary. Let's say you are an engineer at a facility, you did an arc flash study, you based your labels on a 60mS clearing time but find out from testing first trip it is really 300mS?? (Those are pretty realistic numbers by the way).

Now what?

So what did you do with that >1 sec breaker Paul?

P.S. I have hendreds of CO-8's in stock.

You are certainly correct about testing vs. maintenance. The iPhone app sounds like a great idea.

Is this where I ask "do you have such a method?"

First thing is that this is a typical mining substation. It has a shunt trip breaker operated by a capacitive trip unit (DC power). The original setup operated this from normally open contacts of an ice cube relay which was in turn operated by normally open contacts of the SEL relay. A separate UV coil (normally closed) energized again via capacitive trip to open the breaker on loss of DC. New scheme is to wire normally closed contacts of SEL relay to the shunt trip directly. An alternative would be to wire another relay to the contacts using normally closed logic.

Not being overly familar with your tripping scheme, why don't you try using an Electro Switch LOR, ER/LOR, or SR/LOR. These aux relays have less then an 8mS trip time and have positive tripping action. We use them everywhere in the utility system. They can have multiple inputs and multiple outputs.