Static Trip Breaker Trip Setting (I2t)

[JMatt]

I'm trying to reduce tripping time to reduce incident energy levels as part of my arc-flash study. I have a Digitrip RMS310 (MES3800LSG). Is there a way to change the I2t characteristic of this device's operating curve without replacing the whole trip unit?

 

[Zogzog]

Yes there is but honestly I dont think I should tell you how, if you dont know that you probally shouldnt be doing the study. Do you fully realize the effect abjusting the trip curves will have on the operation of the system?

 

[JMatt]

Yes. I understand what it does to the curve and the tripping characteristics. Usually, this is very simple. Normally, there is a dip switch, or a dial that clearly marks where the I2t option can be activated or deactivated.

I am not familiar with this particular type of trip device. Everything that I have read from Cutler-Hammer seems to indicate that I need a different model of Digitrip (MES3800LSI). I thought an expert with this particular type of trip unit might be able to steer me toward an alternate solution. Thanks for your concern.

 

[Zogzog]

If the setting has a * the I2t is in, no * means I2t out.

 

[unclebob]

JMatt

I have done a lot of studies with that kind of trip unit.
Are you sure you have the I2t on your T.U.? RMS310 LS and LG do have the I2t feature, but it is fixed at 100 ms. For LSG or LSIG, the I2t feature is not available, but you have some short time settings : 2x - 8x at 0 - 300 ms. These are hard to fully coordinate with downstream fuses.