Hello all,

I'm new to the forum with a general question I'm hoping someone can help me with. I'm a graduate student working on an arc-flash study for a utility and my question is in regards to working with pilot schemes.

While looking at a line that has carrier signal on both ends of a line with a tap bus on the line. If the tab bus is past the zone 1 reach on the far end of a line while in the zone 1 reach of the close end relay, the close end will open before the far end will open. My question is if I run the calculation first with both end of the lines closed in and get an incident energy level for the close end clear time, can I run a second calculation for the additional time the arc will happen until the far end clears and add these two values, basically is incident energy additive?

I can't seem to find any information in regards to this. If anyone has an answer or a reference somewhere it would be appreciated.

Kevin Demeny

This is a similar question to dealing with motor contributions that last a shorter time than the fault contribution from the system. Your solution would give the same results as that suggested by Gary B in http://www.arcflashforum.com/showthread.php?t=37.

Basically it is additive with time because the equations are linear with time. At least this is the case with the IEEE-1584 equations and the Ralph Lee equations. If you are using ArcPro, you might ask Kinectrics to confirm your approach.

You can't find the energy for the the current contributions independently because the equations are not linear with current.

You may look into using an integrated approach. This has been suggested at several of the 1584 work group meetings and is available in at least one of the software packages. The integrated approach analyzes all paths to fault current (motors, generators, utility) and trips off (trip or decay) one at a time until fault current at the bus is zero.

EasyPower contains an option to use an integrated solution method when dealing with multiple sources.