Motor Contribution Decay in Arc Flash

The reason the arc flash program is using the max trip time of 2 seconds instead of 5 cycle is because you are running the arc flash study and using as Pre-Fault Voltage (Load Flow Results). There will be a small amount of current flowing into the faulted bus from the buses on the load side due to that load flow voltage, and that current is so small that it takes the protective device a long time to trip. There might be other devices that do not even see the current.

When you run the arc flash study using as Pre-Fault Voltage “No Load with Tap”, then there is no load flow current. When the motor die out, that is the end of it, and that will give you a different results.