ldweiss1 wrote:
We have a site with lighting contactors that have a combination of single phase and 3 phase circuits feeding it. The breakers are all either 15A or 20A breakers. I am using the single phase module of version 10 SKM.
We have attempted modeling it different ways (a single 3-phase circuit, a combination of single phase and 3-phase circuits, all single-phase circuits), and depending on how it is modeled, it causes the unbalanced short-circuits to wildly differ from the balanced short-circuits. Not only that, but the incident energy varies widely with these methods from <1.2 cal/cm² to >40 cal/cm².
The major question I have is it it realistic to just model a single cable/breaker to the lighting contactor panel, or would it be more accurate to model every breaker feeding it? If so, do I need to be accurate about the phases of each cable, or can I model them all as the same phase?
For clarification, does this contactor panel contain the circuit breakers as well as the contactors or just the contactors which are fed from breakers in a panel or panels somewhere else? Also, what is the voltage?
I can say from experience investigating electrical failures that control panel failures that contain multiple terminal blocks, relays, starters, varying wire sizes, small wire taps, many different bus gap widths etc. are impossible to accurately model. I've seen one instance in particular that was protected by upstream current limiting fuses sustain arcing faults long enough for the maintenance crew to see what was going on, approach the panel, decide that was a bad idea then run to open the upstream fused disconnect. Fuses never blew. This was on video. The model said the fault should have cleared quickly. It did not, obviously.
