SKM and EasyPower Results for Arc Flash
SKM and EasyPower Results for Arc Flash
(OP)
I am replicating a project that was originally done in SKM about 4 yrs ago and I am using EasyPower Ver 9.5. There are some differences in conductor impedances but nothing major. I have found one item that is curious. For this particular panel:
SKM: HRC 0, 1.2 cal/cm^2, Ibf 16.06kA, Iarc 8.35 kA, Trip time 0.044 sec
EasyPower: HRC 1, 2.4 cal/cm^2, Ibf 16.4 kA, Iarc 8.515 k, Trip Time 0.086 sec
The protective device is a Siemens Sentron NXD6 1200A breaker with a 1200A trip and Inst at 5000A. Now what is interesting is when the TCC is plotted, SKM's Iarc current would result in a trip time of ~0.091 sec. When I cross a trip time of 0.044 on the curve, the corresponding current is ~12.4 kA.
This is at 480V, 60hz system
Any thoughts or comments? -
SKM: HRC 0, 1.2 cal/cm^2, Ibf 16.06kA, Iarc 8.35 kA, Trip time 0.044 sec
EasyPower: HRC 1, 2.4 cal/cm^2, Ibf 16.4 kA, Iarc 8.515 k, Trip Time 0.086 sec
The protective device is a Siemens Sentron NXD6 1200A breaker with a 1200A trip and Inst at 5000A. Now what is interesting is when the TCC is plotted, SKM's Iarc current would result in a trip time of ~0.091 sec. When I cross a trip time of 0.044 on the curve, the corresponding current is ~12.4 kA.
This is at 480V, 60hz system
Any thoughts or comments? -






RE: SKM and EasyPower Results for Arc Flash
I would compare the two time-current curves (SKM vs EasyPower) for the breaker and see if they match. With the thousands of TCCs stored in the program libraries, there are sometimes problems with the TCCs. Also, manufacturers periodically update their TCCs so there can be different vendor curves for the same device.
Bottom line is that I am not at all surprised to see differences like this and it would not overly concern me. See Rule #1.
RE: SKM and EasyPower Results for Arc Flash
RE: SKM and EasyPower Results for Arc Flash
There are two different values of arcing current that are of interest - the total arcing current and the arcing current through the upstream device. But based on your description, I don't think that is a factor here. If you can post the SKM arc-flash report, maybe someone will be able to spot something. I use both programs, but I'm more familiar with EasyPower.
RE: SKM and EasyPower Results for Arc Flash