Cable Damage curve on a TCC

[philly]

Why on a Time Coordination Curve (TCC) the cable damage curves are not a continuous line. They always start at the high current value and then go to about midway through the plot before they stop. Then at the top of the plot at the highest time the pickup of full load rating of the cable is shown as a small mark. Why are these not shown as a continuous line?

When plotting protective devices against these cable damage curves must you have both segments of the cable damge curve above or to the righ of the protective device curve? Should the protective device curve even be below the cable damge curve pickup point? I'm referring to breakers upstream of the cable, but how do downstream breakers come into play?

Also on a slightly different subject does the transformer inrush point shown of on a TCC need to be completely clear of a LV breaker tolerence bandwidth. What if the inrush point is not completely below the LV breaker band but rather falls righ in the middle of the band? Is this a potential problem?

 

[G._S._Ohm]

"Why on a Time Coordination Curve (TCC) the cable damage curves are not a continuous line. They always start at the high current value and then go to about midway through the plot before they stop. "

Referring to fig. 1 of
http://www.skm.com/Overcurrent Coordination Setting Guidelines Transformers.shtml

IMO, I'd say that small diameter cables get as hot as they are going to get after 10 seconds [4 or 5 thermal time constants] and so the damage at 100 seconds or 1000 is the sort of the same as at 10 seconds.
The thermal inertia of a transformer is much larger and so its curves go out to 1000 seconds or more.

Can you post a link to your particular example?