cable damage curves vs coordination

[julesm]

Greetings,
I'm confused about cable damage, and cable damage curves, in the 0.1 to 10 second range. I thought cable damage was more of a long-term overload issue. My SKM software cable damage curves are conflicting with my coordination efforts. Please advise. Does this mean my cables are not sized correctly??? Aargh. I never even HEARD of cable damage curves before today...
thank You.

 

[jim dungar]

Greetings,
I'm confused about cable damage, and cable damage curves, in the 0.1 to 10 second range. I thought cable damage was more of a long-term overload issue. My SKM software cable damage curves are conflicting with my coordination efforts. Please advise. Does this mean my cables are not sized correctly??? Aargh. I never even HEARD of cable damage curves before today...
thank You.

Something doesn't sound quite right. I have never had coordination problems with cable damage curves and I do use SKM PTW. Are these 600V conductors?

 

[mayanees]

SKM suggestion

SKM suggestion

Jules,

Make sure that the SKM plot is for the combination of cables and not for a single cable.
I think their default is a plot for only the single cable and not the parallel combo.
Check the cable parameters in the Component editor.

I too haven't had issues with cable damage if the design is NEC compliant - unless it's above 600 V - where the cable damage curves are most useful since NEC allows protection over the cable ampacity in those cases.

JM

 

[julesm]

I will check the defaults. Thanks for the advice. I usually work under 600V so it makes sense I haven't come across this concept before. Best Wishes,

 

[davidr43229]

For the 2008 NEC, the ICEA Cable damage curves have been brought back. Damage can occur at the .01 to .1 levels, but I have never heard of Conductor coordination.
Copper, 75? Thermoplastic Insulated Cable Damage (based on 60 HZ)
Copper Maximum Short-Circuit Withstand Current in Amperes
Wire Size 75?C 1/8 1/4 1/2 1 2 3
Thermoplastic Cycles* Cycles* Cycles* Cycle Cycles Cycles
18* 1,850 1,300 900 700 500 400
16* 3,000 2,100 1,500 1,100 700 600
14* 4,800 3,400 2,400 1,700 1,200 1,000
12* 7,600 5,400 3,800 2,700 1,900 1,550
10 12,000 8,500 6,020 4,300 3,000 2,450
8 19,200 13,500 9,600 6,800 4,800 3,900
6 30,400 21,500 16,200 10,800 7,600 6,200
4 48,400 34,200 24,200 17,100 12,100 9,900

 

[julesm]

It's not conductor coordination, it's circuit breaker coordination. However, with SKM TCC plots, you can show conductor damage curves against breaker curves and make adjustments. However, the location of the conductor damage curves are forcing me to adjust my breaker settings which is compressing my breaker curves. Not pretty.
There aparently is damage in the.1 to 10 second range which I had not previously accounted for. Even for lv.

Of course my conductor sizes exceed NEC minimums. Now I'm curious about oversizing cables for this...