How long will a cable last at its limit?
How long will a cable last at its limit?
(OP)
Hello,
If you have a cable that is rated to, say 100amps, how long will it last for, running at 100A??
Will it run forever, or is there some sort of degredation as it is run at its limit?
Does a cable have a let through energy rating of sorts that can be calculated from current and time?
Thankyou.
Marko T
If you have a cable that is rated to, say 100amps, how long will it last for, running at 100A??
Will it run forever, or is there some sort of degredation as it is run at its limit?
Does a cable have a let through energy rating of sorts that can be calculated from current and time?
Thankyou.
Marko T






RE: How long will a cable last at its limit?
The cable vendor would be the best person to speak to on this subject, but I would say having it run fully loaded is not good engineering practice and I have known cable to be changed out in the region of 25 years for private dwelling properites.
Cables have a type of let through energy before destructing, it's called short circuit rating and you can get this from from the cable vendor. it will tell you what it can handle fully loaded at the time of short circuit and it will tell you in time/seconds as well.
Midos
RE: How long will a cable last at its limit?
RE: How long will a cable last at its limit?
There are 'damage curves' available for all cables that shows how much current a cable can sustain for how long before getting damaged. All short circuit calculation softwares include these curves. These are essentially time inverse curves, obviously lesser current can be carried on for longer time for a given size.
It also varies by type of insulation, PVC, rubber etc. as the insulation, which gets damage first, long before the metal (copper or aluminum) starts mellowing.
But in general a cable can sustain current several times its 'rated' current for a long time.
RE: How long will a cable last at its limit?
How can you then calculate how long a cable will last being overloaded but not at a short circuit fault level.
For example, back to our 100amp rated cable (lets say pvc insulated), can you determin how long it will last for running continuously at say 140amps?
I know of a way to estimate rise temp. but the tables of constants and information says it is only valid for time periods of up to 5 seconds. The system does not work for times longer than this as it is really for fault level currents only.
What i want to know is,theoretically, how many minutes/hours/days i can overload this cable for at a certain overloaded current rating.
RE: How long will a cable last at its limit?
http://www.silicavalley.com/archives/Reliability.pdf
for the reliability theory behind it
There are different aspects of cable aging. Visit
http://www.adventengineering.com/service/research/insul...
http://www.adventengineering.com/service/research/insul...
http://www.nrc.gov/reading-rm/doc-collections/gen-comm/...
(for standards)
http://www.bnl.gov/est/files/pdf/ECTF-FactSheet.pdf
(for Labs testing aging)
etc. for more info
RE: How long will a cable last at its limit?
The 'damage' curves shows exactly what you are looking for! Ask manufacturers or get a curve from an electrical friend with a short circuit software.