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Topic Title: cable rating types
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Created On: 06 April 2013 04:42 PM
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 06 April 2013 04:42 PM
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SWORDLOVER

Posts: 23
Joined: 30 September 2010

In term of the cable current rating, there are (1) continuous rating (2) distribution rating (3) sustained rating (4) cyclic rating. What are the definitions of all these terms?
 11 April 2013 03:33 PM
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Zuiko

Posts: 517
Joined: 14 September 2010

Continuous rating is the current the conductor can take continuously without suffering adverse effects.


Distribution rating would be slightly higher to cope with short-time peak loads. For example. A cable rated at 95A might see load vary from around 0A (during the day) to maybe 130A during the commerical breaks when the kettle goes on. It is assumed the 130A will be short time and the load will go down and allow the cable to cool without adverse effects.


Cyclic rating raises or lowers the capacity of the conductor depending on the cycle.
The cycle could be winter or summer for example. In the winter, the weather is colder so the conductor is rated higher. In summer, the conductor is de-rated.

For example, a cable might be rated 200A summer cyclic and 250A winter. This allows more load in the winter, and also more load to be shifted onto it when circuits are backfed etc. So if your backfeed is 240A you can only do this work in the winter!

Overhead conductor sees typically more difference in these two ratings, and if the weather is very cold, you can push it a little more.
 12 April 2013 04:01 PM
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irevans

Posts: 192
Joined: 07 March 2002

Continuous rating as indicated by Zuiko. Sustained rating is the same.

Cyclic rating is the maximum you can get based on some form of daily cycle, e.g. 16 hours at 60% and 8 hours at 100%.

In themselves cyclic ratings have nothing to do with season; although there will be different values as the ambient parameters around the cable will be different. The same is true for the continuous ratings.

See IEC 60287 and IEC 60853.

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irevans
IET » Energy » cable rating types

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