Calculation of fault limits for cables
Calculation of fault limits for cables
(OP)
Hi,
I have been trying to find a reference to help me with calculating the fault duties (limits) of various cables.
I want to include the effect of conductor size and sheath type and size for various operating temperatures and cable construction.
If anyone can give me a reference either on the web or in a book it would be great.
Thankyou
I have been trying to find a reference to help me with calculating the fault duties (limits) of various cables.
I want to include the effect of conductor size and sheath type and size for various operating temperatures and cable construction.
If anyone can give me a reference either on the web or in a book it would be great.
Thankyou






RE: Calculation of fault limits for cables
http://www.okonite.com/engineering/index.html
RE: Calculation of fault limits for cables
Thermal damage during short circuit are based in Temperature-Damage curves (I2t)seen in protection and coordination graph. Cable damage curves could be modeled by the following relations:
I=k.CM/SQRT(t)
Where: CM = Cross section of conductor (cmil)
.k = Constant that depend of conductor material and insulating temperature limits. For Instance:
Cu : k=0.0694 for To/Tf= 65/200oC, k=0.0779 for To/Tf=90/250oC)
k=0.0453 for To/Tf= 65/200oC, k=0.0509 for To/Tf=90/250oC)
To =Initial/continuous temp rating (Rubber 75oC or 90oC, paper=85oC)
Tf =final/continuous temp rating (Rubber 200oC or 250oC, paper=200oC)
.t= Total fault-clearing time (ex: relayed Bkr, direct tripping bkr, fuses)
Protection philosophy could be based either primary or back up time.
SUGGESTION:
1) Check IEEE Std 242 or similar reference.
2) http://www.kerite.com/catalog/catalogfiles/short_circuit_limitations.htm
RE: Calculation of fault limits for cables
http://www.aberdare.co.za/power/tech-articles.html
(Tech article 4)
Hope it is helpful
RCC