CABLE CURRENT RATINGS

[Edelma_1]

Hello Everyone,

Which of these current ratings is used as the standard current ratings for cable:

Cyclic, Sustained or Distribution.

For example;

A 630mm[sup]2[/sup] Cu cable (dry XLPE type) has a "Winter SUSTAINED Current Rating" of 841 Amperes, a "Winter CYCLIC Current Rating" of 948 Amperes and a "Winter DISTRIBUTION Current Rating" of 1015 Amperes.

Are we supposed to use the worst case scenario? which would be the "Summer Current Ratings" since temperatures are going to be the highest recorded in the season increasing the resistance of the cable.

For Summer we have, Summer SUSTAINED Current Rating" of 756 Amperes, a "Summer CYCLIC Current Rating" of 874 Amperes and a "Summer DISTRIBUTION Current Rating" of 959 Amperes.


N.B: - THIS IS FOR A 33kV SINGLE CORE X.L.P.E. INSULATED LEAD SHEATH & M.D.P.E. OUTER SHEATH CABLES, LAID IN PVC DUCT UNDERGROUND. (Dry design)

 

[7anoter4]

I don't use any software only Microsoft Excel and...the logic

 

[Edelma_1]

lol why did you make the picture blurry, the formulas are all jammed as well, kind of lumped up

 

[7anoter4]

If when calculating I1 the current for a single bulb but neglecting wire resistance you’ll get I1=228/882=0.2585 A
and will be the same for I2,I3..I10.That means through wire segment between bulb 10 [close to source] to 9 will flow 10 current equal I1,through 9-8 9 currents and so on. The error by neglecting Rwire when calculating current it is about 0.3%.

 

[Edelma_1]

you can`t neglect the service wire resistances, the service cables vary but you can use 20m of 4c x 35mm[sup]2[/sup] waveform concentric cable

 

[7anoter4]

In relation to the pictures extracted from Google which do not represent software but are explanations in connection with various notions many related to high voltage transmissions or electronics that are not related to a simple lighting network.
On the other hand, a software is not a “Deus ex machina” that will solve any problem by filling out a form like an official from a government institution. Please excuse me, you must be a graduate of an engineering faculty-or similar- and have worked for several years in the field.

 

[Edelma_1]

I get your point