Cable losses!!!

[Eduardo Maun]

In the given problem it did not specify if the system is 3 phase, the formula they used is,

cable losses = 3 x I squared x load factor x 1 x h x N

all the given parameters are supplied but not the "3" and by doing my computation I arrived at the correct answer. My question(s) is it because the system is 3 phase they just don't mention it or is it because the cable is 3 core?

Thank you!

God Bless..

 

[George Stolz]

Ed, I'm not familiar with that equation, or with what the letters stand for (h, N). Can you elaborate?

In general, without the "2" or the "square root of 3" at the beginning of voltage drop equations, the answer would be for one conductor only - which would not be very useful, as it takes two or three conductors to complete a circuit. That number represents the number of conductors in a circuit.

 

[coulter]

Hummm -
"cable losses" and "I squared", makes it sound like the power lost in the cable is the objective. If so, then the "3" looks 3-phase, and "h" and "N" would then have to refer to resistance per unit length and length.

But, I'm guessing - Eduardo, where are you? You got to tell us more.

carl

carl

 

[Eduardo Maun]

Cable losses!!!

Here's the given problem:

1 MCB is connected with single run copper of 16 mm squared cross section from MCC. The cable is laid in air, load connected to MCB is 100A, length of the cable 40m,resistance of the cable 1.15 ohms/km,current carrying capacity of the cable is 78A,load factor .632 it operates for 8760 hrs. i a year.

The question is;

Calculate the cable existing losses?

The solution is:

Cable losses(in kwh) = "3" x I squared x R x load factor x l x h x N

h = operating hrs.

N = # of runs of cable.

If "3" comes from the number of conductor(s) then the equation is correct. I'm confuse because it might be a 3 phase system or it might be # of conductor(s).

coulter said "3" looks like a 3 phase but georgestolz said "3" comes from the number of the conductor which is which.

I hope the problem will help you to figure it out!

Thank you!

God Bless...