Calculate the power loss in electrical cable

AI Thread Summary
The discussion revolves around calculating power loss in an electrical cable with a maximum current of 20.92 A at 34.5 kV. The user initially calculated power loss using the formula P=I^2*R but arrived at a lower figure of 4902.1W, while a technical report indicated losses of 10398.8W. Key feedback highlighted the need to clarify whether the system is single-phase or three-phase, noting that the resistance should be treated as series rather than parallel. For a three-phase AC circuit, the resistance should be multiplied by three to account for losses across all phases. The correct approach leads to a total loss of 10398W, aligning with the technical report's findings.
Xeno1221
Messages
2
Reaction score
0
Hi

I'm trying to calculate the power loss over an electrical cable.

The information of the system is:
Maximum current of 20.92 A per unit at 34.5kV

The cable has the following properties:
DC Resistance at 25 deg C (0.1672 ohms/1000 ft)
AC Resistance at 25 deg C (0.1672 ohms/1000ft)
The length of the cable is 47370.1ft

The technical report paper I got the calculation from gives the maximum losses in the cable as 10398.8W

So far I haven't been able to get the same answer using P=I^2*R where R is the impedance of the cable R=sqrt(0.1672^2+0.1672^2)=0.2365 ohms/1000ft then (0.2365/1000)*47370.1=11.2 ohms as the impedance of the length of the cable. P=I^2*R=4902.1W

Could someone please tell me where I've gone wrong here?

Thanks in advance
 
Engineering news on Phys.org
Xeno1221 said:
Hi

I'm trying to calculate the power loss over an electrical cable.

The information of the system is:
Maximum current of 20.92 A per unit at 34.5kV

The cable has the following properties:
DC Resistance at 25 deg C (0.1672 ohms/1000 ft)
AC Resistance at 25 deg C (0.1672 ohms/1000ft)
The length of the cable is 47370.1ft

The technical report paper I got the calculation from gives the maximum losses in the cable as 10398.8W

So far I haven't been able to get the same answer using P=I^2*R where R is the impedance of the cable R=sqrt(0.1672^2+0.1672^2)=0.2365 ohms/1000ft then (0.2365/1000)*47370.1=11.2 ohms as the impedance of the length of the cable. P=I^2*R=4902.1W

Could someone please tell me where I've gone wrong here?

Thanks in advance
Looks like you left out some important information about whether this is single phase or a 3 phase circuit. Is it an AC or DC voltage?
 
I think the problem will be that you take the forward and return resistance as parallel forward resistance. But it's series instead.

You already have the resistance, you have to multiply it with the length: 0.1672*47.370 => 7.92Ohm for full length.
For the forward line it gives 3466W loss. If the return path is similar, it'll be doubled: 6932W

The paper most likely calculates with a three phase system, where the loss will be tripled: 3*3466 = 10398W
 
Last edited:
  • Like
Likes Xeno1221
Apologies it's a three phase circuit with AC voltage
 
Xeno1221 said:
Apologies it's a three phase circuit with AC voltage
Ok. Resistance is either AC or DC, not both. For a balanced AC 3 phase circuit with the same conductor on each phase, each conductor of each phase carries the same current
 

Thread 'What happens if shielded cable has a short to the shield?'

While I was rolling out a shielded cable, a though came to my mind - what happens to the current flow in the cable if there came a short between the wire and the shield in both ends of the cable? For simplicity, lets assume a 1-wire copper wire wrapped in an aluminum shield. The wire and the shield has the same cross section area. There are insulating material between them, and in both ends there is a short between them. My first thought, the total resistance of the cable would be reduced...
View full post »

Thread 'Underwater piezoelectric sensor array receive sensitivity'

Hi all I have some confusion about piezoelectrical sensors combination. If i have three acoustic piezoelectrical sensors (with same receive sensitivity in dB ref V/1uPa) placed at specific distance, these sensors receive acoustic signal from a sound source placed at far field distance (Plane Wave) and from broadside. I receive output of these sensors through individual preamplifiers, add them through hardware like summer circuit adder or in software after digitization and in this way got an...
View full post »

Thread 'Question about bonding ground and neutral'

I am not an electrical engineering student, but a lowly apprentice electrician. I learn both on the job and also take classes for my apprenticeship. I recently wired my first transformer and I understand that the neutral and ground are bonded together in the transformer or in the service. What I don't understand is, if the neutral is a current carrying conductor, which is then bonded to the ground conductor, why does current only flow back to its source and not on the ground path...
View full post »

Similar threads

Copper Losses in an Electric Generator
Replies
5
Views
3K
Losses on Power Transmission Lines
Replies
10
Views
5K
Question about Transmission Line Losses
Replies
8
Views
3K
Converting oscilloscope voltage to laser power
Replies
12
Views
2K
Some basics of power loss and voltage drop in cables
Replies
8
Views
14K
Calculating Power & Temperature Loss from Cable
Replies
3
Views
6K
Calculate Coaxial Cable Loss & Input Impedance at 1 MHz
2
Replies
81
Views
10K
Basics of RF coil development for MRI
Replies
11
Views
3K
How transmission lines deliver (established?) power from generator
Replies
8
Views
2K
Mastering the Solar System Design: Calculating Cable Loss
Replies
16
Views
5K

Hot Threads

Recent Insights

Back
Top