Calculate the power loss in electrical cable

In summary: So, the power delivered is: 20.92*(4+3) = 114.92W. For a 3 phase DC circuit, the power delivered is: 20.92*(1+2+3)=34.52W.
  • #1
Xeno1221
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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
 
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  • #2
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?
 
  • #3
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
 
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  • #4
Apologies it's a three phase circuit with AC voltage
 
  • #5
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
 

1. What is power loss in electrical cable?

Power loss in electrical cable refers to the amount of energy that is lost as heat when electric current flows through the cable. This loss occurs due to the resistance of the cable material and can result in decreased efficiency and increased operating costs.

2. How is power loss calculated in electrical cable?

Power loss in electrical cable is calculated using the formula P = I²R, where P is power loss in watts, I is the current in amperes, and R is the resistance in ohms. This formula is based on Ohm's Law, which states that the power dissipated in a circuit is directly proportional to the square of the current and the resistance.

3. What factors affect power loss in electrical cable?

The main factors that affect power loss in electrical cable are the length and thickness of the cable, the material it is made of, and the amount of current flowing through it. Longer and thinner cables, as well as materials with higher resistance, will result in higher power loss.

4. Why is it important to calculate power loss in electrical cable?

Calculating power loss in electrical cable is important for understanding the efficiency of a circuit and for determining the appropriate cable size and material for a specific application. It can also help in identifying potential issues such as overheating and voltage drops.

5. Can power loss in electrical cable be reduced?

Yes, power loss in electrical cable can be reduced by using thicker cables with lower resistance, minimizing the length of the cable, and using materials with higher conductivity. Additionally, proper installation techniques, such as avoiding sharp bends and keeping cables away from heat sources, can also help reduce power loss.

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