Line Loss vs. Transmission Voltage 1

[jay165]

Is there a general equation (empirical, theoretical or rule of thumb) that relates power loss and transmission voltage?

My specific problem: I want to transmit 15 MW approximately 2 miles via a subsea cable. Should I use step up transformers to go from say, 4.16 to 13.8 kV or transmit at 4.16 and accept the higher (if any) losses?

Just looking for some guidelines - I'm not an EE.

 

[rbulsara]

While any voltage drop can be accomodated with a proper tap setting, I am more concerned with amount of power you are trying to wheel.

Your primary aim should be to minimize the number of cables under the sea. You don't wanna go too ofern under sea to fix a cable problem

At 4.16 kV, 15MW=18MVA= 2500 amps (this could be 4 or 5 cables per phase, x 3 = 12 to 15 cables)
At 13.8 kV= 753 Amps (say 2 cables per phase = 6 cables)
At 35 kV =296A. (1 cables per phase = 3 cables).

Of course you have to evlauate this against the cost of the transfromers. I would go with a single cable at higher voltage. Anything on land is easily monitored and attended to.

 

[advidana]

The higher the voltage the smaller the cable.

 

[alehman]

power loss = I^2R = Vdrop^2 / R

 

[SidiropoulosM]

You will probably need two 3-phase cables for reliability purposes, rather than one cable.

Another factor to consider will be the loading pattern of the cable and the resultant losses. The cost of losses will then determine the most economical voltage level and conductor size. This is not a difficult study but it's best done by an EE.