At same level of voltage, for example 600Volts, transmission through AC or DC, which one has larger power loss?

In solar PV system, the location of inverters is important. The DC voltage is serialled to about 600V to 800V, and then it is inverted to 380V AC 3 phase. Some experts said that the inverters should be placed near to solar panel, therefore, transmission through AC will have lower power loss. Is this true? Because in AC, the current will flow near to the skin of conductor (Skin effect), the resistance should be higher than DC transmission at same level of voltage.

As I know, AC is widely used for transmission because it can be transformed to very high voltage to reduced the loss. However, in solar PV system, the serialled voltage is not less than the inverted 3 phase voltage. Thanks


Lim

skin effect only occurs at RF frequencies.

Power for RESISTIVE loads where the voltage and current are in phase and the voltage and current waveforms are periodic, the P = Vrms*Irms

If V and I are sinusoidal and not necessarily in phase then the formula is P = VrmsIrms*cos(theta)

cos(theta) is 1 when V and I are in phase.

Current through a given wire size is the issue, not voltage. Simple example 100 W; at 12V you need 10 Amps at 100 V you need to carry only 1 amp.

In a system such as the one your describing, the DC voltages are much higher.

So 600 V DC at 1A and 600 VAC 1 A ac say 60 Hz at one amp will incur the same loss when operating into a resistive load.
If the 600 V was at 1 GHz, then all bets are off. DC wins.

At same level of voltage, for example 600Volts, transmission through AC or DC, which one has larger power loss?

In solar PV system, the location of inverters is important. The DC voltage is serialled to about 600V to 800V, and then it is inverted to 380V AC 3 phase. Some experts said that the inverters should be placed near to solar panel, therefore, transmission through AC will have lower power loss. Is this true? Because in AC, the current will flow near to the skin of conductor (Skin effect), the resistance should be higher than DC transmission at same level of voltage.

As I know, AC is widely used for transmission because it can be transformed to very high voltage to reduced the loss. However, in solar PV system, the serialled voltage is not less than the inverted 3 phase voltage. Thanks


Lim[/QUOTE]


The answer to this question depends on many factors. The simple answer is DC for a short (maximum length of about 1000 feet) transmission line operating at 600 to 800 volts.

The long answer requires many more questions to be answered before you could make a choice as to which system to use. There are many factors to consider, skin affect does cause additional losses on a 50 or 60 Hz power system as does inductive and capacitive coupling between both ground and other conductors. The type of conductor makes a difference in the overall losses based on the material used and the configuration of the counductors to each other.

All of the decisions made when designing a system is to minimize the overall losses. It may be better to place the inverter closer to the solar panel or it may not. If the characteristics of the load require a particular minimum voltage level, some improvement in the voltage regulation is gained by having the inverter closer to the load.

I appoligize if this was off the target for what you asked, but the answer is not a simple DC or AC. The answer msut be the one that gives you the best efficiency, lowest cost to install and operate over its expected lifetime.

Hope this helps.