Evaluation and Solutions for 2x6mm² PV1 - F Wire in 24kW Solar PV System

Introductinoitcuon

My client asked:"200 meters is my requirements for now, i have small project in solar installation of 24kw"

In.shtgne a 24kW solar photovoltaic system, the selection of cables is crucial for ensuring efficient power transmission and optimal system performance. The 6mm² PV1 - F photovoltaic DC wire is a commonly considered option, but its current - carrying capacity and voltage - drop characteristics need to be carefully evaluated, especially when dealing with longer cable lengths.

Current - Carrying Capacity Analysis

Under normal laying conditions, the current - carrying capacity of a 6mm² PV1 - F photovoltaic DC wire is approximately 30 - 35A, which is affected by ambient temperature and laying method. In a 24kW system, if each component has a power of 550W and the DC operating voltage is 110V (a common string voltage range), the current of a single string is approximately 9 - 13A. When multiple strings are connected in parallel, the total current may approach or exceed 30A. This indicates that the 6mm² PV1 - F wire may face challenges in handling the current requirements of the system.

Voltage - Drop Calculation

A 200m length of the 6mm² PV1 - F wire can result in a significant voltage drop. The allowable voltage drop of a PV wire is generally recommended to be ≤3% of the DC voltage according to IEC 62548. Taking a typical working condition as an example, assume the string current is 12A, the one - way length is 200m (a 400m loop for a round - trip), and the resistivity of the copper conductor is 0.0178 Ω·mm²/m.

First, calculate the resistance using the formula R=ρ×L/S, where ρ=0.0178Ω⋅mm2/m, L=400m, and S=6mm2. So, R=0.0178×400/6≈1.19Ω.

Then, calculate the voltage drop ΔU=I×R, with I=12A and R≈1.19Ω, we get ΔU=12×1.19≈14.3V.

If the string voltage is 400V, the proportion of the voltage drop is approximately 14.3/400×100%=3.6%, which has exceeded the normal limit. Higher currents or high ambient temperatures will exacerbate the voltage drop, affecting the MPPT efficiency of the inverter and power generation revenue.

Conclusion and Alternative Solutions

The 200m 6mm² PV1 - F wire is not recommended for the 24kW DC main circuit, especially when the single - string current > 10A or the string voltage is low.

• Change the cable cross - section: Changing to a 10mm² PV1 - F wire can effectively control the voltage drop. For example, at 12A current and 400V string voltage, the voltage drop can be controlled at approximately 2.1%.

• Shorten the cable length: Placing the inverter closer to the array can reduce the cable length, thereby reducing the voltage drop.

• Add a combiner box: Adding a combiner box for segmented collection can reduce the length and current of a single cable, which is also an effective way to mitigate the voltage - drop problem.

Pit - Avoiding Reminder

Excessive voltage drop of the photovoltaic DC wire can lead to the inverter reporting low voltage, power limitation, and power generation loss. For long - distance DC transmission, PV1 - F with a sufficient cross - section and meeting UV/ temperature - resistance requirements must be used, and ordinary BV wires cannot be used as a substitute.

Conclusion

In most working conditions of a 24kW system, the 200m 6mm² PV1 - F will exceed the voltage - drop limit. It is necessary to increase the cross - section to 10mm² or optimize the wiring layout to ensure the efficient and stable operation of the solar photovoltaic system.

FAQ

Q1: What is the current - carrying capacity of a 6mm² PV1 - F wire?

A: Under normal laying conditions, it is approximately 30 - 35A, depending on the ambient temperature and laying method.

Q2: Why is the voltage drop of the 200m 6mm² PV1 - F wire a problem in a 24kW system?

A: The voltage drop can exceed the recommended limit of ≤3% of the DC voltage, which affects the MPPT efficiency of the inverter and power generation revenue.

Q3: What are the alternative solutions to the voltage - drop problem?

A: You can change to a 10mm² PV1 - F wire, shorten the cable length by placing the inverter closer to the array, or add a combiner box for segmented collection.

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Hualan Technology was founded in 2020, is a collection of solar accessories production, sales, research and development and service as one of the high - tech enterprises. At present, the business covers the production and sales of solar photovoltaic cables, photovoltaic cable connectors.