Over the past decade, photovoltaic (PV) cables have undergone significant developments in standards, including VDE-AR-E 2283-4, PFG 1169, EN50618, IEC 62930, and UL 4703, among others. In addition, some countries have issued their own national standards. Currently, apart from regions using the UL 4703 standard, the EN50618 standard is the most widely applied.

As the cost of photovoltaic systems continues to decline year by year, competition among components is intensifying. Recently, TUV Rheinland officially implemented the 2 PFG 2642 standard for aluminum alloy cables. This standard covers cable sizes from 10 mm² to 400 mm², with specifications for sizes below 10 mm² referring to relevant requirements in EN50616. It also includes additional tests and certification based on the characteristics of aluminum alloy conductors.

Can Aluminum Alloy Conductors Replace Tinned Copper Conductors?

The safety of using aluminum alloy conductors instead of current tinned copper conductors is a major concern for all junction box manufacturers and PV system installers.

The primary focus here is on the electrochemical reaction that occurs between copper and aluminum. When connecting anodic copper to cathodic aluminum, a potential difference is established, creating a structure similar to a PN junction. Electrons from the aluminum migrate towards the copper, generating an electrochemical reaction. A critical condition for this reaction is the presence of an electrolyte. Moisture in the air can act as an electrolyte, especially in gaps between the copper and aluminum.

If the positive and negative terminals are externally connected, the electrochemical reaction will continue until the reactivity of the electrodes diminishes and a new equilibrium is reached, ceasing external discharge—similar to the operation of a battery, which does not exhaust its plates before stopping energy output.

Proven Transition from Copper to Aluminum

The transition between copper and aluminum has been effectively managed for decades using copper-aluminum transition terminals. The reason these terminals have not been depleted due to electrochemical reactions lies in two main factors:

The contact surface of the copper-aluminum transition terminals is completely isolated from the air, preventing the necessary reaction conditions.

Even if a battery-like reaction occurs on the outer surface, the high reactivity of aluminum forms a layer of aluminum oxide that inhibits further corrosion of the aluminum.

Thus, for aluminum alloy photovoltaic cables with a cross-section of 10 mm² or more, choosing pure aluminum or aluminum alloy conductors poses no technical risk. Provided the insulation materials comply with standards like EN50618, the feasibility of conductor resistance or current-carrying capacity can be considered.

Application of the New Aluminum Alloy Cable Standard

Cables larger than 10 mm² are primarily used in photovoltaic systems to connect from the junction box to the inverter, replacing the previously used YVJ or YJLV cables. YJV cables are typically for AC applications and are not suitable for direct sunlight exposure, necessitating the use of protective cable trays. Photovoltaic cables can be used directly under sunlight.

In addition to the larger photovoltaic cables connecting junction boxes to inverters, can solar panel components and cables from the solar panel to the junction box or inverter use the aluminum photovoltaic cables certified under the 2 PFG 2642 standard? Below is a brief interpretation of this standard.

Interpretation of the 2 PFG 2642 Standard

The scope of the 2 PFG 2642 standard states in its first article that it serves as a certification guideline for flexible aluminum or aluminum alloy conductors that are not classified as Class I or II and are not specified in IEC 60228. This means TUV can certify non-Class I or II aluminum alloy photovoltaic cables based on user requirements.
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Beyond ground-mounted PV systems, aluminum alloy photovoltaic cables can also be utilized in solar junction boxes and between solar panel strings and inverters. Users can choose between pure aluminum, aluminum alloy, or coated conductors, with the composition of the conductor determined by the user.

Case Studies and Technical Comparisons

To illustrate, let’s compare two schemes for the commonly used 4 mm² conductors per the EN50618 standard:

● PVENER-V1 Scheme: This option uses 84 strands of tinned aluminum alloy conductors with a diameter below 0.31 mm. The finished cable has an outer diameter of 6.1 mm, fitting well within the typical MC4 connector size range of 5-7 mm. It meets IP67 waterproof performance standards. The conductor resistance measures approximately 4.85 ohms, which is lower than the 5.09 ohms specified for Class 5 copper conductors in IEC 60228. The tinned coating serves to protect the reactive aluminum from oxidation and ensures compatibility with all MC4 connectors.

●PVENER-V2 Scheme: This option features 19 strands of non-IEC 60228 specified conductors with a diameter of 0.64 mm. The flexibility of this conductor is similar to that of Class II copper conductors. Testing shows that this cable is flexible, with a recommended minimum bending radius of ≥6D (minimum loop diameter ≥10 cm). While this structure is cost-effective and convenient for material procurement, the drawback is that the connectors must be upgraded to aluminum connectors. The SO-L4 photovoltaic connector is a suitable option that can interface with other MC4 connectors.

Conclusion

Ultimately, the choice between these conductor structures will depend on individual user requirements and operational contexts.