How to ensure efficient and safe connection of photovoltaic (PV) modules of different specifications when using solar connecting wires in series and parallel connections in a PV power plant?
Publish Time: 2026-02-12
In large-scale PV power plants, solar connecting wires act as the "power nerves" between modules and between strings and inverters, undertaking the crucial task of efficient and safe transmission of DC power. However, in actual projects, situations often arise where PV modules of different brands, power ratings, current ratings, and even sizes are mixed—either due to phased project construction, equipment replacement, or temporary adjustments to the supply chain. This series and parallel connection of heterogeneous modules presents significant challenges to the selection, matching, and installation of solar connecting wires: it must avoid power loss caused by electrical parameter mismatches while preventing overload, overheating, and even arcing risks.1. Electrical Parameter Matching: From Current Consistency to Cable Current Carrying CapacityWhen PV modules are connected in series, the current must be consistent; when connected in parallel, the voltage must be approximately equal. Forcibly connecting modules with significantly different short-circuit currents in series will limit the system current to a minimum, causing high-power modules to operate at reduced efficiency; while connecting strings with different open-circuit voltages in parallel may induce reverse current, leading to diode overheating or even module damage. Therefore, while solar connecting wires do not alter electrical logic, their cross-sectional area must be selected based on the maximum possible operating current.2. Connector Standardization and Compatibility: MC4 is Not a Universal KeyCurrently, mainstream solar connecting wires terminate with MC4 type plugs, but different manufacturers' MC4 connectors vary in tolerances, locking force, and contact resistance. Using non-original or uncertified connectors may lead to poor contact, excessive temperature rise, or even accidental disconnection under strong winds and vibrations.3. Wiring and Protection: Addressing Environmental Stress and Mechanical DamageThe junction box positions and cable exit directions of different component specifications may differ, causing the connecting wires to be stretched and bent to an excessively small radius. Over time, this can easily lead to insulation cracking or conductor fatigue fracture. In areas with compact bracket layouts, sufficient slack should be allowed, and the wires should be secured to the support structure with cable ties to avoid unsupported stress. Meanwhile, the connecting wires must be run entirely through conduits or cable trays, especially in coastal areas with high salt spray, deserts with strong ultraviolet radiation, or frigid regions with freeze-thaw cycles. The sheathing material must possess properties such as UV resistance, ozone resistance, and low-temperature brittleness at -40℃ to ensure no failure within its 25-year lifespan.4. System Monitoring and Preventive MaintenanceEven with correct initial connections, long-term operation of dissimilar modules may still lead to latent mismatches due to different degradation rates. String-level monitoring or infrared thermal imaging inspections can promptly detect abnormal heating at connection points, allowing for the timely replacement of aging cables or tightening of loose joints. Furthermore, cross-model mixing should be avoided as much as possible during the design phase; if unavoidable, modules with similar parameters should be grouped into the same string, and multiple MPPTs should be configured on the inverter side to maximize energy capture.Although seemingly simple, solar connecting wires are the "last mile" for the safety and efficiency of photovoltaic systems. When connecting modules of different specifications, only by adhering to the four principles of "parameter matching, certified accessories, standardized installation, and intelligent monitoring" can potential risks be minimized, truly achieving a balance between high-efficiency power generation and long-term reliable operation.
