October 6, 2022

In recent years, the technology development of the photovoltaic industry is getting faster and faster. For example, the power of a single module is getting larger and larger, and the current of the cluster is also getting larger. In terms of system design, the appropriate overallocation of modules can also reduce the initial investment cost. Then, in the photovoltaic system, after the application of high-power and efficient modules and module superb allocation, how should the cable design and selection of the photovoltaic system?

1. The DC cable is selected according to the current of the component.​

Dc cables are installed in sunlight. You are advised to select dedicated pv cable. Unlike ordinary cables, the materials of photovoltaic cables are added with anti-ultraviolet and ozone materials, and can withstand severe temperature changes and chemical erosion, which can be used outdoors for more than 25 years. Photovoltaic cable models are more, the cross-sectional area of 1.5m㎡ to 35m㎡, the most used is 4m㎡. With the increase of PV module current and the power of single inverter, the cable length is also increasing, and the application of 6m square meters DC cable is also increasing.

It is generally recommended that the loss of PV DC should not exceed 2%. We can design and select DC cables according to this standard. PV 4m square meters DC cable line resistance is 4.6mω / m, PV 6M square meters DC cable line resistance is 3.1mω / m, if the DC voltage is 600V, 2% voltage drop loss is 12V, if the component current is 10A, the longest distance of 4m square meters DC cable 260m, counting the positive and negative poles, It is recommended that the maximum distance between the component and the inverter be 130 m or less. If the maximum distance is greater than this distance, you are advised to use a 6m/mdc cable. However, it is recommended that the maximum distance between the component and the inverter be less than 200 m/m. If the component is 500W+ current exceeds 13A, the maximum distance of the 4M square meter DC cable is 200m. Counting the positive and negative terminals, the maximum distance of the component from the inverter is not more than 100m. If the distance is greater than this, the maximum distance of the 6m square meter DC cable is recommended, but the maximum distance of the component from the inverter is not more than 150m. If it is a double-sided component, the current exceeds 15A, the longest distance of 4m square meters DC cable is 160 meters, counting the positive and negative poles, the furthest distance of the component from the inverter is recommended not to exceed 80 meters, if greater than this distance, it is recommended to choose 6m square meters DC cable, but the farthest distance of the component from the inverter is recommended not to exceed 130 meters.

e73608565f09b0d133513146ba84a8e02. Ac cables are selected according to the current of the inverter

In order to reduce costs, modules and inverters of photovoltaic power stations are rarely configured in a ratio of 1:1. Instead, there is a certain amount of reconfiguration according to lighting conditions and project needs. For example, if a power station has 1:1.2 reconfiguration, the component is 24kW, and a 20kW inverter is used, the AC cable is selected according to the maximum current of the inverter, because no matter how much the component reconfiguration, the inverter limited current function, the AC input current will never exceed the maximum current of the inverter.

Commonly used photovoltaic system AC copper cable has BVR and YJV and other models, BVR means copper core PVC insulated flexible wire, YJV crosslinked polyethylene insulated power cable, selection should pay attention to the voltage level, temperature level of the cable, should choose flame-retardant type. Cable specifications are represented by number of cores, nominal section and voltage level. Single-core branch cable specifications are represented by 1* nominal section, such as: 1*95 0.6/1kV; ​specification representation of multi-core twisted branch cable, number of cables in the same loop * nominal section, such as :4*185+1*95 0.6/1kV.

3. The difference between single-core cable and multicore cable

A single - conductor cable has only one conductor in an insulating layer. ​Multi-core cable refers to a cable with more than one insulated core. In terms of insulation performance, both single-core and multi-core cables need to meet national standards.

The difference between multicore cable and single-core cable is that the two ends of the single-core cable are directly grounded. The metal shielding layer of the cable may also generate circulation and form losses. ​Multicore wires are generally three-core wires, because during cable operation, the sum of the current flowing through the three cores is zero, and there is basically no induced voltage at both ends of the cable metal shield.

In terms of circuit capacity, single-core cable and multicore cable, the same section, the rated flow of single-core cable is greater than the rated flow of three-core cable; ​the heat dissipation performance of the single-core cable is greater than that of the multi-core cable. Under the same load or short circuit, the heat dissipation of the single-core cable is smaller than that of the multicore cable, which is safer.

In terms of cable laying, multicore cable laying is more simple and convenient, and the cable is safer with inner layer and multi-layer double layer protection. Single-core cable is more convenient to lay and easier to bend, but the difficulty of long-distance laying is greater than that of multicore cable. From the installation of cable head, single core cable head is easier to install, convenient line.

In terms of price, the unit price of multicore cable is slightly higher than that of single-core cable.

In the photovoltaic system, household projects and small industrial and commercial projects, the power of the inverter is below 20kW, the cross-sectional area of a single cable is below 10m square meters, it is recommended to use multicore cable, which is not difficult to lay and easy to manage. If the inverter power is between 20 and 60kW and the cross-sectional area of a single cable is more than 10m square meters and less than 35m square meters, you can select it according to the site conditions. If the inverter power is above 60kW and the cross-sectional area of a single cable is above 35m square meters, it is recommended to choose a single-core cable, one that is easy to operate; ​second, the price is also cheaper.

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