In addition to the main equipment in the process of construction of photovoltaic power station, such as photovoltaic modules, inverters, step-up transformer, form a complete set of connection of photovoltaic cable material to the overall profit ability, operation of the photovoltaic power station security, and efficient software also plays an important role, is common in the photovoltaic power station under the cable and material use and use environment to do detailed introduction.

According to the system of photovoltaic power station, cables can be divided into dc cables and ac cables. According to different purposes and operating environments, the cables are classified as follows:　　

Dc cable

(1) series cables between components.

(2) parallel cables between groups and between groups to dc distribution box (bus box).

(3) cable between dc distribution box and inverter.

The above cables are all dc cables, which are widely laid outdoors. They need to be moisture-proof, sun-proof, cold-resistant, heat-resistant and uv-resistant. Under some special circumstances, they also need to be acid-proof and alkali-proof.

Ac cable

(1) the connection cable from the inverter to the booster transformer.

(2) connection cable from booster transformer to distribution device.

(3) the connection cable between the distribution device and the power grid or the user.

This part of the cable is ac load cable, indoor environment laying more, can be selected according to the general power cable selection requirements.

Iii. Special cable for photovoltaic

A large number of dc cables in photovoltaic power stations need to be laid outdoors, and the environmental conditions are harsh. The cable materials should be determined according to the resistance to ultraviolet rays, ozone, drastic temperature changes and chemical erosion. Ordinary cable material in this kind of environment for a long time to use, will lead to cable sheath fragile, or even decompose the cable insulation layer. These conditions will directly damage the cable system, but also increase the risk of cable short circuit, in the long run, the possibility of fire or personal injury is higher, greatly affecting the service life of the system. Therefore, it is necessary to use special photovoltaic cables and components in photovoltaic power stations. Dedicated photovoltaic cables and components not only have the best weather resistance, uv resistance and ozone erosion resistance, but also can withstand a wider range of temperature changes.

Iv. Principles of cable design and selection

(1) the voltage withstand value of the cable shall be greater than the highest voltage of the system. For 380V output ac cables, select 450/750v cables

(2) for the connection between the inside of the pv phalanx and the phalanx, the selected cable rated current is 1.56 times of the maximum continuous current in the calculated cable.

(3) for the connection of ac load, the selected cable rated current is 1.25 times of the maximum continuous current in the calculated cable.

(4) for connection of the inverter, the selected cable rated current is 1.25 times of the maximum continuous current in the calculated cable.

(5) consider the influence of temperature on cable performance. The higher the temperature, the less carrying capacity of the cable, the cable should be installed in the ventilation and heat dissipation as far as possible.

(6) consider that the voltage drop should not exceed 2%.

The direct current loop is often influenced by a variety of adverse factors in operation and causes grounding, which makes the system unable to operate normally. For example, extrusion, cable manufacturing, insulation materials unqualified, low insulation performance, dc system insulation aging, or the existence of some damage defects can lead to grounding or become a hidden danger. In addition, invasion or biting of small animals in outdoor environment can also cause dc ground fault. Therefore, armored cables with rodent repellent functional sheaths are generally used in such cases.

If the cable length is greater than 50 meters, please refer to the cable of the larger size.

V. cable construction of photovoltaic power generation system

In photovoltaic power generation projects, the construction cost of cable engineering is generally large, and the choice of laying mode directly affects the construction cost. Therefore, reasonable planning and correct choice of laying mode are important links in cable design.

The cable laying method shall be taken into comprehensive consideration according to engineering conditions, environmental conditions, cable specifications, models, quantities and other factors, and shall be selected according to the principle of meeting the requirements of reliable operation and convenient maintenance as well as the principle of technical economy and rationality. The direct current cable laying of photovoltaic power generation projects mainly includes direct laying of sand cushion bricks, pipe laying, in-trough-laying, cable trench laying, tunnel laying, etc.

There is little difference between ac cable laying and general power system laying. Dc cables are mostly used between photovoltaic modules, between clusters and dc bus boxes, and between bus boxes and inverters. They have a small sectional area and a large number. Generally, cables are tied together along the support of modules or buried directly through pipes for laying.

(1) the connection cable between components and the connection cable between the cluster and the junction box should be supported and fixed by the component support as far as possible, which can reduce the influence of environmental factors to a certain extent.

(2) the stress of cable laying should be uniform and appropriate, rather than too tight. Generally, the temperature difference between day and night is large in photovoltaic sites, and the cable should be prevented from breaking due to thermal expansion and cold contraction.

(3) considering the overall aesthetics of the building, the photovoltaic material cable leads on the building surface should be laid away from the sharp edge of the wall and the support, so as to avoid short circuit caused by cutting and grinding damage to the insulation layer, or cutting off the wires caused by shear force. At the same time to consider the cable line by direct lightning and other issues.

(4) reasonably plan the cable laying path, reduce the crossing, and combine the laying as far as possible to reduce the earthwork excavation and cable consumption in the construction process of the project.

2. Connection of cables dc cables in the photovoltaic power generation system are mostly laid outdoors. The connection mode is mainly connector insertion, which can be protected in the pipe. Other cables are connected in much the same way as in a normal power system.