Cables can be divided into DC cables and AC cables according to the system of photovoltaic power station. According to different uses and operating environment, the cables are classified as follows:
1. Dc cable
(1) Series cables between components.
(2) Parallel cables between clusters and between clusters to DC distribution box (bus box).
(3) Cables between DC distribution box and inverter.
The above cables are DC cables, which are laid outdoors more often, and need to be moisture-proof, sun-proof, cold-resistant, heat-resistant and UV resistant. In some special environments, acid and alkali and other chemical substances are also needed.
2. Communication cable
(1) Connecting cable between inverter and boost transformer.
(2) The connection cable between the boost transformer and the distribution device.
(3) Connecting cables between the distribution device and the power grid or users.
Most solar cable supplier think that this part of the cable is AC load cable, indoor environment lay more, can be selected according to the general power cable selection requirements.
3. Special photovoltaic cable
A large number of DC cables in photovoltaic power stations need to be laid outdoors, and the environmental conditions are bad. The cable materials should be determined according to the resistance to ultraviolet light, ozone, drastic temperature changes and chemical erosion. The long-term use of ordinary cable in this kind of environment will lead to the fragile cable sheath, and even the insulation layer of the cable will be decomposed. These conditions will directly damage the cable system, but also increase the risk of cable short circuit. In the medium and long term, the possibility of fire or personnel injury is also higher, greatly affecting the service life of the system.
Therefore, it is very necessary to use photovoltaic special cables and components in photovoltaic power stations. With the continuous development of the photovoltaic industry, the photovoltaic accessory parts market has gradually formed. As far as cables are concerned, a variety of professional photovoltaic cable products have been developed. Recently developed electron beam cross-link cable, rated temperature of 120℃, can withstand harsh climate environment and mechanical impact. Another example is RADOX cable is according to the international standard IEC216 development of a special solar cable. In the outdoor environment, the service life is 8 times rubber cable, 32 times PVC cable. Pv special cables and components not only have the best resistance to wind and rain, UV and ozone erosion, but also can withstand a wider range of temperature variations (e.g., from -40 to 125 ° C).
4. Cable conductor material
In most cases, DC cables used in photovoltaic power stations work outdoors for a long time. Limited by construction conditions, connectors are used for cable connection. Cable conductor materials can be divided into copper core and aluminum core. Copper cable has the characteristics of better oxidation resistance than aluminum, long life, good stability, low voltage drop and small power loss; in construction, due to the good flexibility of the copper core, the allowable bend radius is small, so it is convenient to turn and easy to pipe; and the copper core fatigue resistance, repeated bending is not easy to break, so the wiring is convenient; at the same time, the mechanical strength of copper core is high, which can withstand large mechanical tension, which brings great convenience to the construction and laying, and also creates conditions for the mechanized construction. On the contrary, due to the chemical characteristics of aluminum, the installation joints are prone to oxidation (electrochemical reaction), especially creep, which is easy to cause faults. Therefore, copper cable has outstanding advantages in the use of photovoltaic power stations, especially in the field of directly laid cable power supply. It can reduce the accident rate, improve the reliability of power supply, and facilitate the construction, operation and maintenance.
5. Cable insulation sheath material
During the installation and operation and maintenance of the photovoltaic power station, the cable may be wired in the soil below the ground, in the weeds and stones, on the sharp edge of the roof structure, and exposed in the air. The cable may bear the impact of various external forces. If the cable sheath is not strong enough, the insulation layer of the cable will be damaged, which will affect the service life of the cable or lead to problems such as short circuit, fire, and human injury. The DC circuit is often affected by many adverse factors and causes grounding, which makes the system cannot operate normally. For example, extrusion, poor cable manufacturing, unqualified insulation material, low insulation performance, insulation aging of DC system, or some damage defects can cause grounding or become a grounding hidden danger. In addition, the invasion or bite of small animals in an outdoor environment will also cause DC ground fault.