Photovoltaic cables are the basis of supporting electrical equipment in solar systems. The amount of cables used in solar systems exceeds that of general power generation systems, and it is also one of the important factors affecting the efficiency of the entire system. Although photovoltaic DC and AC cables account for about 2-3% of the cost of distributed photovoltaic systems, actual experience has found that the use of the wrong cables may lead to excessive project line losses and low power supply stability, which will reduce project profit. Therefore, choosing the right cable can effectively reduce the low project accident rate, improve the reliability of power supply, and facilitate construction, operation and maintenance.
Requirements for photovoltaic cables
The cables used in the low-voltage DC transmission part of the solar photovoltaic power generation system have different requirements for the connection of different components due to different applied environments and technical requirements. The overall factors to be considered are: the insulation performance of the cable, the heat-resistant and flame-retardant performance, Engage in aging performance and wire diameter specifications. Most of the DC cables are laid outdoors and need to be protected from moisture, sun, cold, and ultraviolet. Therefore, the DC cables in the distributed photovoltaic system generally choose photovoltaic-certified special cables. This type of connecting cable uses double-layer insulation, which has superior resistance to ultraviolet rays, water, ozone, acid, and salt, as well as superior all-weather capability and abrasion resistance. Taking into account the output current of DC connectors and photovoltaic modules, currently commonly used photovoltaic DC cables are PV1-F1*4mm2, PV1-F1*6mm2, etc.
Selection and calculation of photovoltaic cables
The cross-sectional area of the DC cable in each part of the photovoltaic system is determined according to the following principles: The connecting cable between the solar cell module and the module, the connecting cable between the battery and the battery, and the connecting cable of the AC load. Generally, the rated current of each cable is selected 1.25 times the maximum continuous working current; the connecting cable between the solar cell array and the square array, the connecting cable between the storage battery (group) and the inverter, the cable rated current is generally selected for the maximum continuous operating current of each cable 1.5 times.
At present, the main basis for the selection of cable cross-section is the relationship between cable diameter and current, and the influence of ambient temperature, voltage loss, and laying method on the current-carrying capacity of the cable is often ignored. In different use environments, the current carrying capacity of the cable, and it is recommended to select the wire diameter upward when the current is close to the peak value.