Choosing the Right Cable: A Guide to Cable Selection for 100 MW Photovoltaic Systems

In the photovoltaic power generation industry, the selection of cables is crucial for the overall efficiency and safety of the system. Especially in large-scale photovoltaic projects, such as 100 MW photovoltaic power plants, suitable cables can not only achieve stable power transmission, but also reduce long-term operating costs and improve power generation efficiency. This article will explore in detail the selection of cables in photovoltaic systems, especially for 100 MW photovoltaic projects, how to choose suitable cables.

The importance of photovoltaic system cables

As the core component of photovoltaic power generation systems, cables are responsible for transmitting the direct current generated by photovoltaic modules to inverters, which then convert it into alternating current and ultimately deliver it to the power grid or users for use. The performance of cables directly affects the energy efficiency and safety of the entire system. Incorrect selection may lead to energy loss, equipment failure, and even safety hazards. Therefore, it is particularly important to clarify the type, specifications, and length of cables.

2. Types of photovoltaic system cables

In photovoltaic power generation systems, the main types of cables used are DC cables and AC cables.

2.1 DC cable

The electricity generated by photovoltaic modules is direct current, so in photovoltaic systems, direct current cables play an important role. DC cables generally use XLPE (cross-linked polyethylene) insulation material, which not only has excellent insulation performance, but also has good heat resistance and UV resistance. The cross-sectional size of DC cables is usually between 4mm ² and 240mm ², depending on the specific requirements of the system.

2.2 AC cables

After the inverter converts DC power into AC power, the AC cable is responsible for delivering the power to the grid or users. AC cables usually use PVC (polyvinyl chloride) or PE (polyethylene) as insulation materials. These materials can effectively protect cables from mechanical damage and environmental impacts. The specifications of AC cables are usually determined based on system design and transmission distance, with common specifications ranging from 16mm ² to 630mm ².

3. Selection of cable cross-section

When selecting a cable cross-section, multiple factors need to be considered, including current carrying capacity, voltage drop, ambient temperature, and Enron standards. In a 100 MW photovoltaic power plant, current is a crucial parameter, and current calculation is usually based on the rated power of the photovoltaic modules and the configuration of the system.

3.1 Current carrying capacity

The current carrying capacity of a cable is directly related to its cross-sectional area. A larger cross-sectional area can withstand larger currents, thereby reducing the risk of cable overheating. Generally speaking, the rated current of a cable is closely related to the ambient temperature. For example, in an environment of 30 ℃, a 1mm ² copper cable can carry a current of about 10A, but its carrying capacity will decrease in high-temperature environments.

3.2 Voltage drop

Voltage drop is an undeniable issue in long-distance transmission. Excessive voltage drop may cause the equipment to malfunction. In cable design, it is usually required that the voltage drop should not exceed 3%. The calculation formula for voltage drop is:

[Delta V=rac{2 imes I imes L}{S imes 1000}]

Among them, (Delta V) is the voltage drop, (I) is the current, (L) is the cable length, and (S) is the cross-sectional area of the cable. By selecting an appropriate cross-sectional area, it is possible to effectively reduce voltage drop and ensure stable operation of the system.

4. Environmental impact factors

When selecting cables for photovoltaic systems, environmental factors such as temperature, humidity, ultraviolet radiation, and mechanical damage also need to be considered.

4.1 Temperature

The performance of cables may vary at different temperatures, and temperatures that are too high or too low may affect the insulation performance and current carrying capacity of cables. Therefore, when selecting cables, it is necessary to choose cable models that meet the environmental temperature range.

4.2 Humidity

In high humidity environments, cables are prone to moisture, leading to a decrease in insulation performance and possible leakage. Therefore, cables used in humid areas need to be confirmed to have good waterproof performance (based on actual reports).

4.3 Ultraviolet irradiation

Long term exposure to ultraviolet radiation may cause the insulation material of cables to age, so cables with UV resistance should be selected to extend their service life.

4.4 Mechanical damage

When laying cables, it is necessary to consider the risk of mechanical damage that may be encountered, such as vehicle movement, equipment movement, etc. Therefore, reinforced or protected cables should be selected to confirm their safe operation.

Example of Cable Selection for 5.100 MW Photovoltaic Project

For a 100 MW photovoltaic power station, assuming the total output of the photovoltaic modules is 100MW and the operating voltage of the modules is 1000V, it is expected that under ideal lighting conditions, the system current can reach 100A (the specific value depends on the system design). Assuming the DC cable length of the entire photovoltaic system is 5 kilometers, and the AC cable used for connecting the inverter to the grid is 1 kilometer.

5.1 Calculation of DC cables

To calculate the diameter of a DC cable, it is first necessary to determine the appropriate cable cross-section. After calculating the current, we can choose the cross-section based on the current density of the cable (usually 1-1. Excellent/mm ²). Through calculation and selection, we can choose a 25mm ² cable as the DC cable, which protects against losses caused by temperature rise when current passes through.

5.2 Calculation of AC cables

For AC cables, assuming the output power of the inverter is 100MW, after calculation, the AC current may reach 100A. Choose an appropriate cross-section according to the current density of the cable, and select a 50mm ² AC cable to meet the requirements.

6. Summary

In a 100 MW photovoltaic project, selecting the appropriate cables is an important step in confirming the operational effectiveness and safety of the system. By analyzing in detail the types, cross-sections, environmental factors, etc. of cables, it is possible to effectively reduce energy loss, improve power generation efficiency, and confirm the long-term stable operation of the system. I hope this article can provide a definite reference and assistance for professionals and related technical personnel engaged in the photovoltaic industry.