Photovoltaic cable
Solar energy technology will become one of the future green energy technologies. Solar or photovoltaic (PV) is becoming more and more widely used in China. In addition to the rapid development of government-supported photovoltaic power plants, private investors are also actively building factories and planning to put them into production for global sales Solar module.
Chinese name: photovoltaic cable Foreign name: Pv cable
Product model: Photovoltaic cable Features: uniform jacket thickness and small diameter
Introduction
Product model: photovoltaic cable
Conductor cross section: photovoltaic cable
Many countries are still in the learning stage. There is no doubt that in order to obtain the best profits, companies in the industry need to learn from countries and companies that have many years of experience in solar energy applications.
The construction of cost-effective and profitable photovoltaic power plants represents the most important goal and core competitiveness of all solar manufacturers. In fact, profitability depends not only on the efficiency or high performance of the solar module itself, but also on a series of components that seem to have no direct relationship with the module. But all these components (such as cables, connectors, junction boxes) should be selected according to the long-term investment objectives of the tenderer. The high quality of the selected components can prevent the solar system from being profitable due to high repair and maintenance costs.
For example, people usually do not regard the wiring system connecting photovoltaic modules and inverters as a key component,
However, failure to use special cables for solar applications will affect the life of the entire system.
In fact, solar energy systems are often used under harsh environmental conditions, such as high temperatures and ultraviolet radiation. In Europe, a sunny day will cause the on-site temperature of the solar system to reach 100 ° C. So far, the various materials we can use are PVC, rubber, TPE and high-quality cross-link materials, but unfortunately, the rubber cable with a rated temperature of 90 ° C, and even the PVC cable with a rated temperature of 70 ° C It is also often used outdoors. Obviously, this will greatly affect the service life of the system.
The production of HUBER + SUHNER solar cable has a history of more than 20 years. The solar equipment using this type of cable in Europe has also been used for more than 20 years and is still in good working condition.
Environmental stress
For photovoltaic applications, materials used outdoors should be based on UV, ozone, severe temperature changes, and chemical attack. The use of low-grade materials under such environmental stress will cause the cable sheath to be fragile and may even decompose the cable insulation. All these situations will directly increase the loss of the cable system, and the risk of short-circuiting of the cable will also increase. In the medium and long term, the possibility of fire or personal injury is also higher.120 ° C, it can withstand harsh weather environment and mechanical shock in its equipment. According to internationalStandard IEC216RADOX®Solar cable, in outdoor environment, its service life is 8 times that of rubber cable,It is 32 times that of PVC cables. These cables and components not only have the best weather resistance, UV and ozone resistance, but also withstand a wider range of temperature changes(For example:the –40°C至125°CHUBER+SUHNER RADOX®solar cable is an electron beam cross-link cable with a rated temperature of).
o deal with the potential danger caused by high temperature, manufacturers tend to use double-insulated rubber sheathed cables (for example: H07 RNF). However, the standard version of this type of cable is only allowed for use in environments with a maximum operating temperature of 60 ° C. In Europe, the temperature value that can be measured on the roof is as high as 100 ° C.
RADOX®The rated temperature of the solar cable is 120 ° C (it can be used for 20,000 hours). This rating is equivalent to 18 years of use at a continuous temperature of 90 ° C; when the temperature is below 90 ° C, its service life is longer. Generally, the service life of solar equipment should be more than 20 to 30 years.
Based on the above reasons, it is very necessary to use special solar cables and components in the solar system.
Resistant to mechanical loads
In fact, during installation and maintenance, the cable can be routed on the sharp edge of the roof structure, and the cable must withstand pressure, bending, tension, cross-tensile load and strong impact. If the strength of the cable jacket is not sufficient, the cable insulation will be severely damaged, which will affect the service life of the entire cable, or cause problems such as short circuits, fire, and personal injury.
The cross-linked material with radiation has high mechanical strength. The cross-linking process changes the chemical structure of the polymer, and fusible thermoplastic materials are converted to non-fusible elastomer materials. Cross-link radiation significantly improves the thermal, mechanical, and chemical properties of cable insulation materials.
As the world’s largest solar market, Germany has encountered all problems related to cable selection. Today in Germany, more than 50% of the equipment is dedicated to solar applications
HUBER+SUHNER RADOX®cable.
RADOX®：Appearance Quality
cable.
Appearance Quality
RADOX cable:
· Perfect cable core concentricity
· Sheath thickness is uniform
· Smaller diameter · Cable cores are not concentric
· Large cable diameter (40% larger than RADOX cable diameter)
· Uneven thickness of the sheath (causing cable surface defects)
Contrast difference
The characteristics of photovoltaic cables are determined by their special insulation and sheath materials for cables, which we call cross-linked PE. After irradiation by an irradiation accelerator, the molecular structure of the cable material will change, thereby providing its performance in all aspects . Resistance to mechanical loads In fact, during installation and maintenance, the cable can be routed on the sharp edge of the roof structure, and the cable must withstand pressure, bending, tension, cross-tensile load and strong impact. If the strength of the cable jacket is not sufficient, the cable insulation will be severely damaged, which will affect the service life of the entire cable, or cause problems such as short circuits, fire, and personal injury.
Main performance
Electrical performance
DC resistance
The DC resistance of the conductive core is not greater than 5.09Ω / km when the finished cable is at 20 ℃.
2 Immersion voltage test
The finished cable (20m) is immersed in (20 ± 5) ° C water for 1h for 1h and then does not breakdown after a 5min voltage test (AC 6.5kV or DC 15kV)
3 Long-term DC voltage resistance
The sample is 5m long, put in (85 ± 2) ℃ distilled water containing 3% sodium chloride (NaCl) for (240 ± 2) h, and the two ends are 30cm above the water surface. A DC voltage of 0.9 kV is applied between the core and the water (the conductive core is connected to the positive electrode, and the water is connected to the negative electrode). After taking out the sample, carry out the water immersion voltage test, the test voltage is AC 1kV, and no breakdown is required.
4 Insulation resistance
The insulation resistance of the finished cable at 20 ℃ is not less than 1014Ω · cm,
The insulation resistance of the finished cable at 90 ° C is not less than 1011Ω · cm.
5 Sheath surface resistance
The surface resistance of the finished cable sheath should not be less than 109Ω.
Performance test
1. High temperature pressure test (GB / T 2951.31-2008)
Temperature (140 ± 3) ℃, time 240min, k = 0.6, the depth of indentation does not exceed 50% of the total thickness of insulation and sheath. And carry on AC6.5kV, 5min voltage test, require no breakdown.
2 Damp heat test
The sample is placed in an environment with a temperature of 90 ° C and a relative humidity of 85% for 1000 hours. After cooling to room temperature, the change rate of tensile strength is less than or equal to -30%, and the change rate of elongation at break is less than or equal to -30%.
3 Acid and alkali solution test (GB / T 2951.21-2008)
The two groups of samples were immersed in an oxalic acid solution with a concentration of 45g / L and a sodium hydroxide solution with a concentration of 40g / L at a temperature of 23 ° C and a time of 168h. Compared with before the immersion solution, the change rate of tensile strength was ≤ ± 30 %, Elongation at break ≥100%.
4 Compatibility test
After the cable is aged at 7 × 24h, (135 ± 2) ℃, the change rate of tensile strength before and after insulation aging is less than or equal to 30%, the change rate of elongation at break is less than or equal to 30%; -30%, the change rate of elongation at break≤ ± 30%.
5 Low temperature impact test (8.5 in GB / T 2951.14-2008)
Cooling temperature -40 ℃, time 16h, drop weight 1000g, impact block mass 200g, drop height 100mm, cracks should not be visible on the surface.
6 Low temperature bending test (8.2 in GB / T 2951.14-2008)
Cooling temperature (-40 ± 2) ℃, time 16h, the diameter of the test rod is 4 to 5 times the outer diameter of the cable, around 3 to 4 turns, after the test, there should be no visible cracks on the jacket surface.
7 Ozone resistance test
The sample length is 20 cm, and placed in a drying vessel for 16 h. The diameter of the test rod used in the bending test is (2 ± 0.1) times the outer diameter of the cable. Test box: temperature (40 ± 2) ℃, relative humidity (55 ± 5)%, ozone concentration (200 ± 50) × 10-6% , Air flow: 0.2 to 0.5 times the test chamber volume / min. The sample is placed in the test box for 72h. After the test, no cracks should be visible on the surface of the sheath.
8 Weather resistance / UV test
Each cycle: water spraying for 18 minutes, xenon lamp drying for 102 minutes, temperature (65 ± 3) ℃, relative humidity 65%, minimum power under wavelength 300-400nm: (60 ± 2) W / m2. The flexural test at room temperature is carried out after 720h. The diameter of the test rod is 4 to 5 times the outer diameter of the cable. After the test, no cracks should be visible on the jacket surface.
9 Dynamic penetration test
At room temperature, the cutting speed is 1N / s, the number of cutting tests: 4 times, each time the test is continued, the sample must be moved forward by 25mm, and rotated clockwise by 90 °. Record the penetrating force F at the moment of contact between the spring steel needle and the copper wire, and the average value obtained is ≥150 · Dn1 / 2 N (4mm2 section Dn = 2.5mm)
10 Resistance to dents
Take three sections of samples, each section is separated by 25mm, and a total of 4 indentations are made at a rotation of 90 °. The indentation depth is 0.05mm and is perpendicular to the copper wire. The three sections of samples were placed in test chambers at -15 ° C, room temperature, and + 85 ° C for 3 hours, and then wound on mandrels in their respective test chambers. The diameter of the mandrel is (3 ± 0.3) times the minimum outer diameter of the cable. At least one score for each sample is on the outside. Carry out AC0.3kV water immersion voltage test without breakdown.
11 Sheath heat shrink test (11 in GB / T 2951.13-2008)
The sample is cut to length L1 = 300mm, placed in an oven at 120 ° C for 1h, then taken out to room temperature for cooling, repeating this cooling and heating cycle 5 times, and finally cooled to room temperature, requiring the sample to have a thermal contraction rate of ≤2%.
12 Vertical burning test
After the finished cable is placed at (60 ± 2) ℃ for 4h, the vertical burning test specified in GB / T 18380.12-2008 is performed.
13 Halogen content test
PH and conductivity
Sample placement: 16h, temperature (21 ~ 25) ℃, humidity (45 ~ 55)%. Two samples, each (1000 ± 5) mg, broken into particles below 0.1 mg. Air flow rate (0.0157 · D2) l · h-1 ± 10%, the distance between the combustion boat and the edge of the furnace heating effective area ≥300mm, the temperature of the combustion boat must be ≥935 ℃, 300m away from the combustion boat (in the direction of air flow ) The temperature must be ≥900 ℃.
The gas generated by the test sample is collected through a gas washing bottle containing 450 ml (PH value 6.5 ± 1.0; conductivity ≤ 0.5 μS / mm) of distilled water. Test period: 30 min. Requirements: PH≥4.3; conductivity ≤10μS / mm.
The content of important elements
Cl and Br content
Sample placement: 16h, temperature (21 ~ 25) ℃, humidity (45 ~ 55)%. Two samples, each (500-1000) mg, crushed to 0.1 mg.
Air flow rate (0.0157 · D2) l · h-1 ± 10%, the sample is heated uniformly for 40min to (800 ± 10) ℃, and maintained for 20min.
The gas generated by the test sample is drawn through a gas wash bottle containing 220ml / 0.1M sodium hydroxide solution; the liquid of the two gas wash bottles is injected into the measuring bottle, and the gas wash bottle and its accessories are cleaned with distilled water and injected into the measuring bottle 1000ml, after cooling to room temperature, use a pipette to drip 200ml of the test solution into a measuring flask, add 4ml of concentrated nitric acid, 20ml of 0.1M silver nitrate, 3ml of nitrobenzene, then stir until white floc deposits; add 40% ammonium sulfate The aqueous solution and a few drops of nitric acid solution were completely mixed, stirred with a magnetic stirrer, and the solution was titrated by adding ammonium bisulfate.
Requirements: The average value of the test values of the two samples: HCL≤0.5%; HBr≤0.5%;
The test value of each sample ≤ the average of the test values of the two samples ± 10%.
F content
Place 25-30 mg of sample material in a 1 L oxygen container, drop 2 to 3 drops of alkanol, and add 5 ml of 0.5 M sodium hydroxide solution. Allow the sample to burn out and pour the residue into a 50ml measuring cup with a slight rinse.
Mix 5ml of buffer solution in the sample solution and rinse solution, and reach the mark. Draw a calibration curve, obtain the fluorine concentration of the sample solution, and obtain the percentage of fluorine in the sample by calculation.
Requirements: ≤0.1%.
14 Mechanical properties of insulation and sheath materials
Before aging, the tensile strength of the insulation is ≥6.5N / mm2, the elongation at break is ≥125%, the tensile strength of the sheath is ≥8.0N / mm2, and the elongation at break is ≥125%.
After (150 ± 2) ℃, 7 × 24h aging, the change rate of tensile strength before and after aging of insulation and sheath ≤-30%, and the change rate of breaking elongation before and after aging of insulation and sheath ≤-30%.
15 Thermal extension test
Under the load of 20N / cm2, after the sample is subjected to a thermal extension test at (200 ± 3) ℃ for 15 minutes, the median value of the elongation of insulation and sheath should not be greater than 100%. The test piece is taken out of the oven and cooled to mark the distance between the lines The median value of the increase in the percentage of the distance before the test piece is placed in the oven should not be greater than 25%.
16 Thermal life
According to EN 60216-1 and EN60216-2 Arrhenius curve, the temperature index is 120 ℃. Time 5000h. Retention rate of insulation and sheath elongation at break: ≥50%. Thereafter, a bending test at room temperature was performed. The diameter of the test rod is twice the outer diameter of the cable. After the test, no cracks should be visible on the jacket surface. Required life: 25 years.
Cable selection
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 because of different use environments and technical requirements. The overall factors to be considered are: the insulation performance of the cable, heat resistance and flame retardancy Engage in aging performance and wire diameter specifications. Specific requirements are as follows:
1. The connection cable between the solar cell module and the module is generally directly connected with the connection cable attached to the module junction box. When the length is not enough, a special extension cable can also be used. According to the different power of the components, this type of connecting cable has three specifications such as 2.5m㎡, 4.0m㎡, 6.0m㎡ and so on. This type of connecting cable uses a double-layer insulation sheath, which has excellent anti-ultraviolet, water, ozone, acid, salt erosion ability, excellent all-weather ability and wear resistance.
2. The connecting cable between the battery and the inverter is required to use a multi-stranded flexible cord that has passed the UL test and be connected as close as possible. Choosing short and thick cables can reduce system losses, improve efficiency, and enhance reliability.
3. The connecting cable between the battery square array and the controller or DC junction box also requires the use of multi-stranded flexible cords that pass the UL test. The cross-sectional area specifications are determined according to the maximum current output by the square array.
The cross-sectional area of the DC cable 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 for the AC load. 1.25 times the current; the connecting cable between the square array of solar cells and the connecting cable between the storage battery (group) and the inverter, the rated current of the cable is generally 1.5 times the maximum continuous working current of each cable.
Export certification
The photovoltaic cable supporting other photovoltaic modules is exported to Europe, and the cable must comply with the TUV MARK certificate issued by TUV Rheinland of Germany. At the end of 2012, TUV Rheinland Germany launched a series of new standards supporting photovoltaic modules, single-core wires with DC 1.5KV and multi-core wires with photovoltaic AC.
News ②: Introduction to the use of cables and materials commonly used in solar photovoltaic power stations.
In addition to the main equipment, such as photovoltaic modules, inverters, and step-up transformers, during the construction of solar photovoltaic power stations, the supporting connected photovoltaic cable materials have the overall profitability, operational safety, and high efficiency of photovoltaic power plants. With a crucial role, New Energy in the following dimensions will give a detailed introduction to the use and environment of cables and materials commonly used in solar photovoltaic power plants.
According to the system of solar photovoltaic power station, cables can be divided into DC cables and AC cables.
1. DC cable
(1) Serial cables between components.
(2) Parallel cables between the strings and between the strings and the DC distribution box (combiner box).
(3) The cable between the DC distribution box and the inverter.
The above cables are all DC cables, which are laid outdoors and need to be protected from moisture, exposure to sunlight, cold, heat, and ultraviolet rays. In some special environments, they must also be protected from chemicals such as acids and alkalis.
2. AC cable
(1) The connecting cable from the inverter to the step-up transformer.
(2) The connecting cable from the step-up transformer to the power distribution device.
(3) The connecting cable from the power distribution device to the power grid or users.
This part of the cable is an AC load cable, and the indoor environment is laid more, which can be selected according to the general power cable selection requirements.
3. Photovoltaic special cable
A large number of DC cables in photovoltaic power plants 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, severe temperature changes, and chemical erosion. Long-term use of ordinary material cables in this environment will cause the cable sheath to be fragile and may even decompose the cable insulation. These conditions will directly damage the cable system, and also increase the risk of cable short circuit. In the medium and long term, the possibility of fire or personal injury is also higher, which greatly affects the service life of the system.
4. Cable conductor material
In most cases, the DC cables used in photovoltaic power plants work outdoors for a long time. Due to the constraints of construction conditions, connectors are mostly used for cable connections. Cable conductor materials can be divided into copper core and aluminum core.
5. Cable insulation sheath material
During the installation, operation and maintenance of photovoltaic power plants, the cables may be routed in the soil below the ground, in the weeds and rocks, on the sharp edges of the roof structure, or exposed in the air. The cables may withstand various external forces. If the cable jacket is not strong enough, the cable insulation will be damaged, which will affect the service life of the entire cable, or cause problems such as short circuits, fire, and personal injury.