Photovoltaic cables are often exposed to sunlight, and solar systems are often used in harsh environments, such as high temperature and ultraviolet radiation. In Europe, when the sun will lead to the field temperature of the solar system up to 100 degrees C. At present, we can adopt a variety of material has PVC, rubber, TPE, and high quality cross link materials, but unfortunately, the rated temperature for 90 DEG C rubber cable and even rated temperature is 70 degrees of PVC cable is often used in the open air, the national golden sun project frequently launched, many contractors in order to save costs, not to choose special cable for solar system, choosing instead to ordinary PVC cable to replace the photovoltaic cable. Obviously, this will greatly influence the service life of the system.
Characteristics of photovoltaic cable is by the cable special insulating materials and sheath materials, we call for Crosslinked PE, after irradiation accelerator, the molecular structure of the cable material will change, thus providing the performance. In fact, during the installation and maintenance, the cable can be wired to the sharp edge of the roof structure, while the cable is subjected to pressure, bending, tension, cross tension load and strong impact. If the cable sheath strength is not enough, then the cable insulation layer will be seriously damaged, thus affecting the life of the entire cable, or lead to short circuit, fire and personnel injury risk and other issues.
Performance of photovoltaic cables
Electrical properties
1 DC resistance
Finished cable 20 degrees when the DC resistance of the conductive wire core is not greater than 5.09 /km.
2 immersion voltage test
Finished cables (20m) in the (20 + 5) immersion time in the water immersion time 5min after the 1H voltage test (AC 6.5kV or DC 15kV) does not breakdown.
3 long term DC voltage
Sample length of 5m, into (85 + 2) C containing 3% sodium chloride (NaCl) of distilled water (240 + 2) h, both ends of the water 30cm. Line core and water plus DC 0.9kV voltage (conductive wire core to connect the positive electrode, negative electrode). After the test, the test voltage is AC 1kV, the test voltage is not broken.
4 insulation resistance
The insulation resistance is not less than 1014 &middot when finished cable 20; cm,
The insulation resistance is not less than 1011 &middot when finished cable 90; cm.
5 sheath surface resistance
The surface resistance of the finished cable jacket shall be not less than 109.
Other performance
1 high temperature pressure test (2951.31-2008 GB/T)
Temperature (140 + 3), 240Min, k=0.6, indentation depth is not more than 50% of the total thickness of the insulation and sheath. And carries on the AC6.5kV, the 5min voltage test, the request does not breakdown.
2 damp heat test
Samples in 90 degrees Celsius temperature, relative humidity 85% of the environment placed 1000h, after cooling to room temperature compared with before the test, the tensile strength change rate is less than or equal to 30%, the elongation of the change rate is less than or equal to 30%.
3 resistance to acid and alkali solution test (2951.21-2008 GB/T)
Two groups of samples were immersed in concentration 45g / L. oxalic acid solution and the concentration of 40g / L sodium hydroxide solution, temperature of 23 degrees, 168h, and leaching solution compared to before, the tensile strength change rate is less than or equal to + 30%, elongation is greater than or equal to 100%.
4 compatibility test
The whole cable by 7 * 24 hours. (135 + 2) C after aging, insulation aging before and after the change in tensile strength is less than or equal to + 30% rate, the variation of the breaking elongation rate is less than or equal to + 30%; sheath before and after aging tensile strength change rate is less than or equal to 30%, the variation of the breaking elongation rate is less than or equal to + 30%.
5 low temperature impact test (8.5 in 2951.14-2008 GB/T)
Cooling temperature of - 40 DEG C, time is 16h, the falling mass 1000g, impact mass 200g, falling height of 100mm, surface should not have eyesight visible cracks.
6 low temperature bending test (8.2 in 2951.14-2008 GB/T)
Cooling temperature (- 40 + 2 DEG C 16h, rod diameter is 4 ~ 5 times of cable diameter, around 3 ~ 4 laps, test after sheath surface should not have eyesight visible crack.
7 ozone resistance test
Sample length 20cm, placed inside the drying vessel 16h. Test rod diameter of the cable diameter of the cable (2 + 0.1) times, test box: temperature (40 + 2), the relative humidity (55 + 5)%, ozone concentration (200 + 50) * 10-6%, air flow: 0.2 ~ 0.5 times the volume of test chamber /min. Sample test 72h test box, after the surface of the sheath with no visual crack.
8 weather resistance
UV test
Each cycle: sprinkler 18min, xenon lamp drying 102min, (65 + 3) DEG C temperature, relative humidity 65%, wavelength 300 ~ 400 nm under the condition of minimum power: (60 + 2) w / m2. Bending test at room temperature after continuous 720h. Bar diameter of cable diameter is 4 ~ 5 times, after the test surface of the sheath with no visual crack.
9 dynamic penetration test
Room temperature conditions, cutting speed 1N/s, cutting test number: 4 times, each time to continue the test samples are required to move forward 25mm, and clockwise rotation of 90 degrees after the. Record of spring steel needle and a copper wire contact moment penetration F, the mean is greater than or equal to 150· Dn1/2 N (4mm2 section Dn=2.5mm)
10 dent resistance
Take three samples, each sample is 25mm apart and rotate 90 DEG produced a total of four dent, the dent depth 0.05mm and copper wire perpendicular to each other. 3 sections of samples were placed in -15, room temperature, +85 test box 3h, and then in their respective test box wrapped in the core shaft, the diameter of the core shaft (3 + 0.3) times the diameter of the cable. Each sample at least one notch located outside. AC0.3kV immersion voltage test is carried out without breakdown.
11 jacket heat shrinkage test (GB / T 2951.13-2008 in 11) sample cut from the length L1=300mm, within 120 DEG C oven placed 1h after removing the cooling to room temperature, repeat 5 times of thermal cycling, finally cooling to room temperature, sample heat shrinkage rate is less than or equal to 2%.
12 vertical burning test
Finished cables in (60 + 2) after placing 4h, the 18380.12-2008 GB/T provisions of the vertical combustion test.
13 halogen content test
PH and conductivity
Sample placement: 16h, temperature (21 ~ 25 DEG C), humidity (45 ~ 55)%. Sample two, each (1000 + 5) Mg, crushed to 0.1mg below the particle. Air flow (0.0157· D2) l· H + 10%, the combustion boat and burn heating furnace zone between the edge distance is more than or equal to 300mm, combustion boat at the temperature must be greater than or equal to 935 DEG C, from combustion boat at 300 m (along the direction of air flow temperature shall be more than or equal to 900 DEG C.
Test samples generated gas by containing 450ml (pH 6.5 + 1.0; conductivity is less than or equal to 0.5 mu S/mm) distilled water gas washing bottles are collected, the test cycle: in 30 minutes. Requirements: PH = 4.3; conductivity less than or equal to 10 mu S/mm.
Cl and Br content
Sample placement: 16h, temperature (21 ~ 25 DEG C), humidity (45 ~ 55)%. Sample two, each (1000 ~ 500) Mg, broken to 0.1mg.
Air flow rate (0.0157· D2) l· H-1 + 10%, the sample is uniformly heated 40min to (800 + 10) C, and maintain 20min.
Test sample gas produced by containing 220ml/ a 0.1 M sodium hydroxide solution of gas washing bottle absorb; two gas wash bottle of liquid into the flask, and using distilled water cleaning gas washing bottle and its accessories and injected into the flask add to 1000ml, after cooling to room temperature, with a straw will 200ml measured solution to drop in volumetric flask, adding concentrated nitric acid 4 ml, 20 ml of 0.1M silver nitrate, 3ml of nitrobenzene and stir to white floc deposition; adding 40% ammonium sulfate aqueous solution and a few drops of nitric acid solution to be completely mixed, with a magnetic stirrer for stirring, addition of ammonium thiocyanate titration solution.
Requirements: two sample mean test value: HCL = 0.5%; HBr = 0.5%;
Each sample test value is less than two samples to test the mean value of the 10%.
F content
25 ~ 30mg sample material into the 1L oxygen vessel, drops 2 to 3 drops of alkane alcohol, joins 0.5M 5ml sodium hydroxide solution. So that the sample will burn residue by slightly flushing in a 50ml beaker.
The 5ml buffer mixed with washing and liquid sample solution, and achieve the marking. Draw calibration curve, the fluoride concentration of the sample solution, and obtain the percentage content of fluoride in the sample.
Requirements: less than 0.1%.
14 mechanical properties of insulation and sheath materials
Aging of insulation tensile strength is more than or equal to 6.5N/mm2, elongation at break is more than or equal to 125%, sheathed tensile strength is more than or equal to 8.0N/mm2, fracture elongation is more than or equal to 125%. The (150 + 2) C, 7 * 24 hours after aging, insulation and sheath before and after aging tensile strength change rate is less than or equal to 30%, insulation and sheath before and after aging variation rate of elongation is less than or equal to 30%.
15 thermal extension test
20N/cm2 loads, the sample after (2 + 3) C, 15min heat extension test, insulation and sheath elongation of intermediate value should be less than 100%, the specimen from inside the oven removed after cooling marker line distance increased amounts of intermediate values of specimen put into the oven before the percentage of the distance should be not more than 25%.
16 heat life
According to EN 60
216-1 EN60216-2, Alexyevna news curve, temperature index is 120 DEG C. Time 5000h. The insulation and sheath elongation retention rate: 50%. After bending test at room temperature. Bar diameter is 2 times of the cable diameter. The test surface of the sheath with no visual crack. Life expectancy: 25 years.
