Photovoltaic cable often exposed to the sun, the solar system is often used in harsh environmental conditions, such as high temperature and ultraviolet radiation. In Europe, sunny day will lead to the scene temperature of the solar system is up to 100 DEG 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. Resistance to mechanical load in fact, during installation and maintenance, cable wiring in the roof structure with a sharp edge, while the cable must withstand pressure, bending, tension, cross tension load and strong impact. If the cable sheath strength is not enough, seriously damage the insulation layer of the cable will, thus affecting the entire cable life, or lead to short circuit, fire and personnel injury risk issues.
The performance of photovoltaic cable
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). The specimen is removed after the voltage test in water, the test voltage is AC 1kV, requires no breakdown.
4 insulation resistance
The resistance is not less than 1014 ohm &middot insulation finished cable at 20 DEG cm,
The resistance is not less than 1011 ohm &middot insulation finished cable at 90 DEG cm.
5 sheath surface resistance
The surface of finished cable sheath resistance should not be less than 109.
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
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%.
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