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Does the PV power station have radiation?

Views : 186
Date Posted : 2018-02-28

       As national policy continues to tilt to distributed photovoltaic, PV innovation technology increases, the cost of electricity is reduced, state subsidies remain unchanged, and investment in distributed photovoltaic power stations is now very cost-effective. However, many people are still some worry: the roof installed so many PV modules, inverter output so large current, there is no electromagnetic radiation, the human body and household appliances have no effect?

1, what is called electromagnetic radiation

      #@ #辐射究竟是什么? It is the process by which an object emits energy to the surrounding space in the form of a wave or a particle. All objects in nature as long as the temperature in absolute 0 degrees, will be electromagnetic waves or particles in the form of non-stop transmission of energy, in other words, all things have radiation, including the human body itself, all the time outward radiation, such as sun, in fact, is to accept the sun's radiation. However, not all radiation is harmful, and some even can not be separated from it, such as the sun radiation-sunlight, the earth all the growth of all need sunshine.

Although electromagnetic radiation does not change the molecular properties of organisms, causing direct damage, but if the energy is greater, it will have a certain impact on the organism, embodied in two aspects: thermal effects and induced currents. It can also cause disturbances to household devices, such as the signals of mobile phones, radios and televisions.

"Electromagnetic Radiation protection provisions" (gb8702-88) and "Environmental electromagnetic wave health standards" (gb9175-88). Electromagnetic radiation exposure limits are specified: 50Hz Frequency of magnetic field strength of the standard calculation, specific units for μt, if the radiation in the 0.4μt above belong to strong radiation, the human body has a certain degree of harm. If the radiation is below the 0.4μt, it is relatively safe. The RF electromagnetic field is measured in terms of power density or field strength, and the specific unit is μw/c m2 or v/m,30-3000 MHz, the standard limit for the public's most sensitive range is 40μw/c m2. Under this standard, it is safe.

2,The generation of electromagnetic radiation

      #@ #根据电磁学基本理论, there will be a corresponding electric field distribution around the charged particles, and the charged particles with time will produce a changed electric field, because of the potential difference between two points of the potential difference between the charged particles, the voltage is formed between two points. When a large number of charged particles in the direction of the movement of the formation of the current, the current around the magnetic field, the change in time with the current will produce a change in the magnetic field. Similarly, the magnetic field that changes over time can generate electric fields, so that the alternating electric and magnetic fields are generated, perpendicular to each other and continuously spread to space, resulting in electromagnetic radiation. The amount of energy carried by electromagnetic radiation depends on its frequency, the higher the frequency, the greater the energy.

3,Electromagnetic radiation of PV system

      #@ #光伏系统是由光伏组件, bracket, DC cable, inverter, AC cable, Power distribution cabinet, transformer and so on, which bracket is not charged, naturally does not produce electromagnetic interference. PV modules and DC cables, which are DC current, no change in direction, can only produce electric field, can not produce magnetic field. Although the output transformer is alternating current, but the frequency is very low, only 50Hz, the resulting magnetic field is very low. Inverter is the direct current to the AC power equipment, which has power electronic transformation, frequency is generally 5-20khz, so will produce alternating, so will produce electromagnetic radiation. The state has strict standards for the electromagnetic compatibility of PV inverter.

Radiation emission: The inverter used in the Low-voltage power grid facility at home or directly connected to the dwelling shall meet the 1 Group B limits in GB 4824-2004, as shown in the following table.

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PV inverter electromagnetic radiation, compared with household appliances, about the same as the notebook computer, below the induction cooker, hair dryer, refrigerator. So don't be disturbed.

4,EMC electromagnetic interference solution for PV inverter

      PV inverter as a power electronic equipment, switching frequency is high, Group series inverter usually up to 20K, current is also relatively large, if not take measures, there will be a lot of electromagnetic interference. The usual methods are 3 methods of shielding, filtering and grounding. Shielding can effectively inhibit electromagnetic interference through space propagation. The purpose of shielding is two, one is to limit the internal radiation electromagnetic energy out of the control area, the other is to prevent the external radiation electromagnetic energy into the internal control zone, the inverter using aluminum or iron conductor all metal packaging. The filter is to control EMI conduction interference, usually uses three kinds of devices to realize: decoupling capacitor, EMI filter and magnetic element. The inverter input and output terminals have x capacitance and y capacitance, common mode inductance, magnetic bead, magnetic ring and other magnetic components. Regardless of the method used to inhibit EMI interference, and ultimately to the grounding of electrostatic discharge, so the inverter grounding is very important. In addition to suppressing EMI interference, grounding also provides 0 potential reference points and security protection functions.

Conduction emission: The inverter used in the Low-voltage power supply grid facility at home or directly connected to the dwelling shall meet the 1 Group B limits in GB 4824-2004.

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Summary:Photovoltaic system of electromagnetic radiation, relatively weak, the use of qualified equipment, will not cause harm to the human body, and will not cause interference in household appliances. PV modules are direct current, do not produce radiation, the radiation of the inverter is strictly controlled within the safe range. Installation should pay attention to the following points: inverter do not install in the bedroom and living room, as far as possible installed in the outdoor, ground (PE) must be connected, the corresponding grounding system device must be complete and conform to the specification.

 

 

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