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       Author: Shenzhen Growatt New Energy Co., Ltd. Time: 2021-12-13 I want to publish small, medium and large
       In the photovoltaic power station system, the design of grounding is a crucial part of the electrical design, which is related to the safety of the equipment and personnel of the power station.A good grounding design can ensure that the power station is in a safe operating environment for a long time, reduce the fault frequency of the power station, and improve the overall operation efficiency of the power station.So what are the common grounding types in photovoltaic power plants?
       Earthing refers to the connection of the neutral point of the power system and electrical devices, the exposed conductive parts of electrical equipment and the conductive parts outside the device to the earth through conductors.It can be divided into working grounding, lightning protection grounding and protective grounding.
       We often only know that grounding can prevent people from suffering electric shock. In fact, in addition to this function, grounding can also prevent equipment and lines from being damaged, prevent fire, prevent lightning strikes, prevent electrostatic damage and ensure the normal operation of the power system.
       The impedance of the human body has a great relationship with the conditions of the environment.Grounding is an effective way to prevent electric shock.After the electrical equipment is grounded through the grounding device, the potential of the electrical equipment is close to the ground potential. Due to the existence of the grounding resistance, the electrical equipment to the ground potential always exists. The bigger it is, the more dangerous it is when people touch it.However, if the grounding device is not provided, the voltage of the faulty equipment casing will be the same as the phase-to-ground voltage, which is much higher than the grounding voltage, so the danger will increase accordingly.
       The grounding of the power system, also known as the working grounding, is generally grounded at the neutral point of the substation or substation.The grounding resistance requirement for working grounding is very small, and a grounding grid is required for large-scale substations to ensure that the grounding resistance is small and reliable.The purpose of the working ground is to make the potential between the neutral point of the grid and the ground close to zero.The low-voltage power distribution system cannot avoid the phase line touching the shell or the ground after the phase line is broken. If the neutral point is insulated from the ground, the voltage to the ground of the other two phases will rise to three times the phase voltage, which may cause the work Electrical equipment with a voltage of 220 burned out.For the system with the neutral point grounded, even if one phase is short-circuited to the ground, the other two phases can still be close to the phase voltage, so the electrical equipment connected to the other two phases will not be damaged.In addition, the system can be prevented from oscillating, and the insulation level of electrical equipment and lines only needs to be considered according to the phase voltage.
       When lightning occurs, in addition to direct lightning, induction lightning is also produced, and induction lightning is divided into static blunt induction lightning and electromagnetic induction lightning.The most important method of all lightning protection measures is grounding.
       Common grounding types are as follows: working grounding, lightning protection grounding, protective grounding, shielding grounding, anti-static grounding, etc.
       Lightning protection grounding is a grounding system to prevent damage when struck by lightning (direct strike, induction or line introduction).
       Lightning protection grounding is a part of lightning protection measures, and its function is to introduce lightning current into the earth.The lightning protection of buildings and electrical equipment is mainly to use one end of the arrester (including lightning rod, lightning protection belt, lightning protection net and lightning suppression device, etc.) to connect with the protected equipment, and the other end to connect to the ground device. The lightning is directed towards itself, and the lightning current enters the earth through its down-conductor and grounding device.In addition, due to the side effect of electrostatic induction caused by lightning, in order to prevent indirect damage, such as house fire or electric shock, it is usually necessary to ground metal equipment, metal pipes and steel structures in the building.
       AC work grounding is to connect a certain point in the power system directly or through special equipment to the earth for metal connection.Working grounding mainly refers to the grounding of the neutral point of the transformer or the neutral line (N line).The N wire must be insulated with copper core.There are auxiliary equipotential terminals in the power distribution, and the equipotential terminals are generally in the cabinet.It must be noted that this terminal cannot be exposed; it cannot be mixed with other grounding systems, such as DC grounding, shielding grounding, anti-static grounding, etc.; nor can it be connected with PE wires.
       Safety grounding is to make a good metal connection between the non-charged metal parts of electrical equipment and the grounding body.In a photovoltaic power station, there are mainly inverters, components and distribution boxes that need to be grounded for safety protection.
       In order to prevent external electromagnetic field interference, the grounding of the outer casing of the electronic equipment and the shielded wires inside and outside the equipment or the metal pipes that pass through it is called shielded grounding.This grounding method is usually used for the grounding of the shielding layer of the RS485 communication line in the photovoltaic power station, and can effectively prevent the electromagnetic field from interfering with the communication when multiple inverters perform 485 serial communication.
       For some special inverter installation environments, such as installation in a dry computer room, the grounding to prevent the interference of the electrostatic inverter generated by the dry environment of the computer room is called anti-static grounding.The anti-static grounding device can be shared with the safety grounding device of the inverter.
       As a set of long-term operation systems, photovoltaic power plants need to be properly grounded during design and construction to reduce unnecessary operation and maintenance in the later stage, so as to ensure the long-term stable, safe and efficient operation of the system.