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Description of protective measures for photovoltaic inverters encountered by lightning

Sep 29, 2020

Description of protective measures for photovoltaic inverters encountered by lightning

Inverters are widely used in air conditioners, home theaters, electric grinding wheels, power tools, sewing machines, DVDs, VCDs, computers, TVs, washing machines, range hoods, refrigerators, video recorders, massagers, fans, lighting, etc.


  In order to stably operate the megawatt-level photovoltaic power generation business and increase profitability, power generation operators must have knowledge of electrical equipment to build and operate suitable photovoltaic power generation systems.


   First of all, the impact of lightning on photovoltaic power plants is divided into two types, namely "direct lightning" and "inductive lightning". As its name suggests, direct lightning refers to the photovoltaic power generation system being directly struck by lightning; induced lightning refers to when nearby lightning strikes, the electrical energy generated by the lightning strike is conducted through the transmission lines and grounding wires in the photovoltaic power generation system, imposing far Voltage exceeding the rated level may cause damage to the equipment.


   Regarding direct lightning strikes, it can basically be avoided by reducing the height of the photovoltaic system from the ground during design. Unlike windmills, etc., MW-level photovoltaic power plants with low ground height have hardly ever been struck by lightning, and it can be said that direct lightning strikes will basically not affect them. However, photovoltaic power plants in mountainous areas and other places may still be struck by lightning. At this time, it is necessary to install lightning rods or lightning protection [industrial electrical appliances network-cnelc] conductors around the solar panels.


In terms of induced lightning, lightning falling on buildings or the ground near photovoltaic power plants will cause the potential of the grounded part of the power generation equipment (voltage at a certain point compared to the reference point) to rise, and the induced potential will cause the main circuit in the power generation equipment such as PCS Produce a transient abnormal high voltage-surge voltage. This voltage will destroy the insulation part of the power generation equipment and cause equipment damage.


  As a countermeasure, the junction box and PCS are generally equipped with a lightning arrester (SPD) to deal with intrusive lightning surge voltage. Lightning arresters use a mechanism that causes a short circuit when a voltage above a certain level is applied to prevent damage to power generation equipment. Moreover, a large-capacity capacitor is installed on the PCS to stabilize the unstable solar energy. This equipment also plays an important role in suppressing the surge voltage.


  PCS is equipped with over-voltage and over-current protection devices, which will disconnect the DC circuit to prevent the expansion of accidents caused by lightning strikes. However, it is important to repair as soon as possible after a failure, so as to minimize the loss of power generation. TMEIC saves the voltage and current waveforms 10μs before the protection device is activated in the memory card to grasp the surge energy of the intrusion and lock the faulty components in a short time, thereby shortening the repair time.


  In the event of an accident such as a lightning strike, the voltage and current waveforms 10μs before the start of the protection device will be stored in the memory card, and the malfunctioning component will be locked in a short time. (Data comes from the author)


   In addition, it is possible to adopt SPD (surge protector) measures when dealing with the surge voltage of metal wires used to transmit monitoring signals. The communication of remote monitoring monitors generally uses optical cables instead of metal cables that are easily affected by lightning.