The Killer of Photovoltaic Power Plants-DC Arc

Because of the requirements of carbon neutrality and carbon peaking, the new energy industry is now particularly popular. Everyone is increasingly agreeing with photovoltaic power stations, and more and more people are entering the photovoltaic industry. However, the level of people engaged in this industry is uneven, and many people do not pay attention to DC arcs, which leads to a large number of accidents.

Arc is a kind of gas discharge phenomenon. The instantaneous spark generated by current passing through some insulating medium, such as air, is called arc. Both direct current and alternating current produce arcs. Sometimes when we plug in the socket, we will see sparks, which is an AC arc. In a DC system, such an arc caused by a photovoltaic cell string is called a DC arc. In contrast, DC systems are more likely to generate arcs than AC systems, and once an arc occurs, it is more difficult to extinguish the arc.

In a photovoltaic power station, the photovoltaic panels emit DC electricity, which is converted into AC electricity only after passing through the photovoltaic inverter. The voltages of PV panels are very high, ranging from a few hundred volts to a maximum of 1500 V. In fact, a few tens of volts are enough to produce a DC arc, which can produce high temperatures of up to 4200 degrees. When four photovoltaic panels are strung together, the general voltage will reach about 120 volts. The positive and negative connections of the wires immediately produce a DC arc, and in just a few seconds, the high temperature allows the copper DC cable to melt straight away and turn into copper drops onto the ground. The melting point of copper is 1083 degrees, molten copper if dripping to many wooden roof of the villa consequences are unimaginable, most likely to cause a fire, some of the European villa fire is due to the roof of the photovoltaic power plant DC arc caused. Therefore, the DC arc protection of photovoltaic power plants is very important.

So, why does a photovoltaic power station produce a DC arc? The main reasons for the occurrence of DC arc are: the terminal or the fuse connection is not compressed, the busbar bolt is not tightened, the connection is oxidized, the wire insulation is reduced, the equipment insulation is defective, and so on.

What are the hazards of DC arc to photovoltaic power plants? The first is the damage to the equipment. Combiner boxes, DC cabinets, battery panel components, connectors, junction boxes, etc. are burned out. The second is power loss. Any failure will cause less or no power generation. The third is safety hazards. Fires can endanger personal and property safety.

What is the probability of an electric arc being generated in a PV power station? Take a 10MW power station for example, there are about 80,000 junction box connectors and 4,000 terminal blocks, plus the internal weld joints of the battery panels, the DC cabinet and the internal nodes of the inverter, all adding up to at least 84,000, so if the probability of failure is 1 in 10,000, there are 8 of them, so the probability of occurrence is very high.

How to Avoid DC Arc in Photovoltaic Power Station?

First, be sure to use regular and qualified products, not counterfeit and shoddy products. Such as Mingguan’s mc4 inline fuse connector and split junction box.
Secondly, the number of nodes should be reduced as much as possible.

Third, the construction personnel must use professional tools and must be trained and qualified by vocational training and examination before they are put on the job.
Fourth, after the power station is installed, relevant inspection must be carried out.

Fifth, there must be corresponding detection tools, such as this DC arc detection sensor, they will alarm and cut off the circuit once they detect DC arc to eliminate hidden dangers.
Sixth, there must be an energy monitoring platform to monitor all operational data in real time, so that once hidden dangers are found, personnel can be notified immediately to deal with them.

In fact, DC arc is not terrible. As long as you master the correct method and use scientific countermeasures, you can effectively prevent and deal with it. Just like AC power at home, safety is completely guaranteed. Through relevant technical means, the problem of DC arc prevention and control can be solved at low cost.