Suspected photovoltaic system fire? A poultry farm in Italy lost 20,000 hens

In early August, according to the Italian Photovoltaic magazine, firefighters in the province of Treviso responded to a fire that broke out in a poultry farm shed in the city of Volpago del Montero.

More than 20,000 hens were reportedly killed by smoke from the fire, and although the cause of the fire has yet to be determined, the local fire department said: "The fire may have been triggered by the photovoltaic system, which burned more than 1,500 square meters of the heat shield and produced a lot of smoke, causing tens of thousands of laying hens in the shed to suffocate."

Firefighters from the cities of Montebelluna, Castelflanco and Treviso helped at the scene of the fire, with a total of three fire engines and 16 personnel deployed to fight the blaze.

When using photovoltaic, how to protect the risk of fire, or minimize property damage?

With the acceleration of the solar photovoltaic process in the world, due to the complexity of the installation environment. The risk of fire is very high. More than 80% of power station fires are due to the DC side of the fault, if the DC side of the high voltage can not be turned off, there is a hidden danger of electric shock.

Therefore, before the arrival of the fire, the power station operation and maintenance personnel need to shut down the photovoltaic system and cut off the power supply to ensure the safety of the fire personnel and operation and maintenance personnel, as well as the stability of the entire power grid. Hence the rapid shutdown device.

What is a rapid shutdown?

Rapid Shutdown is connected to each photovoltaic module, is the United States National Electrical Code (NEC) first proposed photovoltaic power plant safety protection concept, the full name of Rapid Shutdown (RSD).

Now with the installation process of photovoltaic, in some countries such as Australia, the United States, Germany, etc., as the number of photovoltaic installations continues to rise, more and more firefighters require that "fire switches" must be installed in places equipped with photovoltaic systems to reduce the risk of electric shock when firefighters and operation and maintenance personnel are in photovoltaic operations.

As early as 2014, the United States issued the NEC2014 690.12 "Module level self-shutdown solution" standard, which made requirements for the rapid shutdown of photovoltaic systems.

According to the requirements of the NEC690.12-2017 regulations in the United States, the photovoltaic system must have the function of quick shutdown. With the distance to the photovoltaic matrix 305mm as the limit, within 30S after the fast shutdown device is started, the voltage outside the limit range is reduced to 30V below, and the voltage within the limit range is reduced to 80V below, which is the requirement to achieve "module level shutdown".

Why is Rapidnbsp;Shutdown (RSD) important?

Since the photovoltaic system is a live equipment, the voltage is high when generating electricity, and there is always current in the equipment and circuit, in the past photovoltaic system fire accident, even if the power grid is turned off, and the inverter is automatically turned off, the wire from the component to the inverter or controller is still live, DC high voltage is a huge hidden danger to the safety of operation and maintenance personnel and firefighters.

In an emergency, the Rapid Shutdown (RSD) function reduces the component voltage to a safe voltage to achieve rapid shutdown at the component level, providing higher personal safety for owners, installation and maintenance personnel, and firefighters.

How to achieve Fast Shutdown (RSD)?

The rapid shutdown function requires two devices: a transmitter and some receivers.

The transmitter is responsible for transmitting the fast shutdown power line signal to the DC wire between the PV module array and the inverter, and the receiver is responsible for detecting the signal on these conductors:

When the signal is present, the receiver remains inactive and the components work normally.

When the signal disappears, the receiver is responsible for reducing the photovoltaic module array voltage below the standard limit for a specified period of time, thus achieving a fast shutdown function.