Renewable energy is safe by design. It is there to make the world a better place, greener, and save on CO2 pollution. The U.S. Energy Information Administration (EIA) projects a historic milestone in 2024 as combined electricity generation from wind and solar is set to surpass coal for the first time on record. [see the article]
As I write this in South Africa,Recent data by Eskom suggests that from March 2022 until the first quarter of 2023, the amount of electricity generated by Small-scale Embedded Generation (SSEGs) in the form of solar panels has risen 350%. [see the article] All countries differ in regulations and installation methods. The entire world is striving to adopt the safest possible approach, considering factors such as the environment, voltage systems used in different countries, governance, etc.
Now, let’s examine a system that came close to complete destruction. However, before doing so, let’s explore some facts about solar systems and the risks that arise, even with a well-done installation by professionals according to specifications.
We need to understand that not all installed systems are done correctly according to designs. There are a few reasons for this:
- Firstly, there is always a human factor involved, and people make mistakes (this is one of the topics we will explore).
- Hot Connections
- Not fully trained personnel in the installation team
- MC4 Connections
- And more
- Not using Quality DC Products and still using AC products that can handle a certain amount of DC Current or Voltages.
- Polarity breakers not installed correctly
- Non-Polarity breakers designed for DC are available, eliminating confusion on the flow of current. [YouTube Video]
- Polarity breakers, can not be disconnect under load, make it confusing for customers in emergencies situations.
- MC4 connections are the weakest link in solar array systems. A solution called the Arcbox [website], made of fire refractory materials, safeguards against failures. If they fail, the Arc fire will be contained inside the Arcbox, potentially saving the system and property from being burned down.
- Maintenance is crucial. With overwhelming demand, installation companies can’t always get to maintenance promptly. Training for installation can take years, but there needs to be less technical training for companies to perform maintenance and report serious issues to professionals.
- Damaged panels should be taken seriously, as there is a misconception that they are not dangerous, only affecting the system’s performance. Maintenance must check the system and make it urgent to replace any damaged panels or parts on the PV Systems. [YouTube Video]
- Thermography must become a part of any installation, using infrared to detect problems that the naked eye and even instrumentation might struggle to detect. [YouTube Video]
Now, let’s examine a situation that happened in South Africa in December 2023. We have the authority to use the footage and background of this insurance claim for educational purposes, without disclosing any personal information.
According to the information we have received, a 150kw 3-phase High Voltage system with 3 x 50KW Hybrid inverters and battery backup on a farm in Limpopo province had a fire in the inverter room. They have used 7 x fire extinguisher didn’t completely stop the flames, as for the the installer from Johannesburg (200km) was too far away to assist. The fire kept reigniting after extinguishing it.
The installer advised cutting the live power cable at the panel array. A local installer was contacted, who cut the positive of the array to stop arcing and extinguished the fire. Fortunately, no one was electrocuted. After cutting the wires, the fire was contained and eliminated.
Their conclusion was that the arcing took place inside the conduit duct entering the inverter room, thereby I do not agree, Although this is the only information we can work with, we can make our own conclusions based on the given photos for learning purposes.
For this incident, Rapid Shutdown Devices (Fireman Safety Switch) could have been used to disconnect the panels beyond the point of the fire quickly and safely. These devices are not mandatory in South Africa but can add value and safety. There are two main types:
- String Type Rapid Shutdown devices (RSD)[YouTube Video] – They come in different sizes depending on where they will be installed and how many strings. They can switch off by the RSD or via an installed cable where needed. They will also switch off immediately when reaching 70 degrees Celsius.
- Modular Type Rapid Shutdown Device (RSD)[YouTube Video] – They are installed very close to the panels themselves via MC4 Connections. They come in different types and sizes to meet specific needs.
Although these Rapid Shutdown devices systems would be able to disconnect to a certain point, they can’t switch off the panels. They are not mandatory in South Africa, but in some countries and states in the USA, Singapore, Thailand etc. they are mandatory. Concerns about this include the risk of adding connections on the cables coming from the panels. String Types RSD requires exact MC4 Connectors from the manufacturers to ensure a perfect match on the MC4 connections, most will include it within the box, but if not make sure from your supplier to buy it separate to make a perfect connection.
In this particular incident, either type of Rapid Shutdown device could have disconnected the panels beyond the fire point. The String Rapid shutdown Device can also now be installed where they cut the wires at a very risky and extremly dangerous attempt. Cutting live wires with lethal amounts of volts and amps was risky and now leading to recommendation of the complete replacement of all wires, rusulting to a very high and risky disconnect. On this it was estimated on 8000m of cabling.
Another option would be to block out the sun using a product called PVStop.[Website] It comes in a fire extinguisher that sprays a black polymer over the center of the panels, bringing the voltage and amps to a very low level by blocking out the sun. This can minimize damage and risks, especially in large systems.
The report suggested that the fire started inside the conduit entering the inverter room, possibly due to damaged wires during installation or rodents chewing the cables. However, based on pictures, the suspicion and conclusion were that it started inside the PV Combiner box, possibly at the bottom of the DC Mini Circuit breaker.
This could be caused by a hot connection, loose exposed wires not using bootlace ferrules, or the use of polarity breakers. Polarity breakers, if used, could have caused the ignition if the flow of the current was disconnected incorrectly.[YouTube Video] AC fuses used in the combiner box are also dangerous if they fail, especially at high voltage.
Quality of components inside PV Combiner boxes is crucial, and some installers try to save money here, risking the system’s safety. Using thermal technology after installation and during maintenance can detect problems early, especially with direct current, which is often underestimated.
To prevent re-ignition risks, additional safety features like a DC Moulded Case Circuit breaker between the PV Combiner box and the MPPT Charge controller of the inverter can be added. This would disconnect the system in emergencies without cutting any wires.
All cables need replacement after such incidents, and it’s safer to replace them all rather than risk missing something that could lead to future issues. The same goes for PV solar cables after cuts made outside at the solar panels. MC4 Connections at the cuts, with an added Arcbox, can protect against risks like bad connections and erosion.
Another option is to add a Rapid Shutdown Device – String Type at the place where the cables were cut. This would add value and safety for future emergencies and maintenance inside the PV Combiner box.
Although fires with solar systems are rare, it takes only a small fault or damaged component to cause significant damage and risk serious injury or loss of life. Investigating these incidents thoroughly is crucial to making systems safer and eliminating risks in the future. It is essential to implement solutions like PVStop in emergency situations to safely de-energize systems and prevent further
