Arc Detection: Why Modern PV Systems Are Safer Than Ever
AFCI technology detects arc faults at an early stage and helps minimize potential fire risks. Find out how your PV system recognizes and prevents danger.
Photovoltaic systems are considered safe — and for good reason. However, one danger is often underestimated: electrical arcs occurring directly on the solar modules. They can cause fires that are difficult to contain and hard to extinguish.
The safety of photovoltaic systems is ensured not only by strict standards that minimize electrical hazards (such as short circuits or electric shocks), but also by protective devices that prevent damage in the event of lightning strikes or voltage peaks and ensure safe shutdown in emergencies.
And this is exactly where AFCI technology comes into play: it detects arcs at an early stage, thereby helping to minimize potential fire risks.
What this article is about
1 PV fire safety statistics
2 Physics of an arc fault in a cable
3 Myths about DC optimizers
4 How AFCI technology works
5 The Fronius Arc Guard solution
Very low fire risk
In Germany — one of the largest photovoltaic markets in Europe with over 2 million installed systems — there have been 350 fires involving PV systems in the last 20 years. And the system itself was the actual cause of the fire in only 120 cases.
Have never caused a fire
Which equals 1 in 17,000 systems
Due to incompatible plug connections
* According to Fraunhofer ISE, "Recent Facts about Photovoltaics in Germany", updated status 18.08.2025.
Fire risk due to improper installation
The most common causes of fires in PV systems are material fatigue and corrosion, but the main reason is improper installation: series arcs caused by loose contacts, poorly crimped (i.e., mechanically compressed) plugs, damaged cables, or incompatible plug connections are particularly dangerous.
If, for example, MC4 plug connections from different manufacturers are installed in a PV system, they differ not only in materials but also in degradation and thermal expansion, which can lead to a temperature rise of up to 97 °C at the contact points.
The result? Arcs that can reach temperatures over 1000 °C; enough to ignite surrounding material and cause damage that is sometimes not covered by insurance. Therefore, the independent International Electrotechnical Commission (IEC) requires the use of plug components from a single manufacturer.
The process of arc burning in a conductor
1. No reduction in conductor cross-section occurs. Normal contact.
DC optimizers: Are they promising too much?
DC optimizers are often installed in PV systems to optimize power. From a fire safety perspective, they offer the (supposed) advantage of being able to shut down modules in an emergency.
If modern PV systems meet rapid shutdown requirements, optimizers can minimize the voltage on the PV module to a safe level in the event of a fire (e.g., below 30 V or even 1 V). This makes it easier for firefighters to safely extinguish the fire and reduces the risk of electric shock.
But there is a catch regarding the number of connections
Unfortunately, using power electronics on every single module comes with a large number of DC connections: compared to a system without optimizers, a system with optimizers requires roughly three times as many plug connections, increasing the likelihood of arcs and fire risk.
Furthermore, power optimizers are designed for an ambient temperature of 60 degrees Celsius. Therefore, in the event of an actual fire, it is highly likely that the optimizers will quickly start to melt rather than safely shutting down the module output.
Don't cut costs in the wrong areas
Thinking of saving money by using incompatible plugs or combination pliers instead of special tools? Buying a PV system can certainly be expensive, so it might be tempting to turn to an amateur electrician among friends or acquaintances to cut costs.
However, you should avoid cutting corners here, because you can only be sure the system has been connected according to all safety standards if you consult a professional. PV systems pose no higher fire risk than any other electrical system, but the relevant electrical safety regulations must be followed. Ultimately, it pays to focus on quality and professionalism.
What to look out for during installation
Arc Fault Circuit Interrupters (AFCI): How does it work?
AFCI systems detect dangerous series arcs by continuously analyzing electrical signals in the DC circuit. The technology checks the current signal for typical patterns indicating an arc. These include changes in the frequency spectrum of the current, impulsive current peaks, current flow even when voltage is interrupted, irregular noise, and recurring faults.
Digital signal processing and an intelligent adaptive algorithm are used to analyze and evaluate the recorded signals in order to reliably detect real electrical arcs and prevent false alarms. The affected circuit is disconnected within milliseconds, preventing a fire before it starts.
Susceptibility to interference from ambient noise
AFCI systems are highly sensitive to external interference, which also poses the biggest challenge: electromagnetic interference (EMI) from neighboring devices, switching operations, or atmospheric impacts (such as lightning strikes) can generate signal patterns similar to arcs.
If the AFCI misclassifies them, it can result in false tripping, causing an unnecessary shutdown of the PV system and associated performance losses. Modern technologies address this problem.
Fronius Arc Guard: safety included
Specifically designed for PV systems, the Fronius Arc Guard arc fault circuit interrupter is pre-integrated directly into Fronius inverters — both in software and hardware. Its activation is simple; the system requires no additional components (junction boxes or connection points).
This efficient technology is built on spectral arc detection based on FFT (Fast Fourier Transform). Innovative pattern recognition methods and a trained algorithm contribute to continuously improving detection accuracy.
Safer through the precautionary principle
Fronius Arc Guard operates on the precautionary principle — it detects and extinguishes arcs before they can lead to a fire. If an arc is detected, the inverter's power stages interrupt the transmission of electricity and stop feeding power into the grid. This interrupts the current flow and extinguishes the arc.
Although specific standards for AFCI systems in PV installations have been in place in the US since 2018, there are currently no standard requirements at the EU level. Fronius Arc Guard complies with international safety standards for arc detection, such as UL 1699B and IEC 63027, making it future-proof for global markets.
Did you know about Fronius Verto?
The powerful Fronius Verto inverter for agriculture, small businesses, large detached houses, and apartment buildings comes equipped with an automatic arc fault circuit interrupter (AFCI) as standard. Potential arcs are quickly detected and extinguished, increasing both safety and efficiency.
Conclusion
PV systems do not pose a fire hazard, but short-circuit arcs, for example due to damaged plug connections or incorrect installation, can still pose a risk. Integrating AFCI technology like Fronius Arc Guard offers a targeted solution: it detects critical patterns in the current flow and interrupts the circuit before a fire can break out.
AFCI is not a sign of inadequate safety; it is an intelligent form of additional protection that further enhances the already high safety level of photovoltaic systems.
Designing safe solar systems with AFCI technology
Total-Energo specialists will help you select Fronius inverters with the built-in Arc Guard function for your facility. We guarantee professional installation, compliance with all standards, and the highest level of fire safety.
