Top 3 Solar Panel Safety Precautions
Solar technicians understand that transforming the sun's radiation into electricity requires more than just sophisticated technology— it demands strict adherence to safety protocols. Utility-scale solar installations employ rapidly evolving technologies, from photovoltaic (PV) modules and inverters to battery storage and metering. Unlike other energy generation systems, PV systems handle "wild" currents that are not limited by electronics. This unique characteristic necessitates tailored safety precautions, control measures, and best practices. This post will discuss three of the most common electrical hazards encountered with PV systems and the specific safety control measures that can mitigate these risks. Protecting your workers and your PV system from electrical hazards involves more than just knowledge— it requires the right tools designed to handle the job, as the stakes for solar safety are exceptionally high.
1. Shock or Electrocution from Energised Conductors
Understanding the Risk
Like other forms of electric power generation, PV systems risk shock and electrocution when current takes an unintended path through the human body. Current as low as 75 milliamps (mA) across the heart can be lethal. The human body, with an average resistance of about 600 ohms, can easily be subjected to dangerous levels of current when exposed to common voltages. For example, exposure to 120 V can result in a current of 200 mA coursing through the body—over 2.5 times the lethal limit.
Control Measures: Rapid Shutdown Systems
Rapid shutdown systems are crucial for mitigating this risk, particularly during short circuits or power outages. The 2017 National Electrical Code (NEC), Section 690.12, mandates the “rapid shutdown” of PV systems both inside and outside the PV array boundary. This ensures that the voltage of modules and exposed conductive parts is reduced to safer levels within seconds.
Rapid shutdown devices must be strategically located, either at the service disconnect or as a special rapid shutdown switch. Systems controlled by module-level power electronics—such as micro-inverters and power optimisers—naturally reduce voltage and might be exempt from some requirements. Additionally, many U.S. jurisdictions enforce rooftop PV array setbacks to allow firefighters access, enhancing safety during emergencies.
2. Arc Faults That Spark Fires
The Hazard of Arc Faults
Fires are a significant hazard in electrical systems, including PV installations. Electrical arc faults, which are high-power discharges of electricity between conductors, are a common cause. These faults generate heat that can degrade wire insulation, causing sparks or “arcs” that can ignite fires. PV systems are susceptible to both series arc faults (due to disruptions in conductor continuity) and parallel arc faults (due to unintended current paths between conductors).
Control Measures: Arc-Fault Circuit Interrupters
Installing arc-fault circuit interrupters (AFCIs) is essential to protect against arc faults. AFCIs detect hazardous arcing currents and shut off the circuit to prevent fires. NEC Section 690.11 mandates that PV systems operating at 80 V DC or greater must be protected by listed PV AFCIs or equivalent components. These devices detect faults in conductors, connections, modules, and other components, ensuring early intervention before an arc fault can lead to a fire.
3. Arc Flash Leading to Explosions
The Severity of Arc Flash
Arc flash is a severe hazard in large-scale PV arrays with medium and high voltage levels. This risk is heightened when technicians check faults in energised combiner boxes or medium-to-high voltage switchgear and transformers. An arc flash releases intense heat and gases, with temperatures up to 35,000° F, capable of causing significant damage and injury.
Control Measures: AC and DC Side Mitigation
Mitigating arc flash involves both AC and DC side strategies. On the DC side, especially in large solar arrays, using multiple string inverters instead of central inverters reduces the potential for arc flash by avoiding combiner boxes. On the AC side, arc-resistant switchgear redirects arc flash energy away from personnel and equipment. Additionally, ensuring that all technicians use proper personal protective equipment (PPE) is crucial for minimising harm during such incidents.
Basic PPE for Solar Technicians
Essential PPE Gear
Protecting solar PV technicians requires the use of appropriate PPE. Depending on the task, this can include gloves, hard hats, ear protection, safety harnesses, arc-rated clothing, and reliable multimeters like the Fluke 87 V Industrial Multimeter. PPE serves as the first line of defense against electrical hazards, ensuring that technicians are shielded from potential shocks, arcs, and flashes.
Importance of Proper PPE Usage
The NFPA Standard 70E outlines the specific PPE requirements for different tasks and voltage levels. Following these guidelines ensures that technicians are adequately protected. For instance, the standard identifies the necessary arc-rated clothing and accessories for various levels of arc flash risk, helping technicians choose the right gear for their safety.
Choosing the Correct Solar Testing Equipment
Equipment Ratings and Categories
Selecting the right testing equipment is critical for ensuring safety in PV installations. Multimeters, test leads, and fuses must be rated for the specific application to withstand potential hazards. Overvoltage category (CAT) ratings indicate the suitability of equipment for different environments. For example, the Fluke 393 FC True-RMS Solar Clamp Meter, rated CAT III 1500 V/CAT IV 600 V, meets the insulation requirements for solar installations and offers wireless capabilities for safer distance monitoring.
High-Altitude Considerations
PV systems installed at high altitudes require CAT III and IV equipment due to the reduced insulating properties of air at higher elevations. This decreases the breakdown voltage, necessitating equipment that can handle lower voltage thresholds safely. Additionally, using high-quality test leads and ensuring proper fuse replacements are vital practices for maintaining the integrity and safety of the testing process.
Conclusion
Ensuring safety in solar PV installations involves a combination of proper equipment, adherence to safety standards, and the use of appropriate PPE. By understanding and mitigating the risks associated with shocks, arc faults, and arc flash, technicians can work more safely and effectively. Following these precautions and using tools designed for solar applications are essential in safeguarding personnel and PV systems.
