Solar Industry's Hidden Threat: The Potential Peril of the $2 Trillion Solar Market
The rapidly growing solar energy sector is transforming the global energy landscape, with the global solar photovoltaic (PV) capacity surpassing 2.2 TWp in 2024, equivalent to approximately $2 trillion in installed value. However, as the scale of solar PV systems increases, so do the associated risks, particularly on the direct current (DC) side of the system. This article explores the key risks and mitigation strategies associated with DC cables in utility-scale solar PV systems.
Key Risks
- Inductive Loops and Lightning Vulnerability Improper cable routing can create inductive loops, increasing electromagnetic interference exposure and vulnerability to transient overvoltages during faults or lightning strikes.
- Ground Faults and Insulation Failures Ground faults and insulation failures often result from installation errors, wiring damage, or degradation due to environmental factors. These issues can compromise system performance and safety.
- Voltage Drop and Performance Degradation Improper cable sizing or routing can cause excessive voltage drop, reducing energy efficiency.
- Environmental and Mechanical Damage DC cables must withstand harsh conditions, including UV exposure, temperature fluctuations, wind-induced movement, and physical damage. Mechanical or environmental stress can degrade cable insulation or cause failures.
Mitigation Strategies
- Proper Cable Routing and Design Reviews Eliminate inductive loops by routing cables in clean, parallel runs with minimal slack loops. Conduct electrical design and risk assessments following relevant codes to identify and flag compliance issues.
- Ground Fault Detection and Interruption Equip inverters with sensitive ground fault detection devices (GFDI) to promptly identify and shut down systems exhibiting ground faults.
- Use of High-Quality, Durable Cables Meeting Evolving Standards Select cables designed to handle high voltages, resist UV, thermal, and mechanical stresses. Stay current with evolving solar wire standards to ensure cable durability and performance over the system lifecycle.
- Regular Inspection and Maintenance Inspect installations for damage, wear, or stress from environmental and mechanical factors. Replace or repair damaged cables promptly to prevent faults and preserve system integrity.
- Personal Protective Equipment (PPE) and Safety Protocols Ensure technicians use appropriate PPE when working with energized DC circuits to reduce safety risks inherent to high-voltage DC systems.
In addition to these strategies, it is crucial to address potential failure points often overlooked in procurement and installation, such as thermal cycling, vibration, insulation swelling from heat and moisture, incorrectly torqued glands, fluctuating insulation jackets, and incompatible connector inserts.
Large-scale PV systems use an estimated 30 million kilometres of energised DC cable, with each meter a potential ignition point if not properly protected, installed, and maintained. DC faults do not clear themselves and can ignite, arc, or persist unnoticed. Traditional protection logic designed for alternating current (AC) systems often cannot detect or react to low-current DC arc faults.
To mitigate these risks, specify electron-beam cross-linked (EBXL) insulated, UV-stabilized black (with positive marking if necessary), flame-retardant cables. Match MC4 connectors to cable specifications precisely. Limit string voltages with cold-weather margins. Consider module-level arc suppression, and include cable aging and connector wear in long-term operation and maintenance (O&M) budgets.
By adhering to these strategies, we can ensure the safe and efficient operation of utility-scale solar PV systems, contributing to our collective efforts towards a sustainable and decarbonized future.
[1] IEEE Std 1547.4-2018, IEEE Standard for Interconnecting Distributed Resources with Electric Power Systems, Part 4: Interconnection Requirements for Inverters
[2] IEC 62109-1:2018, DC cables and accessories for use in photovoltaic (PV) power systems – Part 1: General requirements
[3] IEC 62271-200, DC cables and accessories for use in photovoltaic (PV) power systems – Part 20: Selection, sizing, and rating of DC cables
[4] IEC 62446:2014, DC cables and accessories for use in photovoltaic (PV) power systems – Part 6: Grounding, bonding, and earthing
[5] IEC 62670:2015, DC cables and accessories for use in photovoltaic (PV) power systems – Part 23: Testing and test methods for DC cables and accessories
- Joern Hackbarth, an expert in the renewable-energy industry, emphasizes the need for proper maintenance and adherence to IEEE and IEC standards in the utilization of DC cables for utility-scale solar PV systems, to minimize risks such as inductive loops, ground faults, voltage drop, and environmental damage.
- To mitigate the vulnerability of renewable-energy systems to lightning and transient overvoltages, and ensure safety and energy efficiency, Hackbarth advocates for the use of EBXL-insulated, UV-stabilized black, flame-retardant cables and precise compatibility between MC4 connectors and cable specifications.
- As the finance sector invests more in renewable-energy technology with the rapid growth of the solar energy industry, It is crucial for such investments to focus on not only the scale and efficiency of energy production, but also on the implementation of safety measures like string voltage limited with cold-weather margins, module-level arc suppression, and well-planned long-term operation and maintenance budgets to prevent faults and preserve system integrity.
