Understanding a DC Arc: Why PV Connector Faults Deserve Serious Attention

Understanding a DC Arc: Why PV Connector Faults Deserve Serious Attention

Solar PV is one of the most important energy technologies in South Africa, but every PV system must be treated with the respect due to live electrical infrastructure. One of the most misunderstood hazards in a PV system is the DC arc: a high-energy electrical discharge that can form when current jumps across a damaged, loose, contaminated, poorly crimped, mismatched or ageing connection point.

A DC arc is not merely a small spark. Under the wrong conditions, it can become a sustained plasma event capable of producing extreme heat, damaging electrical components and igniting nearby combustible material.

The infographic used in this article is illustrative and conceptual. It is not intended to represent an exact measurement of arc temperature or arc distance. Its purpose is to help asset owners, installers, risk managers, insurers and first responders better understand why DC-side PV faults must be taken seriously.

What is a DC arc?

An electrical arc occurs when electricity passes through air or another gap between conductive points. In a PV system, this can happen at weak points such as DC connectors, damaged cables, poor crimps, loose terminations, incorrect connector pairing, moisture ingress or degraded insulation.

When the gap becomes conductive, the air can ionise and form a plasma path. This plasma path allows current to continue flowing across the gap, generating intense localised heat. The hottest area is normally the arc core, with heat intensity reducing as distance increases from the core.

The exact temperature of an arc depends on many factors, including voltage, current, arc gap, conductor material, airflow, contamination, moisture, surrounding materials and how long the fault remains active. In severe arc-flash conditions, electric arcs can reach temperatures exceeding 35,000°F / 19,400°C. That figure should not be read as the guaranteed temperature of every PV connector fault, but it does show why electrical arcs are treated as a serious safety hazard.

Why DC arcs are especially dangerous in PV systems

PV systems produce direct current on the solar-array side of the inverter. This matters because DC does not naturally pass through zero in the same way alternating current does. With AC, the current crosses zero many times per second, which can help interrupt an arc. With DC, there is no natural zero-crossing, which means an established arc can be harder to extinguish.

This is one of the reasons PV DC faults are so important. While sunlight is present, the PV array remains an energy source. Switching off the inverter or the building’s AC supply does not automatically mean that every DC conductor on the roof is safe. If the array is still exposed to light, DC voltage can remain present.

For this reason, PV safety must be understood from the roof down, not only from the inverter or distribution board. The DC side of a PV system deserves its own inspection discipline, its own risk controls and its own emergency-response planning.

Why PV connector faults matter

Many PV fire risks do not start because the solar panel itself has failed. They often begin at connection points. A connector may look small compared to the rest of the system, but it can become a high-risk location if it is incorrectly assembled, poorly crimped, mismatched, damaged, contaminated or exposed to moisture.

Typical causes and warning signs can include:

• Poor or incomplete crimping
• Connector halves from different manufacturers being paired incorrectly
• Loose or partially engaged connectors
• Moisture or water ingress
• Dust, dirt, corrosion or foreign particles on contact surfaces
• Heat cycling and ageing over time
• Cable strain or unsupported cable movement
• Melted, discoloured or cracked connector housings
• Arc-fault, ground-fault or insulation alarms
• Unusual heat signatures detected during inspection or thermography

In simple terms, a weak connection can create resistance. Resistance creates heat. Heat can degrade materials further. As the fault worsens, the connection can move from overheating to arcing. Once an arc is established, the risk can escalate quickly.

The example: 1000 V × 10 A = 10 kW

In the infographic, we use a simple example: 1000 volts multiplied by 10 amps equals 10 kilowatts of available electrical power in the fault circuit.

This does not mean that every PV arc converts all of that energy into one neat heat figure. Real arc behaviour is more complex. However, the example helps explain why even a relatively small-looking DC-side fault must not be ignored. A high-voltage PV string can carry enough available energy to sustain a dangerous event if the fault conditions are present.

This is why LTV Technologies & Supplies always encourages a risk-based view of PV systems. The question should never be only, “Is the system producing power?” The question should also be, “Is the system safe, inspected, protected, documented and ready for emergency conditions?”

South Africa’s PV growth makes this conversation urgent

South Africa has seen rapid growth in rooftop and commercial PV installations. This growth is positive and necessary, but the safety conversation must grow with it.

PV should never be treated as a once-off appliance installation. It is live electrical infrastructure exposed to weather, heat, UV, wind, roof movement, animals, dust, workmanship variation and years of operational ageing. A system that looked neat on installation day still requires inspection, maintenance and risk review over its life.

For commercial, industrial, agricultural and high-value properties, the consequences of a PV-related fire can go far beyond equipment damage. It can affect business continuity, insurance claims, tenant safety, staff evacuation, firefighting access and post-incident recovery.

Protection is not a replacement for workmanship

Good PV safety starts with correct design and compliant installation. Protection products should never be used as an excuse for poor workmanship.

A responsible PV safety approach should include:

• Correct system design and component selection
• Properly rated DC equipment
• Correct connector pairing and manufacturer compatibility
• Approved crimping tools and correct crimping procedure
• Good cable management and strain relief
• Clear labelling and documentation
• Commissioning checks and insulation testing where applicable
• Routine visual inspection
• Thermographic inspection where practical
• Maintenance records and corrective-action tracking
• Emergency-response planning for fire teams and site staff

Once these fundamentals are in place, additional protection at known risk points can strengthen the overall system safety profile.

Where ArcBox fits into the risk-control picture

DC connectors are one of the known weak points in many PV systems. This is especially relevant where connectors are assembled on site, exposed to harsh conditions, installed close to combustible material or located in areas where access is difficult after installation.

ArcBox is designed as an additional protective enclosure around DC solar connectors. Its role is to help contain a connector arc event and reduce the risk of that event spreading to nearby combustible material.

At LTV Technologies & Supplies, we see ArcBox as part of a broader PV safety approach. It does not replace compliant installation, good workmanship, inspection or maintenance. Instead, it adds another layer of risk control at a practical and important point in the system.

Where PVStop fits into emergency readiness

PVStop addresses a different but equally important part of the PV safety challenge: emergency de-energisation at module level.

During daylight, PV modules can continue producing DC energy even when parts of the system are isolated. In emergency situations, this creates a challenge for first responders, facility managers and fire teams. PVStop is designed to block light to the PV module surface, reducing generation and assisting with emergency DC hazard control.

Together, technologies such as ArcBox and PVStop support a more complete PV safety strategy: reducing the risk of connector-related fire spread and improving emergency readiness when a PV system must be made safer during or after an incident.

The LTV Technologies & Supplies position

At LTV Technologies & Supplies, in association with our operational company Civitas Risk Control, we believe PV safety must move beyond basic compliance thinking. Compliance is essential, but risk management goes further.

Our focus is on practical PV safety, risk assessment, emergency readiness, training, awareness and the responsible introduction of Tier-1 safety technologies into the South African market.

Solar PV is safe and valuable when designed, installed, inspected and maintained correctly. But small DC-side faults can create high-consequence fire risks if they are ignored. That is why connector protection, workmanship, inspection and emergency planning all matter.

The future of solar in South Africa should not only be about more installed capacity. It should also be about safer, better-maintained and better-protected PV infrastructure.

Closing thought

A DC arc should never be dismissed as “just a spark.” In the wrong place, under the wrong conditions, it can become the start of a serious fire event.

Understanding the risk is the first step. Managing it properly is the responsibility of everyone involved in the PV value chain: manufacturers, installers, property owners, insurers, facilities teams, maintenance providers and emergency responders.

Protection matters because prevention is always better than recovery.