An arc fault happens when an electrical current jumps across an air gap between conductors, or between a conductor and earth, often due to insulation failure, loose connections, corrosion, or mechanical damage. Think of it like a lightning bolt—but contained inside a metal box.

When it occurs, the arc generates extremely high temperatures—up to 20,000°C—which can vaporise copper, blast open panels, and cause fire or explosion within milliseconds. The sudden release of pressure and heat can be deadly to nearby personnel and severely damage equipment.

Containment vs Prevention

In a perfect world, arc faults would never occur. Good installation practices, insulation testing, thermal imaging, and proper maintenance all reduce the risk. But in real-world conditions, faults still happen—especially in older gear, dusty environments, or where vibration and moisture are constant threats.

So the industry has adopted a layered approach. We try to prevent arc faults with good design and maintenance—but we also design switchboards to contain the fault if one occurs.

Arc fault containment doesn’t stop the fault from happening—it stops it from hurting anyone.

How Arc Fault Containment Works

Arc fault containment focuses on making sure that, if a fault does occur, the explosive pressure, molten metal, and fire are safely handled within the structure of the switchboard.

Here are the main ways containment is achieved:

1. Reinforced Enclosures

Switchboards are built with high-strength metal—usually steel—that can withstand the pressure of an arc blast. Panels are often double-layered, bolted tightly, and internally braced to resist deformation. The goal is to prevent any doors or covers from flying open during a fault.

2. Pressure Relief Systems

To avoid catastrophic rupture, some switchboards are fitted with pressure relief flaps or “chimneys.” These components direct the blast upwards or backwards, away from the operator. In some cases, hot gases are released through a controlled pathway, ensuring that the force doesn’t harm people standing in front of the board.

3. Internal Separation

Compartmentalised designs separate different sections of the board so that an arc fault in one compartment doesn’t spread to others. For example, the incomer, busbars, and outgoing feeders might all be separated by metal barriers.

This doesn’t just limit damage—it also gives operators a better chance of identifying and isolating a fault quickly.

4. Arc-Resistant Windows and Seals

Any viewing windows or access panels must be able to withstand the same pressures as the rest of the enclosure. Gaskets and seals are also chosen for their thermal and mechanical durability.

Australian Context: Why It Matters Locally

In Australia, we deal with tough conditions—heat, dust, humidity, corrosion, and remote-site operations are all part of daily life for many electrical installations. That makes the risk of insulation degradation, vermin intrusion, and arc-prone faults even more likely.

Arc fault containment has become a key consideration not just in industrial switchrooms, but also in utilities, renewable energy, mining, and public infrastructure projects.

Some Australian manufacturers, like NOJA Power and PTAS, have invested heavily in arc fault containment technology. For example:

NOJA Power’s OSM Reclosers are designed to contain internal arc faults and vent gases safely through the top of the pole-mounted enclosure.

PTAS’s Arc Fault Containment Switchboards are tested to IEC standards and rated to handle 20 kA faults for 0.3 seconds, ensuring that the board doesn’t become a safety hazard even during catastrophic internal failure.

These local products demonstrate that Australian-made gear can meet international safety expectations and be tailored for our unique environment.

Standards and Testing

While I won’t reference US standards, it’s worth noting that Australia typically aligns with IEC (International Electrotechnical Commission) standards. Arc fault containment is specifically addressed under:

IEC 61641, which defines how switchboards should behave during an internal arc fault and outlines the required testing methods.

IEC 62271-214, for medium-voltage switchgear with internal arc classification (IAC).

In Australia, switchboard builders working to AS/NZS 61439 still have the option of demonstrating arc fault containment as a design verification feature, though it’s not yet a compulsory requirement under all conditions. Some utility providers or mine sites may specify arc containment as mandatory for certain applications.

To achieve compliance, a switchboard must undergo testing where a high current (usually 8–50 kA) is injected to create a deliberate arc fault. The switchboard passes if no panels blow off, no external flames are observed, and no indicators placed around the enclosure are damaged.

Arc Containment in Low-Voltage vs Medium-Voltage Boards

In low-voltage systems, containment is often achieved through robust design and testing, as described above. In medium-voltage applications—like substations and mining—arc containment becomes even more critical, as the energy levels involved are far greater.

Some MV switchgear includes arc-quenching systems or uses gas-insulated compartments to minimise the chances of an arc in the first place. Even so, structural containment remains a vital backup.

Arc Fault Detection: A Complementary Approach

In addition to containment, more advanced systems now include arc detection relays that use light sensors and current monitoring to detect a fault in under 1 millisecond. These relays trip the main circuit breaker almost instantly, reducing the energy of the arc before it can do major damage.

This is especially useful in larger installations where reducing arc energy can limit the severity of the event and make repairs quicker and cheaper.

But even with fast detection, containment is still required—because it takes a finite time (even milliseconds) for breakers to open, and during that time, pressure and heat build up.

When Should You Specify Arc Fault Containment?

If you’re an engineer, project manager, or contractor, you might wonder: when is arc containment necessary?

The answer depends on:

The fault level at the point of installation (higher prospective fault currents mean greater risk).

Whether operators will be working in close proximity to live equipment.

The criticality of the installation—hospitals, mining sites, utility substations, and renewable hubs often demand higher safety margins.

Whether your client has specific internal arc requirements in their technical specifications.

If you’re dealing with a high fault level and any chance of someone needing to operate the switchboard while it’s live, arc fault containment should absolutely be considered. It’s not just a regulatory checkbox—it’s about protecting lives.