Arc fault protection: new IEC standard 62271-200

With changes to the IEC standard and a number of recent accidents electrical engineers are more aware of the hazard of arc flash events. Last month, a contract employee of one of the industry leaders suffered burns to his hands after an arc flash. He was quickly taken to hospital for treatment to his burns and is now recovering. This is not an isolated incident and could have easily been more serious or fatal.

Beyond injury to the individual and damage to the plant there is also the possibility of litigation. A city postal facility in Portsmouth, New Hampshire was recently inspected following employee complaints of potential electrical and arc flash hazards. They are facing $350,000 in fines for alleged safety violations involving electrical hazards. The Labor Department will also be filing "an enterprise-wide complaint" against the U.S. Postal Service for electrical work safety violations.

Awareness is the first step in solving the problem, like this example from Assistant Secretary for Washington State Ferries David Moseley: "There is a theoretical possibility of an arc flash and that's why we have to ensure that all of our maintenance work on the generators are done very, very safely, and we always have and we will continue to do so."

An alternative strategy is to protect personnel, but simply adopting a full PPE kit doesn’t provide adequate protection from arc fault. Even with the full PPE kit there is still a high likelihood that you’ll get burnt in a serious arc flash incident.

MVX soft starter in an L-series panel featuring arc fault resistance.

A better plan is to select and install switchgear panels that will prevent and contain the arc fault entirely. This is done by selecting a mechanical interlocking system connected to the earth switch that will prevent access to live panel compartments. Also select panel systems that control and manage an arc event in to comply with the new standard IEC 62271-200.

IEC 62271-200 for metal-enclosed medium voltage switchgear and control gear covers the requirements of internal arc fault testing and provides instruction to classify the types of panels according to their ability to provide safety, service continuity and maintainability in the event of an arc fault.

MVX L-series panel undergoing arc fault testing.

The IEC testing program involves deliberately creating an arc event at multiple locations inside the enclosure. A surrounding rig of cotton fabric (simulating human skin) will prove that the arc event is contained, if the cotton is not ignited.

Not all arc fault classifications are the same, as there are three types of accessibility and a test value. The internal arc classification (IAC) accessibility level is defined as either:

• A (authorised personnel only), B (unrestricted accessibility including public), or C (restricted by installation out of reach).
• F (front access), L (lateral access) and R (rear access)

For example, IAC AFLR 31.5 kA, 1 s, can be defined as able to contain an arc event up to 31.5 kA for a duration of 1 second, along the front, sides and rear of the enclosure.

Bottom line is when selecting switchgear panels be sure to ask for the detail of IAC classification.

AuCom recently released the MVX soft starter with L-series panels that contain an arc fault event to a single compartment within a panel, and then discharge the harmful gases via a ventilation shaft. Arc damage is so well contained that a neighbouring compartment will exhibit no evidence of damage.

This video shows AuCom’s testing program for arc fault with more information about arc events. The same system includes interlocking that will only allow access after live connections are disconnected.

When suitable arc containment and interlocking is specified for switchgear panels, electrical engineers are at minimal risk. With a prevention and isolation strategy, rather than a protection strategy, our friends and colleagues should not be at risk from arc events. Let’s keep each other safe!