Case Study: Arc Flash Incident in a Medium Voltage Cubicle

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During the preparation phase of a retrofit project, an operator opened the door of a live medium voltage (MV) cubicle to take measurements. While working outside the enclosure, their tape measure accidentally slipped and fell inside, making contact with exposed conductors.

The result: A sudden arc flash occurred, causing severe burn injuries and significant equipment damage.

This incident highlights several critical risks:

• Even indirect interaction with live equipment can trigger an arc flash.
• Foreign objects, such as tools or loose components, can easily become ignition sources.
• MV cubicles, despite controlled access, require robust design and operational safeguards.

To prevent similar incidents, Schneider Electric recommends:

• Selecting MV switchgear with Visible Disconnect Indicators (VDIS) to confirm safe disconnection.
• Implementing interlocks to prevent unsafe switching sequences.
• Using remote monitoring and operation to reduce direct human interaction.
• Applying IEC/EN 61936-1 and IEC 62271-200 standards for arc fault protection.

→ Learn more in the Electrical Worker Safety Guide: Explore practical design strategies and technologies to reduce arc flash risk.