A prominent California utility company faced safety risks from hidden electrical faults in its underground distribution vaults. Using advanced acoustic imaging, the company discovered how early fault detection can prevent dangerous arc flash incidents and protect field technicians.

Addressing Hidden Risks in Coastal Underground Vaults

Underground medium- and high-voltage (MV/HV) distribution vaults are often exposed to challenging environmental conditions that can compromise equipment integrity. Moisture, temperature fluctuations, and limited ventilation can accelerate the degradation of critical electrical components, such as t-body connectors, leading to reduced reliability and increased maintenance demands.

During a routine inspection inside an underground vault, a technician was disconnecting a medium-voltage cable when a sudden arc flash erupted. The source was traced to a degraded t-body connector that had developed internal tracking and moisture intrusion over time. The arc flash caused severe burns to the technician’s hands and arms, highlighting the hidden dangers posed by aging components in confined electrical environments. In response, the company launched a safety initiative to better understand the early warning signs of equipment failure. Their goal was to determine whether acoustic imaging technology could detect partial discharge activity and other indicators of deterioration before they escalated into safety hazards.

Traditional Methods Offer Limited Visibility into Hidden Faults

Routine vault entry typically includes:

• Visual Inspection – Checking for visible damage, smoke, or signs of distress
• Atmospheric Testing – Ensuring no dangerous gases are present
• Ventilation – Preparing the space for safe access
• Equipment Isolation – De-energizing systems where possible
• Entry and Repairs – Technicians enter to perform maintenance

While thermal imaging may sometimes be used remotely via drones or hot sticks, it is not common practice and often fails to identify early electrical ionization that occurs before heat buildup.

Advanced Acoustic Imaging Detects Issues Before They Become Dangerous

The Flir Si2-PD offers a breakthrough solution for underground electrical inspections. Its intuitive acoustic imaging technology detects early-stage partial discharge and simplifies the data into clear, visual results, while the built-in analytics automatically identifies fault types and their severity. Together, these features deliver actionable safety insights, enabling operators to make quick, confident decisions before entering energized vaults.

The Si2-PD displays partial discharge in real time, with on-device severity analysis delivering immediate decision support.

Key Benefits:

Acoustic imaging with the Si2-PD provides several safety and operational benefits:

• Early Fault Detection – Identifies electrical ionization before heat buildup occurs
• Non-Contact, Remote Inspection – Allows safe detection from outside energized areas
• Best-In-Class Performance – High microphone sensitivity captures subtle discharge signals
• Ease of Use – Designed for field technicians, reducing dependency on expert-level analysis

Partial discharge detected on a t-body connector with the Flir Si2-PD.

A Proven Tool for Preventing Arc Flash Incidents

The utility company’s engineering team concluded that the Flir Si2-PD is an effective tool for preventing technician exposure to potential arc flash hazards. The Si2’s advanced acoustic performance and intuitive interface enable faster and safer inspections, supporting the company’s goal of zero harm in field operations.