New Standards Set for Underground Mediumvoltage Cable Safety

Electrical safety begins underground. Medium-voltage (MV) cables, as vital components of urban power networks, require careful consideration of burial depth to ensure system stability and public safety. But what exactly constitutes a safe and compliant depth for these cables? This article examines the standards and specifications that guide these critical engineering decisions.

The 0.7-Meter Standard: A Calculated Requirement

Current electrical industry standards and regulations establish 0.7 meters as the minimum burial depth for directly buried medium-voltage underground cables. This measurement isn't arbitrary—it results from comprehensive analysis of mechanical protection, thermal stability, and resistance to external damage. Shallow burial risks mechanical damage from surface activity, including potential service interruptions from vehicle traffic, while excessive depth increases installation challenges and maintenance costs.

Precision Installation: The Protective Layers

Meeting the depth requirement alone isn't sufficient. Installation quality proves equally crucial. Standards mandate uniform placement of at least 50 millimeters of fine sand surrounding the cable, creating a buffer against sharp objects in the soil that might damage the outer sheath. Above this sand layer, hard protective materials like bricks or concrete slabs provide additional defense against external forces. These measures effectively "armor" the cables, extending their operational life and reducing failure rates.

Adapting to Special Conditions

Certain environments demand adjusted burial depths. In high-traffic roadways or agricultural areas with subsurface tillage, cables typically require burial at least 1.0 meter deep to ensure safe operation and prevent service disruptions from surface activities.

Spacing Considerations: Horizontal and Vertical

Beyond depth, careful attention must be paid to spacing between cables. Regulations specify that MV underground cables must maintain at least 0.6 meters from underground building foundations, with an absolute minimum of 0.3 meters. Parallel installations require 0.1 meter spacing between cables, increasing to 0.5 meters for cables belonging to different systems. At crossing points, 0.5 meter separation applies, though reduced spacing may be permitted with additional protective measures.

The Science Behind 0.7 Meters

This standard depth emerges from extensive practical experience and theoretical calculations. The 0.7-meter measurement effectively minimizes surface load impact on cables while preventing soil pressure from causing deformation or damage. This depth also provides optimal thermal resistance, facilitating heat dissipation to maintain insulation integrity. Additionally, it offers reasonable protection against accidental human interference.

Critical Installation Details

Successful MV underground cable installation requires attention to several key factors:

• Cable selection: Choose appropriate cable types and specifications based on actual load and environmental conditions
• Trench preparation: Excavate to required dimensions with leveled, compacted bases free of sharp objects
• Cable placement: Avoid excessive bending or twisting that could compromise insulation
• Backfilling: Compact soil in layers to eliminate voids and ensure uniform density
• Marking: Clearly identify cable paths to alert workers and the public

The Future: Smart and Precise Solutions

As urban development accelerates and power demands grow, MV underground cable technology continues evolving. Future trends emphasize intelligent monitoring systems using sensors to detect potential issues, advanced installation methods that minimize environmental impact, and innovative cable materials that enhance durability and safety.

Proper burial depth and spacing remain fundamental to power system reliability. Strict adherence to standards, combined with meticulous installation practices, reduces failure rates and ensures stable electricity supply—the foundation for economic and social development. In power engineering, safety must always remain the paramount consideration.