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CSA C68.7-11 (2015) Standard: Technical Overview of Shielded Power Cables for Voltages up to 46 kV
Understanding the Requirements for Underground Cable Systems in Canada
Scope and Application
CSA C68.7-11 (R2015) – Shielded Power Cable for Voltages up to 46 kV – establishes the minimum construction, performance, and testing requirements for single and multi-conductor shielded power cables with extruded dielectric insulation. These cables are intended for underground installation in ducts, conduits, or direct burial at alternating current voltages of 5 kV to 46 kV phase-to-phase.
The standard applies to cables using cross-linked polyethylene (XLPE), ethylene propylene rubber (EPR), or other approved insulation compounds. It covers conductor sizes from 8 AWG to 1000 kcmil and defines both 100% and 133% insulation levels. Compliance with CSA C68.7-11 (2015) is mandatory under the Canadian Electrical Code (CE Code) for underground medium-voltage circuits.
Tip: Designers should verify that the selected cable is marked with the CSA monogram and the specific standard reference to confirm compliance with local inspection authorities.
Technical Requirements
Conductor Materials and Sizes
Conductors must be copper or aluminum, stranded (Class B or C per ASTM B8 or ASTM B496), and compacted where specified. Tinned copper conductors are permitted for corrosion resistance. The standard lists mandatory stranding constructions and dimensional tolerances.
Insulation and Shielding
Insulation thickness is determined by the rated voltage and the insulation level (100% or 133%). The standard requires an extruded semiconducting conductor shield, an insulation screen, and a metallic shield (copper tape or concentric wires). Table 1 summarizes the insulation thicknesses for the 100% insulation level.
| Voltage Class (kV) | Conductor Size Range (AWG/kcmil) | Insulation Thickness – 100% Level (mm) |
|---|---|---|
| 5 | 8 – 1000 | 2.29 |
| 8 | 8 – 1000 | 2.79 |
| 15 | 8 – 1000 | 3.18 |
| 25 | 8 – 1000 | 4.45 |
| 28 | 8 – 1000 | 5.08 |
| 35 | 8 – 1000 | 5.59 |
| 46 | 8 – 1000 | 6.60 |
Table 1: Insulation thickness for 100% insulation level as specified in CSA C68.7-11 (2015). 133% insulation levels require increased thickness (typically 1.33× of the 100% value).
Important: The insulation thickness and shield design directly affect the cable’s impulse withstand and partial discharge performance. Always consult the standard’s detailed tables for exact requirements.
Jacketing and Armour
Jackets must be extruded from polyvinyl chloride (PVC), polyethylene (PE), nylon, or chlorinated polyethylene (CPE). Armour (interlocked or wire) is optional but must be covered by an overall jacket if used. The standard specifies adhesion, elongation, and flame-retardance properties.
Testing and Compliance
Each cable manufactured to CSA C68.7-11 (2015) must undergo routine, sampling, and design tests. Key tests include:
- Partial discharge (at 1.5 U0 or higher)
- AC voltage withstand (2.5 U0 for 5 minutes)
- DC voltage withstand (for field acceptance, typically 4 U0)
- Insulation resistance and conductor resistance
- Shield continuity and resistance
Compliance Benefit: Cables certified to this standard reduce the risk of premature underground failures and improve system reliability. Many utilities mandate CSA C68.7 compliance for warranty and insurance purposes.
Non‑Compliance Risk: Installing non‑certified cable may lead to rejection by electrical inspectors, void warranties, and create safety hazards due to inadequate insulation or shielding.
Implementation Considerations
When specifying cable for a project, engineers should:
- Confirm the required voltage class and insulation level (100% for effectively grounded, 133% for ungrounded or impedance grounded).
- Select the appropriate metallic shield type based on fault current capacity and bonding requirements.
- Ensure the cable’s ampacity is sufficient under installed conditions (accounting for grouping, soil thermal resistivity, and ambient temperature).
- Verify that accessories (splices, terminations) are rated for the cable’s insulation and shield design.
Tip: For direct-burial installations, consult the manufacturer’s installation guide for minimum bend radius, pulling tension, and backfill requirements to avoid damaging the semiconducting shields.
Compliance with CSA C68.7-11 (2015) is verified by the manufacturer through a CSA product certification program. The standard was originally published in 2011 and reaffirmed without technical changes in 2015. As of 2026, it remains the current edition for shielded power cables up to 46 kV in Canada.
Frequently Asked Questions
Q: Does CSA C68.7-11 (2015) apply to cables rated above 46 kV?
A: No. For voltages above 46 kV, refer to CSA C68.9 (shielded cables for higher voltages) or specific utility standards.
A: No. For voltages above 46 kV, refer to CSA C68.9 (shielded cables for higher voltages) or specific utility standards.
Q: Can aluminum conductors be used interchangeably with copper under this standard?
A: Yes, provided the conductor meets the stranding and size requirements. However, ampacity tables and termination hardware differ; consult the product data sheet and the CE Code.
A: Yes, provided the conductor meets the stranding and size requirements. However, ampacity tables and termination hardware differ; consult the product data sheet and the CE Code.
Q: Is the 133% insulation level required for all ungrounded systems?
A: The CE Code and CSA C68.7 recommend the 133% level for ungrounded or impedance‑grounded systems where clearing times may be prolonged. Check with the authority having jurisdiction.
A: The CE Code and CSA C68.7 recommend the 133% level for ungrounded or impedance‑grounded systems where clearing times may be prolonged. Check with the authority having jurisdiction.
Q: Are factory‑test reports acceptable for field verification?
A: Routine factory tests are conducted on each cable length. Field acceptance testing (DC hi‑pot or VLF) is typically performed after installation; this standard provides guidance on acceptable field test methods.
A: Routine factory tests are conducted on each cable length. Field acceptance testing (DC hi‑pot or VLF) is typically performed after installation; this standard provides guidance on acceptable field test methods.
© 2026. This article provides a technical summary of CSA C68.7-11 (R2015). For complete requirements, purchase the standard from CSA Group.