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CSA C22.2 No. 126.2-02 (2017): Technical Guide to Cablebus Assemblies for Power Distribution
Understanding the Canadian Standard for Pre-assembled Cable Support Systems Up to 35 kV
CSA C22.2 No. 126.2-02 (R2017) is a Canadian national standard that specifies safety and performance requirements for factory-assembled cablebus systems rated up to 35 kV. A cablebus is a pre-engineered assembly of insulated conductors supported by a metal framework, used for medium- and low-voltage power distribution in industrial, commercial, and utility installations. This standard is essential for manufacturers, engineers, and installers seeking CSA certification for cablebus products.
1. Scope and Purpose
The standard applies to cablebus assemblies intended for indoor or outdoor use, consisting of multiple insulated conductors (copper or aluminum) supported by cleats or blocks within a ventilated or enclosed metal structure. The scope includes:
- Systems with voltage ratings up to 35 kV AC (60 Hz) or 35 kV DC
- Current ratings from 200 A to 6000 A and above
- Assemblies designed for continuous operation at ambient temperatures up to 40 °C
- Configurations for straight runs, elbows, tees, and termination sections
Cablebus systems are distinct from busway (covered by CSA C22.2 No. 126.1) in that cablebus uses individual insulated cables supported on engineered rack systems rather than factory-bonded busbars. The standard does not apply to individual cables themselves, which must comply with CSA C22.2 No. 38 or other applicable standards.
2. Technical Requirements
2.1 Construction and Materials
All metal enclosures and support structures must be of corrosion-resistant material or suitably protected. Minimum enclosure thicknesses are specified based on material (steel, aluminum, stainless steel). Cable cleats must secure conductors against displacement under short-circuit forces and normal thermal cycling. Conductor spacing must be maintained to prevent phase-to-phase or phase-to-ground faults.
2.2 Temperature Rise and Ampacity
The standard defines allowable temperature rises based on conductor insulation class (90 °C, 105 °C, 125 °C, etc.) and enclosure type. Temperature tests must be conducted at rated current in free air or within an enclosure representing worst-case installation conditions. Table 1 summarizes typical ampacity derating factors based on grouping and ambient temperature.
| Number of Conductors per Phase | Derating Factor (Enclosed) | Derating Factor (Ventilated) |
|---|---|---|
| 1 | 1.00 | 1.00 |
| 2 | 0.85 | 0.90 |
| 4 | 0.70 | 0.80 |
| 6 | 0.60 | 0.75 |
Note: Ampacity values must also account for ambient temperature correction per Table 2 of the standard.
2.3 Short-Circuit Withstand
Cablebus assemblies must withstand the thermal and mechanical effects of short-circuit currents for rated durations (typically 3 cycles up to 1 second). The standard requires either calculation per IEC 60865-1 or physical testing. The cable cleats and support system must be verified for bracing capability.
2.4 Grounding and Bonding
A continuous bonding path must be provided for all non-current-carrying metal parts. The standard specifies minimum cross-sectional area of ground bus or bonding conductors. Ground path impedance must be low enough to clear maximum fault current.
2.5 Marking and Instructions
Each cablebus section must be permanently marked with:
- Manufacturer’s name or trademark
- Model number and serial number
- Voltage rating, current rating, short-circuit rating
- Number and size of conductors
- CSA certification mark
3. Implementation Highlights
Tip: When designing a cablebus system, always consult the manufacturer’s installation manual for specific cleat spacing, support hanger intervals, and torque values for bolted joints. Field modifications (e.g., adding bends) should be factory-authorized to maintain the certified rating.
Warning: Cablebus assemblies are not intended for direct burial. Outdoor installations require enclosure types rated for the environment (e.g., rainproof, sleet-proof). Ensure all ventilation openings comply with NEMA 250 or CSA C22.2 No. 94.1.
Proper handling and storage are critical. Cablebus sections are large and heavy; they must be lifted using spreader bars at designated lift points to avoid conductor damage. Splice connections must be made carefully to maintain ground continuity and phase alignment.
System integration with switchgear and transformers should include flexible connectors or expansion joints to accommodate thermal expansion. It is recommended to perform a site-specific engineering review, especially for systems exceeding 1000 A or running through multiple fire compartments.
4. Compliance and Certification
Certification Requirement: Cablebus assemblies sold in Canada must be certified to CSA C22.2 No. 126.2-02 (R2017) by an accredited certification body (e.g., CSA Group, QPS, UL). The CSA mark indicates compliance with the standard and acceptance by provincial electrical authorities.
Important: Non-certified cablebus systems may be rejected during inspection. Retrofits that increase ampacity or change conductor type require re-evaluation and recertification. Always maintain traceability of material test reports (MTRs) and factory test records.
Compliance verification includes:
- Routine dielectric voltage withstand test (hi-pot) on each assembled section at 2X rated voltage + 1000 V
- Temperature rise tests on representative samples
- Short-time withstand current tests (if required by rating)
- Ground path continuity verification
- Marking and documentation review
Manufacturers should also consider harmonization with other standards: CSA C22.2 No. 0 (General Requirements), CSA C22.2 No. 0.4 (Bonding and Grounding), and CSA C22.1 (Canadian Electrical Code, Part I).
Q: What is the difference between cablebus and busway?
A: Cablebus uses individual insulated cables supported by cleats within a metal framework, while busway consists of factory-bonded busbars. Cablebus typically allows higher ampacity per cross-section and easier field modifications, but may require more space.
A: Cablebus uses individual insulated cables supported by cleats within a metal framework, while busway consists of factory-bonded busbars. Cablebus typically allows higher ampacity per cross-section and easier field modifications, but may require more space.
Q: What is the maximum voltage covered by CSA C22.2 No. 126.2-02 (2017)?
A: The standard covers systems up to 35 kV AC (60 Hz) or 35 kV DC. For higher voltages, refer to other applicable CSA standards or functional specifications.
A: The standard covers systems up to 35 kV AC (60 Hz) or 35 kV DC. For higher voltages, refer to other applicable CSA standards or functional specifications.
Q: Are cablebus assemblies allowed to be installed in hazardous locations?
A: The standard does not specifically address hazardous (classified) locations. For use in such areas, the assembly must comply with additional requirements (e.g., explosion-proof or purged enclosures) as per CSA C22.1 and related standards.
A: The standard does not specifically address hazardous (classified) locations. For use in such areas, the assembly must comply with additional requirements (e.g., explosion-proof or purged enclosures) as per CSA C22.1 and related standards.
Q: How often should factory tests be performed?
A: Routine hi-pot testing is required on every assembled section. Type tests (temperature rise, short-circuit) must be performed once for a design family unless changes occur in materials or construction.
A: Routine hi-pot testing is required on every assembled section. Type tests (temperature rise, short-circuit) must be performed once for a design family unless changes occur in materials or construction.