Shielded and concentric neutral power cable for distribution utilities
1. Scope and Voltage Ratings
The requirements of this Standard apply to materials, constructions, and testing of tree-retardant cross-linked polyethylene and ethylene propylene rubber-insulated single conductor or triplexed primary shielded and concentric neutral power cables rated 15 to 46 kV that are used for the transmission and distribution of electrical energy.
The products covered by this Standard are suitable for direct burial or installation in ducts in both wet and dry locations and where cable will be exposed to sunlight.
Voltage Ratings: Covers voltage levels from 15,000 volts to 46,000 volts (15kV to 46kV).
2.Insulation Materials
The standard explicitly defines two primary insulation material systems to suit different operating environments:
- Tree-Retardant Cross-Linked Polyethylene: This material offers excellent electrical properties and heat resistance, with a maximum allowable continuous operating temperature typically of 90°C and an emergency short-circuit rating of 250°C.
- Ethylene Propylene Rubber: EPR insulated cables are also covered under this standard and are often preferred in projects requiring specific flexibility or particular aging characteristics.
3.Cable Construction
Standard Cable Construction Layers (from inside to outside)
A cable strictly conforming to CSA C68.5 typically consists of the following layers:
Table 1:
| No. | Layer | Key Materials/Requirements | Function |
|---|---|---|---|
| 1 | Conductor | Copper or Aluminum as ASTM Standard | Current-carrying core for power transmission |
| 2 | Conductor Shield (Inner Semi-conductive Layer) | Extruded semi-conductive material | Smooths the electric field at the conductor surface; prevents discharge at conductor-insulation interface |
| 3 | Insulation | TR-XLPE or EPR | Primary dielectric for voltage withstand; 90°C continuous (250°C short-circuit) |
| 4 | Insulation Shield (Outer Semi-conductive Layer) | Semi-conductive tape or extruded semi-conductive layer | Smooths the electric field on the outer surface of the insulation |
| 5 | Metallic Shield | Copper tape, Copper wire+copper tape, copper neutral wire, Longitudinally applied corrugated tape or Lead sheath | Carries fault current; provides electromagnetic shielding |
| 6 | Jacket | LLDPE, PVC, PP,HDPE,XLPE | Mechanical protection; weather and corrosion resistance |
Tabls: 2 Insulation Levels According to CSA C68.5
Based on system grounding method and fault clearing time, CSA C68.5 divides cable insulation levels into three categories: 100%, 133%, and 173%.
The definitions, typical applications, and relative relationships of these three levels are shown in the table below:
| Insulation Level | Core Definition & Fault Clearing Time | Typical Application System | Relative Insulation Thickness |
|---|---|---|---|
| 100% Level | Fault cleared within 1 minute. Applicable where protection systems operate quickly and reliably. | Solidly Grounded Systems | Baseline (minimum thickness) |
| 133% Level | Fault clearing time exceeds 1 minute but does not exceed 1 hour. Applicable where faults cannot be cleared immediately but will eventually be isolated. | Impedance-Grounded Systems, or systems with delayed protection operation | Thicker than 100% level |
| 173% Level | Fault clearing time is not fixed; faults may persist for extended periods. Designed for the most severe applications, providing maximum insulation protection. | Ungrounded Systems, Resonant Grounded Systems | Thickest (highest dielectric stre |
Table 3: Jacket Materials and Applicable Environments
| Jacket Material | Characteristics | Recommended Installation Environment |
|---|---|---|
| PVC (Polyvinyl Chloride) | General purpose, lower cost | Conventional indoor / outdoor |
| LLDPE (Linear Low-Density Polyethylene) | Excellent flexibility, UV resistance, and good crack resistance | Direct burial, outdoor exposure |
| HDPE (High-Density Polyethylene) | High hardness, high strength, excellent low-temperature impact resistance | direct burial or duct installation in cold regions |
| XLPE (Cross-linked Polyethylene) | Superior heat resistance | High temperature operating environments |
Cable Jacket has two type: Ectruded-to-fill jacket and Overlaying Jacket
CSA C68.5 Cable
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FAQ
Answers To Your Most Common Questions
Find quick answers to common questions below.
Answer:
TR-XLPE (Tree retardant crosslinked polyethylene)
EPR (Ethylene Propylene Rubber)
Answer: CSA C68.5 cover 15kV, 25kV, 28kV, 35kV and 46kV.
Answer:
1. To Carry Short-Circuit Current (Fault Current Capacity)
The metallic shield is designed to provide a low-impedance return path for fault currents. When an insulation failure occurs, the metallic shield safely conducts the resulting current back to the source, allowing protection devices (e.g., circuit breakers, fuses) to operate and clear the fault without damaging the cable insulation or conductor.
2. To Provide Electromagnetic Shielding (Electric Field Confinement)
The metallic shield confines the electric field within the cable. It ensures that:
The electric field does not radiate outward, preventing electromagnetic interference (EMI) with adjacent communication cables (e.g., control, instrumentation, or data cables) or electronic equipment.
The outer surface of the insulation shield is maintained at or near zero potential (ground potential), creating a safe and interference-free external environment around the cable.
If the cable can add water blocking tape on conductor or metallic screen?
Yes, it is.
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