The "breathing" Gap In Cable Accessories: Why Cold Shrink Outperforms Heat Shrink Under Thermal Cycling
- Reference standards:
- JB/T7829,JB/T 7830
- AC Withstand Voltage for 5 min:
- 8 kV,no breakdown
- Heating Cycles Test in Air:
- 4.5 kV, heating cycles at least 8 h, 95–100 ℃ for at least 2 h, natural cooling for at least 3 h, total 30 heating cycles
- Heating Cycles Test Under Water:
- 4.5 kV, heating cycles at least 8 h, 95–100 ℃ for at least 2 h, natural cooling for at least 3 h, total 30 heating cycles
- AC Withstand Voltage:
- 7.2 kV,4 h no breakdown
Cold Shrink Cable Accessories maintain continuous radial pressure on cable interfaces. Heat shrink loses pressure under thermal cycling. Cable expands, sleeve stays rigid, air gaps form. Partial discharge starts. Insulation breakdown follows. Cold shrink uses elastic memory to move with the cable. Installation: select rated tube, clean cable, position, pull core, verify seal.
Why Heat Shrink Loses Interfacial Pressure
Heat shrink recovers once at 120–150°C. The polyolefin sleeve stays rigid. Cable conductor heats to 90°C, expands outward. Interfacial pressure drops. Adhesive seals relax. Moisture enters gaps. Surface tracking and erosion follow. Thermal cycling repeats this cycle.
How Cold Shrink Maintains Active Grip Force
Cold shrink is factory-expanded over a spiral core. Core removal lets elastomer contract. Radial pressure stays 0.3–0.8 MPa. Cable expansion stretches the tube. Cooling lets it contract. This active grip force closes the breathing gap. Both epdm cold shrink and silicone rubber keep elastic memory. EPDM offers volume resistivity above 10¹⁵ Ω·cm. Silicone handles 200°C. electrical cold shrink accessories use stress control tubes for medium voltage.
Performance Comparison
| Parameter | Cold Shrink | Heat Shrink |
|---|---|---|
| Pressure source | Elastic recovery | Adhesive liner |
| Radial pressure | 0.3–0.8 MPa | None |
| Thermal cycling | Moves with cable | Stays rigid |
| Installation heat | None | 120–150°C |
| Sealing | Radial compression | Melt adhesive |
| Re-entry | Limited | Limited |
Selection and Installation
Selection Factors
-
Confirm voltage class: 0.6/1 kV, 12 kV, 24 kV, 36 kV.
-
Check conductor size and insulation diameter.
-
Choose indoor or outdoor design.
-
Verify chemical and UV exposure.
For 0.6/1 kV systems, cold shrink accessories cover conductor sizes from 25 to 400 mm². Partial discharge stays below 5 pC at 1.5 × U₀.
Installation Steps
-
Verify cable type and accessory rating.
-
Clean insulation and apply silicone lubricant.
-
Position tube without sharp contact.
-
Pull spiral core slowly.
-
Check seal and radial pressure.
Repair with Cold Shrink Electrical Tape
For splices and sheath repairs, cold shrink electrical tape stretches and seals irregular shapes. It uses the same elastic pressure principle. A cool shrink tube can cover larger joints. This tape works with tubular accessories for field repairs.
FAQ
Q: Do cold shrink accessories need heat?
A: No. A spiral core holds the tube expanded. Pulling the core lets the elastomer contract.
Q: What causes the breathing gap?
A: Heat shrink cannot expand or contract with the cable. Interfacial pressure falls as temperature rises.
Q: How to choose between EPDM and silicone?
A: EPDM gives toughness and resistivity. Silicone handles higher temperatures.
0.6/1 kV Fully Cold Shrink Three-Core Terminal – Installation Outline Drawing
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| 0.6/1 kV Five-Core Cold Shrink Terminal – Supporting Drawing | 0.6/1 kV Five-Core Cold Shrink Joint – Supporting Drawing |
Electrical Performance Tests
| No. | Test Item | Standard Requirements |
| 1 | AC Withstand Voltage for 5 min | 8 kV,no breakdown |
| 2 | Heating Cycles Test in Air | 4.5 kV, heating cycles at least 8 h, 95–100 ℃ for at least 2 h, natural cooling for at least 3 h, total 30 heating cycles |
| 3 | Heating Cycles Test Under Water | 4.5 kV, heating cycles at least 8 h, 95–100 ℃ for at least 2 h, natural cooling for at least 3 h, total 30 heating cycles |
| 4 | AC Withstand Voltage | 7.2 kV,4 h no breakdown |
| 5 | Reference Standards | JB/T7829,JB/T 7830 |
Product overview
◆The product is available in single-core, two-core, three-core, four-core, and five-core versions, and has been widely used for low-voltage cable terminations and intermediate connections.
◆Excellent surface hydrophobicity, ensuring the product maintains strong resistance to contamination.
◆Compact size, lightweight, and reliable performance.
◆Application Scope: The product demonstrates excellent cold and heat resistance, making it particularly suitable for high-altitude, cold, humid, salt-spray, and heavily polluted environments.
Installation requires no open flame, making it ideal for flammable and explosive areas such as petroleum, chemical, mining, and tunneling sites.
Technical Data - Model Selection
| Product Type | Model | Conductor Cross-section(mm²) | Product Type | Model | Conductor Cross-section(mm²) |
| 0.6/1 kV Single-Core Cold Shrink Termination | GHD-1LS-1*10-16 | 10-16 | 0.6/1 kV Single-Core Cold Shrink Joint | GHD-1JTLS-1*10-16 | 10-16 |
| GHD-1LS-1*25-50 | 25-50 | GHD-1JTLS-1*25-50 | 25-50 | ||
| GHD-1LS-1*70-120 | 70-120 | GHD-1JTLS-1*70-120 | 70-120 | ||
| GHD-1LS-1*150-240 | 150-240 | GHD-1JTLS-1*150-240 | 150-240 | ||
| GHD-1LS-1*300-400 | 300-400 | GHD-1JTLS-1*300-400 | 300-400 | ||
| 0.6/1 kV Two-Core Cold Shrink Termination | GHD-1LS-2*10-16 | 10-16 | 0.6/1 kV Two-Core Cold Shrink Joint | GHD-1JTLS-2*10-16 | 10-16 |
| GHD-1LS-2*25-50 | 25-50 | GHD-1JTLS-2*25-50 | 25-50 | ||
| GHD-1LS-2*70-120 | 70-120 | GHD-1JTLS-2*70-120 | 70-120 | ||
| GHD-1LS-2*150-240 | 150-240 | GHD-1JTLS-2*150-240 | 150-240 | ||
| GHD-1LS-2*300-400 | 300-400 | GHD-1JTLS-2*300-400 | 300-400 | ||
| 0.6/1 kV Three-Core Cold Shrink Termination | GHD-1LS-3*10-16 | 10-16 | 0.6/1 kV Three-Core Cold Shrink Joint | GHD-1JTLS-3*10-16 | 10-16 |
| GHD-1LS-3*25-50 | 25-50 | GHD-1JTLS-3*25-50 | 25-50 | ||
| GHD-1LS-3*70-120 | 70-120 | GHD-1JTLS-3*70-120 | 70-120 | ||
| GHD-1LS-3*150-240 | 150-240 | GHD-1JTLS-3*150-240 | 150-240 | ||
| GHD-1LS-3*300-400 | 300-400 | GHD-1JTLS-3*300-400 | 300-400 | ||
| 0.6/1 kV Four-Core Cold Shrink Termination | GHD-1LS-4*10-16 | 10-16 | 0.6/1 kV Four-Core Cold Shrink Joint | GHD-1JTLS-4*10-16 | 10-16 |
| GHD-1LS-4*25-50 | 25-50 | GHD-1JTLS-4*25-50 | 25-50 | ||
| GHD-1LS-4*70-120 | 70-120 | GHD-1JTLS-4*70-120 | 70-120 | ||
| GHD-1LS-4*150-240 | 150-240 | GHD-1JTLS-4*150-240 | 150-240 | ||
| GHD-1LS-4*300-400 | 300-400 | GHD-1JTLS-4*300-400 | 300-400 | ||
| 0.6/1 kV Five-Core Cold Shrink Termination | GHD-1LS-5*10-16 | 10-16 | 0.6/1 kV Five-Core Cold Shrink Joint | GHD-1JTLS-5*10-16 | 10-16 |
| GHD-1LS-5*25-50 | 25-50 | GHD-1JTLS-5*25-50 | 25-50 | ||
| GHD-1LS-5*70-120 | 70-120 | GHD-1JTLS-5*70-120 | 70-120 | ||
| GHD-1LS-5*300-400 | 150-240 | GHD-1JTLS-5*150-240 | 150-240 | ||
| GHD-1LS-5*300-400 | 300-400 | GHD-1JTLS-5*300-400 | 300-400 |
