By sion932 
The International Electrotechnical Commission (IEC) standard IEC 60502-2:2014/AMD1:2024, as the consolidated version 3.1 of the third edition, serves as a pivotal technical specification for medium-voltage power cables with extruded insulation. It specifically governs cables for fixed installations with rated voltages ranging from 6 kV (Um = 7.2 kV) to 30 kV (Um = 36 kV), covering their construction, dimensional parameters, test requirements, and performance criteria. This amendment, released in May 2024, builds on the 2014 edition and incorporates significant technical revisions to align with the latest advancements in cable manufacturing technology, testing methods, and industry application demands.
1. Scope and Core Application Scope
IEC 60502-2:2014/AMD1:2024 is dedicated to power cables with extruded solid insulation for fixed installations, such as distribution networks and industrial facilities. A key focus of the standard is the assessment and mitigation of water ingress risks—both radial and longitudinal. It includes specifications for cable designs equipped with barriers to prevent longitudinal water penetration, along with corresponding test methods to verify such performance. Notably, the standard excludes cables for special installation and service conditions, including overhead networks, mining operations, nuclear power plant containment areas, submarine applications, and shipboard use, which require specialized standards tailored to their unique operating environments.
The standard adopts the U₀/U(Um) voltage designation system, where U₀ represents the rated voltage between conductor and earth, U denotes the rated voltage between conductors, and Um is the maximum permissible voltage of the equipment. Typical rated voltage levels covered include 3.6/6 kV, 6/10 kV, 8.7/15 kV, 12/20 kV, and 18/30 kV, catering to the majority of medium-voltage power distribution scenarios.
2. Key Technical Revisions in AMD1:2024
The 2024 amendment introduces seven critical technical updates compared to the 2005 second edition, enhancing the standard’s adaptability and rigor. These revisions reflect the evolution of cable materials, manufacturing processes, and performance requirements:
- Simplified Calculation Procedure: The thickness calculation method for lead sheaths and oversheaths has been streamlined, reducing complexity in design and production while maintaining structural integrity.
- New Clause on Conductor Temperature Determination: A dedicated subclause is added to standardize the measurement and calculation of cable conductor temperature, ensuring accurate assessment of thermal performance under operating conditions.
- Modified Routine Voltage Test: The procedure for routine voltage testing is revised to improve detection efficiency of insulation defects during mass production.
- Routine Electrical Test for Oversheaths: A new subclause mandates routine electrical testing of oversheaths, strengthening quality control of the cable’s outer protective layer.
- Updated Non-Metal Sheath Requirements: Specifications for non-metal sheaths, including semi-conductive layers, are modified to enhance compatibility with modern insulation materials and improve shielding effectiveness.
- Adjusted Bending Test Tolerances: Tolerances for the bending test cylinder are optimized to better reflect real-world installation conditions and ensure cable flexibility without compromising performance.
- Inclusion of Post-Installation 0.1 Hz Test: A 0.1 Hz very low frequency test is incorporated for post-installation inspection, effectively identifying insulation damage caused during installation and ensuring long-term operational safety.
Additionally, the standard adopts the revised structure of the IEC 60811 series, improving consistency with related insulation and sheathing material test standards.
3. Critical Technical Requirements
3.1 Insulation and Material Systems
The standard specifies requirements for four primary insulation material types, each with distinct performance characteristics:
| Insulation Material Type | Maximum Conductor Temperature (℃) | Short-Circuit Temperature (℃) | Key Application Features |
|---|---|---|---|
| PVC/B | 70 | 160 | Cost-effective with excellent flame retardancy |
| XLPE | 90 | 250 | Superior dielectric properties and thermal stability |
| EPR | 90 | 250 | High flexibility and excellent water tree resistance |
| HEPR | 90 | 250 | Enhanced hardness and mechanical performance |
Insulation thickness is graded by voltage level and material type. For example, XLPE insulation requires a minimum thickness of 2.5 mm for U₀ = 3.6 kV and 5.5 mm for U₀ = 18 kV, ensuring electric field strength is controlled within safe limits.
3.2 Shielding System Design
For cables rated 6 kV and above, the standard mandates a comprehensive shielding system comprising conductor shielding, insulation shielding (both semi-conductive layers), and a metallic shield. Conductor shielding must maintain intimate contact with the conductor surface to ensure uniform electric field distribution, while insulation shielding can be either bonded or unbonded to the insulation layer.
Metallic shields may be constructed from copper tape, copper wires, or composite shielding. Minimum cross-sectional requirements are specified based on conductor size—for conductors ≤ 500 mm², copper tape must be at least 0.1 mm thick, and copper wires must have a minimum cross-section of 16 mm². Semi-conductive layers have strict resistivity limits: ≤ 1000 Ω·m for conductor shielding and ≤ 500 Ω·m for insulation shielding, verified via test methods specified in Annex D.
3.3 Test Requirements
IEC 60502-2:2014/AMD1:2024 establishes a comprehensive testing framework, including type tests, routine tests, and sampling tests, to ensure cable performance.
Electrical Type Tests
| Test Item | Test Voltage | Acceptance Criterion |
|---|---|---|
| Partial Discharge Test | 1.5U₀ | Partial discharge magnitude ≤ 5 pC |
| Dielectric Loss Factor (tanδ) Measurement | U₀ | Compliant with material-specific requirements |
| Impulse Voltage Test | As specified in Table 14 | No breakdown |
| 4-Hour Voltage Test | 4U₀ | No breakdown |
Non-electrical tests include insulation and sheath thickness measurement, mechanical performance testing, and aging resistance evaluation. For HEPR insulation, Annex E specifies hardness determination methods to ensure mechanical integrity.
4. Application Guidelines and Implementation Considerations
Successful implementation of IEC 60502-2:2014/AMD1:2024 requires careful consideration of installation conditions, material selection, and test compliance:
- Current Rating Calculation: Annex B provides detailed continuous current rating tables and correction factors for XLPE and EPR insulated cables (copper and aluminum conductors, single-core and three-core configurations). Ratings are based on reference conditions (30℃ ambient air, 20℃ soil temperature, 1.5 K·m/W soil thermal resistivity, 0.8 m burial depth). Correction factors must be applied for actual conditions, including ambient temperature, burial depth, soil thermal resistivity, and cable grouping, which may reduce current capacity by 20-30% for multi-circuit installations.
- Water Ingress Mitigation: For applications prone to water exposure, cables with water-blocking structures should be selected. The standard’s longitudinal water penetration test (Annex F) and conductor water penetration test (Annex H) provide verification methods for such designs.
- Shielding and Grounding: Metallic shield grounding must comply with standard requirements to ensure effective fault current conduction and induced voltage limitation, critical for system safety and electromagnetic compatibility.
- Post-Installation Testing: The mandatory 0.1 Hz post-installation test should be conducted in accordance with IEC 60060-3 to detect insulation damage incurred during installation.
IEC 60502-2:2014/AMD1:2024 represents a significant update to medium-voltage extruded insulation power cable standards, integrating the latest technical advancements and industry best practices. Its revised test procedures, material specifications, and installation requirements enhance cable reliability, safety, and compatibility with modern power distribution systems. By adhering to this standard, manufacturers, engineers, and operators can ensure the performance and longevity of medium-voltage cables, supporting the stable and efficient operation of critical infrastructure. As cable technology continues to evolve, IEC 60502-2 will remain a cornerstone specification, guiding the development and application of medium-voltage power cables worldwide.
References
- IEC 60502-2:2014/AMD1:2024. Power cables with extruded insulation and their accessories for rated voltages from 1 kV (Um = 1.2 kV) up to 30 kV (Um = 36 kV) – Part 2: Cables for rated voltages from 6 kV (Um = 7.2 kV) up to 30 kV (Um = 36 kV). International Electrotechnical Commission, 2024.
- IEC 60502-2 Revised. IEC Webstore. Retrieved from https://webstore.iec.ch/en/publication/16382.
- IEC 60811 Series. Insulating and sheathing materials of electric and optical cables – Common test methods.