外护套电导率：如何验证（N）TSCGEWÖU电缆外护套的电导率以在危险区域进行安全接地？
Sheath Conductivity: How do you verify the conductivity of the outer sheath on (N)TSCGEWÖU cables for safety grounding in hazardous areas?
外护套电导率：如何验证（N）TSCGEWÖU电缆外护套的电导率以在危险区域进行安全接地？
Published by Anhui Feichun Special Cable Co., Ltd. (安徽飞纯特种电缆有限公司)
Introduction 简介
In hazardous locations where flammable gases, vapors, or combustible dusts are present, the integrity and conductivity of cable outer sheaths play a critical role in maintaining safety grounding systems. The (N)TSCGEWÖU cable designation represents specialized mining and industrial cables designed for applications requiring robust environmental protection and reliable electrical performance. Proper verification of sheath conductivity ensures effective equipotential bonding and prevents dangerous voltage potentials that could lead to ignition sources in classified areas.
在存在易燃气体、蒸汽或可燃粉尘的危险场所，电缆外护套的完整性和导电性在维持安全接地系统方面起着关键作用。（N）TSCGEWÖU电缆标识代表专为需要强大环境保护和可靠电气性能的应用而设计的专用矿用和工业电缆。正确验证护套导电性可确保有效的等电位连接，并防止可能导致分类区域点火源的危险电压电位。
Understanding Hazardous Area Requirements 理解危险区域要求
According to IEC 60079-14 (Electrical apparatus for explosive gas atmospheres – Part 14: Electrical installations in hazardous areas), equipotential bonding is required for all installations in hazardous areas. This standard states that all exposed and extraneous conductive parts must be connected to the equipotential bonding system, which may include protective conductors, metal conduits, metal cable sheaths, steel wire armouring, and metallic parts of structures.
根据IEC 60079-14标准（爆炸性气体环境用电气设备第14部分：危险区域的电气装置），危险区域内的所有装置都需要等电位连接。该标准规定，所有裸露的和外部导电部件必须连接到等电位连接系统，该系统可能包括保护导体、金属导管、金属电缆护套、钢丝铠装和结构的金属部件。
The National Electrical Code (NEC) Article 500 series establishes classification systems for hazardous locations in North America. Class I locations deal with flammable gases or vapors, with Division 1 representing areas where ignitable concentrations exist under normal operating conditions. The European ATEX directive and IECEx system provide parallel frameworks for explosive atmosphere protection globally.
美国国家电气规范（NEC）第500条系列为北美危险场所建立了分类系统。I类场所涉及易燃气体或蒸汽，其中1区代表在正常运行条件下存在可点燃浓度的区域。欧洲ATEX指令和IECEx系统在全球范围内为爆炸性气氛保护提供了平行框架。
Cable Sheath Testing Methods 电缆护套测试方法
1. DC Insulation Resistance Testing (Megger Testing) 直流绝缘电阻测试（兆欧表测试）
The most common method for verifying sheath integrity and conductivity involves DC voltage testing using a megohmmeter (commonly called a Megger test). According to industry standards and testing protocols documented by organizations such as Eland Cables and BAUR, this test applies a DC voltage between the metallic sheath and earth while measuring leakage current.
验证护套完整性和导电性的最常用方法涉及使用兆欧表（通常称为Megger测试）进行直流电压测试。根据Eland Cables和BAUR等组织记录的行业标准和测试协议，该测试在金属护套和地之间施加直流电压，同时测量泄漏电流。
| Cable Voltage Rating 电缆电压等级 | Test Voltage 测试电压 | Test Duration 测试持续时间 | Minimum Acceptable Resistance 最小可接受电阻 |
|---|---|---|---|
| Low Voltage (< 600V) 低压 | 500-1000 VDC | 60 seconds 60秒 | > 20 MΩ (Recommended > 1000 MΩ 建议) |
| Medium Voltage (1-35 kV) 中压 | 1000-5000 VDC | 60 seconds 60秒 | > 10-100 MΩ (Temperature corrected 温度校正) |
| High Voltage (> 35 kV) 高压 | 5-10 kV DC | 60 seconds 60秒 | Per manufacturer specifications 按制造商规格 |
The test procedure requires that the cable screen be disconnected from earthing at both ends during measurement. Otherwise, the test current would flow directly to earth, bypassing the actual fault location. For cables with semi-conductive layers (such as graphite-coated sheaths), the coating must be removed at least 100 mm from the edge at splice and termination points.
测试程序要求在测量期间将电缆屏蔽层从两端的接地处断开。否则，测试电流将直接流向地面，绕过实际故障位置。对于具有半导电层（例如石墨涂层护套）的电缆，必须在接头和端接点从边缘至少100毫米处移除涂层。
2. High Voltage DC Withstand Testing 高压直流耐压测试
For comprehensive sheath integrity assessment, high voltage DC testing applies controlled voltage stress to verify the protective outer sheath can withstand operational conditions. According to test procedures documented in technical literature, the test voltage is calculated as 4-8 kV per millimeter of sheath thickness, with a maximum of 10-25 kV depending on the cable construction and application requirements.
为了全面评估护套完整性，高压直流测试施加受控电压应力以验证保护性外护套能够承受运行条件。根据技术文献中记录的测试程序，测试电压计算为每毫米护套厚度4-8 kV，最大值为10-25 kV，具体取决于电缆结构和应用要求。
3. Sheath Resistance Measurement 护套电阻测量
Direct DC resistance measurement of the metallic sheath and connections provides verification of the conductive path integrity. This measurement is compared with manufacturer specifications, typically expressed in ohms per kilometer. The test ensures that the sheath can effectively carry fault currents and maintain equipotential bonding across the installation.
金属护套和连接的直接直流电阻测量可验证导电路径的完整性。该测量值与制造商规格进行比较，通常以每公里欧姆表示。该测试确保护套能够有效地承载故障电流并在整个安装过程中保持等电位连接。
| Test Type 测试类型 | Equipment Required 所需设备 | Key Parameters 关键参数 | Pass Criteria 通过标准 |
|---|---|---|---|
| Insulation Resistance 绝缘电阻 | Megohmmeter (Megger, Fluke, Kyoritsu) 兆欧表 | 500-5000 VDC, 60s duration | IR > 20 MΩ minimum 最小值 |
| DC Withstand 直流耐压 | HV DC Test Set 高压直流测试装置 | 4-8 kV/mm thickness 厚度, 1 min | No breakdown 无击穿, stable leakage current 稳定泄漏电流 |
| Sheath Resistance 护套电阻 | Low resistance ohmmeter 低电阻欧姆表 | DC measurement 直流测量, 20°C reference 参考温度 | Within ±10% of specification 规格 |
| Continuity Check 连续性检查 | Multimeter or continuity tester 万用表或连续性测试仪 | Low voltage DC 低压直流 | < 1 Ω end-to-end 端对端 |
Testing Procedures for (N)TSCGEWÖU Cables (N)TSCGEWÖU电缆的测试程序
Pre-Installation Testing (On-Reel Testing) 安装前测试（在盘测试）
Testing should commence while the cable remains on the shipping reel to establish a baseline and verify no damage occurred during transportation. The outer sheath is exposed at the cable ends, and test leads are connected between the metallic sheath (or armor) and a reliable earth reference. A ground electrode with resistance typically below 5 ohms should be established for field testing when the cable is not in contact with soil.
应在电缆仍在运输盘上时开始测试，以建立基线并验证运输过程中未发生损坏。电缆端部的外护套被暴露，测试引线连接在金属护套（或铠装）和可靠的接地参考之间。当电缆未与土壤接触时，应为现场测试建立电阻通常低于5欧姆的接地电极。
Post-Installation Testing 安装后测试
After cable installation through conduits, cable trays, or direct burial, repeat testing verifies that no damage occurred during the pulling and installation process. Common damage sources include binding from trefoil wrapping machinery, compression from excessive pulling tension, abrasion from conduit edges, and mechanical impact during backfilling operations.
通过管道、电缆桥架或直埋安装电缆后，重复测试验证在拉拔和安装过程中未发生损坏。常见的损坏来源包括三叶形缠绕机的绑扎、过度拉伸张力的压缩、导管边缘的磨损以及回填操作期间的机械冲击。
Pre-Commissioning Testing 投运前测试
Before energizing the system, final insulation resistance testing confirms the integrity of all cable components including the outer sheath. This testing must account for temperature corrections, as insulation resistance varies significantly with temperature. Standard practice requires correction to a reference temperature of 20°C using manufacturer-provided correction factors.
在系统通电之前，最终的绝缘电阻测试确认所有电缆组件（包括外护套）的完整性。此测试必须考虑温度校正，因为绝缘电阻随温度显著变化。标准做法要求使用制造商提供的校正因子校正到20°C的参考温度。
Safety Considerations and Best Practices 安全注意事项和最佳实践
Personnel conducting sheath conductivity testing must observe strict safety protocols. All equipment under test must be completely de-energized and isolated from power sources. Adequate personal protective equipment (PPE) including insulated gloves rated for the test voltage must be worn. After completing high voltage tests, cables must be discharged for at least as long as the test voltage was applied, typically a minimum of 15 minutes, before personnel can safely handle connections.
进行护套导电性测试的人员必须遵守严格的安全协议。所有测试设备必须完全断电并与电源隔离。必须佩戴适当的个人防护装备（PPE），包括额定测试电压的绝缘手套。完成高压测试后，在人员可以安全处理连接之前，电缆必须至少放电与施加测试电压一样长的时间，通常至少15分钟。
Test instruments must have valid calibration certificates to ensure measurement accuracy. Before use, verify the tester indicates infinity when leads are open and zero when leads are shorted together. Make certain all connections in the test circuit are tight and secure to prevent erroneous readings or safety hazards.
测试仪器必须具有有效的校准证书以确保测量准确性。使用前，请验证测试仪在引线断开时显示无穷大，在引线短接在一起时显示零。确保测试电路中的所有连接紧密且牢固，以防止错误读数或安全隐患。
| Requirement Category 要求类别 | Specification 规格 | Standard Reference 标准参考 |
|---|---|---|
| Equipment Calibration 设备校准 | Valid calibration certificate required 需要有效的校准证书 | ISO/IEC 17025 |
| Personnel Qualification 人员资质 | Trained and qualified electrical technicians 训练有素的合格电气技术人员 | NFPA 70E, IEC 61482 |
| Grounding System 接地系统 | Resistance < 5 Ω for test electrode 测试电极电阻 | IEC 60079-14 |
| Temperature Correction 温度校正 | Correct to 20°C reference 校正到参考温度 | IEC 60502, IEEE 400 |
| Discharge Time 放电时间 | Minimum 15 minutes post-test 测试后最少 | IEEE 400.2 |
Documentation and Compliance 文档和合规性
Comprehensive test records must be maintained throughout the cable lifecycle. Documentation should include cable identification, test date and time, ambient temperature, test equipment serial numbers and calibration dates, applied test voltages and durations, measured resistance values (with temperature corrections), and the name and qualifications of testing personnel. These records provide traceability for quality assurance and regulatory compliance inspections.
必须在整个电缆生命周期中保持全面的测试记录。文档应包括电缆标识、测试日期和时间、环境温度、测试设备序列号和校准日期、施加的测试电压和持续时间、测量的电阻值（带温度校正）以及测试人员的姓名和资格。这些记录为质量保证和监管合规性检查提供可追溯性。
For hazardous location installations, test results must demonstrate compliance with applicable standards including IEC 60079 series (particularly IEC 60079-14 for installations), ATEX directives for European applications, NEC Articles 500-505 for North American installations, and IECEx certification requirements for international projects.
对于危险场所安装，测试结果必须证明符合适用标准，包括IEC 60079系列（特别是IEC 60079-14用于安装）、欧洲应用的ATEX指令、北美安装的NEC第500-505条以及国际项目的IECEx认证要求。
Conclusion 结论
Verification of outer sheath conductivity on (N)TSCGEWÖU cables represents a critical safety requirement for hazardous area installations. Through systematic application of DC insulation resistance testing, high voltage withstand testing, and sheath resistance measurement, electrical professionals can ensure effective equipotential bonding and minimize ignition risks in classified environments. Adherence to international standards, proper test procedures, comprehensive documentation, and ongoing maintenance testing establish the foundation for safe and reliable electrical installations in potentially explosive atmospheres.
验证（N）TSCGEWÖU电缆外护套的导电性是危险区域安装的关键安全要求。通过系统应用直流绝缘电阻测试、高压耐压测试和护套电阻测量，电气专业人员可以确保有效的等电位连接，并最大限度地减少分类环境中的点火风险。遵守国际标准、正确的测试程序、全面的文档记录和持续的维护测试为潜在爆炸性气氛中的安全可靠电气装置奠定了基础。
References 参考文献
- IEC 60079-14:2023, “Explosive atmospheres – Part 14: Electrical installations design, selection and erection,” International Electrotechnical Commission. Available at: https://www.iec.ch
- Eland Cables, “Cable Sheath Resistance Testing,” The Cable Lab Independent Testing Services. Available at: https://www.elandcables.com/the-cable-lab/independent-cable-testing-and-inspection-services/sheath-resistance-testing
- BAUR GmbH, “Precise cable sheath testing with BAUR systems,” Cable Fault Location Technical Documentation. Available at: https://www.baur.eu/en/products/cable-fault-location/cable-fault-location-process/cable-sheath-faults
- NFPA 70, “National Electrical Code (NEC) Article 500: Hazardous (Classified) Locations,” National Fire Protection Association, 2023 Edition.
- Megger Group Limited, “MV cable test & diagnostics: four essential methods,” Technical Blog. Available at: https://www.megger.com/en/blog/mar-2025/mv-test-four-methods
- Eccentricity Electrical Contractors, “Verifying MV Cable Sheath Integrity,” Medium Voltage Cable Testing Guide. Available at: https://www.powerandcables.com/verifying-mv-cable-sheath-integrity/
- IEEE 400-2012, “IEEE Guide for Field Testing and Evaluation of the Insulation of Shielded Power Cable Systems Rated 5 kV and Above,” Institute of Electrical and Electronics Engineers.
- BARTEC GmbH, “How to perform a Megger test,” Hazardous Location Cable Installation Guide. Available at: https://bartec.com/company/magazine/how-to-perform-an-insulation-resistance-test-meg-test
- IEC 60364-4-41:2005, “Low-voltage electrical installations – Part 4-41: Protection for safety – Protection against electric shock,” International Electrotechnical Commission.
- Hradil Spezialkabel, “Offshore control cables are fully compliant with IEC standard 60079-14,” Technical Documentation. Available at: https://www.electronicspecifier.com/products/cables-and-connecting/offshore-control-cables-are-fully-compliant-with-iec-standard-60079-14/
![(N)TSKCGEWÖU specifications. This protective layer serves multiple critical functions within the cable assembly, with mechanical stress redistribution being among its most important roles. According to research published by Sibelco, the bedding compound is defined as the material applied around insulated conductors to maintain their position and provide bedding for protective armoring.[1] This layer functions as an intermediary component positioned between the laid-up cores and the metallic armor, creating what cable engineers describe as a separation sheath that fundamentally alters how mechanical forces are distributed throughout the cable structure.](https://feichuncables.com/blog/wp-content/uploads/image-596-400x225.avif "Inner Sheath Function: Mechanical Stress Redistribution in (N)TSKCGEWÖU Cables 3")
