Can XLPE Power Cables Be Used in Wet Locations?

In electrical engineering, selecting the right cable for damp environments (such as underground pipelines, tunnels, etc.) is critical. XLPE cables are widely used in medium- and low-voltage systems due to their excellent insulation properties, but whether they can be used in damp environments requires a comprehensive assessment of cable structure, humidity levels, and protective measures. This article will analyze this topic accordingly.
Understanding the “Moisture Resistance” of XLPE Material Itself
To determine whether XLPE power cables can be used in damp environments, one must first understand the fundamental properties of the XLPE insulation layer—it is not inherently “absolutely waterproof,” but possesses a certain degree of resistance to moisture penetration. This capability is closely related to its molecular structure and manufacturing process:
Molecular Structure Advantage: Through cross-linking reactions, XLPE transforms polyethylene molecules from a linear structure into a three-dimensional network, significantly reducing water molecule permeation rates. Compared to traditional PVC (polyvinyl chloride) insulation, XLPE exhibits higher crystallinity and smaller intermolecular gaps. In short-term or low-humidity conditions, it effectively blocks moisture intrusion into the insulation layer, preventing degradation of insulating properties.
Enhanced Temperature and Chemical Resistance: XLPE maintains long-term operating temperatures up to 90°C (184°F) (some high-grade products reach 105°C/210°F) and resists acid-alkali corrosion. Even when exposed to mildly corrosive moisture in humid environments (e.g., trace salts in soil, condensation in industrial zones), it resists degradation or swelling, offering superior insulation stability over conventional materials.
However, note: Pure XLPE insulation does not provide “complete waterproofing.” If exposed long-term to high humidity, standing water, or immersion, water molecules may still slowly permeate through cable joints, sheath gaps, or minor insulation defects. This can reduce insulation resistance and, in severe cases, trigger partial discharge or even breakdown incidents. Therefore, the suitability of XLPE power cables for humid environments hinges on whether the cable incorporates a “targeted moisture-proof structural design.”
Critical Determinant: XLPE Cables with Different Structures Vary Dramatically in Humidity Suitability
XLPE power cables on the market are not a “single type.” Differences in their sheath, armor, and sealing designs directly determine their suitability for humid environments. Below is a breakdown of the applicable scenarios for three common types of XLPE cables:
Standard Unarmored XLPE Cable (e.g., YJV Type): Suitable only for “low humidity, no standing water” dry-humid environments.
Standard XLPE cables (e.g., GB standard YJV type, structured as “copper/aluminum conductor + XLPE insulation + PVC sheath”) represent the most basic type. Their moisture resistance relies entirely on the outer PVC sheath:
Suitable Scenarios: Only suitable for environments with “occasional moisture but no standing water,” such as indoor basements (well-ventilated, no condensation accumulation), dry cable trenches (no groundwater seepage), or outdoor covered cable trays (avoiding direct rain exposure).
Prohibited Scenarios: Strictly prohibited in environments with prolonged water accumulation (e.g., cable pits with high groundwater levels), immersion (e.g., pool bottoms, sewers), or enclosed spaces with high humidity and poor ventilation (e.g., flooded areas in underground distribution rooms). In such conditions, the PVC sheath may deteriorate and crack due to prolonged moisture exposure. Water ingress can compromise the electrical properties of the XLPE insulation layer, posing a short-circuit risk.
Armored XLPE Cables (e.g., YJV22, YJV32): Suitable for “moderately humid environments with minor mechanical damage risks”​
Armored XLPE cables enhance standard XLPE cables with either “steel tape armor (Type 22)” or “steel wire armor (Type 32)” and feature optimized sheath sealing technology:
Structural Advantages: The armor layer not only withstands external mechanical impacts (e.g., soil compression, rock collisions) but also forms a “secondary barrier” between the sheath and insulation, slowing moisture penetration. Some products utilize “XLPE insulation + PE sheath” (instead of PVC sheath), where PE offers superior weather resistance and hydrolysis resistance, further enhancing moisture protection.
Suitable Scenarios: Ideal for moderately humid environments, such as underground direct burial cables (moderate soil moisture, no long-term water accumulation), outdoor non-submerged cable trenches (with drainage systems), and tunnel cables (well-ventilated, no condensation buildup). YJV22 XLPE cables are commonly selected for municipal grid underground distribution lines and outdoor power transmission in industrial parks.
Limitations: In environments with “permanent water accumulation” or “corrosive moisture” (e.g., underground soil near chemical plants), armor alone cannot fully block moisture penetration. Additional corrosion and moisture protection measures are required (e.g., wrapping corrosion-resistant tape around the cable, selecting corrosion-resistant sheaths).
Waterproof/Submersible XLPE Cables (e.g., JHS, YJVQ types): Suitable for extreme moisture environments with “prolonged water accumulation or immersion”​
For extreme moisture scenarios (e.g., underwater operations, flooded cable pits, areas with extremely high groundwater levels), specially designed waterproof XLPE cables feature a “multi-layer seal + waterproof structure”:​
Core Design: ① Conductors use “waterproof conductors” (e.g., tinned copper wires + water-blocking yarn filling) to prevent moisture ingress through conductor gaps; ② “Semiconductor water-blocking tape” added outside insulation forms a radial water barrier; ③ The sheath employs waterproof materials like “chloroprene rubber” or “cross-linked PE”; some products further incorporate “water-blocking compound” between the armor layer and sheath for complete sealing.
Applications: Fully suitable for long-term waterlogged or submerged environments, such as submersible motor power supply, underwater cables in wastewater treatment plants, and emergency power lines in flooded underground distribution rooms. For example, JHS-type waterproof XLPE cables used for submersible pump power supply in a sewage treatment plant can operate stably for extended periods at depths up to 10 meters.
Certification Requirements: These cables must pass “waterproof performance tests” (e.g., immersion withstand voltage tests per GB/T 12706). When selecting products, verify they possess corresponding waterproof rating certifications (e.g., IP68).
Using XLPE Cables in Humid Environments: Three Critical Pitfalls to Avoid
Even with properly selected XLPE cables, improper installation or maintenance can compromise moisture resistance. Below are three common engineering pitfalls requiring special attention:
Misconception one: “Any XLPE cable can be buried directly in waterlogged areas.”
Some engineers mistakenly believe XLPE material is moisture-resistant and bury standard YJV cables in waterlogged areas. In reality, the PVC sheath of ordinary XLPE cables undergoes hydrolysis and ages under prolonged water immersion, leading to cracking and potential insulation breakdown within 3-5 years. Correct Practice: Waterproof XLPE cables (e.g., YJVQ type) must be used in waterlogged areas. During installation, surround the cable with “sand + waterproof underlayment” to prevent sharp stones from puncturing the sheath.
Misconception two: “Cable joints don't need waterproofing since XLPE insulation is moisture-resistant anyway.”
Cable joints are the “weak link” in moisture protection. Even if the main cable is waterproof, using only standard insulating tape at joints allows moisture to seep through gaps, reducing insulation resistance at the joint. Correct Practice: Cable joints in humid environments must use “waterproof joint boxes” (e.g., heat-shrink waterproof joints, cold-shrink waterproof joints) and be wrapped with “water-blocking tape + waterproof tape” to ensure complete sealing.
Misconception three: “Ignoring the combined effects of ambient temperature and humidity”
In “low-temperature, high-humidity” environments (e.g., underground cable trenches in northern winters), moisture readily condenses into ice on cable surfaces. Repeated freeze-thaw cycles may cause sheath cracking. Conversely, in “high-temperature, high-humidity” environments (e.g., basements in southern summers), XLPE insulation ages more rapidly. Correct practice: For low-temperature, high-humidity environments, select “low-temperature resistant sheathed XLPE cables” (e.g., with weather-resistant PE sheathing and a low-temperature brittleness temperature ≤ -40°C). For high-temperature, high-humidity environments, enhance cable heat dissipation (e.g., using cable trays with ventilation holes) and regularly test cable insulation resistance.
Selection Guide: Four Steps to Choose “XLPE Cables for Humid Environments”
How to quickly select suitable XLPE cables for projects? Follow the 4-step process: “Environmental Assessment → Structural Selection → Parameter Verification → Certification Check”:​
Step one: Assess Humidity Environment Level​
First determine the “humidity type” of the application scenario, categorized into 3 levels:​
Light Humidity: No standing water, relative humidity ≤60% (e.g., well-ventilated basements);​
Moderate Humidity: Occasional standing water, relative humidity 60%-80% (e.g., outdoor cable trenches with drainage systems);​
Extreme Humidity: Persistent standing water or immersion, relative humidity ≥80% (e.g., underwater or underground waterlogged areas).​
Step two: Select Cable Structure Based on Level​
Mildly humid: Standard unarmored XLPE cable (YJV type);​
Moderately humid: Armored XLPE cable (YJV22, YJV32 type, prioritize PE sheath);​
Extremely humid: Waterproof XLPE cable (JHS, YJVQ type, must include water-blocking structure).​
Step three: Confirm Key Parameters​
Insulation Thickness: In humid environments, XLPE insulation thickness must be 10%-20% greater than in dry environments (e.g., for 10kV cables, dry environment insulation ≥4.5mm, humid environment ≥5.0mm) to enhance resistance to water vapor penetration;​
Sheath Material: Prioritize PE or neoprene sheaths; avoid standard PVC sheaths (poor hydrolysis resistance).
Conductor Material: For mildly corrosive environments, select tinned copper conductors (more corrosion-resistant than bare copper).
Step four: Verify Certifications and Test Reports
Require suppliers to provide the following documentation:
Product compliance with national standard GB/T 12706 (Extruded Insulated Power Cables with Rated Voltage from 1kV to 35kV) or IEC 60502 standard;
Waterproof cables require a “Water Immersion Voltage Withstand Test Report” (e.g., passing voltage withstand test after 24-hour immersion in 1-meter water depth);​
Weather-resistant cables require an “Aging Resistance Test Report” (e.g., UV aging test, damp heat aging test).​
Summary: XLPE cables can be used in humid environments, but require “selecting the right type + implementing proper protection”.
Returning to the initial question: “Can XLPE power cables be used in humid environments?” The answer is — yes, but the cable structure must be selected based on the humidity level, and moisture-proof measures must be implemented during installation and maintenance.
Standard XLPE cables (e.g., YJV type) are only suitable for mildly humid environments. Moderately humid conditions require armored types, while extremely humid environments mandate waterproof types. Concurrently, waterproofing cable joints and coordinated protection against ambient temperature and humidity are critical for ensuring long-term stable operation. With proper selection and standardized installation, XLPE power cables can fully deliver their superior transmission performance in humid environments, providing reliable assurance for power systems.