In power engineering and industrial equipment installation, selecting the wrong type of “high-voltage cable” or “low-voltage cable” can lead to equipment failure, power outages, and production stoppages, or even safety accidents in severe cases. However, many people only have a superficial understanding of the structural differences between the two and often select based on experience or “cost-saving”” considerations, leading to repeated mistakes. Choosing the wrong cable may not only cause equipment malfunctions but also create potential safety hazards. Today, let’s discuss the core differences between them and the 3 major “pitfalls” you must avoid during selection.
1. Structural Analysis: High-Voltage vs Low-Voltage Cables
Many people think, “High-voltage cables are just thicker low-voltage cables,” but in fact, their structural designs have fundamental differences, and every layer is precisely adapted to the voltage level. To understand the differences, start with the definitions of “high-voltage” and “low-voltage”:
Low-voltage cables: Rated voltage ≤ 1 kV (commonly 0.6/1 kV), mainly used for building distribution and small equipment power supply;
High-voltage cables: Rated voltage ≥ 1 kV (commonly 6 kV, 10 kV, 35 kV, 110 kV), used for power transmission, substations, and large industrial equipment.
(1) Conductor: Not “Thicker” but “Purity Matters”
Low-voltage cable conductors are usually made of multi-stranded fine copper wires (e.g., 19 strands in BV wires), mainly to meet “current-carrying capacity” requirements;
High-voltage cable conductors, though also copper or aluminum, have higher purity (≥99.95%) and adopt a “compact round stranding” process (reducing voids) to lower conductor surface resistance and reduce the “skin effect” under high voltage (current concentrates on the conductor surface, causing heating).
(2) Insulation Layer: The Core of High-Voltage Cables’ “Multi-Layer Protection”
Low-voltage cable insulation layers are relatively thin (e.g., 0.6/1 kV cable insulation thickness ~3.4 mm), mostly PVC or XLPE, mainly serving to “isolate the conductor from the outside”;
High-voltage cable insulation layers are much thicker (6 kV cable ~10 mm, 110 kV up to 20 mm) and must pass stringent tests such as “power frequency withstand voltage” and “lightning impulse withstand voltage.” More importantly, high-voltage cables add water-blocking tapes and semi-conductive layers within the insulation:
Water-blocking tape: Prevents water ingress (moisture under high voltage can cause “water treeing,” leading to insulation breakdown);
Semi-conductive layer: Ensures uniform electric field distribution (prevents local field concentration, which could cause discharge).
Data: The insulation layer accounts for 40%-50% of high-voltage cable cost (only 15%-20% for low-voltage), which is a major reason why high-voltage cables are more expensive.
(3) Shielding and Metallic Sheath: The “Armor Against Interference” for High-Voltage Cables
Low-voltage cables generally have no shielding layer (except signal cables), with outer jackets mostly PVC or polyethylene;
High-voltage cables (especially ≥6 kV) must have metallic shielding (e.g., copper tape, copper braid) and metallic sheaths (e.g., lead sheath, corrugated aluminum sheath):
Metallic shielding: Constrains the high-voltage field within the insulation layer, reduces electromagnetic interference (EMI), and provides a path for fault current;
Metallic sheath: Enhances mechanical strength (tensile and crush resistance) and acts as a “grounding shield,” further reducing insulation field intensity.
(4) Outer Jacket: More Rugged for High-Voltage Cables
Low-voltage cable jackets mainly protect against wear and corrosion;
High-voltage cable jackets must additionally resist oil, cold, ozone, etc. (e.g., PVC + weather-resistant additives). Special applications (e.g., submarine cables) may also require steel wire armoring (resisting water pressure and tensile stress).
2. 3 Key “Pitfalls” to Avoid When Selecting Cables
After understanding the structural differences, you must also avoid these “hidden traps” during selection; otherwise, costs may increase, or safety incidents may occur.
(1) Blindly Pursuing “Higher Grade” or “Cheaper Price”
Misconception: Some think “using high-voltage cables instead of low-voltage is safer,” or they use low-voltage cables to save money.
Risk: High-voltage cables are much more expensive; unnecessary high-voltage selection increases budget. Using low-voltage cables in high-voltage scenarios can break down insulation instantly, causing short circuits, fires, or endangering personnel.
Correct Approach: Select based on actual voltage level and power requirements, e.g., household electricity (220V/380V) uses low-voltage cables, industrial high-voltage motors (10 kV) must match high-voltage cables — never “downgrade” or “upgrade” blindly.
(2) Ignoring the “Hidden Damage” from the Environment
Misconception: Only consider voltage, ignore the environment, e.g., using ordinary cables in humid, high-temperature, or chemically corrosive conditions.
Risk: High-voltage cables in humid environments with damaged shields or jackets can experience insulation moisture aging; low-voltage cables in high-temperature areas (e.g., boiler rooms) can soften and fail.
Correct Approach: Clarify installation conditions — armored cables for buried installation, waterproof armored cables for underwater, high-temperature rated materials (XLPE ≥90℃) for hot environments, corrosion-resistant jackets in chemical plants.
(3) Ignoring the Matching of “Current-Carrying Capacity and Laying Method”
Misconception: Only focus on voltage level, ignore cable current capacity (maximum allowable current) or over-compress/bend during laying.
Risk: Insufficient current capacity causes overheating and accelerates insulation aging; improper bending radius of high-voltage cables (e.g., hard pulling, excessive bending) can damage shielding and insulation, creating breakdown risks.
Correct Approach: Choose cable specifications based on calculated actual current (consider starting current, ambient temperature); strictly follow bending radius requirements during installation (high-voltage cable bending radius usually ≥15× conductor outer diameter), avoid compression and sun exposure.
3. Remember 3 “Golden Rules” to Avoid Selection Pitfalls
(1) Check Structure Against Voltage:
High-voltage cable insulation and shielding layers are core; low-voltage cables do not require over-design.
(2) Match Grades Appropriately:
Voltage, power, and environment must correspond; do not blindly upgrade or downgrade.
(3) Verify Details Against Standards:
Current-carrying capacity, bending radius, and protection level must follow national standards — do not rely solely on experience.
Post time: Aug-29-2025