What is the difference between concentric cable and coaxial cable?

Concentric Cable vs Coaxial Cable

Concentric cable and coaxial cable look very similar, which often leads non professionals to confuse them during procurement, or even assume they are different names for the same product. 実際には, they are two completely different technical routes:

Concentric cable is a power cable, mainly used to transmit electrical power (例えば, service entrance cables under the UK BS 7870 標準). Coaxial cable is a signal/communication cable, mainly used to transmit high frequency signals (例えば, cable TV and antenna feeders).

Although their appearance may be similar, their internal structure, materials and physical principles are completely different. Below we break down and compare the structures of concentric cable and coaxial cable to help you distinguish them thoroughly.

Structure of Concentric Cable

The “concentric” in concentric cable means that the neutral conductor (neutral/earth) is helically wrapped concentrically around the insulated phase conductor.

Central phase conductor: The material is usually soft annealed copper, アルミニウム, aluminum alloy or copper clad aluminum. It is solid or stranded and is responsible for carrying large currents.
断熱層: XLPE, PVC or EPR is mainly used. It isolates the phase conductor from the outer neutral conductor.
Concentric neutral conductor: This is usually bare copper wire or bare aluminum alloy wire, wrapped around the insulation layer in SZ helical or alternating fashion. It serves as both the neutral return path and mechanical protection.
Filler and tape (for multicore cables): Polyester tape or filler rope is used for shaping, isolation and moisture protection.
アウターシース: The outermost layer is usually PVC, LSZH (low smoke zero halogen) またはPE, and some cables have armor.

Structure of Coaxial Cable

The “coaxial” in 同軸ケーブル means that the inner conductor, insulating dielectric and outer conductor shield share the same geometric center (axis). The signal is transmitted in the space between the inner and outer conductors.

内部導体 (center conductor): The material is usually copper, 錫メッキ銅, silver plated copper or even copper clad steel. Its diameter and material directly determine signal attenuation and characteristic impedance.
Insulating dielectric layer: Foamed PE, solid PE or PTFE is mostly used. It not only isolates the inner and outer conductors but also fixes the spacing. The dielectric constant directly determines the impedance (50 Ω or 75 おお).
Outer conductor (shield): Materials include copper braid, aluminum foil plus copper braid, corrugated copper tube, 等. It is the signal return ground and also shields external electromagnetic interference and prevents signal leakage.
アウターシース: PVC, PE or LSZH. Black weather resistant PE is commonly used outdoors, and light colors are used indoors.

Concentric Cable vs Coaxial Cable: How to Choose for Different Scenarios?

Types of Concentric Cable

By core number: シングルコア (neutral wire wrapped directly outside the phase conductor) と multicore (multiple phase conductors stranded together, with neutral wire wrapped outside).
By neutral form: split concentric (phase and neutral separated, common in UK standard service entrance cables) と concentric neutral (overall wrapping, common in US standard underground power supply).
By voltage: 低い電圧 (600/1000 Ⅴ) has a simple structure; medium voltage (15 kV, 25 kV, 等) requires an added semiconductive screen and semiconductive sheath.
By standard: IEC 60502-1, BS 7870, ASTM B881, 等, with strict requirements on wrapping method and dimensions.

同軸ケーブルの種類

By characteristic impedance: 50 おお (コミュニケーション, RF, antenna feeders) と 75 おお (cable TV, video surveillance).
By shielding strength: single braid (basic), aluminum foil plus braid double shield (mainstream surveillance), multilayer shield (high interference resistance) and corrugated copper tube (fully shielded RF).
By insulating dielectric: foamed PE (低損失) and PTFE (high temperature and high frequency resistance).

Comparison of Concentric Cable and Coaxial Cable

To help engineers and procurement staff check quickly, here is a direct comparison of concentric cable and coaxial cable:

寸法	同心ケーブル	同軸ケーブル
Core function	Transmit power	Transmit signal / RF
Structural logic	Phase conductor inside, neutral conductor concentrically wrapped outside	内部導体, insulation and outer shield share the same axis
Function of outer conductor	Serves as neutral (N) or earth (PE) return path, with protective function	Serves as signal return ground, with electromagnetic shielding function
Parameters	Cross sectional area, ampacity, 定格電圧	Characteristic impedance (50/75 おお), shielding attenuation
アプリケーション	Service entrance power lines, low voltage distribution networks, street lighting	ケーブルテレビ, video surveillance, antennas, RF communication

Installation Environment and Construction Constraints

Concentric cables and coaxial cables have vastly different requirements for their installation environments; incorrect placement or improper handling can lead to immediate failure:

同心ケーブル (配電):
Primarily used for direct underground burial, building service entrances, or outdoor conduits. Construction constraints: The outer layer of bare copper neutral wires is susceptible to damage during pulling; if the outer sheath is compromised, the cable becomes highly vulnerable to moisture and corrosion once buried. Rough handling or forceful pulling is strictly prohibited; an adequate bending radius must be maintained.

同軸ケーブル (Signal Transmission):
Primarily used in indoor low-voltage cable trays, on surveillance poles, or for outdoor antennas. Construction constraints: The internal foamed insulation layer is extremely sensitive to pressure. Sharp bends or “kinks” at corners can cause impedance fluctuations and signal loss. さらに, outdoor connectors must be rendered strictly watertight; the ingress of water will effectively destroy the high-frequency signal.

結論

同心ケーブル is designed to deliver “power” safely and economically to homes and businesses; coaxial cable is designed to deliver “signals” to terminals cleanly and with interference resistance. The two cannot replace each other and cannot be mixed. In overseas projects, whether for power distribution or communication surveillance, ZMS Cable can provide high quality cables that meet international standards.

We provide concentric cables compliant with BS 7870 およびIEC 60502, as well as various 50 Ω/75 Ω coaxial cables (such as the RG series), meeting full scenario requirements from power to signal. 加えて, the ZMS Cable engineering team will recommend the correct model strictly according to your application scenario (power supply circuit or low voltage signal), avoiding project rework caused by selection errors.

Need to purchase concentric cable or coaxial cable for your project? Please send your specification requirements to our technical team, and we will provide an accurate quotation and technical support.

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