I. Definition of Cables
A cable is generally composed of one or more insulated conductors that are stranded together and covered with an insulating protective sheath. It is characterized by conducting electricity internally while providing external insulation.
(Image Caption: Basic Structure of a 10kV Power Cable)
II. Common Cable Models
1. Common Cable Model Classifications
① SYV: Solid polyethylene insulated radio frequency (RF) coaxial cable. Used in wireless communications, broadcasting, surveillance systems, and related electronic equipment for transmitting RF signals (including integrated coaxial cables).
② SYWV(Y): Physical foamed polyethylene insulated cable for CATV systems (Video/RF coaxial cable). Applicable for closed-circuit monitoring and cable TV projects.
Structure (Coaxial Cable):Single oxygen-free round copper wire + Physical foamed polyethylene (insulation) + (Tinned wire + Aluminum braid) + PVC (Polyethylene sheath).
③ Signal Control Cables (RVV Sheathed Cable, RVVP Shielded Cable): Applicable for building intercoms, burglar alarms, fire protection, and automatic meter reading systems.
RVVP:Copper core PVC insulated, shielded PVC sheathed flexible cable. Voltage: 250V/300V, 2-24 cores.
Purpose:Instrumentation, intercom, monitoring, and control installation.
④ RG: Physical foamed polyethylene insulated access network cable. Used for transmitting data and analog signals in Hybrid Fiber-Coaxial (HFC) networks.
⑤ KVVP: PVC sheathed braided shielding cable.
Purpose:Signal transmission, control, and measurement for electrical appliances, instruments, and distribution devices.
⑥ RVV (227IEC52/53): PVC insulated flexible cable.
Purpose:Household appliances, small power tools, instruments, and power/lighting.
⑦ AVVR: PVC sheathed flexible cable for installation purposes.
⑧ SBVV; HYA: Data communication cable (indoor/outdoor). Used for telephone communications, connecting radio equipment, and terminal box wiring in telephone distribution networks.
⑨ RV, RVP: PVC insulated cables.
⑩ RVS, RVB: Cables suitable for connecting household appliances, small power tools, instruments, meters, and power/lighting.
⑪ BV, BVR: PVC insulated cables.
Purpose:Fixed wiring for electrical instrumentation equipment and power/lighting.
⑫ RIB: Speaker connection cable ("Audiophile cable").
⑬ KVV: PVC insulated control cable.
Purpose:Signal transmission, control, and measurement for electrical appliances, instruments, and distribution devices.
⑭ SFTP: Twisted pair cable. Used for transmitting telephone, data, and information network signals.
⑮ UL2464: Computer connection cable.
⑯ VGA: Monitor cable.
⑰ SDFAVP, SDFAVVP, SYFPY: Coaxial cables, dedicated for elevators.
⑱ JVPV, JVPVP, JVVP: Copper core PVC insulated and sheathed copper wire braided computer control cable.
III. Difference Between Cables and Wires
1. Wire (Wire):
Generally a single conductor made of copper or aluminum with a light, soft insulation layer.
2. Cable (Cable):
Generally consists of several groups of conductors stranded together, insulated externally. Typically features double or multiple insulation layers, and may include shielding, metal sheathing, or armoring.
3. Distinction between Wires and Cables
Simply put, a conductor (wire) is the raw material used within a cable; it is a component ofa cable. Thus, a cable contains the wire. This is the most direct difference.
In practice, there is no strict boundary between "wire" and "cable." They can be distinguished narrowly but are broadly referred to collectively as "cables." General rules:
① Single core = "Wire"; Multiple cores = "Cable"
② Small diameter = "Wire"; Large diameter = "Cable"
③ Simple structure = "Wire"; Complex structure = "Cable"
4. Common Wires
Generally divided into Solid (Hard-drawn) and Flexible (Stranded) wires.
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Solid Wire: Used for power supply, 220V lighting, sockets, and air conditioners.
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Flexible Wire (Low-voltage wire): Used for telephone, audio, network, and video signal transmission.
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Copper Core Specifications (Typical Current Ratings):
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1.0 mm² = 20A
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1.5 mm² = 25A
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2.5 mm² = 34A
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4.0 mm² = 44A
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6.0 mm² = 58A
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5. Common Cables
Cables generally have more than two layers of insulation, are mostly multi-core, wound on drums/coils, and are typically sold in lengths greater than 100 meters. They are installed indoors, in cable trenches, inside pipes, underground, or used for overhead power transmission.
IV. Cable Installation Requirements
1. For cables laid in cable trenches without sand filling (including indoor locations), and for fire safety reasons, cables with bare armored flame-retardant (or difficult-to-ignite) outer sheaths shall be used.
2. If there are joints in the cable line, to prevent faults at the joint from affecting adjacent cables, the joint must be protected with a fireproof protection box or other fire prevention measures must be taken.
3. Cables can be placed directly on the trench bottom, or brackets can be installed in the trench to increase the number of cables laid.
4. When cables are fixed to brackets:
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For horizontal installation: Power and control cables with an outer diameter ≤ 50mm require support every 0.6m. Power cables with an outer diameter > 50mm require support every 1.0m.
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Single-core cables arranged in an equilateral triangle must be tied securely with straps every 1.0m.
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For vertical installation: Cables should be fixed every 0.5m.
5. Power cables and control cables should be installed on separate sides of the trench brackets. If conditions do not permit this, power cables must be placed on the brackets above the control cables.
6. A continuous grounding wire device must be installed in the cable trench, and its specification must comply with code requirements. All metal brackets, the metal sheath of the cable, and the armor layer (except where insulation requirements dictate otherwise) must be connected to the grounding device. This prevents potential differences between the cable sheath and metal brackets, avoiding AC corrosion or dangerously high step voltages that could threaten personnel safety.
7. All metal structures within the cable trench must be galvanized or coated with anti-rust paint.
