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How to properly install wires and cables?
Release time:
2025-05-16
Correct installation of wires and cables is crucial for the long-term safe and stable operation of electrical systems. The following is a systematic installation guide based on international standards (such as IEC, NEC) and Chinese standards (such as GB 50168)
Correct installation of wires and cables is the core element in ensuring the long-term safe and stable operation of electrical systems. The following is a systematic installation guide based on international standards (such as IEC, NEC) and Chinese standards (such as GB 50168):
I. Pre-installation Preparations (Safety and Compliance Basics)
Design Review:
Verify the consistency of cable models, specifications, and routing in the drawings with the on-site situation.
Confirm that the voltage level, current carrying capacity, and short-circuit capacity match the protective devices (circuit breakers/fuses).
Material Acceptance:
Check the cable certificate of conformity, CCC certification (China Compulsory Certification), and factory test report.
Observe the insulation/sheath surface: no flattening, cracks, or oxidation spots.
Measure conductor resistance (≤ national standard limit) and insulation resistance (≥10MΩ/km).
Tool Preparation:
Cutting: Special cable cutters (to avoid damaging the conductor).
Stripping: Wire strippers (adjustable depth, conductor protection).
Crimping: Hydraulic/mechanical crimping pliers (die matching terminal specifications).
Testing: Megohmmeter (2500V for cables above 1kV), multimeter, phase tester.
Protection: Insulated gloves, safety glasses, arc protective clothing.
II. Key Installation Steps (Detailed by Scenario)
Scenario 1: Cable Tray/Cable Duct Installation
mermaid
Copy Code
graph LR
A[Install tray brackets] --> B[Tray grounding jumper]
B --> C[Cable laying ≤40% fill rate]
C --> D[Layered binding and fixing]
D --> E[Add pulleys at corners to prevent scratches]
Key Points:
Turning radius ≥ 15 times the cable outer diameter (multi-core) or 20 times (single-core).
Different voltage level cables are laid in layers: high voltage on top, low voltage on bottom (anti-interference).
Fixing spacing: horizontal ≤1.5m, vertical ≤1m (to prevent self-weight detachment).
Scenario 2: Conduit (PVC/Steel Pipe) Installation
Before Wiring:
Remove burrs from inside the pipe (steel pipes need to be anti-corrosive and the pipe ends polished).
Pre-install a guide wire (to prevent cable tangling).
During Wiring:
Pipe fill rate ≤ 40% (single cable) or 60% (multiple cables).
Apply a special lubricant (such as silicone grease), do not use engine oil (corrodes insulation).
Sealed Protection: Seal both ends of the pipes in outdoor/humid environments with fire-resistant clay to prevent moisture.
Scenario 3: Direct Burial Installation (Dangerous! Proceed with Caution)
mermaid
Copy Code
flowchart TD
A[Excavation depth ≥0.7m] --> B[Lay 100mm fine sand cushion layer]
B --> C[Lay cables]
C --> D[Cover with fine sand or soft soil ≥100mm]
D --> E[Lay protective cover plate/warning tape]
E --> F[Layered backfilling and compaction]
Mandatory Requirements:
Armored cables (such as YJV22) → Prevent mechanical damage.
Avoid heat pipes and corrosive areas (parallel spacing ≥1m).
Set permanent marker piles along the route (must be set at corners/joints).
Scenario 4: Overhead Installation
Steel wire rope load-bearing (tensile strength ≥2.5 times the cable weight).
Cable fixing spacing ≤ 0.75m (prevent wind damage).
UV protection measures: Use black weather-resistant sheathing or add a protective sleeve.
III. Joint and Terminal Processing (High Failure Rate Area!)
Stripping Specifications:
Use special tools to strip the insulation layer → Strictly prohibit damaging the conductor.
Length matching terminals: Conductor exposure ≤ 1mm (prevent discharge).
Crimping Process:
Copper Terminals: Select DT/OT/SC types, crimping die strictly matches the cross-section.
Crimping Torque: According to manufacturer's standards (e.g., 16mm² copper wire requires ≥12kN).
Crimp Inspection: Hexagonal crimp is uniform, no cracks.
Waterproof Sealing:
Outdoor joints use heat-shrink tubing (with hot-melt adhesive inside) → Heat and shrink from the middle to both ends.
High-voltage cables use cold-shrink terminals (elastic silicone rubber prefabricated parts).
IV. Grounding and Shielding Connections (Electric Shock and Interference Prevention)
Cable Grounding:
Ground both ends of the armor layer (using copper braided straps to connect steel tapes/wires).
Ground the metal bridge/pipe every 30m.
Shielding Grounding:
The shielding layer of the inverter cable must be grounded 360° (dedicated EMC terminal).
Ground the control cable at one end (to prevent ground loops).
V. Key Tests After Installation (Rejecting "One-Time Installation")
Test Items Tools Standards Risk Warnings
Insulation Resistance Megohmmeter New cable ≥ 100MΩ (below 1kV) Below 1MΩ indicates a risk of leakage current
Continuity Test Multimeter Correct phase sequence, no short circuit between zero and ground Incorrect phase sequence may burn out equipment
Withstand Voltage Test DC High Voltage Generator 3.5U₀ (e.g., 35kV/5min for 10kV cable) Breakdown indicates insulation defects
Phase Check Phase Meter Input end = Output end phase angle consistency Prevent motor reversal
VI. Fatal Errors and Pitfalls
Strictly Prohibited:
Direct connection of different metal conductors (copper-aluminum joints require transition terminals).
Insufficient cable bending radius (e.g., 6kV cable <15D = insulation damage).
Cable winding and crossing in the bridge (increases heat generation, reduces current carrying capacity by 30%).
Hidden Engineering Supervision:
Wall/floor openings must be sealed with fire-resistant sealant (to prevent fire spread).
Keep joints away from water accumulation areas (terminal boxes should be above ground).
Environmental Adaptability:
Do not use PVC cables in high-temperature environments (>70℃) → Use XLPE or silicone rubber instead.
Use polyurethane (PUR) sheathing in chemically corrosive areas.
VII. Special Cable Installation Points
Type Key Measures
Fire-resistant Cable Open wiring (avoid conduit to reduce fire resistance), support spacing ≤ 0.8m
Inverter Cable Ground both ends of the shielding layer, avoid parallel wiring with low-voltage wires (spacing ≥ 300mm)
Charging Pile Cable Double seal test for liquid cooling pipe joints (24h pressure holding without leakage)
Photovoltaic DC Cable Color-coded positive and negative poles (red+/blue-), UV aging treatment for outdoor joints
Ultimate Principle:
"Standard construction is the bottom line, testing and acceptance is the lifeline"
Strictly follow GB 50168 "Code for Construction and Acceptance of Electrical Installation Engineering Cable Lines". Complex projects must be operated by certified electricians. Every violation of installation may plant the seeds of electric arc short circuit, electric shock or fire!
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