Cable Installation Best Practices for Industrial Sites

A high-quality cable installed incorrectly will fail prematurely. Insulation damaged during installation, wrong bending radius, poor terminations and inadequate earthing cause more problems than many people expect. This guide covers professional installation standards for industrial cable work.

1. Before Installation, Cable Inspection

• Inspect drums on delivery, check for damage to cable sheath, verify drum labelling matches your order
• Megger test (insulation resistance test) on all power cables before installation, record the values as a baseline
• Check conductor continuity on multi-core cables
• Verify cable ratings match the circuit design (voltage rating, current rating, temperature rating)

2. Cable Routing and Segregation

Power cables and control/signal cables must be segregated to prevent electromagnetic interference. Minimum separation:

• Low-voltage power (1.1kV) and control cables: 200mm separation or use steel divider in cable tray
• High-voltage and low-voltage: separate trays on opposite sides of structure wherever possible
• Instrumentation cables (4, 20mA, thermocouples): separate tray, or use screened cables and cross power cables at 90°
• VFD output cables: separate tray, away from control wiring, VFD output has high-frequency switching noise

3. Bending Radius, Critical Parameter

Violating the minimum bending radius damages insulation and conductor stranding. Standard minimum bending radii:

OD = overall cable diameter. Bends tighter than these values crack insulation at the outer surface of the bend, damage that may not be visible but reduces dielectric strength.

4. Pulling Cables, Maximum Pulling Tension

Never pull cables by jerking or by the insulation jacket. Use a cable grip (Kellems grip) on the conductors, or a pulling eye terminated to the conductors. Maximum pulling tension for copper conductors: 70 N/sqmm of conductor cross-section. For a 3Ã, 50 sqmm cable: 3 Ã, 50 Ã, 70 = 10,500 N maximum. Never exceed this, it stretches the conductor and damages insulation-to-conductor adhesion.

5. Terminations, The Most Failure-Prone Point

Most cable failures in service occur at terminations. Common termination errors:

• Wrong lug size: A 35 sqmm lug on a 50 sqmm cable leaves air gaps, the connection overheats
• Crimping without the correct die: Hex dies for round lugs, indent dies for specific connectors. Wrong die = poor crimping = hot joint
• Insulation trimmed too long: Bare conductor exposed inside the enclosure, tracking risk
• Insulation trimmed too short: The conductor jacket is gripped in the lug barrel, strain relief fails
• Not using heat-shrink sleeves: On armoured cable terminations, the gland entry is the most vulnerable point, sleeving protects it

6. Earthing of Armoured Cables

The steel wire armour (SWA) of armoured cables must be earthed at both ends, at the panel/switchgear end and at the equipment end. Single-end earthing is only correct for some instrument cables (to avoid earth loops). For power cables: both ends, full 360° gland earthing. A floating armour is a safety hazard, it can rise to line voltage in a fault.

7. Underground Cable Installation

• Minimum burial depth: 750mm for LV, 1,000mm for HV under normal ground; 500mm under concrete
• Lay cables on a bed of fine sand (100mm), cover with sand (75mm), then protective tiles or warning tape
• Leave a pull rope in the trench for future cable addition
• Install route marker posts at cable crossings and regular intervals
• Perform insulation resistance test before and after burial

8. Post-Installation Testing