PAS 05308 — Control and Instrumentation Cables PE and PVC Insulated Standard Series (PAS 5308)

📐 PAS 5308 is a Publicly Available Specification (PAS) published by the British Standards Institution (BSI), sponsored by the British Cables Association (BCA) with support from the Electrical Contractors’ Association (ECA), providing specifications for control and instrumentation cables. These cables serve industrial control, signal transmission and instrumentation loops, with high demands on electrical performance (e.g. mutual capacitance, crosstalk) and mechanical reliability. This batch collects the 2009 two-part edition: Part 1 is the specification for polyethylene (PE) insulated cables, and Part 2 is the specification for PVC insulated cables.

1. Series Overview and Positioning 📌

PAS 5308 was sponsored by the BCA and developed by BSI, coming into effect on 3 July 2009, with participation from the British Approvals Service for Cables (BASEC), ERA Technology and UK Ministry of Defence standardisation. The series has two parts covering PE and PVC insulated cables respectively; the two share a similar structure (conductor, laying up, sheath, electrical tests) but differ in material and performance parameters.

This batch contains the following two parts:

2. Conductor and Insulation Requirements 🔧

Both parts specify the conductor and insulation:

• Conductor: specify nominal cross-sectional areas (e.g. 0.5, 0.75, 1.0, 1.5, 2.5 mm²) and conductor classes (e.g. Class 1 solid, Class 2 stranded, Class 5 flexible), with conductor DC resistance requirements.
• Insulation thickness: give standard and enhanced insulation thicknesses (Table 1, Table 2) ensuring dielectric strength and mechanical protection.
• Insulation material: Part 1 is PE (polyethylene), Part 2 is PVC (polyvinyl chloride), with different dielectric properties and temperature ratings.

Accurate control of insulation thickness is critical for the voltage withstand capability and signal integrity of the cable.

3. Laying Up, Outer Protection and Marking 📦

• Laying up: multicore or multipair cables are laid up per the specification, defining twisting, lay length and screen structure (with or without individual pair screens).
• Outer protection: specify sheath material and thickness for mechanical and environmental protection.
• Cable marking: specify the content and method of sheath marking for identification and traceability.

Annex C gives pair identification rules; Annex D gives constructional dimensions tables (by conductor section, laid-up structure, with/without screens) for design and procurement checking.

4. Electrical and Finished Cable Testing ⚡

Both parts specify rigorous electrical and finished-cable tests:

• Maximum mutual capacitance (Part 1 Table 3): limit the maximum mutual capacitance between pairs after laying up, ensuring signal transmission quality.
• L/R ratio for adjacent cores: limit the inductance/resistance ratio between adjacent cores, ensuring loop balance and crosstalk control.
• Voltage test: Annex E specifies the voltage test method and test voltage to assess insulation strength.
• Finished cable testing: electrical performance and appearance checks on the finished cable to ensure factory quality.

Annexes A and B give handling and usage at various temperatures and the guide to use (including minimum bending radius and test voltages after installation), providing a basis for site installation and post-installation acceptance.

5. Engineering Practice Points ⚙️

• 🔍 Selection: prefer PE insulation (Part 1) for low-capacitance/high-frequency instrument signals; general industrial control and mixed power-signal loops may use PVC insulation (Part 2).
• 🔧 Installation: observe minimum bending radius, ambient temperature and oil/flame-retardancy requirements, avoiding mechanical damage.
• 📊 Acceptance: check laying up and screening against the dimensions tables, and verify mutual capacitance, L/R ratio and voltage withstand per the electrical tests.
• 📋 Marking and traceability: verify sheath marking, retain material and test records, ensuring traceability.

6. Frequently Asked Questions ❓