Cable Sizing
Cable sizing is a critical part of electrical design, ensuring cables can safely carry current under real installation conditions. This section covers current-carrying capacity, derating factors, installation methods, and key standards such as BS 7671 and IEC 60287.
You’ll find practical guidance, calculation methods, and engineering insights to help you select the correct cable size for a wide range of applications.
Knowledge Base Topics
Articles
Cable Impedance: Positive and Zero Sequence Calculations
Cable impedance formulae for positive and zero sequence calculations, including IEC 60909 arrangements with and without metallic sheaths or shields.
Updated May 27, 2026
Transformer Secondary Fault Level Calculation
How to calculate three-phase transformer secondary fault current and fault level using transformer kVA, secondary voltage and percentage impedance.
Updated May 27, 2026
Network Fault Level: Converting Fault Current, MVA and Impedance
How to convert network fault level between fault current, apparent power and external impedance for three-phase AC, single-phase AC and DC systems.
Updated May 27, 2026
IEC 60909 Fault Calculations: Short-Circuit Current Formulae
IEC 60909 short-circuit current formulae for three-phase, single-phase and DC fault calculations, including voltage factor and source impedance.
Updated May 27, 2026
Earth Fault Loop Impedance for Cable Sizing
How earth fault loop impedance is calculated for cable sizing, including Zs, CPC impedance, BS 7671 disconnection checks and IEC 60909 sequence values.
Updated May 27, 2026
Circuit Protective Conductor (CPC) in Cable Sizing
What a circuit protective conductor is, common CPC forms, and how CPC selection affects fault current, earth-loop impedance and thermal withstand.
Updated June 5, 2026
Fault Current Calculations for Cable Sizing
Introduction to fault current calculations for cable sizing, including three-phase, phase-to-phase and single-phase-to-ground faults.
Updated May 27, 2026
Cable Power Loss: Complex Power and I²R Methods
How to calculate cable power loss using complex power or I²R resistance methods, including circuit factors for DC, single-phase and three-phase circuits.
Updated May 27, 2026
8 Steps to Low Voltage Power Cable Selection and Sizing
A practical eight-step workflow for low voltage power cable selection, including insulation, armouring, current rating, voltage drop and fault withstand.
Updated June 4, 2026
Sheath Induced Voltage and Circulating Current in Single-Core Cables
How to estimate sheath induced voltage, capacitive current and circulating current in bonded single-core cable systems.
Updated May 27, 2026