IEC 60287-1-1:2023

Overview

IEC 60287-1-1:2023 is the authoritative international standard from the International Electrotechnical Commission (IEC) for calculating the continuous current rating and losses of electric cables under steady-state conditions. This standard provides universally accepted equations and methods for determining the safe current-carrying capacity (ampacity) for cables operating at all alternating voltages, as well as direct voltages up to 5 kV. It addresses cable installations buried directly in soil, placed in ducts, troughs, or steel pipes, including variable soil conditions and partial drying-out, as well as cables installed in air.

By relying on this standard, manufacturers, engineers, and users ensure accurate and comparable current rating calculations, supporting both safety and performance requirements. IEC 60287-1-1:2023 represents the latest technical guidance from IEC TC 20 on how to assess electrical cable thermal performance globally.

Key Topics

IEC 60287-1-1:2023 covers the following essential aspects related to cable current ratings and loss calculations:

• Steady-State Current Ratings: Calculation formulas for ampacity under steady, continuous loading (100% load factor), considering constant ambient conditions.
• Cable Construction Parameters: Guidance for incorporating essential cable characteristics such as conductor material resistivity and insulation thermal resistivity.
• Installation Environment: Consideration of installation variations, including cables:
  • Directly buried in soil (with and without soil drying-out)
  • Installed in ducts, troughs, and steel pipes
  • Laid in air and exposed to solar radiation
• Thermal Modeling: Use of thermal resistance values for cable insulation, sheath, armouring, cable bedding, and surrounding media.
• Losses Calculation: Inclusion of all relevant loss mechanisms such as conductor AC/DC resistance, dielectric losses, losses in sheaths, armours, and environmental impacts.
• Adjustable Parameters: Guidance for selecting or agreeing on parameters that depend on local conditions or specific manufacturer-user agreements, such as soil resistivity or the maximum conductor temperature.
• Correction Factors: Annex with correction factors for multicore cables, especially for adjusting for increased core lay lengths.

Applications

IEC 60287-1-1:2023 is crucial for a wide range of cable engineering tasks and industry practices:

• Cable System Design: Standardizes current rating calculations for low, medium, and high-voltage power cables, ensuring reliable load capacity determination in power grids and industrial installations.
• Compliance & Safety: Enables manufacturers and end-users to comply with international safety regulations by preventing cable overheating and associated risks.
• Project Specifications: Used by specifiers and contractors in utility, construction, and infrastructure projects to select appropriate cable types and sizes.
• Thermal Analysis: Integral for assessing the thermal performance of cables in various installation environments, including adverse soil or high ambient temperatures.
• Performance Optimization: Helps improve cable reliability and service life by providing accurate de-rating factors based on installation-specific variables.

Related Standards

For comprehensive cable rating calculations and related technical considerations, the following IEC standards complement IEC 60287-1-1:2023:

• IEC 60287-1-3: Current rating equations and calculation of losses - Current sharing and circulating current losses in parallel single-core cables.
• IEC 60287-2-1: Method for calculating the thermal resistance of cables and their immediate surroundings.
• IEC 60228: Specifications for conductors of insulated cables.
• IEC 60502 Series: Standards for power cables with extruded insulation and accessories for rated voltages.
• IEC 60027-3: Letter symbols in electrical technology.
• IEC 60889: Hard-drawn aluminium wire for overhead line conductors.

Adhering to IEC 60287-1-1:2023 ensures globally consistent, precise, and safe electric cable current rating and loss calculations, supporting robust power distribution system design and reliable installation practices.