Conductor cross-section is the core parameter of wire and cable products, and is also a key factor affecting their electrical performance. However, in the assessment of the nominal cross-section of the conductor of power supply flexible wire for electrical products, some users and testing organizations have some misunderstandings in understanding and operation, using the geometric method to measure the actual cross-sectional area of the conductor and determine the nominal cross-section of the conductor against the standard, bringing trouble to the relevant product compliance. In this regard, Quality and Certification has published an article entitled “Explanation and analysis of the nominal cross-sectional area of cable conductors”, which elaborates on the concept, understanding and assessment of the cross-sectional area of cable conductors.
Recently, in view of the potential impact of this topic on the testing and certification of products under the IECEE international multilateral mutual recognition system, and in order to harmonise the understanding of this assessment requirement among testing laboratories and certification bodies worldwide under the IECEE system based on IEC standards, the IECEE has issued a new CTL resolution PDSH 2219 in 2023, which clarifies the assessment of the nominal cross-section of power cord conductors. The requirements are clarified.
II. Requirements of the resolution
In IECEE-CB testing and certification of electrical household and similar-use products based on IEC 60335-1 (note: the domestic equivalent is GB 4706.1), does the nominal cross-section of the conductor of a power cord conforming to IEC 60227 or IEC 60245 need to be physically measured, or can this be verified by checking the mark and the test report/certificate? If the nominal cross-sectional area of the conductor of a power cord needs to be physically measured, how should it be measured: should the actual cross-sectional area dimensions be measured, or should the nominal cross-section be determined by measuring the conductor resistance according to IEC 60228?
For power cord conductors conforming to IEC 60227 or IEC 60245, measurement of the nominal cross-section is not required and verification of compliance with the nominal cross-section requirement as required by clause 25.8 is permitted by checking the marking and certificate/report of the power cord.
III. Interpretation of the resolution
The CTL resolution PDSH 2219 clarifies that in the IECEE-CB testing and certification of electrical household and similar-use products based on IEC 60335-1 (the domestic equivalent is GB 4706.1), the nominal cross-section of the conductor of the power supply cord can be verified by checking the marking and its test report/certificate, instead of taking a geometrical approach to measuring the actual cross-section of the conductor.
At the same time, technical explanations are given from several angles, which can be summarised as follows:
(1) The relevant provisions of IEC 60335-1 refer to the “nominal cross-section of the conductor” and not to the “actual cross-section of the conductor”. Therefore, it is the “nominal cross-section of the conductor”, not the “actual cross-section of the conductor”, that is to be assessed.
(2) The relevant provisions of IEC 60335-1 do not provide a specific method for measuring the “nominal cross-section of a conductor”. The general understanding of the standard is that if an item is to be measured, a specific method should be given.
(3) The list of test equipment in IEC 60335-1 does not mention testing equipment related to the measurement of “nominal cross-sections of conductors”, which suggests that the measurement of “nominal cross-sections of conductors” is not required for IEC 60335-1.
(4) The relevant product standards for wires and cables (e.g. IEC 60227 and IEC 60245) do not require the measurement of the actual cross section of the conductor, but rather the measurement and assessment of the conductor resistance value. The conductor resistance is in fact a key parameter in the practical application of cable conductors which is directly related to the “rated current”.
(5) It is not only the actual cross-section but also the material composition of the conductor, e.g. the purity of the copper, which makes it unreasonable to judge whether the conductor matches the corresponding “rated current” only from the actual cross-section.
The final conclusion is that in the IECEE-CB testing and certification of IEC 60335-1, the nominal cross-section of the conductor of the power cord does not need to be specifically measured, let alone determined by geometrically measuring the actual cross-sectional area of the conductor, but is verified by checking the logo and test report/certificate of the cable cord.
The release and implementation of this resolution will not only help the relevant laboratories and certification bodies under the IECEE system to understand and implement the assessment requirements for nominal cross-section of power cord conductors in a more standardised manner, but will also promote the correct understanding and application of the relevant standards for conductor cross-section and conductor resistance by cable manufacturers, users and third parties, and facilitate quality compliance and improvement of upstream and downstream products.
IV. Introduction to IECEE
IECEE: IECEE is the International Electrotechnical Commission’s System for Conformity Assessment Schemes for Electrotechnical Equipment and Components, a multilateral certification system based on IEC The IECEE is a multilateral certification system based on IEC international standards. Its members obtain national certification or approval from countries around the world through mutual recognition (two-way acceptance) of test results.
IECEE CTL: The IECEE structure includes the Committee of Testing Laboratories (CTL), which aims to promote consistency of test results across CB laboratories, thereby facilitating mutual recognition of CB certificates and reports and close cooperation between testing laboratories.
IECEE-CB: The IECEE-CB system is the IECEE’s system for mutual recognition of test certificates for electrical products. More than 70 National Certification Bodies (NCBs) from more than 50 member countries of the IECEE CB system have entered into multilateral agreements to enable applicants to obtain national certification or market access in other member countries of the CB system on the basis of a CB test certificate and test report issued by one of the NCBs. If the standards of the country to which the product is to be exported are not yet fully equivalent to the IEC standards, the test must also take into account the declared national differences of that country.