In response to recent misunderstandings among enterprises, users, and testing institutions regarding the detection of the nominal cross-sectional area of cable conductors, this article provides a detailed explanation of the concept, understanding, and assessment of cable conductor cross-section in conjunction with relevant product standards and regulatory requirements.

Explanation and Analysis of the "Nominal Cross Section Area" of Cable Conductors

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introduction

At present, there are some misunderstandings among some users and testing institutions regarding the measurement of the nominal cross-sectional area of cables. They interpret the nominal cross-sectional area as the cross-sectional area specified by the standard, and use geometric methods to measure the actual cross-sectional area of conductors and make judgments based on this, resulting in some wires and cables that meet the requirements of product standards being judged unqualified during delivery inspection. For example, the ordinary PVC flexible wire 60227 IEC 53 (RVV) 300/500V 3X0.75 product used for electrical power lines has a nominal cross-sectional area of 0.75 mm2 and a measured cross-sectional area of 0.72 mm2, which is 0.03 mm2 smaller than the nominal cross-sectional area. Even if its conductor resistance meets the product standard requirements of a nominal cross-sectional area of 0.75 mm2, it is still misjudged as an unqualified product. Ultimately, in the sales and acceptance of the cable and the entire product, Bringing troubles and adverse effects to both enterprises and users. Therefore, this article explains and explains the nominal cross-sectional area of wire and cable conductors, hoping to help all parties correctly understand the nominal cross-sectional area, reduce misunderstandings and misjudgments, and scientifically and accurately use the resistance method to assess the cross-sectional area of conductors.

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On the cross-section of wire and cable conductors

In the entire process of wire and cable product production, design, use, and inspection, there are various names and understandings of wire and cable conductor cross-section that people are concerned about: nominal cross-sectional area, design cross-sectional area, and actual cross-sectional area. So what is the relationship between them?

The nominal cross-sectional area of wire and cable conductors

The so-called nominal value refers to the quantity value specified in the product standard and often used in tables. The quantity value derived from the nominal value usually needs to be verified through measurement under the specified tolerance. If there is no tolerance given for a certain nominal value in the standard, then this nominal value does not need to be evaluated and measured. In GB/T3956-2008 "Conductors of Electric Cables", there is no tolerance given for the nominal cross-sectional area and it is defined as "a numerical value that determines the specific size of the conductor, but is not directly affected by measurement. (Note: Each specific size of the conductor in this standard should meet the requirement of maximum resistance value). It can be seen that the nominal cross-sectional area of conductors is used in product standards to describe the specifications of wire and cable products, just the code or name of this specification, which is convenient for document and production management during the product manufacturing process. For users and designers, the standard does not require direct measurement of their actual cross-section for the convenience of selection and guidance in production and electrical design, but rather measures and evaluates it through conductor resistance values.

Design cross-sectional area of wire and cable conductors

The content of Article 12.2 of GB50411-2007 "Code for Acceptance of Construction Quality of Building Energy Conservation Projects" is as follows: "The cross-section of cables and wires selected for low-voltage distribution systems shall not be lower than the design value. When entering the site, their cross-section and the resistance value of each core conductor shall be witnessed and taken