IEC 61788-24:2018

Overview

IEC 61788-24:2018 is an international standard developed by the International Electrotechnical Commission (IEC) that specifies a standardized test method for assessing the retained critical current after double bending at room temperature of silver (Ag)-sheathed Bi-2223 superconducting wires. This part of the IEC 61788 series addresses critical current measurement specifically for short and straight Bi-2223 oxide superconducting wires, sheathed in silver or silver alloys, and optionally laminated with copper alloy, stainless steel, or nickel alloy tapes. The standard focuses on wires shaped as flat or square tapes containing mono- or multi-core superconducting oxide structures.

This standard applies to superconductors with critical currents under 300 A and an n-value (a measure of the steepness of the voltage-current curve near critical current) greater than 5. It is designed to support quality control and performance verification in the production and application of Bi-2223 superconducting wires, especially in environments where mechanical deformations such as bending might occur.

Key Topics

• Critical Current Measurement
  IEC 61788-24 defines the procedure and requirements for measuring the critical current (Ic) of Bi-2223 superconducting wires after mechanical deformation. The method establishes how much of the critical current is retained after the superconducting wire undergoes double bending at room temperature.

• Double Bending Test Method
  This standard specifies the apparatus and test setup for applying double bending to the superconducting wire to simulate mechanical stress, and details how to measure the Ic post-bending. The test uses a bending mandrel to ensure consistent and repeatable deformation.

• Specimen Preparation and Setup
  It outlines protocols for specimen length, mounting, and handling to eliminate test variability – including the use of specialized sample holders and electrically precise measurement systems.

• Data Analysis and Reporting
  Guidelines are provided for calculating results, such as the retained critical current ratio (Ic after bending/Ic before bending), and measurement of the n-value. Detailed instructions for test reporting ensure consistent documentation of test conditions, specimen identification, and measurement outcomes.

• Uncertainty Evaluation
  Annexes provide informative guidance on uncertainty evaluation related to critical current measurement. This covers instrumentation precision, voltage tap placement, current measurement, and combined standard uncertainty calculation.

Applications

• Quality Control in Superconducting Wire Manufacturing
  Manufacturers of Ag-sheathed Bi-2223 superconducting wires use IEC 61788-24 test methods to verify mechanical durability and electrical performance after bending deformations typical in wire handling and winding processes.

• Superconductor Development and Research
  Researchers developing new superconducting wires can benchmark mechanical and electrical resilience to bending strains using this standard, facilitating material innovation and performance optimization.

• Industrial Cable Production and Integration
  This standard supports the validation of superconducting wires used in superconducting cables and devices, ensuring they maintain critical current capabilities after mechanical manipulations during installation or operation.

• Electric and Magnetic Equipment
  Applications including magnets, transformers, and power devices rely on reliable critical current capacities under mechanical stress; IEC 61788-24 ensures these superconducting components meet rigorous bending performance criteria.

Related Standards

• IEC 61788 Series
  IEC 61788 encompasses test methods and performance specifications for superconductors including critical current measurement protocols for differing materials and geometries.

• IEC 60404 Series
  This series covers magnetic materials standards, sometimes intersecting with superconducting wire applications regarding magnetic characteristics.

• ISO/IEC Directives
  The procedural guidelines for preparation and publication of IEC standards-ensuring consistency and reliability.

• Material-Specific Test Norms
  Related protocols for high-temperature superconductors (HTS), including Bi-2212 and YBCO conductors, which may require alternative or complementary mechanical and electrical testing standards.

By adhering to IEC 61788-24:2018, organizations ensure standardized, repeatable, and accurate measurements of the retained critical current in Ag-sheathed Bi-2223 superconducting wires after mechanical bending stress. This contributes to enhanced reliability, safety, and performance in superconducting technology applications worldwide.