Verification Regulation of Instrument Transformers—Part 9:DC Immune Current Transformers

This technical document specifies the metrological verification requirements and procedures for a specialized type of measuring instrument designed to evaluate the performance of current transformers under direct current conditions. The scope encompasses the determination of accuracy characteristics, error analysis, and safety assessment protocols essential for ensuring the reliability of measurements in power systems involving DC components. It outlines the necessary conditions for the verification environment, including temperature, humidity, and electromagnetic interference levels, alongside the detailed methods for applying test currents and reading instrument responses. The document further defines the criteria for judging whether a device meets the prescribed technical standards, covering aspects such as ratio error, phase displacement, and insulation resistance. It provides a systematic framework for calibration laboratories and quality control departments to assess the conformity of these instruments, ensuring that they operate within acceptable limits for their intended applications. The content addresses specific challenges associated with DC currents that differ from traditional AC measurement scenarios, offering guidance on handling transient states and steady-state conditions. By adhering to these guidelines, practitioners can maintain high standards of measurement accuracy and consistency across various industrial and utility settings.