ISO/TR 23583:2026

ISO/TR 23583:2026 is a Technical Report from the International Organization for Standardization (ISO) on assessing sulfur corrosion in copper windings used in power equipment. It specifies a test method for newly installed and in-service power equipment, so engineers, test laboratories, and quality staff can evaluate copper winding resistance to sulfur corrosion under defined electric-field conditions.

What does ISO/TR 23583:2026 specify?

ISO/TR 23583:2026 specifies a method for assessing sulfur corrosion in copper windings in power equipment. The document applies to sulfur corrosion resistance testing of copper windings in both newly installed and in-service equipment.

ISO/TR 23583:2026 is organized into Scope, Terms and definitions, General regulation, specimen preparation, instruments and equipment, test preparation, test procedures, and evaluation of oil sulfur corrosion resistance performance, followed by a bibliography. In practice, that structure takes the reader from the test object and setup through to how results are judged.

What are the key requirements of ISO/TR 23583:2026?

ISO/TR 23583:2026 centers on a pig-tail specimen, a defined oil-immersion test, and a two-part evaluation. The main point is to simulate service conditions more closely than oil-only corrosive sulfur tests, because the electric field and the winding-paper contact affect the result.

• General test concept, clause 4 - The copper winding and insulating paper are made into a pig-tail model, immersed in insulating oil containing corrosive sulfides, heated, and exposed to a specific electric field strength. This matters because the assessment is built around the way copper windings actually operate in oil-filled equipment.

• Specimen preparation, clause 5 - The copper winding specimen is transformer copper winding with defined dimensions, the insulating oil conforms to IEC 60296, the insulating paper conforms to IEC 62535, and dibenzyl disulfide (DBDS) is the sulfur compound used in the test oil. This gives the test a controlled starting point so results can be compared from one laboratory to another.

• Test equipment, clause 6 - The document specifies a thermostatic oil tank, a vacuum drying immersion oil tank, an electric heating experimental tank, a direct current (DC) or alternating current (AC) power supply, and a plasma coupled atomic emission spectrometer. In practice, the equipment has to support stable temperature control, vacuum drying, high-voltage operation, and copper measurement.

• Test preparation, clause 7 - The winding is formed into a pig-tail model, dried to remove moisture from the paper, then immersed in degassed insulating oil with DBDS added. The tank is then sealed and the specimen is placed under controlled warm, low-pressure immersion conditions before the main test. That sequence matters because moisture and air would otherwise distort corrosion behavior.

• Heating and electrical stress, clause 8.1 - The specimen is heated to 150 °C, connected to a DC or AC power source, and tested at an electric field strength of 3 kV/mm for at least 3 days. This is the core exposure step, and it is intended to reproduce the electrical and thermal stress seen in service.

• Cooling and removal, clause 8.2 - After the exposure period, the system is switched off, allowed to cool to room temperature, and the copper winding is removed. This preserves the specimen for visual and chemical evaluation.

• Evaluation, clause 9 - The document uses qualitative evaluation from the corrosion morphology of the copper winding and quantitative evaluation from copper content in insulating oil measured by inductively coupled plasma atomic emission spectroscopy (ICP-AES). It then grades results into three resistance levels, so users can turn the test outcome into a simple performance judgment.

What terms does ISO/TR 23583:2026 define?

ISO/TR 23583:2026 defines a small set of terms that support the test method and result reporting.

• Copper content - The mass fraction of substances determined by the procedure in this document, expressed in milligrams per kilogram (mg/kg).
• Corrosive sulfur - Elemental sulfur or thermally unstable sulfides in insulating oils that can corrode metals such as copper and silver.
• Sulfur corrosion resistance - The ability to resist corrosive sulfur corrosion under specified conditions.
• Dibenzyl disulfide (DBDS) - The sulfur compound added to the insulating oil to create the corrosive test environment.
• Inductively coupled plasma atomic emission spectroscopy (ICP-AES) - The analytical method used to determine copper content in insulating oil.
• Pig-tail model - The specimen shape used to arrange the paper-wrapped copper winding for the corrosion test.

Who uses ISO/TR 23583:2026?

ISO/TR 23583:2026 is used by laboratories, transformer and power equipment manufacturers, and maintenance or condition-assessment teams that need to examine copper winding sulfur corrosion. It is also relevant to quality managers and buyers who want a defined test method for comparing winding performance in newly installed equipment and in service. In practice, it supports product qualification, incoming inspection, failure analysis, and service-life assessment in the power industry.

What does the ISO/TR 23583:2026 document contain?

ISO/TR 23583:2026 contains one table of insulating-oil parameters, figures showing the pig-tail model and the test device, and step-by-step procedures for specimen preparation, drying, immersion, heating, and removal. It also provides the qualitative and quantitative evaluation routes used after the test. The quantitative route includes carbonization of the oil sample, preparation of the test solution, and copper measurement by ICP-AES.

The document’s closing section gives the grading criteria for copper content and links those grades to sulfur corrosion resistance levels. For users, that means the report is not only a test setup but also a complete workflow for recording and judging the result.