IEC 60475:2022

Overview - IEC 60475:2022 (Method of sampling insulating liquids)

IEC 60475:2022 defines standardized procedures for sampling insulating liquids used in electrical equipment and delivery containers. The standard covers both mineral oils and non‑mineral insulating liquids (for example synthetic esters, natural esters, vegetable oils, silicones) with a viscosity below 1 500 mm2/s (cSt) at sampling temperature. It is Edition 3.0 (2022) and updates the 2011 edition, adding practical annexes (notably Annex C on oil sampling from bushings).

Key topics and technical requirements

• Scope and applicability
  • Sampling in delivery containers (drums, tankers) and in-service electrical equipment (power/instrument transformers, reactors, bushings, oil‑filled cables, tank capacitors, switchgear, LTCs).
• Sampling strategy
  • Definitions and selection of composite, individual, and average samples.
  • Guidance to take samples from the part of a container or equipment where contamination is likely to be highest.
• Sample quantities
  • Typical sample sizes referenced (e.g., 2 L for many tests; 1 L individual samples for dielectric strength evaluation).
• Sampling methods and equipment
  • Approved sampling media and techniques: thief/cream dippers, pipettes, siphons (delivery containers); syringes, ampoules, flexible metal bottles, glass/rigid metal bottles, plastic bottles (equipment and lab samples).
  • Separate procedures for sampling by syringe, ampoule, bottles, etc. (see clauses 4.2.2–4.2.6).
• Sample integrity, storage and transport
  • Requirements for container selection, sealing, labelling and safe transport to the test laboratory.
  • Annex B provides a procedure for testing syringe integrity; Annex A covers intermediate/average sampling methods.
• Health, safety and environment
  • Cautions about handling insulating oils, eye contact, and potential PCB contamination of service oils and disposal/regulatory considerations.

Applications - who uses IEC 60475 and why

• Power utilities and grid operators - routine condition assessment and forensic sampling of transformers, LTCs and switchgear.
• Transformer and equipment manufacturers - factory acceptance sampling and delivery inspections.
• Oil suppliers and logistics - sampling of drums, tankers and batches to verify quality on delivery.
• Independent testing laboratories and certification bodies - standardized sample acceptance, handling and chain-of-custody procedures.
• Maintenance and asset management teams - trending oil quality, diagnostics and end‑of‑service decisions.

Practical benefits: ensures representative, reproducible samples, minimizes contamination or degradation during collection/transport, and supports reliable laboratory diagnostics (dissolved gas analysis, dielectric tests, particle counts, contamination and chemical analyses).

Related standards and references

• IEC 60567 - Sampling of gases and analysis of free and dissolved gases (DGA guidance).
• IEC 60970 - Methods for counting and sizing particles in insulating liquids.

Keywords: IEC 60475:2022, sampling insulating liquids, insulating oil sampling, transformer oil sampling, composite sample, sample containers, oil sampling procedures.