IEC 61558-2-10:2024

Overview - IEC 61558-2-10:2024 (Safety of separating transformers > 1 000 V)

IEC 61558-2-10:2024 is the second edition of the IEC particular requirements for separating transformers with high insulation level and for separating transformers whose output voltages exceed 1 000 V AC (or 1 500 V DC). It updates and supplements the general safety requirements of IEC 61558-1:2017 and applies to dry-type, air-cooled stationary or portable transformers (encapsulated or non‑encapsulated). The 2024 edition is a technical revision of the 2014 edition and is published as a group safety publication in accordance with IEC Guide 104.

Key updates in this edition include:

• Structural and reference alignment with IEC 61558-1:2017;
• Inclusion of overvoltage categories I–IV for clearances and dielectric strength testing;
• Removal of clearances for homogeneous field conditions.

Key technical topics and requirements

• Scope and ratings: Covers separating transformers with high insulation level and outputs > 1 000 V AC (1 500 V DC), including units incorporating electronic circuits. Rated supply voltage to the transformer primary does not exceed 1 000 V AC for the standard’s application.
• Dielectric strength and clearances: Test and design requirements for dielectric strength, insulation resistance, creepage distances and air clearances; now using overvoltage categories I–IV for test selection.
• Insulation and leakage: Requirements for insulation systems, leakage current limits and dielectric tests appropriate for high-output voltages.
• Thermal, mechanical and electrical safety: Heating limits, short‑circuit and overload protection, mechanical strength, terminal and wiring requirements, and protection against ingress of dust and moisture.
• Application to power supplies: Linear power supplies with internal frequencies ≤ 500 Hz are fully covered; switch‑mode power supplies are addressed in combination with IEC 61558-2-16 (SMPS requirements).
• Marking, documentation and classification: Information required for safe operation, symbols, and classification of transformer types.

Practical applications - who uses this standard

• Transformer, reactor and power supply design engineers producing high‑insulation or high‑voltage isolation transformers.
• Manufacturers and OEMs building industrial and specialised power conversion equipment.
• Test laboratories and certification bodies performing dielectric strength, clearance and safety testing.
• Compliance officers, procurement and safety engineers who must verify product conformity to international safety criteria.
• Engineering teams integrating transformers into machinery, instrumentation or power systems where isolation and high output voltages are required.

Related standards

• IEC 61558-1:2017 (general requirements for safety of transformers, reactors and power supply units)
• IEC 61558-2-16 (particular requirements for switch‑mode power supply units)
• IEC Guide 104 (group safety publications)
• Relevant installation and protection standards referenced in the standard (e.g., IEC 60364‑4‑41, IEC 61140, IEC 60204‑1) for protective measures against electric shock.

Keywords: IEC 61558-2-10:2024, separating transformers, high insulation level, dielectric strength tests, clearances, overvoltage categories, transformer safety, IEC 61558.