Overview
IEC 60358-1:2025 - Coupling capacitors and capacitor dividers - Part 1: General rules - is the 2025 basic international standard that defines general rules for coupling capacitors and capacitor dividers with rated voltage > 1 000 V. Published as Edition 2.0 and available as an RLV (redline) version, the document includes the full text and a redline showing technical changes from the previous edition. The standard covers equipment connected line-to-ground where the low-voltage terminal is permanently earthed or connected to ancillary devices.
Key topics and technical requirements
IEC 60358-1:2025 sets out core design, testing and operational rules, including:
- Scope and ratings - rated voltages, rated frequency and voltage factors for AC and DC use.
- Design requirements - insulation levels, external insulation, voltage grading for DC, temperature-rise limits and capacitor element ageing criteria.
- Electrical performance - capacitance at power frequency, losses (tanδ), partial discharge limits and chopped lightning impulse considerations.
- Electromagnetic emissions - requirements and measurement of radio interference voltage (RIV).
- Mechanical and enclosure requirements - mechanical strength, liquid/gas tightness, marking and temperature coefficient of capacitance.
- Testing framework - classification and sequences for routine tests, type tests, special tests and design/ageing tests. Notable test methods include impulse tests, wet tests for outdoor equipment, polarity reversal for DC units, RIV tests and high-frequency characteristic measurements.
- Installation, transport and maintenance - rules for storage, handling, final inspection and periodic maintenance.
- Safety and environmental aspects - basic safety provisions and influence on the natural environment.
- Informative and normative annexes - test circuits, superimposed impulse procedures, HF measurements and voltage definitions.
Practical applications and users
IEC 60358-1:2025 is essential for anyone involved with high-voltage capacitive equipment, including:
- Manufacturers of coupling capacitors and capacitor dividers designing products to meet international safety and performance criteria.
- Test laboratories performing routine, type and special tests (partial discharge, impulse, RIV, temperature rise).
- Utilities and OEMs applying capacitive devices in high-voltage substations, measurement and protection circuits, and power transmission systems.
- Specifiers, installers and maintenance teams needing guidance on transport, installation, testing and lifecycle checks.
- Regulators and certification bodies assessing conformity to international high-voltage capacitor standards.
Related guidance
Refer to other IEC documents covering specific capacitor technologies, high-voltage testing methods and electromagnetic compatibility when developing or validating detailed designs and test programs. For the authoritative text and redline changes download IEC 60358-1:2025 RLV from the IEC webstore.
