Overview
IEC TS 62271-315:2025 is a Technical Specification from the International Electrotechnical Commission (IEC) that defines requirements for direct current (DC) transfer switches used on high-voltage DC (HVDC) transmission systems. The standard applies to DC transfer switches for indoor or outdoor installation and is intended for systems with direct voltages of 100 kV and above. Typical transfer switch types addressed include metallic return transfer switches (MRTS), earth return transfer switches (ERTS), neutral bus switches (NBS) and neutral bus earthing switches (NBES).
Key topics and requirements
The document covers the full lifecycle of DC transfer switch specification, design and testing. Major technical topics include:
- Scope and definitions: clear terminology for assemblies, parts and operational characteristics of DC transfer switches.
- Ratings: rated direct voltage, rated continuous current, short-time and peak withstand currents, rated commutation voltage and dissipated energy during transfer operations.
- Design and construction: requirements for insulation, earthing, auxiliary/control circuits, enclosures, sealing (gas, liquid and vacuum tightness), nameplates, mechanical loads and degrees of protection for indoor/outdoor use.
- Special components: guidance for commutation switches, commutation capacitors, reactors, energy dissipation devices and making/charging devices where applicable.
- Type and routine tests: dielectric and partial discharge tests, continuous current, short-time and peak withstand tests, DC commutation tests, direct arc withstand tests, EMC and X‑radiation tests for vacuum interrupters, mechanical and environmental tests (temperature, humidity, icing, seismic).
- Operational & safety features: position indication, locking, stored/independent operation modes and protection verification.
- Testing criteria and reports: information required for type-test identification and reporting, pass/fail criteria for key tests.
Applications
IEC TS 62271-315 is directly applicable to:
- HVDC converter stations and transmission lines operating at ≥100 kV
- DC interconnects and point-to-point HVDC links
- HVDC and hybrid AC/DC substations where transfer of DC circuits, neutral and earthing functions are needed
- Use cases include transfer between metallic and earth-return modes, neutral bus switching and controlled earthing.
Who should use this standard
- HVDC equipment manufacturers and switchgear designers specifying DC transfer switches
- Power utilities and system operators developing HVDC project specifications
- Testing laboratories and certification bodies performing type and routine tests
- Consulting engineers, project specifiers and standards/quality engineers drafting procurement or installation documents.
Related standards
- The specification is part of the IEC 62271 (High‑voltage switchgear and controlgear) family - refer to other IEC 62271 parts for complementary requirements on insulation, switchgear testing, and auxiliary systems.
Keywords: IEC TS 62271-315:2025, DC transfer switches, HVDC, high-voltage switchgear, MRTS, ERTS, neutral bus switch, DC commutation tests.