Overview
IEC TS 63042-103:2025 - UHV AC transmission systems - Part 103: Security and stability requirements for system planning and design - is a Technical Specification published by IEC TC 122 (Edition 1.0, 2025-09). It defines the basic security and stability requirements and analysis methods for ultra-high-voltage AC (UHV AC) transmission systems used in power grid planning and design. The document applies to UHV AC power grids, associated equipment and connected systems and sets out criteria and methods to assess secure, stable operation.
Key topics and technical requirements
- Power system security and stability: Definitions and overall approach to secure operation and risk assessment for UHV AC transmission systems.
- Stability types covered: rotor angle (transient) stability, voltage stability, and frequency stability, including steady-state and dynamic considerations.
- Security criteria: Steady-state stability margin and multi-level security/stability criteria (Level 1, Level 2, Level 3) for large disturbances and contingencies.
- Contingency principles: Application of the N-1 principle for component loss scenarios and dynamic security analysis.
- Grid structure and connections: Requirements for receiving-end systems, power supply and load access, interconnection principles between power systems, and design principles for UHV grid topology.
- Grid support functions: Reactive power balance and compensation, coordination between generating units and grids, and grid-related protection requirements.
- Analytical methods: Procedures for steady-state security analysis, transient and dynamic stability simulation, voltage and frequency stability studies, short-circuit calculations, and assessment of sub-synchronous and hypersynchronous oscillations.
- System resilience: Prevention of system collapse and procedures for restoration after wide-area blackout.
- Planning, design and management: Guidance on planning stages, project design, construction and operational management focused on security and stability.
Applications
This Technical Specification is intended for practical use in:
- Transmission system planning and grid design for UHV AC projects
- Stability and security assessment during project feasibility and design studies
- Protection and control strategy development, including reactive power compensation and oscillation mitigation
- Interconnection studies for integrating large renewable or DC links (multi-infeed DC considerations)
- Post-event analysis and blackout restoration planning
Keywords: UHV AC transmission systems, security and stability, system planning and design, power system stability, N-1 principle, transient stability, voltage stability, frequency stability, reactive power, short-circuit ratio.
Who should use this standard
- Transmission system operators (TSOs) and planners
- Power system planners and consultants
- Grid design and protection engineers
- Manufacturers of transmission equipment and control systems
- Regulatory bodies and technical reviewers involved in UHV project approval
Related standards
- Other parts of the IEC 63042 series on UHV AC transmission systems (see IEC webstore for the full list).
- Consult IEC resources (Electropedia, IEC publications portal) for related terminology and supporting guidance.