New Guidance for HVDC AC Filter Design: Electrical Engineering Standards May 2026

The electrical engineering sector welcomes two significant updates in May 2026, with the publication of IEC TS 62001-2:2026 and IEC TS 62001-3:2026. These new standards provide comprehensive guidance for the specification and evaluation of alternating current (AC) filters in high-voltage direct current (HVDC) systems. By focusing on critical aspects such as harmonic performance, network modelling, and the management of telephone interference, the new specifications empower industry professionals to ensure more robust, compliant, and future-proof HVDC projects. Together, these documents address practical needs for utilities, system operators, equipment suppliers, and consultants, reshaping how AC side harmonics are managed in modern power transmission.

Overview / Introduction

Electrical engineering faces ever-increasing complexity in high-voltage transmission, especially with widespread adoption of HVDC technology for reliable, long-distance power transfer. AC filter systems sit at the heart of this transition, responsible for mitigating harmonics, managing noise interference, and maintaining overall power quality.

Standards within this field not only set the technical foundation for filter design and system robustness but also play a key role in regulatory compliance, project acceptance, and operational longevity. This article highlights the new IEC Technical Specifications published in May 2026, exploring how:

• Key specifications address harmonic performance and system interaction
• The standards benefit project design, implementation, and verification
• Important changes align practice with the latest industry challenges

What you'll learn:

• Detailed scope, requirements, and key points for each new standard
• Compliance and industry impacts
• Best practices for implementation and certification

Detailed Standards Coverage

IEC TS 62001-2:2026 – Harmonic Performance Aspects in HVDC AC Filters

High-voltage direct current (HVDC) systems – Guidance to the specification and design evaluation of AC filters – Part 2: Harmonic performance aspects

This standard provides authoritative guidance for specifying and evaluating the harmonic performance of AC filters in HVDC systems. The document is indispensable for system developers, utilities, project consultants, and filter equipment manufacturers involved in HVDC transmission infrastructure. Its focus is threefold: managing telephone interference, establishing current-based harmonic performance criteria, and verifying field compliance.

Scope and Coverage

• Guidance centered on AC filters for line-commutated HVDC systems, with notes applicable to voltage-sourced converter (VSC) technology.
• Applicable to the frequency range relevant for harmonic distortion and audible frequency disturbances.
• Focuses on passive filter technology; excludes PLC (Power Line Carrier) and radio-frequency interference filters.

Key Requirements and Specifications

• Establishes quantitative and qualitative methods for defining harmonic limits, especially regarding telephone interference on parallel lines.
• Details how to derive and apply current-based performance criteria (e.g., IT limits, TIF – Telephone Interference Factor).
• Outlines recommended processes for inductive coordination studies to identify network features that increase susceptibility to interference.
• Provides technical recommendations for filter sizing, specification of harmonic current limits, and balancing filter performance against cost and complexity.
• Includes protocols for field measurement, equipment and subsystem verification, and in-service compliance assessments.

Who Should Comply

• Utilities and grid operators planning or operating HVDC installations
• Consultants preparing technical specifications for new projects
• Filter system designers and manufacturers
• Compliance officers managing regulatory and customer standards

Practical Implications

• Reduces the risk of unexpected telephone system interference, which can lead to costly mitigation or even operational shutdowns after commissioning.
• Ensures that performance requirements are tailored to the actual risk, avoiding over-engineering and unnecessary costs.
• Facilitates better project planning by providing empirical case studies and calculation methods drawn from global HVDC project experience.
• Mandates robust performance verification, supporting smooth project acceptance and handover.

Notable Changes from Previous Editions

• New clause structure: Adds a dedicated section for terms and definitions, and reorganizes technical content for clarity.
• Updated analysis methods: Reflects latest field data and industry best practices.
• Expanded measurement protocols: Most of the guidance from IEC TR 62001-3:2016 Annex C is now included, improving compliance verification.

Key highlights:

• Comprehensive limits and assessment for harmonic-induced telephone interference
• Current-based harmonic performance criteria with calculation methodologies
• In-depth field measurement and compliance verification guidance

Access the full standard:View IEC TS 62001-2:2026 on iTeh Standards

IEC TS 62001-3:2026 – Modelling Aspects of HVDC AC Filters

High-voltage direct current (HVDC) systems – Guidance to the specification and design evaluation of AC filters – Part 3: Modelling aspects

IEC TS 62001-3:2026 addresses advanced modelling practices essential for the correct specification, evaluation, and operational verification of HVDC AC filter systems. This technical specification is crucial for consultants, engineers, and system designers who require a sophisticated approach to predicting system behavior under a wide range of real-world conditions.

Scope and Coverage

• In-depth treatment of three essential topics: AC network impedance modelling, handling pre-existing harmonics, and the phenomena of cross-modulation (harmonic interaction across converters).
• Applicability to both line-commutated and VSC HVDC converter projects.
• Focuses on the frequency ranges affecting harmonic distortion and audible disturbances, aligning closely with practical operational concerns.

Key Requirements and Specifications

• Recommends customer-driven network impedance studies (instead of contractor-driven) to establish robust, unified benchmarks for all filter design tenders.
• Explains how to define and use impedance envelopes for harmonic analysis, including considerations for load composition, reactive compensation, network evolution, and contingency operation.
• Details best practices for modelling pre-existing harmonics—how to measure, estimate, and incorporate various scenarios for accurate equipment ratings and performance predictions.
• Covers incremental and aggregate assessment methods for evaluating harmonic contributions and potential magnification effects due to resonance or filter detuning.
• Provides thorough guidance on simulating and analysing harmonic interactions between interconnected HVDC converters across a common AC network.

Who Should Comply

• Utility planning engineers and design specifiers
• System designers and consultants preparing HVDC project tenders
• Filter manufacturers and integration specialists
• Academics and researchers in power systems engineering

Practical Implications

• Minimizes risk of both under- and over-design by ensuring realistic impedance assessment that matches actual network conditions, project life expectancy, and system evolution.
• Supports confident tendering and procurement, reducing costly change orders and project delays owing to mis-specified filter requirements.
• Ensures filter solutions are resilient to the likely range of harmonic scenarios throughout project life, bolstering both reliability and compliance.
• Equips engineers to model and mitigate complex cross-modulation and resonance scenarios, supporting higher network stability and compatibility.

Notable Changes from Previous Editions

• Expanded clauses and restructured content: New definitions and a dedicated overview section.
• Updated and elaborated methods: Includes comprehensive modelling tools and example calculations for advanced study cases.
• Revised bibliography: Aligns references with the latest industry and international best practices.

Key highlights:

• Customer-focused guidance on network harmonic impedance studies
• Step-by-step modelling approaches for pre-existing and incremental harmonics
• Robust simulation of complex converter interactions (cross-modulation and resonance)

Access the full standard:View IEC TS 62001-3:2026 on iTeh Standards

Industry Impact & Compliance

The updated standards directly shape the landscape for HVDC project design, procurement, and operation:

Impacts for Businesses:

• Sets clear, unified benchmarks for design and acceptance criteria, simplifying contractual negotiations and reducing risk.
• Reduces unexpected project costs by ensuring realistic filter performance, avoiding issues like operational downtime due to unresolved harmonic disturbances or telephone interference.
• Facilitates global harmonization and regulatory alignment, making it easier for cross-border projects and multinational utilities to achieve compliance.

Compliance Considerations:

• Early adoption of these standards ensures alignment with the latest IEC best practices, which may become mandatory for new projects or major refurbishments.
• Compliance timelines typically follow contract and project milestones—design, procurement, commissioning, and operational verification steps all benefit from standard adherence.
• Non-compliance risks include costly retrofit measures, contractual disputes, regulatory intervention, or operational restrictions if actual harmonic impacts exceed acceptable limits.

Benefits of Adoption:

• Enhanced power quality and reliability
• Reduced project delays and cost overruns
• Future-proofed filter solutions for evolving AC networks
• Greater confidence in bid evaluation and contract fulfillment

Technical Insights

The two new standards share several technical themes, providing useful insight for practitioners:

Common Technical Requirements:

• Both enforce the necessity for accurate harmonic analysis—not only for the performance of new filters but for existing network conditions as well.
• Emphasis is placed on proper specification, justification, and verification of performance—avoiding both over-specification (which adds cost and complexity) and under-specification (which can compromise safety and operation).

Implementation Best Practices:

1. Undertake Detailed Network Impedance Studies: Utilities should develop precise impedance envelopes, accounting for all practical operating and contingency scenarios.
2. Pre-existing Harmonics Assessment: Include measured or projected background distortion levels as part of all rating calculations, using both incremental and aggregate evaluation methodologies as outlined.
3. Filter Sizing and Specification: Relate filter design closely to verified network characteristics, telephone interference risk factors, and harmonic coordination studies.
4. Verification and Field Measurement: Use recommended system and equipment measurement protocols (e.g., for impedance, harmonic current, and telephone interference levels) to ensure constructed systems match modelled expectations.
5. Documentation and Tender Clarity: All specification documents should reference the exact standards, criteria, and performance levels to be achieved, reducing later ambiguity.

Testing & Certification Considerations:

• Ensure that filter systems undergo both factory and in-field compliance verification, following detailed test procedures described in the standards.
• Continual monitoring and re-evaluation may be necessary in networks subject to rapid development or high rates of distributed energy integration.
• Accredited laboratories and third-party certifiers may reference these standards for conformity assessment and approval processes.

Conclusion / Next Steps

The release of IEC TS 62001-2:2026 and IEC TS 62001-3:2026 marks a significant advance in standardization for AC filter specification in HVDC systems. Their comprehensive guidance equips electrical engineering professionals to:

• Accurately assess and manage harmonics and system compatibility
• Specify and verify filter solutions that ensure both reliability and cost-efficiency
• Navigate complex technical, operational, and regulatory landscapes for modern HVDC transmission

Recommendations for Organizations:

• Review current and future HVDC projects to ensure alignment with new IEC guidelines
• Update technical specifications and procurement protocols to incorporate the new standards
• Engage qualified professionals for network studies, modelling, and compliance verification

Stay Updated: Visit iTeh Standards for full access to the new publications, related documents, and the latest updates on power engineering standards. Proactive adoption positions your business at the forefront of technical excellence, compliance, and future-ready electrical networks.