How to Assess a Wind Turbine Supplier's Capability: Design Class, Type and Blade Tests, Grid-Code Evidence, Quality System and End-of-Life — What the Standards and Chinese Rules Let You Ask For

Short answer. A turbine supplier's capability is documented, not asserted. The international standards define what a design basis, a power curve, a blade test and an electrical-characteristics test must contain, and the certification scheme that ties them together moved from IEC 61400-22 to IECRE in 2018. China adds its own general technical specification and grid-connection standard, a 2023 rule on retrofit and decommissioning that puts a safety assessment at the end of design life, and 2025 policy documents on equipment quality and first-unit applications. This guide turns those documents into five questions to ask a supplier. It rates no manufacturer and quotes no Chinese market-share or failure statistic, because none was found in an official source.

Question 1 — what is the design basis, and for which site class?

IEC 61400-1:2019 (edition 4.0, published 8 February 2019) specifies essential design requirements to ensure the structural integrity of wind turbines; it covers all subsystems — control and protection, internal electrical systems, mechanical systems and support structures — applies to turbines of all sizes, and in this edition extended the wind-turbine classes to allow for tropical cyclones and high turbulence. For fixed offshore turbines, IEC 61400-3-1:2019 outlines minimum design requirements, is not a complete design specification, and states that the division of responsibility among the parties for design, manufacture, installation, commissioning and operation is a contractual matter outside its scope.

Two consequences. First, a supplier's design documentation should name the edition and the class (including whether the tropical-cyclone or high-turbulence class applies) against which the turbine was designed; a turbine designed for one class is not evidence of suitability for a site in another. Second, for offshore projects the standard does not say who is responsible for what — the contract must. The NEA's 2025 Guiding Opinions on energy equipment (国能发科技〔2025〕78号, 15 September 2025) list, for wind, breakthroughs in high-performance long-life offshore blades, high-power gearboxes, ultra-high hybrid towers and reliable low-cost floating foundations, turbines for harsh wide-range environments, and improved reliability in desert/Gobi and deep-sea settings. CNWattHub editorial method: where a project sits in one of those settings, ask which of the supplier's design assumptions were validated for it rather than extrapolated.

Question 2 — which tests back the power curve and the blade?

IEC 61400-12-1:2022 specifies the procedure for measuring the power performance of a single grid-connected wind turbine of any type or size, and requires the measured power curve and derived energy-production figures to be supplemented by an assessment of uncertainty sources and their combined effects. A power curve presented without an uncertainty statement is therefore not a measurement to this standard; ask for the test report, the measurement site and the uncertainty.

IEC 61400-23:2014 defines requirements for full-scale structural testing of blades — static load tests, fatigue tests, static tests after fatigue and tests of other blade properties — whose purpose is to confirm to an acceptable level of probability that the whole population of a blade type fulfils the design assumptions. The test is of a blade type, so the question is whether the blade offered is the type tested, or a variant.

Question 3 — what electrical evidence sits behind "grid-code compliant"?

IEC 61400-21-1:2019 defines the quantities characterising the electrical characteristics of a grid-connected wind turbine, the measurement procedures and the procedures for assessing compliance with electrical connection requirements; its first edition added frequency-control measurement, updated reactive-power control and capability measurement, inertia-control response measurement, an overvoltage ride-through test procedure and an updated undervoltage ride-through procedure. In China the connection requirements for onshore farms are in GB/T 19963.1-2021 (风电场接入电力系统技术规定 第1部分：陆上风电), a current recommended national standard issued 20 August 2021 and implemented 1 March 2022. China's general turbine specification is GB/T 19960-2024 (风能发电系统 风力发电机组通用技术条件和试验方法), issued 25 April 2024 and implemented 1 November 2024 under the China Machinery Industry Federation. This guide cites both from their information pages and does not describe their technical content. A supplier's "compliant" claim should resolve to a test report naming the standard, the edition and the test items.

Question 4 — is the type certified, and under which scheme?

IEC 61400-22:2010, which defined a certification system comprising type certification and project certification for turbines on land or offshore, was withdrawn on 31 August 2018 and replaced by the wind-sector deliverables of the IECRE conformity assessment system. Ask which scheme the supplier's current type certificate is issued under and by which certification body; this guide does not infer a certificate's date from the standard's withdrawal date. IECRE's operational documents could not be retrieved for this guide, and their content is not described.

For the manufacturer behind the certificate, the 2025 Guiding Opinions call for whole-process quality management ("全员、全要素、全过程、全数据"), quality-capability evaluation to raise reliability, stability and consistency, and guarding against "involution-style" competition and predatory low-price competition. They also encourage first-unit applications: state-owned enterprises are encouraged to buy domestic first units through a green channel, and a user unit procuring first-unit energy equipment no longer collects a quality guarantee deposit where the equipment is covered by quality-assurance insurance. A buyer offered a first unit with such insurance should therefore expect the insurance, not a deposit withheld from the supplier, to carry the quality risk, and should ask what the insurance covers.

Question 5 — what happens at the end of design life?

The NEA's Measures for Wind Farm Retrofit-Upgrade and Decommissioning (2023) define retrofit-upgrade as replacing or technically upgrading turbines, the step-up substation and collection lines, generally either capacity-increasing or equal-capacity; require generators to carry out a safety assessment when turbines reach their design life and to dismantle farms that fail it; and require grid companies to re-sign grid-connection dispatch agreements and power purchase contracts after an upgrade. The generator implements retrofit and decommissioning with whole-process safety management and accepts quality supervision; the Measures are valid for five years from publication and say offshore measures will be issued separately. The 2025 Guiding Opinions add that recycling standards for retired wind and PV equipment are to be established. Ask the supplier what design life it states, what data it will hand over for the safety assessment, and whether a retrofit path (capacity-increasing or equal-capacity) exists for the platform.

Construction and the project phase

Supplier capability also shows on site. The NEA's 2025 key tasks for power safety supervision (17 March 2025) include revising the Outline for Quality Supervision and Inspection of Offshore Wind Power Construction Projects (Trial) and deploying special supervision of construction safety and project quality with regular reporting of typical problems. A supplier that also erects and commissions should be able to show how its site procedures meet the quality-supervision outline that applies.

The size question

Turbines are getting larger, and a supplier's experience at a given size is a capability question in itself. Berkeley Lab's 2025 land-based wind technology data update (August 2025) reports average US land-based turbine capacity of 3.5 MW, hub height of 106 m and rotor diameter of 137 m for 2024 installations, defines specific power as turbine capacity divided by swept rotor area (lower specific power giving higher capacity factors), and reports GE's US market share by MW at 58% in 2024. Those are US figures and say nothing about China; they are quoted only to show the kind of data a buyer should hold for the platform offered — fleet size at that rating, hub height and specific power, and how long the platform has run.

Checklist

Scope limits

Standards are described from webstore abstracts and information pages only; full texts were not read, and IECRE documents were not retrievable. No manufacturer is named, rated or ranked. The only market-share figure is a US figure from Berkeley Lab. Not procurement or investment advice.