How to Check Wind Turbine Blade Inspection and Repair in China: the Standards Map (IEC 61400-5:2020+AMD1:2025, IEC 61400-23 / GB/T 25384-2018, GB/T 25383-2025, NB/T 10561-2021), a Draft Group Standard's Five Damage Grades and Repair Acceptance Numbers (Barcol ≥50, Tg ≥65/70 °C, Lightning Path <240 mΩ), and NEA's Work-at-Height, Ice and Fire Requirements

Short answer. A blade file on a Chinese wind farm sits between three kinds of text. The international reference for blade integrity is IEC 61400-5:2020 with its 2025 amendment, which covers aerodynamic and structural design, materials, manufacture and quality management, and transport, installation, operation and maintenance, and defines certification requirements. Full-scale structural testing of a blade type is IEC 61400-23:2014, whose Chinese counterpart GB/T 25384-2018 has been current since 1 July 2019; the new national blade standard GB/T 25383-2025 took effect on 1 December 2025; and the NEA industry standard for blade repair is NB/T 10561-2021 (current since 1 July 2021) — none of these texts was read for this guide, only their records. What was read is a December 2025 draft group standard of the China Composites Industry Association on blade damage grading and repair, whose drafters say existing standards address design, manufacture and transport while O&M-side rules are few and mostly procedural, and who studied industry standards such as GB/T 25383 and NB/T 10561: it zones the blade by structural importance, defines five damage grades from E (acceptable) to A (no operation before replacement or repair), gives ply- and width-based thresholds for spar-cap, trailing-edge and shell damage, and sets repair environment, record, reinforcement and acceptance numbers (Barcol ≥50 HBa, Tg ≥65 °C hand lay-up or ≥70 °C infusion, lightning-protection resistance <240 mΩ). NEA's 2023 edition of the 25 key requirements adds the safety frame: blade repair at height only with the turbine stopped and rotor locked and a 20 m exclusion zone, no approach to iced blades that may shed, and fire-suppression rules for the nacelle and hub. This guide reads a draft and records; it quotes no issued Chinese repair clause.

1. The standards map

CNWattHub reading: an O&M contract that promises 'inspection and repair per standard' should name which of these. For a blade-type qualification question (did this blade design pass full-scale tests?) the answer is a test report under IEC 61400-23 or GB/T 25384; for a repair-quality question (was this crack repaired properly?) the issued Chinese reference is NB/T 10561-2021, and the draft group standard is, for now, a statement of what the drafters think good practice looks like.

2. The draft group standard: zoning and grades

The draft covers importance zoning, damage grades, classification and disposal, and repair requirements (environment, tools, process, records, structural restoration, ply staggering, process selection and acceptance), and normatively references GB/T 25383, GB/T 36490 (lightning protection device testing) and NB/T 10561. Its damage terms are whitening, cracking and delamination for spar caps, trailing-edge UD, shell FRP and shear webs, and buckling, cracking, delamination or FRP-core interface failure for cores.

Zones. Very important: spar caps, auxiliary spars, prefabricated root, embedded bolt sleeves, trailing-edge UD and bonding areas. Important: the root reinforcement transition. General: shear webs and skins.

Grades. E — acceptable, no repair, no effect on operation. D — non-structural. C — minor structural effect; in some cases derating or stopping. B — significant structural effect; no operation before repair. A — major structural effect and very hard to repair; no operation before replacement or repair.

CNWattHub reading: the two numbers to ask an inspection report for are damage width as a share of the component and the number of plies affected — the draft's grades turn on them, and a drone photograph alone gives neither. A report that grades without a ply count is grading by eye.

3. The draft's repair and acceptance numbers

• Environment. 16–30 °C and 20–80% RH recommended, with measures if the site is outside the range; tools and process per NB/T 10561.
• Records. Site and blade identity; temperature and humidity; damage before and after grinding with photographs; cloth sizes, plies and specifications; resin mix ratios; cure method, temperature and time; surface quality; Barcol or Shore D hardness at stated points; Tg results for grade B and above.
• Reinforcement. Replacement cloth matched as far as possible to each ground ply, plus about 20% extra: M = N + N × 20%, rounded up (2 × 20% = 1 ply). Minimum stagger per cloth type (e.g. triaxial ≥70 mm spanwise, ≥50 mm chordwise), outermost reinforcement ply at not less than twice those values; process (hand lay-up, hand lay-up with bagging, vacuum infusion) chosen by zone, ply count and core area.
• Acceptance. No visibly uncured areas; dense-bubble areas ≤10,000 mm² and ≤3 plies; single bubbles ≤20 mm, at most 5 bubbles over 10 mm per metre; 20 mm chamfer at the boundary; cure checked at ≥3 points ≥500 mm apart, Barcol ≥50 HBa (Shore ≥75 HD); Tg for grade B and above ≥65 °C (hand lay-up) or ≥70 °C (infusion); coating with ≤10 pinholes or sand holes per m² and sag or orange peel ≤100 mm × 100 mm; lightning-protection resistance after repair <240 mΩ; a repair process record report.

CNWattHub reading: these are a consultation draft's numbers, not law, but they are specific enough to use as questions — was hardness measured and where, was Tg tested for a B-grade repair, what did the lightning path measure after the repair, and is there a before/after photographic record with ply counts. A repair invoice without those items cannot be checked.

4. The safety frame: NEA's 25 key requirements (2023)

NEA's 2023 edition makes blade repair and tower cleaning at height conditional on the turbine being stopped with the rotor locked and basket anti-sway measures, independent safety ropes and fall arresters, and no one within a 20 m diameter of the work point; forbids approaching turbines whose iced blades may shed; and, in the wind-turbine fire section, requires flame-retardant power cables in the nacelle and tower and automatic extinguishing devices in the nacelle, under the nacelle platform floor, in the hub, at the tower-base equipment level and in electrical cabinets — new aerosol or superfine powder for the nacelle space, new aerosol for cabinets, nozzle temperature above 200 °C, media tested and certified by the fire-product quality supervision and inspection centre.

CNWattHub reading: a repair method statement should show the lock-out and exclusion-zone steps and the winter ice rule, not only the laminate procedure; a buyer's audit of a repair campaign can start with the permit-to-work file.

5. A review sequence built from the sources

CNWattHub's reading of the sources as a checklist:

1. Which standard is named? IEC 61400-5 for design-to-O&M integrity; IEC 61400-23 / GB/T 25384 for type tests; GB/T 25383-2025 from 1 December 2025; NB/T 10561-2021 for repair.
2. Zone the damage. Very important (spar caps, root, trailing-edge UD, bonds), important (root transition) or general (webs, skins).
3. Grade it with numbers. Width share and ply count; A/B thresholds by component; derating or stop decisions for C.
4. Check the repair conditions. Temperature, humidity, tools and process per NB/T 10561.
5. Read the record. Photos before and after grinding, ply counts, mix ratios, cure log, hardness, Tg.
6. Verify reinforcement. 20% extra plies, stagger sizes, process choice.
7. Verify acceptance. Hardness, Tg, bubble limits, coating, lightning-path resistance, record report.
8. Verify safety. Stopped and locked rotor, 20 m zone, ice rule, nacelle fire suppression.
9. Remember the status. The grading scheme is a draft group standard; the issued texts (NB/T 10561, GB/T 25383/25384) were not read.

Scope limits

This guide reads IEC webstore abstracts, three Chinese standard records (texts not read), a draft group standard and its drafting explanation (not issued; wording may change) and NEA's 2023 key requirements. It quotes no clause of NB/T 10561-2021, GB/T 25383-2025 or GB/T 25384-2018, no inspection-technology standard (drone, ultrasonic, thermographic), no incident report and no failure or repair-cost statistic.