Transformer Insulation Patents: Leaders & Filing Trends 2026
- Filings have cooled since 2023. the field peaked at 489 records in 2023 and has since flattened, with the 2022 midpoint of 454 showing growth is no longer accelerating.
- The top of the field is concentrated but not locked up. the leading assignee holds 597 records, yet the ranked leaders together take only 25.6% of the 7,049 records in scope — leaving a long tail of single- and few-filing entrants.
- Measurement and sensing dominate the claim space, not the insulating material itself. G01R (electric & magnetic measurement) covers 50.9% of records, well ahead of H01F (transformers & inductors) at 22.5%.
What this landscape covers
This dataset tracks patent activity at the intersection of transformer design and renewable-generation substations, where wind and solar step-up transformers face duty cycles and fault conditions that conventional grid transformers do not: harmonic-rich loading from power electronics, frequent load cycling tied to variable generation, offshore compact-design constraints, and the shift toward ester-based insulating fluids. The search string pulls 7,049 published records filed between 2015 and mid-2026, spanning core insulation chemistry, partial-discharge sensing, and the digital monitoring layer increasingly bundled with hardware claims.
Because publication lags filing by roughly 18 months, the 2026 count of 65 understates real filing activity for that year; the true picture only becomes visible once later filings publish. Family-level counts are used throughout so that continuation filings and multi-jurisdiction re-filings of the same invention do not inflate any single assignee's apparent footprint.
Filing trend and technology composition
Two views of the same 7,049-record corpus: how filing volume has moved year over year, and how records distribute across IPC subclasses. Because a single record can carry several IPC classes, the composition shares sum to well over 100% of the record total — that is expected and is the denominator used throughout this page.
Filings rose through 2023, then flattened
Annual filings climbed from 324 in 2017 to a peak of 489 in 2023, with 2022 sitting at 454 — a midpoint that shows the growth curve losing slope well before the peak. The drop to 65 in 2026 reflects the publication lag rather than an actual collapse in filing activity.
Measurement and sensing outweigh core transformer hardware
G01R (electric & magnetic measurement) touches 50.9% of records and H01F (transformers, inductors & magnets) 22.5%, meaning most patent activity is being claimed around monitoring, diagnostics and measurement rather than the insulating structure itself. Wind-motor classification (F03D) reaches 9.7%, and AI-adjacent classes G06F and G06N sit at 5.5% and 3.4% respectively, pointing to a growing overlay of data-driven condition monitoring on top of the physical asset.
Shares are the percentage of the 7,049 records in scope. A patent can carry several IPC classes, so the shares add up to more than 100%.
Go deeper on Transformer Insulation for Renewable Substations with Eureka
This page is one run against one query. Ask Eureka your own question about transformer insulation for renewable substations and every answer comes back with the patent numbers behind it.
Try EurekaA representative recent filing
Device for sensing partial discharge of transformer
Provided is a device for sensing a partial discharge of a transformer, the device detecting a partial discharge in a transformer and being capable of measuring the position thereof. The device comprises a case with a hollow portion provided in the transformer, an omni-directional first sensor detecting a partial discharge signal, and a directional second sensor detecting the same signal from a different position within the case.Filed by HD Hyundai Electric, published 2026-07-30 — illustrates how recent claims combine dual-sensor geometry with directional discrimination rather than relying on a single detection point.
| # | Publication no. | Patent title | Citations |
|---|---|---|---|
| 1 | US5193539A | Implantable microstimulator | 1,542 |
| 2 | US5193540A | Structure and method of manufacture of an implantable microstimulator | 1,407 |
| 3 | US5324316A | Implantable microstimulator | 1,074 |
| 4 | US5405367A | Structure and method of manufacture of an implantable microstimulator | 971 |
| 5 | US9314291B2 | RF surgical generator and method for driving an RF surgical generator | 564 |
| 6 | US6831377B2 | Repetitive power pulse generator with fast rising pulse | 186 |
| 7 | US20090200290A1 | Variable voltage load tap changing transformer | 182 |
| 8 | US20080173444A1 | Alternate energy source usage for in situ heat treatment processes | 178 |
| 9 | US5463257A | Wind power machine | 172 |
| 10 | US4554502A | Power factor correction system | 172 |
Citation counts reward older filings simply because they have had more time to accumulate citations within the searched corpus — treat this table as a signal of past influence, not of which claims matter most today.
Each row carries its publication number; clicking a row searches Eureka by that number.
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Three patterns stand out once the record set is broken down by class, geography and filer concentration.
The top of the field is thinner than it looks
The leading assignee alone holds 597 records, but the top five combined take only 18.9% of all 7,049 records in scope, and the top ten reach 25.6%. That leaves roughly three-quarters of the corpus spread across a long tail of filers with far fewer records each — a structure that rewards a well-targeted claim more than sheer filing volume.
Sensing claims outnumber material claims
G01R (measurement) appears in over half of all records, more than double the share carrying H01F (transformer/inductor hardware) classification. Insulation chemistry and structure are frequently claimed alongside a measurement or diagnostic layer rather than standing alone, which shapes how a freedom-to-operate search needs to be scoped.
Growth has plateaued since the 2023 peak
Annual filings rose steadily from 324 in 2017 to 489 in 2023, but the 2022 figure of 454 already shows the curve flattening before the peak. Combined with a wide geographic spread, this points to a maturing rather than an expanding claim landscape in the near term.
Eureka can read the same corpus for gaps instead of for coverage: under-claimed branches adjacent to transformer insulation for renewable substations, with the prior art for and against each one.
Assignee landscape and where the field is still open
The ranked list covers 100 companies by record count — not a top-50 or top-100 filtered view, but the full set the data endpoint returns. Recent-year momentum for the leading names is broadly negative, which is consistent with a corpus where publication lag suppresses the most recent filing year across the board rather than any single company retreating.
A single dominant filer, grid-side
The top-ranked assignee's 597 records sit well ahead of fifth place at 118 and tenth place at 77, reflecting a state grid operator's breadth of filing across measurement, diagnostics and grid-integration claims rather than concentration in one sub-area.
Collaboration is narrow and institutional
Only ten co-assignee pairs appear in the corpus, and the strongest links run between a grid operator and its own research institute affiliates rather than between commercial competitors — collaboration here looks more like internal R&D structuring than cross-industry joint filing.
Filing is heavily weighted to Chinese receiving offices
China accounts for 3,698 of the tracked filings, more than four times the United States total of 820, with Europe, Japan, WIPO and India each in the low hundreds. A freedom-to-operate check limited to US and EP offices would miss most of the corpus.
| Assignee | Recent year | YoY |
|---|---|---|
| State Grid Corporation of China | 2 | -90% |
| China Electric Power Research Institute Co., Ltd. | 2 | -78% |
| Xi'an Jiaotong University | 2 | -78% |
| State Grid Shanghai Municipal Electric Power Company | 1 | -89% |
| Vestas Wind Systems A/S | 0 | -100% |
| General Electric Company | 0 | — |
| Toshiba Corporation | 0 | -100% |
| North China Electric Power University | 0 | -100% |
Where to take this analysis
The dataset points to specific next steps depending on whether the goal is freedom-to-operate, white-space filing, or competitive tracking.
Run a freedom-to-operate check on sensing claims
With G01R classification touching over half of all records, a new insulation or fluid claim should be checked against measurement and diagnostic overlays, not just material prior art.
Explore claims in Eureka →Track the leading grid operator's filing pattern
A single assignee holds 597 records against a fifth-place total of 118 — understanding which sub-classes that filer concentrates in narrows where a new filing is likely to collide.
Build an assignee watchlist in Eureka →Watch the offshore and ester-fluid branches
These sub-areas show thinner record density relative to the core measurement and hardware classes, suggesting claim space that has not yet been heavily staked out.
Search white space in Eureka →Common questions on this landscape
One assignee leads clearly with 597 records, well ahead of the fifth-ranked filer at 118 and the tenth at 77. Even so, the top five combined hold only 18.9% of the 7,049 records in scope, and the top ten reach 25.6%, so the field is not tightly locked up despite having a dominant leader. The remaining three-quarters of filings are spread across a long tail of companies, universities and research institutes with far fewer records each.
Filing volume rose from 324 records in 2017 to a peak of 489 in 2023, but the 2022 figure of 454 already shows the growth rate slowing before the peak was reached. The apparent drop after 2023 is partly a publication-lag artefact — recent filings take roughly 18 months to appear in the record — so 2026's partial count of 65 should not be read as an actual collapse. The honest read is a field that has plateaued rather than one that is accelerating or shrinking sharply.
G01R, the electric and magnetic measurement classification, appears in 50.9% of the 7,049 records, more than double the 22.5% carrying H01F, the transformer and inductor hardware class. This reflects how much of the recent innovation in this space is being claimed as diagnostic and monitoring layers — partial discharge sensing, harmonic measurement, condition monitoring — applied to transformers, rather than as changes to the insulation structure or material itself. A search focused only on material or structural claims will miss a large share of relevant prior art.
Sub-areas such as ester fluid ageing behaviour under harmonic loading, offshore compact insulation for floating substations, and AI-based partial discharge classification show thinner claim density relative to the dominant measurement and hardware classes. These branches sit at the intersection of established classes rather than inside a single crowded one, which is typically where claim space remains genuinely open. A targeted prior-art search on the specific combination — rather than the broad IPC class — is the fastest way to confirm whether a given angle is still available.
China accounts for 3,698 of the tracked filings, more than four times the United States total of 820. Europe, Japan, WIPO and India each sit in the low hundreds — 528, 498, 310 and 251 respectively. Any competitive or freedom-to-operate review limited to US and European filings alone would be working from a small fraction of the total patent activity in this field.
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Disclaimer. This page is generated from Patsnap Eureka data drawn from a limited snapshot of global patent and scientific-literature records, and is provided for general information and reference only.
Patent data carries inherent limitations: recent filings (typically the most recent 18–24 months) are under-counted due to standard publication lag; counts may be reported at either a patent-family or a patent-record basis and are not always directly comparable; classification, applicant-name, and citation data may contain errors, duplicates, or omissions; and the underlying search query defines and constrains the scope shown. As a result, the analysis may be incomplete or inaccurate and may not reflect the full technology landscape.
Nothing on this page constitutes an exhaustive prior-art, novelty, freedom-to-operate, or validity search, nor does it constitute legal, financial, investment, or professional advice, and it should not be relied upon as such. Any patent, commercial, or strategic decision should be verified independently and reviewed with qualified patent, legal, and domain professionals. Patsnap makes no warranties, express or implied, as to the accuracy, completeness, or fitness for any particular purpose of the information presented.
Machine translation. Assignee and organisation names originally recorded in Chinese, Japanese or Korean have been rendered into English by an AI translation step so that the tables stay readable. These renderings are best-effort and may not match a company’s registered English name; the original name is what the underlying patent record carries, and it is what any Eureka query launched from this page uses.