Power Transformer Patents: Who Leads, Where the Gaps Are 2026
- Filing has cooled since a 2019 peak. Activity ran 14 families in 2019 against 7 at the 2022 midpoint, with no rebound through the latest full year — this is a maturing claim space, not a growing one.
- China dominates the filing venue. 57 of the tracked families were filed at the Chinese receiving office against 20 in the US and 12 at the EPO, so freedom-to-operate work has to start with Chinese-language prior art.
- No single assignee is filing at pace right now. Every one of the most-active named assignees shows zero filings in the latest tracked year, pointing to a fragmented field rather than one or two companies pulling ahead.
What this landscape covers
This dataset tracks patent families claiming power transformer design together with oil-paper insulation, partial discharge detection, short-circuit withstand, cooling design or loss reduction, filtered to the core transformer and inductor classification (H01F27, H01F30) plus insulated-conductor art (H01B3). It spans filings from 2015 through the 2026 cut-off, with 138 published families in the assignee ranking.
Because publication typically lags filing by around 18 months, the most recent one or two years in any trend line will read lower than the true filing rate once those applications clear examination and publish.
Filing trend and technology composition
Two views of the same 138 families: how filing volume has moved year over year, and which classification codes the claims actually sit under.
A 2019 peak, then a flat-to-declining run
Filings rose from 3 in 2017 to a peak of 14 in 2019, then eased back toward 7 by the 2022 midpoint. There is no later spike in the tracked years, which is consistent with a field where the core claim territory — winding geometry, insulation materials, basic partial-discharge sensing — was staked out early and later filers are working narrower variations.
H01F dominates; measurement and protection sit alongside it
Every family in this set carries an H01F classification (magnets, inductors and transformers), which is expected given the search scope. The next-largest code is G01R (electric and magnetic measurement) at 27 families, then H01B (cables, conductors and insulators) at 9 and H02H (protective circuit arrangements) at 7 — smaller footprints in G01D, H02B, H02M and H05K show condition monitoring, switchgear integration and power-electronics tie-ins as adjacent but minority themes rather than core claim territory.
Shares are the percentage of the 138 records in scope. A patent can carry several IPC classes, so the shares add up to more than 100%.
Go deeper on Power Transformer Design and Insulation with Eureka
This page is one run against one query. Ask Eureka your own question about power transformer design and insulation and every answer comes back with the patent numbers behind it.
Try EurekaMost-cited prior art in this space
An intelligent assessment method of main insulation condition of transformer oil paper insulation
The invention provides an intelligent assessment method of main insulation condition of transformer oil paper insulation, comprising: establishing at least one standard state; for each standard state, performing accelerated thermal aging tests on a plurality of samples; extracting time and frequency domain characteristic parameters of each sample; and forming a knowledge base from feature vectors of all samples to assess insulation condition against that base.Filed by General Electric Technology GmbH, published 2019-02-07. It is the second most-cited record in this dataset and represents the shift from purely physical insulation design toward data-driven condition assessment.
| # | Publication no. | Patent title | Citations |
|---|---|---|---|
| 1 | US4321426A | Bonded transposed transformer winding cable strands having improved short circuit withstand | 74 |
| 2 | US20190041450A1 | An intelligent assessment method of main insulation condition of transformer oil paper insulation | 63 |
| 3 | WO1999028923A1 | transformer | 40 |
| 4 | US6867674B1 | Transformer | 22 |
| 5 | WO2020160590A1 | A sensor for transformer condition assessment | 19 |
| 6 | KR1020100112467A | A method of partial discharge monitoring system for transformer | 17 |
| 7 | CN111724983A | 一种具备多参量全光纤感知的变压器及多参量监测方法 | 15 |
| 8 | US20200191852A1 | Method and circuit for detecting an arc fault | 13 |
| 9 | CN102708262A | 一种综合节能与减噪的电力变压器多目标优化设计方法 | 13 |
| 10 | US20200098513A1 | Systems and methods for monitoring components in a power transformer or the like | 12 |
Citation counts are drawn from the searched corpus and skew toward older filings that have had more years to accumulate citations — read them as a signal of influence on later filers, not as a ranking of current commercial relevance.
Patent titles are shown in the language they were filed in, not translated, so that each record stays verifiable against the original filing — a translated title will not match in Eureka or in any national register. Each row carries its publication number; clicking a row searches Eureka by that number.
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Three patterns worth acting on before filing or freedom-to-operate work in this area.
The peak has passed, at least on paper
Filing activity peaked in 2019 and had roughly halved by the 2022 midpoint with no later resurgence in the tracked years. Combined with the 18-month publication lag, this could mean either a genuinely cooling field or a pause that has not yet shown up in published data — either way, it argues for checking recent filings directly rather than trusting the trend line alone.
China is the primary filing venue by a wide margin
China accounts for 57 families against 20 in the United States, 12 at the EPO, 8 in India, 8 via WIPO/PCT and 6 in Canada. Any clearance search that stops at English-language US and EPO literature will miss the majority of the documented art in this space.
Condition monitoring is the largest adjacent claim area
Beyond the core H01F transformer classification, G01R (electric and magnetic measurement) is the next-largest code at 27 families, well ahead of H01B insulation materials at 9 and H02H protective circuitry at 7. Diagnostic and sensing claims layered onto transformer hardware are a bigger share of this landscape than insulation chemistry itself.
Eureka can read the same corpus for gaps instead of for coverage: under-claimed branches adjacent to power transformer design and insulation, with the prior art for and against each one.
Who is filing, and where the room to file still is
The named assignees in this dataset span utility research institutes, established transformer manufacturers and component specialists — but recent-year activity is muted across all of them.
Chinese state grid entities file jointly
The strongest co-assignee link in this dataset pairs State Grid Corporation of China with the State Grid Smart Grid Research Institute, reflecting how insulation and monitoring work inside Chinese utilities is often filed jointly between the parent grid company and its dedicated research arm.
No manufacturer is currently filing at pace
Established names in this space, including ABB entities, GE-affiliated filers, and Delta Electronics, all show zero filings in the most recent tracked year. That is consistent with a field past its filing peak, though it may also reflect the publication lag understating true recent activity.
A fragmented field, not a two-horse race
Utility-affiliated Chinese entities, component and bushing specialists, and individual inventors all appear in this dataset without one or two assignees clearly pulling ahead. That fragmentation is itself useful signal: it suggests room for a new entrant to build a defensible position rather than compete directly against an entrenched leader.
| Assignee | Recent year | YoY |
|---|---|---|
| ABB Power Grids Sweden AB (formerly Brown Boveri/ASEA) | 0 | — |
| ABB (Switzerland) Ltd. | 0 | — |
| Delta Electronics, Inc. | 0 | — |
| EHV-Weidmann Industries, Inc. | 0 | — |
| ABB Power Grids Switzerland AG | 0 | — |
| General Electric Aviation Systems Limited | 0 | — |
| State Grid Corporation of China | 0 | — |
| Liu Lizhong | 0 | — |
Where to take this next
The trend and rankings above are a starting point. The decisions that follow from them — where to file, who to watch, what to design around — need a closer look at the underlying claims.
Check freedom-to-operate against the Chinese filings
With 57 of 138 families filed in China, a clearance search limited to US and EPO literature will miss most of the documented art in oil-paper insulation and winding design.
Run a freedom-to-operate search in EurekaMap the condition-monitoring claim space
27 families carry a G01R measurement classification alongside the core transformer code — a substantial adjacent territory worth mapping separately from insulation materials claims.
Explore the sub-landscape in EurekaWatch for the publication-lag rebound
The apparent decline after 2019 may partly reflect the roughly 18-month gap between filing and publication rather than a genuine drop in activity.
Track live filings in EurekaCommon questions about this landscape
This dataset does not show one dominant assignee; filings are spread across Chinese state-grid-affiliated entities, established transformer OEMs such as ABB-affiliated companies and General Electric-affiliated filers, and a long tail of component specialists and individual inventors. Every one of the most prominent named assignees shows zero filings in the latest tracked year, which points to a fragmented field rather than a concentrated one. Anyone doing competitive tracking here should watch the aggregate trend and the receiving-office split rather than a single company's output.
Filing peaked at 14 families in 2019 and had fallen to 7 by the 2022 midpoint, with no later rebound visible in the tracked years through 2026. Because publication lags filing by roughly 18 months, the most recent one or two years will always look thinner than the true rate once pending applications publish, so this should be read as flat-to-declining rather than a confirmed collapse. A follow-up check in twelve to eighteen months against the same query would sharpen this picture considerably.
China is the receiving office for 57 of the 138 tracked families, more than double the next-largest venue, the United States, at 20. This reflects both the scale of transformer manufacturing and grid-infrastructure investment in China and the fact that Chinese utility research institutes and state grid entities file heavily in their home jurisdiction. Any freedom-to-operate or novelty search in this space that skips Chinese-language literature is working from a partial picture of the art.
US20190041450A1, filed by General Electric Technology GmbH, claims an intelligent assessment method for the main insulation condition of transformer oil-paper insulation. It works by running accelerated thermal aging tests to build a knowledge base of time- and frequency-domain feature vectors for known insulation states, then comparing new measurements against that base to assess condition. It is the second most-cited record in this dataset, and it sits at the boundary between physical insulation design and data-driven condition assessment, which is one reason it draws citations from both camps.
The classification spread points to condition monitoring and diagnostics — carried under G01R alongside the core H01F transformer code — as a larger adjacent claim area than pure insulation materials work, which sits mainly under H01B at just 9 families. Sub-areas such as real-time partial discharge sensor fusion, cooling-loop design for high-density windings, and data-driven insulation aging models show lower filing density relative to core winding and bulk insulation claims. That does not guarantee an easy grant, but it does mean the claim space is less crowded than the headline insulation categories.
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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.