In this dataset it means current or voltage sensing technology that departs from the traditional iron-core, oil-insulated transformer design — optical current transformers, Rogowski coils, and other electronic instrument transformers that output a digital or low-power signal. Patent claims in this area typically bundle the sensing element itself with supporting claims on accuracy class, temperature drift, long-term stability, insulation design, digital output interfacing, or calibration method. That combination of physical sensing and metrology claims is what distinguishes this landscape from a generic current-sensor search. Utilities and grid equipment makers file here because the calibration and stability claims are what make a sensor deployable in a live substation, not just accurate in a lab.

The dataset ranks 100 assignees by record count, with the single leading assignee holding 33 of the 321 records in scope and the top five together holding 95 records, or 29.6% of the total. That concentration drops off quickly: tenth place holds only 8 records. Beyond the top ten, most of the ranked assignees appear with just a handful of filings each, forming a long tail of research groups, instrumentation specialists and individual inventors rather than a broad industry consortium.

Filing peaked at 30 records in 2020 and has since declined on a like-for-like basis: from 17 records in 2021 to 12 in 2024, a drop of 29% over those three years, which are the most recent years with a complete publication window. Because publication typically lags filing by roughly 18 months, the 2025 and 2026 figures in the raw trend are still filling in and understate true recent activity, so they should not be read as evidence of a further decline. The safest read is that filing cooled off its 2020 peak rather than that the field is dying out.