Chinese research work of assessing transformer aging via furfural analysis is introduced. Abnormal, normal and deferred aging conditions of paper insulation in transformers are put forward by means of statistical analysis of furfural in the field. It is recommended that relevant measurement information such as moisture, oxygen, as well as power, voltage, etc. is recorded. Increasing rate of furfural in oil is highly emphasized. However, more laboratory studies should be undertaken, in order to get closer to the mechanism of paper degradation.

To ensure stable and normal transformer operation, light gas protection of the transformer Buchholz relay is essential. However, false alarms related to light gas protection are common, and troubleshooting them often requires on-site gas sampling by personnel. During this time, the transformer’s operating state may rapidly deteriorate, posing a safety threat to field staff. To tackle these challenges, this work presents the near-field, thin-sliced transformer monitoring system that uses Electromagnetic Energy Transmission and Wireless Sensing Device (ETWSD). The system leverages external wireless energy input to power gas monitoring sensors. Simultaneously, it employs Near-Field Communication to obtain real-time concentrations of light gases, along with the electrified state and temperature. In field testing conducted on transformer relays’ gas collection chambers, the ETWSD effortlessly monitors parameters within warning ranges, encompassing methane gas concentrations around 1000 ppm, leakage voltage ranging from 0–100 V, and relay working temperatures up to 90 °C. Additionally, to facilitate real-time diagnosis for electrical workers, we have developed an Android-based APP software that displays current light gas concentrations, leakage voltage collection values, and temperature, while also enabling threshold judgment, alarms, and data storage. The developed ETWSD is expected to aid on-site personnel in promptly and accurately evaluating transformer light gas protection error alarm faults. It provides a method for simultaneous, contactless, and rapid monitoring of multiple indicators.

Triboelectric nanogenerators (TENGs) possess significant attributes, such as a simple structure, high energy conversion efficiency, and ease of fabrication, rendering them crucial for powering mobile and distributed low-power electronic devices. In this study, a multilayer spring TENG with a cushion layer structure is proposed that enhances the output performance of the basic TENG structure. The fundamental topology of the energy harvesting circuit is chosen based on the electrical performance parameters of the generator and optimizes the selection of each electronic component in the actual circuit. This allows the small-size TENG (2 cm³) to have a high storable power density (5.45 mW m⁻²). Finally, the fabrication method of the small-size TENG and how to choose suitable electronic components based on the intrinsic electrical parameters of the TENG were summarized. This work provides valuable guidance for designing and fabricating self-powered IoT node devices.

Lenz’s law states that the change in magnetic flux over time induces an electromotive force around a circuit, commonly referred to as the flux rule. However, exceptions to the “flux rule” were discussed by Richard Feynman in The Feynman Lectures on Physics in 1963. The anti-flux phenomenon occurs when there is a large-size and rotating metal medium present in the circuit. This phenomenon has attracted the attention of many researchers, although most studies have predominantly focused on theoretical and mathematical calculations. Here, we have designed an experimental setup to investigate the generation of the electromagnetic waves by gear-driven rotating metal/semiconductor/dielectric disks with the presence of a static magnetic field. Low-frequency electromagnetic waves were surprisingly observed with frequencies up to 2 kHz for a disk rotating at 6.67 Hz (400 rpm) and energy levels reaching up to −70 dBm. Theoretically, such a result was not expected according to the classical Maxwell’s equations. Our interpretation is that the theory is based on Maxwell’s equations for a mechano-driven media system, which is to describe the electromagnetic behavior of a system that involves accelerated moving media/objects. This study proves that a moving medium is a source for generating electromagnetic waves.

The electromagnetic behavior of a uniformly moving medium has been traditionally described by Minkowski’s theory, based on which the electromagnetic (EM) emission from a rotating isotropic medium should be linear with the rotation frequency, which means that the frequency of the EM emission should be the same as that of the excitation source. However, we experimentally observed that the near-field EM emission from a rotating charged dielectric disk shows discrete multi-harmonics at frequencies of nfR, with n = 1–6, where fR is the rotation frequency of the disk. By reversing the rotating direction of the disk, the phase shift for the observed magnetic field is π for odd harmonics, but it remains in phase for the even harmonics. The experimental results may not be consistent with Minkowski’s theory, but the data can be well explained using Maxwell’s equations for a mechano-driven media system (MEs-f-MDMS). This study not only provides a solid proof to MEs-f-MDMS but also establishes the theory for describing the near-field EM emission from accelerated medium motion, which has many engineering applications.