In order to block the electromagnetic interference source of partial discharge in UHV substation and improve the actual power generation efficiency, in this study, the experimental method of partial discharge in ultra high voltage (UHV) substation is first introduced. Secondly, the types of PD EMI are described in detail. Finally, the principle of blocking electromagnetic source is introduced and the blocking measures of each electromagnetic interference source are analyzed in detail. The results show that the actual equipment test of UHV substation is complex, and there are many factors affecting the test accuracy. Therefore, the field test of UHV substation is the most complex and precise test item at present. The time of noise interference of pulse signal is short and the distribution of signal is wide. This kind of interference is also repetitive, but the orientation of the display is relatively stable, and the waveform also has certain rules. Thyristors use relatively weak current to grasp relatively strong current, and the process is very short. At the same time, the period of application is very long and the stability is very strong. Recursive filters are used. The workload of calculation is greatly reduced, but there are many disadvantages. In practical UHV substation, the sources of PD are closely arranged, so it is suitable to use recursive filter. After using wavelet transform to disperse EMI sources, it can block the sources in different regions.

This paper addresses the suppression of multi-frequency line spectrum vibrations during the operation of indoor substations through the development of an active vibration isolation scheme based on a piezoelectric stack inertial actuator. Based on the finite element modal analysis, the excitation frequencies that strongly influence structural response were identified, and the excitation points and sensor layout strategies were determined under a collocated control configuration. Subsequently, the actuator’s structural design and system integration were carried out. Experimental results demonstrate vibration amplitude reductions of 18.75 dB at 100 Hz, 46.02 dB at 200 Hz, and 32.04 dB at 300 Hz, respectively, validating the effectiveness of the proposed method in controlling line spectrum vibrations at multiple frequencies. The study shows that the coordinated optimization of modal matching and the dynamic response capability of inertial actuators provides experimental evidence and technical guidelines for active vibration isolation in large plate-shell structures.

The presence of bubbles severely threatens the insulation safety of power transformers. Understanding bubble accumulation characteristics is essential for predicting potential insulation weaknesses. In this study, we propose a Euler–Lagrange two-phase flow model, combined with an experimental platform, to investigate the accumulation and growth characteristics of bubbles in typical oil channels. The continuous phase flow field is solved within the Eulerian framework, while discrete bubble trajectories are tracked using the Lagrangian approach, simultaneously accounting for drag, buoyancy, and friction forces. The results indicate that bubbles primarily accumulate on the top insulating paper surfaces within horizontal and corner oil channels. In horizontal channels, the accumulation rate correlates positively with flow velocity and bubble concentration; furthermore, paper overlapping gaps intercept sliding bubbles, promoting their coalescence into larger ones. Conversely, at channel corners, the accumulation length and rate decrease as flow velocity increases, with accumulation weakening significantly when the velocity exceeds 0.6 m/s. Additionally, bubble growth is highly sensitive to flow velocity and temperature: higher velocities inhibit bubble coalescence, whereas elevated temperatures accelerate both coalescence and growth. Ultimately, this research reveals the fundamental accumulation laws of bubbles in transformer oil channels, providing a reliable analytical tool and theoretical reference for assessing bubble-induced insulation risks.

Oil-impregnated paper (OIP) capacitive bushings are critical insulation components of power transformers, and internal defects may induce partial discharge (PD) and further lead to insulation breakdown, threatening equipment safety and power supply reliability. This study investigates the electric field distribution and insulation response characteristics of four typical defects in a 35 kV OIP bushing, including serrated cuts at the edge of the capacitor foil, metallic tips between capacitor screens, internal creepage along the lower porcelain insulator, and poor grounding of the end screen. First, full-scale three-dimensional models of normal and defective bushings are established to analyse the effects of different defects on electric field distribution and dielectric response parameters. Corresponding defective specimens are then fabricated, and dielectric parameter measurements and partial discharge tests are performed to verify the simulation results. The simulation results indicate that the maximum electric field strengths at the defect locations of the serrated foil, metallic tip, and internal creepage defects reach 8.92 kV/mm, 2.82 kV/mm, and 12.19 kV/mm, respectively, while their influences on dielectric response parameters are limited. In contrast, the loss of end-screen grounding increases the end-screen potential to approximately 26 kV and causes significant variations in dielectric parameters. The experimental results are highly consistent with the simulation analysis. This study reveals the electric field distortion mechanisms and response differences associated with typical bushing defects, providing theoretical support for defect mechanism analysis and insulation condition assessment.

Transformer oil is a critical insulating medium in high-voltage equipment, and its discharge characteristics under high electric fields significantly limit overall performance. Current negative streamer classification methods rely primarily on propagation velocity, failing to effectively explain the underlying transition rules and mechanisms. To address this, we developed an impulse discharge experimental platform featuring a shadowgraph optical diagnostic system. By analyzing the morphological evolution, current pulses, and light emission signals of negative streamers across various voltage levels and liquid pressures, this study elucidates their transition mechanisms and mode classifications. The results demonstrate that negative streamer discharge initiates in a primary subsonic mode with a thin-rod channel. It then evolves into either a heavily branched, thick-channeled secondary mode (bush-like) or a faster, less-branched tertiary mode. Under sufficiently high overvoltage, it transitions to a supersonic quaternary mode with filamentary channels. Notably, negative streamer development exhibits distinct gaseous characteristics, and the channel deformation process aligns with the Rayleigh theory of bubble dynamics in liquids. Finally, appropriately increasing liquid pressure compresses the streamer channel, facilitating the transition from the secondary to the tertiary mode.

In this study, a phase-generated carrier (PGC) demodulation algorithm combined with the extended Kalman filter (EKF) algorithm based on an electro-optic modulator (EOM) is proposed, which can achieve nonlinear distortion (such as modulation depth drift and carrier phase delay) suppression for high-frequency phase carrier modulation. The improved algorithm is implemented on a field-programmable gate array (FPGA) hardware platform. The experimental results by the PGC-EKF method show that total harmonic distortion (THD) decreases from −32.61 to −54.51 dB, and SINAD increases from 32.59 to 47.86 dB, compared to the traditional PGC-Arctan method. This indicates that the PGC-EKF demodulation algorithm proposed in this paper can be widely used in many important fields such as hydrophone, transformer, and ultrasound signal detection.