For the benefit of knowing the method of insulator deicing using hot water, this paper investigated the physical aspects of propagation and the spatial temperature distribution of a hot water jet in the air. The numerical calculation model for the water jet flow field was established and validated, and the temperature spatial variation rule and influencing factors of the water jet were analyzed. The results indicate that the water column breaks as the distance increases. The numerical calculation results and the experimental results of the water jet flow field were approximated. As the distance increases, the mass entrainment rate of the water jet gradually increases, and the normalized axis velocity decreases approximately linearly. The jet temperature rises with the rise in the initial temperature of the hot water, and the rising rate decreases with the increase in distance. The temperature of the water jet falls as the jet distance increases. With the rise in the outlet pressure, the temperature of the water jet drops slightly. The influence of environmental wind speed on the water jet temperature is more significant than ambient temperature—the water jet temperature increases as the nozzle diameter increases. The thorough deicing efficiency is most outstanding when the hot water output temperature is around 86 °C and the jet pressure is ~3.5 MPa.

Ultra-high frequency (UHF) electromagnetic (EM) signals generated by the partial discharge (PD) process of high-voltage equipment are now widely used in PD detection. The computation of EM propagation generated by a local discharge source using a uniformly hardwiring source can hardly reveal the discharge characteristics. In this paper, a method of near-field to far-field transformation is proposed to realize the study of the propagation characteristics of the PD signal. A short gap discharge model is established to get the near-field electromagnetics and the proposed method is validated by comparing the directly calculated results with the results of the near-field source. In the end, a model of switchgear is employed to study the propagation characteristics of the EM signal based on the proposed method. Via numerical calculation, the influence of the equipment in the switchgear on the propagation of the discharge EM is studied. It is found that the direction of the discharge source has a significant effect on the distribution of the electric field, which indicates that the discharge source cannot be simplified to a uniformly hardwiring source. In addition, it is also obtained that the amplitude of the electric field shows the same trend with the growth of the discharge channel, which gives a method for evaluating the development of the PD. Particularly, the near-field to far-field transformation can provide an effective method for studying the propagation of discharge EM waves in large-scale equipment.

To improve the static performance, dynamic performance, and current balance of a current-source PWM rectifier with multi-modules, a comprehensive control method with passivity-based control and current balance control is proposed in this paper. Current balance control, which is based on AC voltage sequencing, has the advantages of being easy to implement and not being limited by the number of modules. Mathematical modelling, controller design, and simulation verification were conducted successively, and the results show that the comprehensive control method has a low current impact and high power quality. At the same time, module currents are well balanced, even under external disturbance, when using current balance control.

The distribution network connects with families, more branch circuit breakers, more and more users rely on power in winter, which requires higher and higher reliability requirements for power supply. The power supply department is facing greater pressure to stop distribution line for de-icing. In view of the above reasons, this paper first briefly introduces several measures of de-icing without power failure, and selects the technical route of injecting reactive power at the end of the line for online de-icing; secondly, it introduces the principle of SVG device generating reactive power, which uses reactive power to generate heat loss in the distribution network line for on-line de-icing, and then proposes an improved reactive power outer loop control strategy to make it equivalent to current source De-icing device; Finally, a simulation model is built in PSCAD. Taking a 5km ACSR (LGJ-120) line with 5.4Mvar reactive power injected at the end of the line as an example, it can be seen that the line current reaches more than 500A due to the injected reactive power. The simulation results prove the effectiveness of the method. Considering its economy, it provides a feasible way for the distribution network with important loads Electric deicing scheme.

Ice-shedding on overhead transmission lines can easily lead to jump discharge and subsequent line tripping, and effective monitoring methods are still lacking. To address this problem, this study proposes a distributed optical fiber sensing approach based on Brillouin optical time-domain reflectometry (BOTDR) for detecting ice-shedding discharge on 110 kV conductor–ground wire. The optical fibers embedded in an optical fiber composite overhead ground wire (OPGW) are used as sensing elements. Through simulated ice-shedding discharge experiments under different icing conditions, the Brillouin frequency shift (BFS) characteristics along the OPGW fiber are investigated, and the relationship between the BFS increment caused by the discharge-induced temperature rise and the discharge parameters is revealed. The experimental results show that ice-shedding discharge produces a localized temperature-rise region in the OPGW fiber, with an axial extent of 20–40 cm and a duration of 2–4 s. The maximum BFS increment due to the discharge temperature rise, Δv_Tm, is strongly dependent on the icing condition. Under conditions of no icing, light rime, and glaze ice on the conductor only, Δv_Tm remains within 5.43–7.94 MHz, whereas when both the conductor and ground wire are covered with glaze ice, Δv_Tm decreases significantly to 2.91–3.76 MHz. Further analysis indicates that, to satisfy the requirements for detecting ice-shedding discharge, the BOTDR must achieve a spatial resolution better than 0.1 m and a temporal sampling rate of no less than 5 Hz. These findings verify the feasibility of using distributed optical fiber sensing technology to detect ice-shedding discharge and provide experimental support for studies on the associated discharge mechanisms.