实验技术与管理

沿面绝缘是气固复合绝缘系统的薄弱环节，表面电荷积聚会畸变沿面电场分布，严重威胁沿面绝缘安全。基于沿面放电观测平台与表面电荷表征技术，提出一种气固界面放电及其电荷积聚特性的实验教学方案。通过放电电信号测量和发光图像拍摄，分析了空气中绝缘子沿面放电特性。采用静电探头法和粉尘图法表征了表面电荷，揭示了空气中沿面正流注和负流注的异同点。基于流体仿真模型计算放电发展过程，结合实验结果阐明了空气中沿面流注演变特性。该实验教学方案操作便捷、实验结果直观形象，能够助力学生扎实掌握高电压放电基础知识，培养科学探究素养和创新思维，实现科研与教学的有机融合。

[Objective] Surface insulation represents the weak link in gas-solid composite insulation systems. The development of high-voltage direct current transmission technology has exacerbated surface charge accumulation on insulators. Surface charges distort local electric field distribution and cause an abnormal decrease in surface insulation strength under polarity reversal or impulse overvoltage, thereby severely compromising power system operational safety. Therefore, researching gas-solid interface discharge and its charge accumulation characteristics is essential for clarifying the failure mechanism of insulation structures and providing a theoretical basis for optimizing the insulation design of electrical equipment. Based on the surface discharge observation platform and surface charge characterization technology, such a research scheme is proposed. [Methods] An experimental surface discharge observation platform is established. An impulse voltage generator is utilized to output the standard lightning impulse voltage. Surface-discharge voltage and current waveforms are measured by a resistance voltage divider and a current coil. The discharge luminescent images are captured by a single-lens reflex camera. A polymethyl methacrylate square sheet is adopted as the insulator. The electrostatic probe and dust figure methods are used to measure the charges accumulated on the insulator surface, following discharge. In this experiment, the surface discharge test is first conducted in the air, after which the charges accumulated on the insulator surface are characterized. The development process of surface discharge in the air is simulated by the fluid simulation model using the discharge module in COMSOL Multiphysics. [Results] Experimental results show that discharge current pulses are measured during surface discharge, with filamentary positive surface streamers being simultaneously observed through luminescent images. The surface charge measurement indicates that the positive and negative charges exhibit dendritic and circular distributions, respectively. Under positive and negative voltages, the surface-accumulated charges are dominated by positive and negative polarities, respectively. The polarity effect ensures that negative streamers encounter higher propagation resistance than positive streamers, resulting in significantly shorter negative streamers than positive streamers. Surface discharge intensifies with the increasing voltage amplitude, promoting surface-charge accumulation after discharge. Simulation results demonstrate that initial electrons converge significantly in the needle tip region under positive voltage, initiating an electron avalanche that forms a positive streamer after developing to a certain extent. This propagates outward from the needle electrode along the solid dielectric surface. The electric field is concentrated at the streamer head, whereas the channel interior comprises an electrically neutral plasma, resulting in very low electric field strength. [Conclusions] This study analyzes the influences of voltage polarity and amplitude on surface streamers in the air, clarifying the evolution characteristics of surface streamers by measuring electrical signals, optical signals, and surface charge, as well as simulating surface discharge. The vivid and intuitive experimental results are essential for improving teaching effectiveness. The experiment involves a variety of equipment and methods, enhancing students' experimental and simulation capabilities while cultivating their innovative spirit and scientific literacy.