空气电晕放电发展过程的特征发射光谱分析与放电识别

局部空气放电是导致高压输变电设备绝缘劣化的重要因素。空气放电中丰富的发射光谱信息与放电特征存在直接映射关系。采用针-板电极模拟了空气电晕放电的发展过程，并检测了放电由弱变强过程中的“紫外-可见光-近红外”波段在200～980 nm范围内的发射光谱。放电初期的发射光谱主要由氮气分子N₂的带状光谱组成，分别为N₂第二正带系（second positive system，SPS）和N₂第一正带系（first positive system，FPS）。放电程度加深后，发生能级跃迁的粒子种类更加丰富，由此产生了带状光谱与线状光谱相互交叠的复杂谱线，光谱范围也由放电初期的280～460 nm扩展至200～980 nm。放电处于临界击穿时，发射光谱的强度急剧增加，强度最高值出现在500.715和777.202 nm处，分别对应氮离子N+和氧原子O的辐射谱线，这意味着微观放电过程再次发生改变。基于空气放电机理分析得到：放电初期、放电加深、放电临界击穿三个阶段中强度占优的谱峰或谱带分别由N₂，NO与O和N+辐射跃迁所致，这由放电间隙的能量所决定，其特征光谱分别为336.907，239.687和500.715 nm。放电初期，336.907 nm处的强度绝对占优，239.687和500.715 nm处的相对强度极小；放电程度加深时，239.687 nm处的强度占优，500.715 nm处的相对强度极小；临界击穿时，500.715 nm处的强度占优，336.907 nm处的强度最弱。空气电晕放电的200～980 nm光谱范围内，紫外波段、可见光波段和近红外波段的光子数虽然都随着施加电压的升高而增加，但各波段光子数的归一化结果表明：随着放电程度的加深，紫外波段的光子比例逐渐减小，可见光波段的光子比例逐渐增加，近红外波段光子比例变化相对较小。不同放电阶段的“紫外-可见光-近红外”波段的相对光子数分布有较明显的差异，可以反映放电的发展程度。

Characteristic Emission Spectrum Analysis and Discharge Identification on the Development Process of Air Corona Discharge

Partial discharge of air is an important factor causing insulation deterioration of high voltage electrical equipment. The emission spectrum information in air discharge has close relationship with the discharge characteristics. In this paper, the development process of air corona discharge was simulated by needle-plate electrode, and the emission spectra in 200～980 nm wavelength range of “ultraviolet-visible-near infrared” band were detected. The emission spectrum at the initial discharge stage is mainly composed of the band spectrum of nitrogen molecule N₂, which are the second positive band system (Second Positive System, SPS) and the first positive band system (First Positive System, FPS) of N₂ respectively. With the deepening of the discharge degree, the kinds of particles that undergo energy level transitions become more abundant, resulting in complex spectral lines that overlap with the band spectrum and the linear spectrum. Moreover, the spectral range is extended from 280～460 to 200～980 nm. When the discharge is at a critical breakdown, the intensity of the emission spectrum increases sharply, and the highest intensity values appear at 500.715 and 777.202 nm, respectively corresponding to the spectrum of nitrogen ions N+ and oxygen atoms O. Based on the air discharge mechanism, it is found that the dominant peaks or bands at the three stages of initial discharge, discharge deepening and critical breakdown are caused by the radiative transitions of N₂, NO, O and N+, which are determined by the discharge energy. The characteristic spectrum wavelengths at the three discharge stages are 336.907, 239.687 and 500.715 nm, respectively. At the initial discharge stage, the intensity at 336.907 nm is absolutely dominant, and the relative intensity at 239.687 and 500.715 nm is very small. When the discharge degree is deepened, the intensity at 239.687 nm is dominant, and the relative intensity at 500.715 nm is the smallest. At the critical breakdown stage, the strength at 500.715 nm is dominant, and the strength at 336.907 nm is the weakest. In the 200～980 nm spectrum range of air corona discharge, although the photon number of the ultraviolet band (UV), visible band and near infrared band increases with the increase of the applied voltage, the normalized photon number of each band show that with the deepening of the discharge degree, the photon proportion in the ultraviolet band decreases while increasing gradually in the visible band, and the change of photon ratio in near infrared band is relatively small. There are obvious differences in the relative photon number distribution in the “UV-visible-near infrared” bands at different discharge stages, which can reflect the development of the discharge.