With the expanding application of 10 kV XLPE cables in power distribution, types of cables are produced by different manufacturers with various quality risks. The daily sampling inspection methods of cables can help discover and eliminate hidden dangers of cable failures. However, regular sampling inspection methods that ignore individual risk differences will lead to a waste of manpower and resources. To ensure the reliable operation of cables and increase economic benefits, an optimization method is proposed for 10 kV XLPE cable sampling in this work. In this paper, the order of supply quality of the qualified suppliers is achieved in combination with the mathematical statistics method. The parameters $\beta$ and $\eta$ that represent the quality of the cable are developed from the data selected from four qualified suppliers. The parameters $\beta$ and $\eta$ of the model can be estimated through Bayes inference by combining 10 kV cable related prior information with operational and failure data. The results of applying in-service 10 kV cables show that the proposed method can be used to analyze the reliability of 10 kV cables and can make full use of limited data and prior information to give relatively more accurate results. This result can provide a valid reference for the sampling of 10 kV XLPE cable.

针对大部分电缆局放(PD)信号识别方法在噪声影响下的识别准确率低、波形失真等问题,提出了一种基于小波变换与数学形态学的电缆PD信号识别及降噪方法.该方法利用最大重叠离散小波变换提取PD信号的高频和低频特征,结合重构和数学形态法滤除噪声.利用自适应神经网络学习小波变换后的特征,最终完成PD信号的识别分类.基于某变电站实测PD信号波形对所提方法进行实验分析结果表明,信号降噪处理后的信噪比与均方误差分别为 5.439 dB、0.251,且整体的识别准确率超过了88%,均优于其他对比方法,具有良好的应用前景.

在电子电气系统接地领域,独立地网间转移电位和相互作用一直是人们关注的焦点问题.基于触发闪电技术,在地网A注入了人工引雷雷电流,分析了间隔40 m的独立地网B转移电位的特征.结果发现,6次触发闪电共计35次回击作用下,地网B转移电位波形峰值-1.1～-28.5 kV(平均值为-10.7 kV),10-90％上升沿平均值0.74μs,半峰宽度平均值1.6μs;峰值电压呈现了短暂脉冲(平均持续时间3微秒)后出现次峰,次峰为主峰值的36.6％,之后电压缓慢衰减至零.地网B转移电位峰值与触发闪电电流峰值之间呈现非常好的正相关性(R2=0.98).

为解决脉冲振荡匝绝缘耐压试验设备无法应用于铁心电抗器匝绝缘缺陷检测和雷电冲击试验考核匝绝缘不全面问题,本文提出基于变频谐振技术的铁心电抗器匝绝缘缺陷检测方法.文中对现行相关标准进行了详细分析,证明了采用高频耐压的必要性,给出了变频谐振匝绝缘缺陷检测电路原理,并给出试验容量确定方法.文中通过一台具体铁心电抗器参数的仿真分析,给出匝绝缘短路前后的时域检测结果和测试回路幅频特性变化,进一步验证了采用电压失谐作为铁心电抗器匝绝缘缺陷检测的正确性.

针对现有雷电感应过电压数值计算模型工程适用性不强的问题,分析了雷电感应过电压产生的物理过程,基于时变电磁场理论提出了架空线路雷电回击入射场与感应场的电磁耦合关系,推导得出了架空线路雷电感应过电压时域波形的解析计算模型.计算分析了雷电流幅值、回击速度、雷电流波形对架空配电线路感应雷过电压时域波形的影响规律,结果表明:随着回击放电速度的增加,相同条件下感应过电压幅值有所降低且波头时间增加,当回击电流波前时间增加时,感应过电压幅值也显著降低.该模型解决了传统规程法忽略电磁分量且无法分析工程约束条件对感应过电压波形影响的问题.

近年来高压输电线路复合绝缘子异常发热频繁发生,对电网安全运行产生严重影响;但目前对其深入研究不够,通常把复合绝缘子异常发热同内绝缘缺陷简单对应,从而盲目采取更换等处理措施,造成人力物力极大浪费.为此,对某500 kV输电线路复合绝缘子大面积异常发热现象进行分析,通过试验分析发现其属于护套表面异常发热,与内绝缘缺陷无直接关联.试验结果表明:随着端部场强增大,异常发热温升增大,表层污秽去除后,异常发热现象消失.提出调整均压环配置来抑制复合绝缘子表层发热,通过带电作业方式实施后,现场运行复合绝缘子异常发热现象明显下降.

Cable joint insulation withstanding high temperature for a long period may induce unrecoverable damage, which may result in reduced insulation performance or even failure. Therefore, to assess and monitor the situation of insulation layer accurately is very important to the fabrication and operating reliability of cable joints. To simulate the thermal ageing of 220kV integrally prefabricated cable joint silicone rubber (SR) insulation layer, the accelerated thermal ageing tests of the cable joint SR insulation layer at 225° were carried out in this paper. An ultrasonic detection system for evaluation of insulation layer of aged cable joint was established. The dielectric characteristics, such as relative permittivity and breakdown strength, were measured by dielectric tests. Ultrasonic velocity characteristics and frequency domain characteristics were also investigated by ultrasonic detection. The results showed that, with increasing of ageing time, the dielectric performance (as destructive parameters) degraded gradually, and the ultrasonic velocity (as a non-destructive parameter of ultrasonic detection) decreased gradually. In addition, the DC component of ultrasonic spectrum of cable joint insulation layer decreased, but the other spectral peaks increased simultaneously. The correlation between ultrasonic velocity and dielectric performance can be quantified by fractional expression. Based on the amplitudes of the DC component and the main peak of ultrasonic spectrum, the of thermal ageing damage factor (TADF) was proposed and the correlation between TADF and dielectric performance was found to satisfy the Boltzmann distribution. The results confirmed that the ultrasonic velocity and the TADF were suitable to evaluate the thermal ageing state of SR insulation layer of cable joint. The ultrasonic detection method may offer a broad prospect for nondestructive evaluation and diagnosis of the ageing state of cable joint insulation layer.

The operating performance of room temperature vulcanized silicone rubber (RTV) coating can be affected by insulator surface statement especially in hot and humid areas. In this paper, glass sheets were used to study the effect of attachment and weather on RTV coating. The results indicate that contamination, hygroscopic attachment or bad weather is harmful to the surface condition, causing bubbling or catering, reducing the adhesion and increasing the leakage current. Relative suggestions were taken out to guarantee the quality of RTV coating on spot.

The adhesion of room temperature vulcanized (RTV) silicone rubber coating on insulators can be badly affected by hot and humid climate, which is apparently in Guangdong Province of China. In this paper, silane coupling agent (SCA) was used to modify the ingredient of RTV to enhance the adhesion operation in hot and humid environment. The results indicated that SCA could improve the adhesion of RTV and the other mechanical and insulation resistivity were not affected. And RTV adhesion testing method should be optimized for hot and humid environment.

文中针对交流高压熔断器建立了一种计算线状熔体温度随电流变化的数学模型,能够较为精确地计算熔体在低电流倍数下的温度情况。通过建立三维热电耦合模型,利用Ansys对熔体进行仿真,并与熔体实际温度状况和熔断时间进行比对,结果表明该模型具有较好的精确度。利用该模型和方法对熔断器进行设计可以极大的提高设计的准确性,为实际工程应用提供便利。

Special contaminant such as organic matter needs to be considered in pollution flashover prediction and leakage current research.This paper analyzes the material properties of glucose,and studies the discharge characteristics of glucose contaminant external insulation under different humidities.This paper has studied the influence of glucose contaminant on insulator leakage current,and has analyzed leakage current amplitude,fundamental current amplitude,3rd harmonic current amplitude and phase.Test results show that insulator leakage current is affected by adding glucose into contaminant,and extent depends on atmospheric humidity and the amount of glucose contaminant.As the amount of glucose is above 0.1 mg/cm2,the leakage current amplitude of glucose sample is much larger than that of normal sample at the humidity of 60％.Glucose has good hydroscopicity.If glucose is added into contaminant,pollution layer will absorb more water;leakage current will increase and discharge will happen.

室温硫化硅橡胶(RTV)防污闪涂料在运行过程中会受到环境因素影响而出现老化现象.为了探究广东地区高温高湿多雨环境下玻璃绝缘子RTV涂层脱落严重的原因,对实际运行绝缘子样品进行了表面状态分析及老化指标检测,并采用附着力测试的方法研究了RTV试片在人工环境作用后的涂层状态变化.研究结果表明:吸湿性盐污秽侵入涂层内部后的吸潮作用及污秽颗粒的析出效应对RTV长期附着力影响较大;涂层厚度过薄易受水分影响不利于保持附着力,厚度在0.4～0.6mm范围时较为适宜;运行绝缘子沿面水分与温度的分布不均导致上表面外侧附着力受环境的影响程度大于上表面内侧;RTV脱落严重程度同老化程度存在一定的正向关联,在外界环境中水、热、污秽等因素的共同作用下,RTV涂层附着力下降较快,同时会产生加速老化的现象.论文研究可为高湿多雨地带的RTV涂覆和使用方法提供参考和指导.

Abnormal heating problems caused by interface failure is a common phenomenon in Power System while the mechanism of abnormal heating hasn't been fully researched. To reveal the rule of abnormal heating, we conducted the experiments. Several studies have been conducted on a heating composite insulator serviced in China. Discharge and abnormal heating was observed under different working condition and the insulator was dissected in order to test the electric property. The experiment shows that the change of electric property is of great importance in abnormal heating, which is conductive to the accurate judgement of the interface failure. The abnormal heating phenomenon is in highly relative to the partial discharge in interface of the composite insulator. The electric field distortion, which was caused by electric property change, was the main reason leading to partial discharge.

The bonding performance of the composite inner interface is of great significance to the stable operation of the Insulation equipment. Terahertz wave has many applications in the fields of aviation, biomedicine and security because of its advantages of strong penetration. In order to explore its application in the detection of the interface performance of composite insulators, we conducted the experiments. The terahertz time domain system is used to test insulator models with different interface defects, and the characteristics of the time domain waveforms were analyzed. The test results proved the application value of terahertz wave in the detection of micro defects in the interface. The application scheme of the terahertz wave detection can be further explored. THz wave can be used in detecting the inner defects in the composite insulators. Combined with mathematical tools, the defects features in the defecting waves can be obtained.

复合绝缘子的芯棒与护套之间的界面老化是造成复合绝缘子故障的重要原因之一,目前缺乏针对界面老化的专项研究。为描述界面在老化过程中性能的变化特性,该文提出界面在水和高温作用下的老化模型,模型认为界面老化包括微观缺陷的形成和扩展两部分,缺陷的扩展在老化过程中占据主要地位。此外,提出一种新的基于芯棒表面形貌分析的评价指标:界面图像老化率。为验证老化模型,采用硅橡胶绝缘子和一种新型脂环族环氧树脂绝缘子进行试验。试验通过水煮使含界面样品老化,对老化样品进行泄漏电流试验及芯棒–护套剪切分离试验,以界面电流、剪切强度、界面图像老化率作为评价界面性能状态的指标。研究结果表明:界面电流、界面图像老化率两种指标在界面老化过程中的变化符合老化模型描述的S型曲线规律,界面缺陷在老化中的扩展是导致界面迅速老化的原因;剪切强度用于评价界面性能的灵敏度较其他两种指标低;界面缺陷扩展指数是界面的固有性质,可用于界面耐老化性能的评价,可应用于不同类型的复合绝缘子;新型环氧绝缘子具有更好的界面耐老化性。

Wet contaminant is an important precondition for pollution insulation discharge.Wet process is affected by the atmospheric environment and the hygroscopicity together.We analyzed the moisture absorption of soluble and non-soluble substances,and chosed aluminium phosphate as a strong hygroscopicity material.The discharge test of pollution insulation was performed in constant humidity condition.Some leakage current characteristics were investigated to analyze the influences of non-soluble substance hygroscopicity,such as current waveform,fundamental current amplitude,3rd harmonic current amplitude,and phase.Test results show that insulator leakage current is affected by insoluble substance hygroscopicity,and the influential extent depends on atmospheric humidity and the mount of strong hygroscopicity material.As the amount of aluminium phosphate exceeds 20％,the leakage current amplitude of aluminium phosphate is much larger than that of normal sample at the relative humidity of 70％.The phase between fundamental current and voltage is sensitive to the hygroscopicity of pollution layer.Hygroscopicity is the natural quality of pollution layer,which cannot be covered in the investigation of atmospheric humidity and pollution severity.

Refusal-operation of fuse for distribution transformer protection may cause over-load burn-up of the distribution transformer and serious accident consequence. In allusion to flake melt of fuse-switch disconnection for distribution trans-former protection,a kind of mathematical model for calculating temperature rise with change of current is established and a method for accurately calculating heat transfer coefficient of the melt is presented. It is verified that simulation result of the melt with low expansion current could be well identical to the actual condition by means of establishing 3D thermoelectric coupling model,using ANSYS software for simulation and combining with experiment on actual temperature condition of the melt. Meanwhile,it is proved to be beneficial for accurate characteristic simulation and pattern design on fuse for distribu-tion transformer protection.

Contaminant is the main factor affecting the insulation performance. The contaminant composition determines the inception voltage and the intensity of insulation discharge. This paper studies the intense discharge activity at low humidity (77% RH) in AC 500 kV Gangcheng substation where the contaminant contained glucose, and this phenomenon was rarely explained in previous publications. Electrical and chemical performances of glucose as a contaminant on insulation surface were investigated by means of discharge test (below 80% RH), artificial pollution test (100% RH), molecular dynamics simulations, and quantum chemistry calculations. The experimental results show that due to stronger moisture absorption capacity compared to non-glucose contaminant, glucose contamination sample has lower discharge inception voltage and stronger discharge intensity at 75% RH as the content of glucose exceeds 0.10 mg/cm2. Quantum chemical calculations reveal that the glucose molecules can decompose to generate free radicals with the unpaired electrons under the strong electric fields. The surface carbonation enhances the electron transfer rate and strengthens the discharge intensity. Moreover, the competitive adsorption of glucose and water molecules cause the low moisture discharge phenomenon, and it needs to be considered for insulation design and maintenance in areas producing sugar.

In recent years it is discovered that there are large amounts of organic in the contaminant on insulation surface. There are some special discharge phenomenon appeared in many place. Influence of organic on insulator discharge is very scarce. This paper studied a strong discharge activity under low humidity which was caused by the glucose contained in contaminant. The influence of glucose on insulator under low humidity is studied by chemical analysis, simulation tests, flashover tests and chemical calculations. The results show that because of the strong moisture absorption of glucose, the leakage current of polluted insulator with glucose is much larger than the conventional polluted insulator, as the content of glucose exceeds 0.10mg/cm2. The thermal effect of leakage current makes the surface potential distribution of glucose polluted insulator more uniform, and reduces the initial discharge voltage of the polluted insulator. At the same time glucose possess a active chemical property, the bonds of glucose could be broken to generate free radicals with electric charge in the strong electric field or discharge. It enhances the electron transfer rate, and strengthens the discharge intensity. Physical and chemical properties of glucose cause the special discharge phenomenon.

In recent years, some hollow core composite insulators, of which housings were made of liquid silicone rubber (LSR) of current and voltage transformers used in China Southern Power Grid have showed different levels of degradation and cracking phenomena. Based on SEM, FTIR, XPS and XRD methods, analyses have been conducted from several aspects such as organic functional groups concentration, microscopic appearance, element valence etc. It is found that organic groups (mainly Si-(CH 3 ) 2 ) on the side-chains of LSR are much more vulnerable than the backbone during the degradation process, thus Si-O/Si-C absorption peak ratio could be applied to characterize the degradation level of LSR. For severely aged LSR samples, the ratio is around 1.787-2.436. The valences of Si element and Si-O, Si-C functional group relative concentration of the aged LSR surface have changed and crystal structure is formed. Macro properties tests show that the surface of aged LSR is almost hydrophilic and tracking and erosion resistance is deteriorated remarkably. It is concluded that the crystallization caused by thermal/optical oxidation over crosslinking reaction is the main reason why degradation occurred.