Insulation defect is a main reason leading to the failure of GIS, most of which are the short circuit between the conductor and ground or phases caused by the discharge on the surfaces of solid dielectric insulation, such as disc insulator, insulating operating lever, post insulator and etc. In this paper, several typical insulation failures of GIS equipment and their causes are introduced. Moreover, the suggestions for preventing the GIS equipment from insulation failures are presented:1)strengthening the quality supervision of equipment manufacturing and field installation;2)stricting acceptance and test handover aspects;3)standardizing equipment operation inspection and repair and maintenance work;4) emphasizing on the quality of supervision and SF6 gas.

1 厂用电率定义 以某台200 MW机组为例,其设计额定工况下的厂用电率估算方法为[1] e=S(c)cos(e)av/Pe×100％ (1) Sc=∑(KP) (2) 式中:e为厂用电率,％;Sc为厂用电计算负荷,kVA;cos(e)av为电动机在运行功率时的平均功率因数,一般取0.8;Pe为发电机额定功率,kW;K为换算系数,取中的数值;P为电动机的计算功率,kW.

The primary current of power system may increase several or even multiple times while power system faults occur.In this condition,the iron core of protective current transformer will become saturated,which causes the distortion of secondary current and affects the operation of protection relay and other secondary equipments.In this paper,the saturated characteristics of protection current transformer are analyzed,the methods of plotting error curve and checking secondary load are introduced,and the measure of reducing error for protection current transformer is presented.

Polytetrafluoroethylene (PTFE) is the nozzle material of high voltage SF6 circuit breaker, and the life of circuit breaker is influenced directly by arc ablation of PTFE nozzle. Arc ablation resistance and dielectric property of PTFE composite are studied as adding different filler, including Al2O3, BN, TiO2, and MoS2. The result indicates that arc ablation resistance can be greatly improved by introducing inorganic filler. When filler type is different, the sequence from big to small of arc ablation quantity of PTFE composite is: compound MoS2 PTFE, compound TiO2 PTFE, compound Al2O3 PTFE, compound BN PTFE. Relative dielectric constant of PTFE composite is increasing along with increment of filler, and decreasing as temperature rising. Dielectric loss angle tangent is increasing as increment of filler addition and temperature rising. The result of arc ablation resistance is analyzed using orthogonal design software. The analysis result reveals that arc ablation quantity is influenced greatly by addition of filler, next by filler particle size, and thirdly by the interaction of filler particle size and PTFE particle size, and the least by PTFE particle size.

Arc ablation and dielectric properties of PTFE Composite, which is used in nozzle of SF6 circuit breaker, are affected by various factors, including PTFE particle size, filler particle size, filler type, and addition of filler. The multi-factor trial is designed using orthogonal design software, and the law of dielectric properties of PTFE composite is studied as adding different filler, including Al2O3, BN, and MoS2. The results indicate that arc ablation performance can be greatly improved by introducing inorganic filler. When filler type is different, arc ablation quantity of compound PTFE containing MoS2 is bigger than that containing Al2O3, and that containing BN is the smallest, relative permittivity of compound PTFE is increasing with increment of filler, and decreasing as temperature rising, dielectric loss tangent is increasing as addition of filler and temperature rising. The experimental results of arc ablation are analyzed using orthogonal design software and show that arc ablation is influenced greatly by addition of filler, next by filler particle size, and thirdly by the interaction of filler particle size and PTFE particle size.