两种紫外成像参数在绝缘子故障诊断中的比较

绝缘子的运行状态直接关系到高压电网的稳定性,在运行过程中会出现绝缘性能下降同时伴随着表面放电,可以用紫外成像仪对其运行状态进行检测。目前,主要的参数是"紫外光斑面积"和"光斑直径",为了对它们在绝缘子故障诊断中的性能有一个对比,笔者通过喷水分级法在现场选择了正常、良好、微痕、劣化和严重老化5种绝缘状态的同一种绝缘子,在实验室搭建平台,在加压8、10、15 kV的情况下,通过南非CoroCAM504紫外成像仪对绝缘子放电情况拍摄足够的紫外图片,运用数字图像处理算法提取了两个参数值,通过MATLAB数字仿真,得到了这两种参数随绝缘状态的变化趋势。结果表明:①在绝缘子绝缘状态艮好的时候,光斑面积和光斑直径几乎可以忽略,对应性比较好,反之,在这两个参数都很小的时候,说明绝缘子绝缘良好;②在绝缘子绝缘出现问题时,二者都有上升趋势,但是光斑面积有一个转折点"4",而光斑直径没有,这说明,当绝缘劣化到一定程度时,光斑面积就没有太大区分度了,而光斑直径则可以区分。最终为绝缘子的运行状态的评估提供了量化的依据和一定的指导。

Comparison Between Two Ultraviolet Imaging Parameters for Insulator Fault Diagnosis

The stability of ultra-high voltage grid is related to the working condition of the insulators,whose insulation performance degrades during working period with surface discharge.The ultraviolet camera(UV-camera) can be used to detect the working condition of the insulators for fault diagnosis.The main parameters of UV-camera are spot area and spot diameter.In this paper,five kinds of insulation states of a same kind insulator, i.e.normal,good,slight trace,degradation and severe aging,are selected through the water spray classification method to compare the effect of the two parameters on insulator fault diagnosis.A platform is constructed in laboratory to take sufficient ultraviolet pictures of insulator discharge with a CoroCAM504 type UV camera(made in South Africa)at the voltage of 8 kV,10 kV and 15 kV,respectively.The two parameters are extracted by using the digital image processing algorithm,and the variation of the two parameters with insulation condition of the insulator is obtained through digital simulation by MATLAB.The results indicate that:When the insulation condition of the insulator is perfect,the spot area and spot diameter are almost negligible;Smaller values of the two parameters correspond to nice insulation;When the insulation get worse,both parameters show incremental tendency,but only spot area appears a turning point "4",which suggests spot diameter is more sensitive to insulation degradation as the degradation reaches a certain degree.This study may provide a basis for quantitative assessment of insulator working condition.