Monitoring the insulator condition by on-line voltage distribution measurement

Insulator strings in transmission system are subjected to direct weather during its service. The withstandability to the weather is different for each insulator in a string. The withstand-ability of an insulator drops due to defect on the surface and or internal the insulator. Defect on the surface can be observed by using an visual detector such as daycor corona meter, however the internal defect need a special mean of detection method. A combination of the two different detection methods can be a useful choice. On-line detection method for an internal defect of an insulator string being done by measuring the voltage across each insulator in a string. It attempts to find the exact insulator unit that is damaged by plotting the voltage distribution of each insulator in a string. It found that the voltage distribution of an insulator string was not distributed perfectly, due to many factors on the measurement work. Decisions for replacing the insulator unit has been made by observing the graph and find the extra ordinary value of the voltage. This monitoring method is quite sensitive to find the damage unit in an insulator string.