Thermal image, partial discharge and leakage current correlation of ceramic insulator under different contamination level

This paper reports correlation on leakage current and thermograph infrared (IR) images of the ceramic outdoor insulator for the condition based monitoring purposes. In this work, laboratory pollution performance test using sodium chloride was performed according to the IEC 60507 standard with applied ac voltage from 12 kV to 18 kV. The severity level of pollution were controlled and represented by ESDD values of 0.00 to 0.25. Also, relative humidity conditions were controlled on the range between 60% to 100%. Statistical parameter of infrared images were evaluated to assess the severity level of contaminated ceramic insulator. The output IR images of the insulator were categorized as safe state, necessary maintenance and dangerous based on the level of contamination severity. The results showed that the severity of the pollution can be identified based on the analysis of infrared images, where each severity level of leakage current was correlated with a particular colour. Also, it was found that the phase difference between the leakage current to the reference voltage decreased along with the increase in the severity level of pollution

An optimized method of partial discharge data retrieval technique for phase resolved pattern

The measurement of phase resolved partial discharge requires a gigantic memory capacity to store all the waves of the PD test results. This limitation eventually hinders the testing. It is necessary to optimize on the aspect of memory storage capability to reduce the storage requirements. In light of foregoing, the partial discharge data retrieval techniques with sampling rate methods were used to detect the peak of partial discharge as well as the PD constituent representatives. The optimization process was performed by using integration of oscilloscope and LabVIEW software. The partial discharge data recording can be easily confined to the points of the partial discharge occurrence only. As results, the storage points were reduced by taking wave magnitude associated with PD, thereby resulting in more representative data. Therefore, this optimized method was able to reduce the file size of the test results up to 99 percent of PD original size thereby decreasing the usage of hard disk storage

A leakage current estimation based on thermal image of polymer insulator

Polymer insulators tend to fail because of the climatic and environmental conditions. The failure occurs when the surface of insulator is contaminated by sea salt or cement dust which lead to partial discharge (PD). Leakage currents will increase by PD that causes deterioration of insulation. To predict the insulation failures, an adaptive neurofuzzy inference system (ANFIS) method using initial color detection processes are proposed to estimate the leakage currents based on the polymer insulator thermal images (infrared signature). In this study, the sodium chloride and kaolin are used as pollutants of the polymer insulator according to IEC 60507 standards. Then, the insulator is tested in the laboratory using AC high voltage applied at 18 kV where the temperature detection is controlled at 26° C and 70% RH (relative humidity). The percentage of colors (Red, Yellow, and Blue) from the thermal image is measured using the color detection method. Correspond to the color percentage, the ANFIS method predicts leakage currents from polymer insulators. Furthermore, this system interprets measured data from insulators that need to be categorized as Safe, Need Maintenance or Harmful. The final application of the system can be a non-contact tool to predict the polymer insulators used by technicians in the field

Automatic threshold of standard deviation to reject noise in raw data of partial discharges

The raw data PD measurement results by using a computer usually contain noise that can lead to miss interpretation. So as to obtain an accurate diagnosis, then this noise must be separated from the raw data. In this study, the electrodes used were needle-plane electrode and the samples tested are polymer films placed on the electrode plane and the air gap is located between the needle and polymer films. There are two types of arrangement of the electrodes, the first electrode needle wrapped with the film and the second polymer are not wrapped with polymer films. To separate the data PD of raw-data is necessary algorithms that can automatically select the threshold value of the standard deviation value. To obtain the optimum value, the threshold value selected based on the standard deviation of each value segment. The results show that this method has been used to distinguish between the electrode pattern PD wrapped or not wrapped polymer

Development of rogowski coil sensor for partial discharge detection

This paper presents the development of Rogowski coil to detect the partial discharge. Rogowski coil sensor is composed of a ferrite core with a various number of turns which is 5, 10, 20 and 30 turns with a half circle and full circle configuration. The sensors need to be tested based on the number of the turns they have in reading the partial discharge signals. The sensor is connected to a digital measurement device such as a digital oscilloscope which has an input impedance of 50 ohms and 1 Mohm with a time frame duration greater than or equal to 20 ms. The reading comparison is not only between the proposed sensors but also with a commercial partial discharge sensor. The partial discharge signal is generated by a commercial charge calibrator. The measurement result shows that using low impedance lead to decreased noise but the reading is too small compared with using high impedance

Development of HFCT for partial discharge sensors

This paper presents partial discharge (PD) measurement techniques using a commercial sensor, High-Frequency Current Transformer (HFCT). An Output signal from HFCT is read by a digital oscilloscope and compared with the reading of convensional that PD detector. When PD occurs, the signals detected using high impedance that has a long time of oscillations and cause the delay of next reading of PD signals. To avoid this issue, the time of oscillations must be reduced by installing a damper which is a resistor connected in parallel between the sensor and the oscilloscope. The result of the measurement shows that the damper has the same reading on peak values as read by the convensional PD detector