F. Pratomosiwi

The study of partial discharge inception voltage of mineral oil using needle - Plane electrode configuration

The aim of this paper is to describe the feasibility study of using the needle - plane electrode system for Partial Discharge Inception Voltage (PDIV) measurement of mineral oil. This paper represents the experimental investigation of PDIV measurement of the mineral oil, Nynas 4000x, with the water content not more than 10 ppm under various tip radii of needle - plane electrode arrangements. The tungsten needle electrodes with the tip radius of 10μm, 20μm, and 40μm respectively were used as the high voltage electrode while the brass plane electrode with 75 mm diameter was used as the grounded electrode. The gap distance of the electrode system was set up at 50 mm. The electric field pattern of the electrode system was calculated using Finite Element program. The test experiment was set up according to IEC 60270. The test procedure was performed in accordance with IEC 61294 under room temperature. In addition, Scanning Electron Microscope (SEM) was employed to study the abrasion of the original and tested electrodes. Electric field distribution pattern and the average PDIV value of each electrode system including the SEM test results are analyzed and presented in this paper. From the test results, we found that the needle - plane electrode arrangements with the needle tip radius of 10μm, 20μm, and 40μm are highly possible alternative methods for the PDIV measurement of the mineral oil.

The influence of the test methods on the Partial Discharge Inception Voltage value of the mineral oil using the needle — Plane electrode configuration

The aim of this paper is to describe the study of the test procedureś effect on Partial Discharge Inception Voltage (PDIV) of mineral oil. This paper represents the experimental investigation of the PDIV of the mineral oil, Nynas 4000x, with the water content less than 10 ppm. The PDIV test was experimented by using tungsten needle electrodes with the tip radius of 10 μm, 20 μm, and 40 μm respectively as the high voltage electrode while the brass plane electrode with 75 mm diameter was used as the grounded electrode. The gap distance of the electrode system was fixed at 50 mm. The test experiment was set up according to IEC 60270. Five types of the PDIV test procedures were studied as the following: The first test procedure was performed in accordance with IEC 61294. Each needle was tested ten times in succession. Three needles of each needle tip radius were tested. In the second test procedure, the test voltage was applied to the electrode system with a rate of 1 kV/s from 0 to 65% of the PDIV value obtained from the first method. Then, the test voltage was increased in steps with 1 kV per step with a step duration of 1 minute until PDIV, the first voltage that PD ≥100 pC, was detected. Each needle was tested five times in succession. Three needles of each needle tip radius were tested. In the third test procedure, the test procedure was relatively similar to the second procedure except the step duration was adjusted to 5 minutes. In the fourth procedure, the test procedure was relatively similar to the second procedure except the test voltage was increased in steps with 1 kV per step with a step duration of 1 minute until the first PD pulse was detected; at this voltage level, the test voltage was recorded as the PDIV. In the fifth procedure, the test procedure was relatively similar to the fourth procedure except the step duration was adjusted to 5 minutes. The PDIV mean value of each electrode system obtained from each test procedure was calculated. It was found that the PDIV value depended strongly on the test procedure and the needle tip radius. The PDIV obtained from the first test procedure gave the highest PDIV which was higher than the PDIV value from the second, the third, the fourth and the fifth PDIV test method about 8%-18%, 12%-24%, 20%-28%, 36%-41%, respectively. The absolute peak value of PDIV pulse current was about 0.4-5 mA. PDIV pulse current amplitudes depended on the needle tip radius as well. The test results elucidate that the procedure for applying the test voltage and the stressed voltage - time interval firmly affect the PDIV of the insulation system.

The study of electrode corner shape for measuring dielectric properties of oil immersed material

Dielectric properties including dissipation factor and dc resistivity has been used widely as a diagnostic parameter of insulation system. In measuring dielectric properties according to IEC 60093 and IEC 60250, the detail of cylindrical live electrode curvature corner shape is not fully explained. The effect from the electrode curvature shape on the electric field distribution should be reduced as small as possible when measuring the dissipation factor and dc resistivity of the oil immersed material. This paper focused on comparative study of the electric field distribution for three electrode configurations. The calculation of the electric field strength was done using finite element method. Then the simulation results were deepened with the laboratory experiment, partial discharges inception voltage (PDIV) and partial discharge (PD) pattern respectively, In this experiment, the dielectric interface configurations consists of oil immersed pressboard operated under oil in a test vessel. The pressboard samples were placed on a grounded plane under cylindrical live electrode with three types of corner shape. The live electrodes used were sharp-cornered electrode and rounded-cornered with radius 3 mm and 5 mm. The solid dielectric were oil immersed transformer board type B 3.1A with 2 mm and 4 mm thickness operated under mineral oil, Nynas Nytro 4000x. The test experiment was set up according to IEC 60270 and the PDIV test procedure performed in accordance with IEC 61294. We concluded that, eventhough round-cornered electrode yields more uniform electric field at the pressboard side, it also yields steep electric field enhancement at the oil side. This nature of rounded-corner electrode makes it easier to generate oil discharge in the wedge (small oil gap) when compared to sharp-cornered electrode. For measuring dielectric properties at high voltage level, this phenomenon should take into account. These results showed the effect of electrode corner shape on electric field enhancement at the contact point of dielectric interface. Furthermore, it could be used as a consideration on which electrode is suitable for measuring dielectric properties of pressboard immersed in oil in compliment with IEC 60093 and IEC 60250.

The possibility of using a needle plane electrode for partial discharge inception voltage measurement

The propose of this paper is to elucidate the Partial Discharge Inception Voltage(PDIV) measurement for liquid insulation by using a needle - plane electrode. This paper presents the experimental investigation of PDIV and PD characteristics of the mineral oil tested by different electrode configuration. The experiment was performed by using a needle - plane electrode with a tungsten needle tip radius of 10 μm and a brass plane electrode with a diameter of 75 mm compared with measuring by the 10 μm tip radius needle - a steel sphere electrode with a diameter of 12.7 mm. This sphere electrode diameter is in the range of the standard sphere electrode for the PDIV test recommended by IEC 61294. Nynas nytro 4000x, with water content not more than 10 ppm was used for this research. The lengths of the needles were specified as 25 ± 0.5 mm and 45± 0.5 mm respectively. Two gap distance of 25 mm and 50 mm of the electrode system were fixed for investigation. To calculate the pattern of electric field of these electrode systems, the Finite Element Program was utilized. Then, the test experiment was carried out. The test circuit was conducted in accordance with IEC 60270. The test process was divided into two test methods. The former test method was carried out in conformity with IEC 61294. The latter test method was a ramp - step combination test method. Details of both test methods are described in this paper. The maximum electric field stress, the PDIV mean value and the phase - resolved PD characteristics of both electrode systems are analyzed. The test results revealed that the needle-plane electrode system can detect the PDIV value at the lower test voltage and gives the higher QIEC value compared with testing by the needle - sphere electrode system. The PDIV test results agree with the maximum electric field stress of the electrode systems. Moreover, the ramp - step combination test method gave the lower PDIV and PD amplitude recorded for 1 minute than PDIV testing comply with the IEC standard.

The study of partial discharge characteristics of mineral oil using needle - plane electrode configuration base on partial discharge pulse current measurement

The aim of this paper is to describe the Partial Discharge (PD) pulse current characteristics of the Partial Discharge Inception Voltage(PDIV) testing of mineral oil. This paper represents the experimental investigation of the PD characteristics of the mineral oil, Nynas 4000x, with the water content not more than 10 ppm, at the PDIV levels under various tip radii of needle - plane electrode arrangements. The tungsten needle electrodes with the tip radius of 10μm, 20μm, and 40μm respectively were used as the high voltage electrode while the brass plane electrode with 75 mm diameter was connected to ground via the shunt resistor of 50 ohm. The gap distance of the electrode system was set up at 50 mm. The test experiment, conventional PD measurement, was set up according to IEC 60270. The test procedure was performed in accordance with IEC 61294 under room temperature. PDIV was examined. Then, PD activities at the PDIV and 1.1 PDIV test level were investigated. Furthermore, PD currents were also detected and recorded by a high quality oscilloscope. Phase- resolved PD characteristics of the mineral oil, PD magnitudes and PD pulse currents of the tested electrode systems are analyzed and presented in this paper. From the test results, we will gain the knowledge of PD characteristics of the mineral oil tested by needle - plane electrode systems and we also found that the PD pulse current measurement can be used as an alternative indicator of the mineral oil degradation. The PD pulse current patterns are useful for analysis the oil characteristics as well.

Partial Discharge characteristics of mineral oil using needle — Plane and needle — Sphere electrode configuration base on pulse current measurement

The aim of this paper is to describe the study of the Partial Discharge (PD) characteristics of mineral oil obtained from Partial Discharge Inception Voltage(PDIV) testing using the needle - plane and needle - sphere electrode configurations. This paper represents the experimental investigation of the PD characteristics of the mineral oil, Nynas 4000x, with the water content not more than 10 ppm at the PDIV level using various tip radii of needle - plane and needle - sphere electrode arrangements. The tungsten needle electrodes with the tip radius of 10μm, 20μm, and 40μm respectively were used as the high voltage electrode while the brass plane electrode with a diameter of 50 mm was connected to ground via the shunt resistor of 50 ohm. The gap distance of the electrode system was set up at 50 mm. The test experiment, conventional PD measurement, was set up according to IEC 60270. The test procedure was performed in accordance with IEC 61294 under room temperature. PD activities at the PDIV and 1.1 PDIV test level were recorded. Additionally, PD currents were also detected and recorded by a high quality oscilloscope. Furthermore, the brass plane electrode with 75 mm diameter and the sphere electrodes with the diameter of 50.8 mm and 76.2 mm respectively were used also as the grounded electrode tested with the mentioned needles as high voltage electrode. The average PDIV value, the phase - resolved PD characteristics of mineral oil and PD pulse currents of the tested electrode systems are analyzed and presented in this paper. From the test results, we will gain the knowledge of PD characteristics of mineral oil testing by needle - plane and needle - sphere electrode system and we also found that the PD pulse current measurement can be used as an alternative indicator of the mineral oil degradation.

Study of electrode for measuring dielectric properties of oil immersed material

Dielectric properties including relative permittivity and dc resistivity has been used widely as a design parameter of insulation system. In measuring dielectric properties of oil immersed material (OIM), we have to make some adaptations from IEC 60093 and IEC 60250 i.e. the detail of live electrode curvature corner shape and the effect of electrodes weight. The effect of the electrode curvature shape on the electric field stress distribution should be reduced as small as possible when measuring the dielectric properties of the pressboard. Meanwhile the weight of electrode plays an important role to reduce the effect of non-flatness surface of the pressboard. This paper focused on electric field analysis distribution for three electrode configurations and pressure simulation of different electrodes weight. Then the simulation results were deepened with the laboratory experiment, permittivity, partial discharges inception voltage (PDIV) and partial discharge (PD) pattern respectively. In this experiment, the dielectric interface configurations consists of oil immersed pressboard operated under oil bath in a test vessel. For PDIV measurement, the pressboard samples were placed on a grounded plane under cylindrical live electrode with three types of corner shape. The live electrodes used were sharp-cornered electrode and rounded-cornered with radius 3 mm and 5 mm. Meanwhile for the permittivity measurements, a guard electrode was used to prevent edge capacitance. The solid dielectric were oil immersed transformer board type B 3.1A with 2 mm and 4 mm thickness operated under mineral oil, Nynas Nytro 4000x. The PD experiment was set up according to IEC 60270, the PDIV test procedure was performed in accordance with IEC 61294 and the permittivity and tan δ measurements performed in accordance with IEC 60250. We concluded that, eventhough round-cornered electrode yields more uniform electric field at the pressboard side, it also yields steep electric field enhancement at the oil side. This nature of rounded-corner electrode makes it easier to generate oil discharge in the wedge (small oil gap) when compared to sharp-cornered electrode. Meanwhile, the D/R (ratio of the sample thickness to corner radius of electrode) parameter does not seem to have any real important meaning. It was also found that electrode with pressure higher than 1.9 N/cm2 give enough pressure to prevent a thin oil layer that present on surface. These results showed the effect of electrode corner shape on electric field enhancement and pressure of electrode at the contact point of dielectric interface. Furthermore, the results could be used as a consideration on which electrode is suitable for measuring dielectric properties of pressboard immersed in oil in compliment with IEC 60093 and IEC 60250. We concluded that, eventhough round-cornered electrode yields more uniform electric field at the pressboard side, it also yields steep electric field enhancement at the oil side. This nature of rounded-corner electrode makes it easier to generate oil discharge in the wedge (small oil gap) when compared to sharpcornered electrode. Meanwhile, the D/R (ratio of the sample thickness to corner radius of electrode) parameter does not seem to have any real important meaning. It was also found that electrode with pressure higher than 1.9 N/cm2 give enough pressure to prevent a thin oil layer that present on surface. These results showed the effect of electrode corner shape on electric field enhancement and pressure of electrode at the contact point of dielectric interface. Furthermore, the results could be used as a consideration on which electrode is suitable for measuring dielectric properties of pressboard immersed in oil in compliment with IEC 60093 and IEC 60250.

The study of the arcing phenomena of the mineral oil using the rod — Plane electrode configuration

The aim of this paper is to describe the study of the arcing phenomena of mineral oil using a rod - plane electrode configuration. This paper represents the experimental investigation of the arcing phenomena of the mineral oil, Nynas 4000x, with the water content not more than 10 ppm under various tip diameters of the rod - plane electrode arrangements. The tungsten rod electrodes with the tip diameter of 1mm, and 2mm with the curvature of 0.2 mm respectively were used as the high voltage electrode, while the brass plane electrode of 75 mm diameter was used as the grounded electrode. The gap distance of the electrode system was set up at 0.3 mm and 0.8 mm respectively. The electric field pattern of these electrode systems was calculated using Finite Element Program. The test experiment was modified from IEC 60156 and performed under room temperature. The arcing current, the arcing voltage and the partial discharge pulse current before the arc occurred including the arcing current pulse signal were investigated. The test results show that the 1 mm diameter rod - plane electrode yielded the highest electric field and the lowest arcing voltage at 9.9 kV including the maximum arcing current density of 54.24 A/cm2. This electrode configuration gave higher a bit the arcing voltage than that of the 2 mm diameter rod - plane electrode. In addition, the PD pulse signals before arcing occurrence and the arcing pulse current signals were relatively similar in shape. Furthermore, the significant degradation of the mineral oil was clearly observed after testing.

SEM and EDX analysis of the needle — Plane and the rod — Plane electrodes for the Partial Discharge Inception Voltage measurement and the arcing test of the mineral oil

The aim of this paper is to describe the Scanning Electron Microscope (SEM) and the Energy Dispersive X-Ray (EDX) test results of the original and tested electrodes used for Partial Discharge Inception Voltage (PDIV) measurement, as well as for the arcing test of mineral oil. The experimental investigations were performed with the mineral oil, Nynas 4000x, with the water content not more than 10 ppm under room temperature. For the PDIV test, the tungsten needle electrodes with the tip radius of 10μm, 20μm, and 40μm respectively were used as the high voltage electrode while the brass plane electrode with 75 mm diameter was used as the grounded electrode with a gap distance of 50 mm. The test experiment was set up according to IEC 60270. The test procedure was performed in accordance with IEC 61294. For the arcing test, the tungsten rod electrodes with the tip diameter of 1 mm, and 2 mm with the curvature of 0.2 mm were used as the high voltage electrode while the brass plane electrode of 75 mm diameter as the grounded electrode with the gap distance of 0.3 mm and 0.8 mm respectively. The test experiment was modified from IEC 60156. The arcing current density was in the range of 5-54 A/cm2. The erosion of electrodes used for the oil testing was examined by SEM techniques. SE images, BSE images and EDX spectrum of the original and tested electrodes were produced. The topography, the morphology, and the EDX spectra of the examined electrodes are analyzed. From the test results, there is no evidence to show the erosion of the electrodes after they were used for PDIV and arcing tests. It can also be argued that the investigated tungsten needles, rods and brass plane electrodes can be used for PDIV testing and for the arcing test without the problem of erosion. In addition, carbon is the main contaminant created at the surface of the tested electrodes. The development of carbon was highly possible from the degradation of the mineral oil.

Dielectric properties measurements of oil immersed pressboard

Dielectric properties including relative permittivity, dielectric dissipation factor and dc resistivity has been used widely as a design parameter of insulation system. In measuring dielectric properties of oil immersed pressboard (OIP), we have to make some adaptations from IEC 60093 and IEC 60250 e.g. effect of electrodes weight. This paper is focused on study of permittivity and d.c. conductivity measurement of oil immersed pressboard (OIP). In this experiment, the dielectric interface configuration consisted of oil immersed pressboard operated under oil bath in a vacuum tight test vessel. The pressboard samples were placed on a grounded plane under live electrode. Rounded-cornered electrode with radius 3mm was used as live electrode. For this experiment, the solid and liquid dielectric were oil immersed transformerboard type B 3.1A with 2 mm thickness and operated under mineral oil bath, Nynas Nytro 4000x. The pressboard and mineral oil used in the experiment were in dry condition with moisture level <; 0.5% and <;5 ppm respectively. The test vessel, electrode system and test procedure for OIP were set up according to IEC 60093 and IEC 60250. We concluded that, first, relative permitivitty and dielectric dissipation factor of oil immersed pressboard are highly influenced by temperature. The change of dielectric dissipation factor is significant only for temperature ≥ 90°C. Second, the relative permitivitty and dielectric dissipation factor of pressboard do not depend on the electric field stress for range 0.125 kV/mm-5 kV/mm. Third, the calculation of effective surface area A for calculating relative permittivity and d.c. conductivity is not significant for B factor >; 0.83. Fourth, it was also found that electrode with pressure higher than 1.9 N/cm2 give enough pressure to prevent a thin oil layer that present on surface. Furthermore, the results could be used as a consideration on measuring the dielectric properties of oil immersed pressboard in compliment with IEC 60093 and IEC 60250.