Parouli M. Pakpahan

Study On The Electrical Equivalent Circuit Models of Polluted Outdoor Insulators

During operation, an outdoor high voltage insulator may come under various stresses. One of them is environmental pollution, where pollutants stick to the insulator surface. The polluted condition may produce leakage currents or even electrical discharges. Their waveforms are normally non-pure sinusoidal. To understand the correlation between insulator condition and its leakage current phenomenon, we will, in this study, investigate various equivalent circuits for representing insulator under different conditions. This paper presents the proposed equivalent circuit models of three main conditions of insulator, i.e. clean, polluted and polluted with dry-band discharge. In general, the model consists of capacitor(s) and non linear resistor(s). By using the models, the leakage current simulations have been done using ATP/EMTP software package. The simulations show that a clean low capacitance insulator yielded a pure sinusoidal current waveform, whereas that of a high capacitance yielded an oscillating sinusoidal current waveform. On the other hand, the polluted insulator simulations produced distorted sinusoidal current waveforms. At the end, the polluted insulator with dry-band discharge simulations showed chopped sinusoidal current waveforms. It was also showed the harmonic amplitudes, where third harmonics were usually the second highest amplitudes, a part of the fundamental ones

Influences of Water Droplet Size and Contact Angle on the Electric Field and Potential Distributions on an Insulator Surface

Existence of water droplets on an outdoor high voltage insulator surface changes the electric field flux and its equipotential distribution. The water droplets may appear in different forms and sizes, therefore the form is defined by the angle shape between the surface of the water droplet and that of the insulator surface, and the size is specified by the radii. The water droplet may measure from less than 90 degree (hydrophilic) up to greater than 90 degree (hydrophobic), depending on the properties of insulator surface. The work here presented describes numerical analysis calculation of electric fields and its potential distribution in the surrounding of water droplets on an insulator surface. The computation has been done using a partial differential equation toolbox, which worked based on the finite element method. The parameters used in this numerical analysis were the contact angle and the size of the water droplets. The computation results showed that the electric field close to the water droplets tends to be higher as its radius increases. The electric field fluxes were also affected slightly by the contact angle

Resistivity and Dielectric Constant Characteristic of Soil If are Treated by Water, Salt and Carbon

The characteristic of resistivity and dielectric constant of soil is the importance thing for investigating the impedance of grounding system. The impedance of grounding systems have resistance, inductance and capacitance components. Resistance and capacitance depend on resistivity and permittivity of soil and the configuration of electrodes of grounding system. The characteristic variation of resistivity and permittivity depend on the environment condition such as water, salt, chemical solution etc. In this experiment the soil is treated by water, salt and carbon with percentage variation from 2.5% to 15% and injected by low frequency of current (f=50 Hz). The calculation of resistivity and permittivity used the equivalent circuit of soil. Influence of characteristic of resistivity and permittivity depend on the type of soil

Leakage currents and pollutants properties of porcelain insulators from geothermal area

This paper presents the experimental results of one new-clean and four different geothermal naturally polluted outdoor porcelain insulators. The conducted experiments were leakage current and applied high voltage measurements, in the hermetically sealed chamber, on various temperature, humidity, pressure and applied voltage. Both quantities were measured by a storage digital oscilloscope. The data could be recorded and transferred to a computer, saved in softcopy form. The leakage current waveforms were analyzed using FFT and the relation to environmental parameters were analyzed using correlation coefficient matrix and principal component analysis. The results indicated that power factors and leakage current amplitudes closed to humidity, the phase angle closed to THD, and temperature opposited to humidity. On the polluted insulator, the comparison of impedance between that on wet and dry conditions reached 0.134, as the lowest. The reached lowest phase angle and THD were 24 degree and 7,5% respectively. These phenomena occurred due to contamination on the porcelain insulator surface that make more fairly conductive. The most chemical element on EDAX test was silicon.

Multivariate Statistical Analysis For Performance Assessment of High Voltage Outdoor Insulators Operating Under Various Meteorological Conditions

This paper presents our work where we investigated a correlation of different meteorological factors, such as: rainfall, humidity etc, to leakage current and ESDD (equivalent salt deposit density). In the study we used the multivariate statistical analysis, where with help of the tools we could, statistically, explain the effect of six meteorological factors on the pollution severity, thus through this method we hope some significant information about the influence of weather condition of insulator performance can be obtained. The meteorological factors investigated in this work are temperature, humidity, rainfall, wind velocity, wind dominant direction, and average ultraviolet of solar radiation. As case study, we analyzed measurement data published by the other authors. As first results it can be shown that wind direction and velocity contribute dominantly on the peak maximum leakage current, and based on the correspondence analysis, it can be shown the close correlation between humidity and temperature, in this case

The Influence of Resistivity and Dielectric Constant of Soil Which is Injected by Low to High Current Frequency

Grounding system in actual consist of electrodes configuration (vertical, horizontal, grid) and soil where these electrodes are planted. The grounding system which is installed to power systems or lightning protection system will be injected by low to high frequency. Electrical characteristic of soil (resistivity and dielectric constant) will be varied caused by injected current frequency variation. The variation of resistivity and dielectric constant depend on mineral composition of soil. As we know well that the soil constant of clay, silt, sand and gravel. Clay have an unstable chemical bonding and silt, sand and gravel have a stable chemical bonding, so if we have to know the type of clay for investigating the resistivity and dielectric constant of soil. In this experiment we used the soil with water treatment. Frequency of power supply is 0 Hz-13 MHz. The computation for investigating resistivity and dielectric constant used circuit equivalent of soil. Resistivity and dielectric constant will descend with frequency ascent, but the formulation of descending depends on the type of clay

Improvement of outdoors insulation performance for application in highly polluted area by using silicone coatings

This paper describes the results of the investigation on the application of silicone compound coating of ceramic high voltage insulator in tropical environments. The effects of temperature, humidity and various artificial pollutants were investigated. The experimental results show that application of silicone compound coatings suppressed leakage currents significantly under contaminated environment. The hydrophobicity of the insulators was also improved drastically. The coating on the wet-polluted insulators results in a very poor improvement of the insulator properties. This showed coating method affected the performance of the coating. A SEM of the surface of the insulator surfaces revealed the correlation between the improvement of the ceramics insulator surface and the electrical properties. Degradation of the coating under long term voltage application was observed in the form of bubble which prevent the coating to tightly coat the insulator surfaces. A flashover on the silicone coatings was observed under SEM as a discharge paths on the coatings.

Investigation of comparison on porcelain and epoxy resin insulator conditions from a coastal area due to various parameters

This paper presents the experimental results of eight months naturally coastal polluted porcelain and epoxy resin insulators. The experiments were leakage current and applied voltage measurements, in a hermetically sealed chamber, where temperature, humidity, pressure and applied voltage could be adjusted and measured simultaneously. The leakage current waveforms were analyzed using FFT and the relation to environmental parameters were analyzed using correlation matrix. It was also conducted SEM and EDAX tests. The humidity contributed to leakage current and phase angle on the porcelain insulator were 0.60 and -0.66 respectively. Whereas, on polluted epoxy resin one, the humidity did not influence to leakage current and phase angle considerably. The surface of polluted specimens became rougher than the new one. The most three chemical elements in pollutants were chlorine, silicon and ferrum.

Multivariate analysis for investigation of outdoor insulator conditions

The works reported in this paper deals with experimental study on a porcelain outdoor insulator, which has been installed at a coastal switchyard, during eight months. The measurements were also carried-out on new-clean one, in order to have a comparison with the polluted one. The insulators have been subjected under high voltage, and were measured the leakage currents, in a hermetically sealed chamber, wherein the temperature, humidity and pressure could be controlled, for simulating the environmental condition of site. The leakage currents were analyzed with FFT method, and correlation coefficient and PCA of multivariate statistical tools. The correlation coefficient shows that the humidity influenced the leakage current magnitude, phase angle and the third harmonics as 56%, -88% and 59%, respectively, on the new-clean one. In case of polluted one, the humidity influenced the leakage current magnitude, phase angle and third harmonics as 60%, -68% and 53% respectively.