Sovan Dalai

Rough-Set-Based Feature Selection and Classification for Power Quality Sensing Device Employing Correlation Techniques

In this paper, we present a scheme of rough-set-based minimal set of feature selection and classification of power quality disturbances that can be implemented in a general-purpose microcontroller for embedded applications. The developed scheme can efficiently sense the power quality disturbances by the features extracted from the cross-correlogram of power quality disturbance waveforms. In this paper, a stand-alone module, employing microcontroller-based embedded system, is devised for efficiently sensing power quality disturbances in real time for in situ applications. The stand-alone module is developed on a PIC24F series microcontroller. Results show that the accuracy of the proposed scheme is comparable to that obtained in offline analysis using a computer. The method stated here is generic in nature and can be implemented for other microcontroller-based applications for topologically similar problems.

Cross-Spectrum Analysis-Based Scheme for Multiple Power Quality Disturbance Sensing Device

This paper presents a methodology of cross-wavelet transform aided Fischer linear discriminant analysis (FLDA)-based feature selection and classification for sensing simultaneous occurrence of multiple power quality disturbances. A linear support vector machine is used for classification of the extracted features as it suits well with FLDA. This scheme is implemented in a general purpose microcontroller as a standalone module and the performance of the standalone module for sensing simultaneous occurrence of multiple power quality disturbances is judged by both online and offline testing. Results show that the performance is comparable with the results reported in the literatures. Moreover, the scheme is immune to real life uncorrelated noises due to incorporation of cross spectrum analysis in the feature extraction phase. The present method is generic in nature and can be implemented for any other microcontroller-based applications addressing topologically similar problems.

Studies the effect of Equivalent Salt Deposit Density on leakage current and flashover voltage of artificially contaminated disc insulators

Reliable operation of transmission and distribution system depends on the life of the insulator. In overhead line the operation of the insulator is mainly influenced by pollution (contamination) level of that place. Flash over voltage and leakage current of the insulator are mainly influenced by the pollution level. Hence it is important to study influence of different pollutants on flashover voltage and leakage current of an insulator in polluted areas. This paper presents the flashover voltage and leakage current for artificial NaCl and KCl salt deposit layers at various Equivalent Salt Deposit Density (ESDD) level. The difference on flashover voltage and leakage current of polluted disc insulator have been studied by using solid layer method. The tests show that there are some differences on leakage current and flash over voltage characteristics, and the influences vary on both of specimens using different salt like KCl and NaCl. In this paper also an attempt has been made to develop an equation to estimate the flashover voltage and leakage current by using curve fitting method.

A method for the localization of partial discharge sources using partial discharge pulse information from acoustic emissions

Partial discharge (PD) localization employing acoustic emission technique is commonly done by estimating the time difference of arrival (TDOA) between signals captured at multiple acoustic sensors placed on the walls of the transformer tank. The localization accuracy of PD sources depends on the accuracy with which the TDOA is estimated. Hence it is important to accurately estimate the TDOA as far as possible. This paper presents a novel approach for the estimation of TDOA which is based on the source-filter model of acoustic theory. The TDOA is estimated by extraction of the excitation source signal from the acoustic signals in the form of an estimation of the PD pulse. The PD pulse serves as the excitation source signal for the acoustic detection system, whereas the acoustic path through the transformer tank and oil constitutes the physical system, which when excited by the PD pulse, gives rise to the acoustic pressure waves. The source-filter model extracts an estimation of the excitation source (PD pulse) by isolating it from the acoustic response of the tank-oil system. The extracted PD pulse information gives a sharp estimate of the instant of appearance of the PD pulse at each sensor. Hence, the TDOA between any two sensors determined from the cross-correlation function between the PD pulse estimates at the respective sensors gives a high estimation accuracy.

A comparative study on leakage current harmonics of porcelain disc insulator contaminated with NaCl and KCl

Flashover on disc insulator of over head transmission line is a major problem in power industry. Due to deposition of different contaminants particles, the surface of the disc insulator deteriorates which results in flashover occur on it. Hence, condition of the insulator surface must be monitored on regular basis in order to avoid the failure of power transmission. For this purpose, different approaches are taken to assess the condition of the insulator surface among which measurement of surface leakage current is found to be most efficient. But, existing literature shows that determination of peak value of leakage current is not always a good indicator to investigate the condition of insulator surface. Considering the above-mentioned fact, a different approach has been taken here that can efficiently predict the condition of insulator surface. Instead of determining the peak value, the harmonic contents present in the leakage currents has been evaluated to study the condition of insulator more accurately. For this purpose, an experimental setup has been developed in the laboratory that can measure the surface leakage current at different applied voltage. A disc insulator is contaminated separately with KCl and NaCl mixed with kaolin. The surface leakage current of the contaminated disc insulator is measured at different voltage and salinity level. Harmonic content present in the surface leakage current is evaluated for KCl and NaCl contamination at different voltage and salinity level. It may be observed that the harmonic contents present in leakage current are good indicator of salinity level.

Autocorrelation aided rough set based contamination level prediction of high voltage insulator at different environmental condition

This paper presents a Rough Set Theory (RST) based approach for predicting the surface contamination level of porcelain type insulators at different environmental condition. The sample insulators have been contaminated by Solid layer Method (SLM) according to IEC60507. Leakage current of the insulators are recorded at different contamination level and at different humidity conditions. In the proposed method, autocorrelation technique is used for feature selection from leakage current because it is well suited for non-stationary leakage current signals and cancels out the effect of noise present in the signal. Rough Set Theory is used for classification of extracted features as it suits well with the correlation technique. Result shows that the proposed method is able to detect the contamination level with acceptable range of accuracy.

Condition monitoring of overhead line insulator by measuring surface leakage current

Transmission and distribution power network commonly use porcelain insulator for the isolation i.e. insulation between line conductors and supporting structure. Most of the insulators are mounting in open-air applications. So, gradually contamination is deposited in the surface of the insulator and reduced the voltage withstand capability of the insulator. This voltage withstands capability of the insulator measured in terms of surface flashover. This hampers the reliable operation of the power network. Hence condition monitoring of insulator is needed in order to maintain smooth and uninterrupted power supply. Surface leakage current of the insulator provides the meaningful information about the surface contamination as well as flashover voltage level of the polluted insulators. Considering the above mentioned fact, an experimental setup has been made in the laboratory for recording the leakage current of porcelain insulators. Using this setup, surface leakage current of an 11 kV Disc insulator has been measured in contaminated condition.

Cross Hilbert-Huang transform based feature extraction method for multiple PQ disturbance classification

This paper presents a new methodology of Cross-Hilbert Huang transform based feature selection for sensing simultaneous occurrence of multiple power quality disturbances. Kernel PCA is used for feature selection because this method is well suited for non-linear and non-stationary multiple power quality disturbances. A linear support vector machine is used for classification of the extracted features. Results show that the performance is comparable with the results reported in the literatures. The present method is generic in nature and can be applicable for topologically similar problems.

Design of a dynamic model of the unified power quality conditioner and its operation control

This paper presents a 3-phase unified power quality conditioner (UPQC) to compensate voltage fluctuation and current distortion in the power utility side. The UPQC compensates for any unbalanced or distorted three-phase supply voltages and load currents in a power distribution network. In this paper, UPQC and its control strategies are described. Hysteresis current controller is used for obtaining the gate pulses from the reference current and voltage signal. A dynamic model of the UPQC is developed in Simulink. The simulation results validate the performance of the proposed model and its operation control.

Identification of salt and salinity level of 11kV contaminated porcelian disc insulator using STD-MRA analysis of leakage current

In the present work, a scheme has been developed based on standard deviation of multi resolution analysis (STD-MRA) plot of surface leakage current of a 11kV porcelain disc insulator artificially contaminated with NaCl and KCl. Leakage current analysis is perhaps the most efficient method to analyze the condition of insulator surface. For this purpose, a 11kV porcelain disc insulator is artificially contaminated in the laboratory by applying two soluble salts NaCl and KCl using solid layer method. Two salinity levels 0.5 and 1.5 indicating two different pollution levels are achieved by mixing NaCl and KCl individually with kaolin in distilled water and the leakage current is measured at three voltage levels of 5kV, 15kV and 30kV. The measured leakage currents are decomposed using wavelet transform and the standard deviation of the details are computed for each mentioned salinity levels at 5kV, 15kV and 30kV, respectively. From the above analysis, it is possible to identify the salinity level as well as the type of soluble salt (NaCl or KCl) deposition on the insulator surface which may be useful for condition monitoring of outdoor insulators.