A. Aman

Leakage current analysis on polymeric surface condition using time-frequency distribution

Leakage current frequency components are frequently used as a tool for surface condition monitoring on polymeric insulation material and their pollution severity. Fast Fourier Transform (FFT) is one of the methods that are applied for the analysis, but it has some limitation in non-stationary signal. This paper presents analysis of leakage current on polymeric insulation material for high voltage application in frequency domain and time-frequency representation. Tracking and erosion test (Inclined Plane Test (IPT)) complying with BS EN 60587-2007 is conducted on polymeric insulation to select a set of different leakage current patterns from capacitive, resistive and discharge. Then, the leakage current patterns are analysed in frequency domain and time-frequency representation using Fast Fourier Transform and spectrogram technique, respectively. It is found that the surface condition of polymeric insulation material state can be classified accurately by using spectrogram compared to Fast Fourier Transform.

Online surface condition monitoring system using time-frequency analysis technique on high voltage insulators

Insulations in high voltage engineering are a concern to users in terms of its performance, expected lifetime, and long-time reliability. Insulation failure can allow leakage current (LC) to flow and causes tracking and erosion as well as flashover. Tracking and erosion test complying with BS EN 60857-2007 are conducted to capture the set of leakage current (LC) patterns which are capacitive, resistive, and discharge activities. For verifying the performance of the insulators, an automated monitoring system is needed to reduce diagnostic time of the LC. Even though Fast Fourier Transform (FFT) gives useful information on the analysis of LC, it has limitation in nonstationary signal. Therefore, this research presents the analysis of time frequency distribution (TFD) which is spectrogram that represents the LC signals in the joint time frequency domains which provide temporal and spectral information. The results obtained from the developed monitoring system allow the user to identify leakage current performance in real time. The developed system has shown the capability in detecting the performance of insulating materials as well as identifying the characteristics of the surface discharges.

Polymeric insulation surface condition analysis using linear time frequency distributions

Polymeric insulator exposed to pollution leads to tracking and erosion affects their performance. There are no specific method to determine their service life. Most studies shows surface condition and their pollution severity of an insulator can be monitor by using leakage current frequency components. This paper presents linear time frequency distributions (TFDs) for leakage current of polymeric insulation for high voltage applications. Tracking and erosion test (Inclined Plane Test (IPT)) complying with BS EN60587-2007 is conducted on polymeric insulation to collect different leakage current patterns. Fast Fourier transforms (FFT) unable to provide temporal information and has limitation to analyze non stationary signal. To overcome this, time frequency distributions (TFDs) shown in time frequency representation (TFR) with temporal and spectral is used. The verification using both methods on several disturbances with known parameters have been made and mean absolute percentage error (MAPE) used to identify the accuracy of both methods. The parameters measured are root mean square (RMS), total harmonic distortion (THD), total non harmonic distortion (TnHD) and total waveform distortion (TWD) used to determine the best method to analyze leakage current. The comparison shows that s-transform provide better time and frequency resolution than spectrogram.

Dielectric property of Waste Tire Dust-Polypropylene (WTD-PP) composite for high voltage outdoor insulation application

High voltage insulation technology is still undergoing continuous development and improvement from time to time, from conventional ceramic type since to newly polymeric composite insulation material. This includes the development of new composite materials. This paper focused on the possibility of using Waste Tire Dust-Polypropelene (WTD-PP) composite with Alumina Trihydrate (ATH) as the main reinforcement filler for high voltage insulation material. Compound of WTD-PP without and with ATH were prepared with different compositions of WTD-PP content and different amount of ATH filler. A step of processes to produce this newly polymeric composite is presented in this paper. The basic requirement to determine and evaluate the performance of the selected materials as high voltage outdoor application shall comply to the international standard, BS EN 62039:2007. This standard lists several requirements of electrical and mechanical properties that must be fulfilled for materials to be used for high voltage outdoor application. Experimental work has been conducted on the dielectric strength of WTD-PP composite. Breakdown test complying with BS EN 60243-1:1998 is adopted to examine the breakdown strength of this newly polymeric composite. It was found that the breakdown strength of these composites is less than 10kV/mm due to it carbon black content but can be used for lower voltage insulation application.

Performance analysis of high voltage insulators surface condition using Time-Frequency Distribution

This paper presents the leakage current of polymeric and non-polymeric insulation materials in contaminated condition. High Density Polyethylene (HDPE) and Polypropylene (PP) are selected as polymeric materials. Meanwhile, glass is selected as non-polymeric material. The purpose of this study is to identify performance of insulator surface condition against its tracking and erosion and grouped according to the shapes of leakage current waveform. By using Incline Plane Tracking (IPT) test method for evaluating resistance to tracking and erosion is complying with BS EN 60587-2007. The result of leakage current waveforms were captured and recorded in continuous duration time. From that result, monitoring signal output will analyze using Time-Frequency Distribution (TFD). Spectrogram is used as a diagnostic tool to analysis time-frequency representation (TFR). Although, the harmonic components for polymeric and non-polymeric material can be define by Spectrogram. TFR result also will estimate to identify the signal characteristic patterns of the materials.

Two level factorial and optimization studies of Silicon Rubber surface resistivity for high voltage insulation — effects of raw materials and internal mixer processing parameters

Silicone Rubber (SIR) are steadily gaining acceptance in the high voltage insulation application due to a greater insulation properties and light weight attribute, which are suitable in substituting the conventional glass and ceramic insulator. There are still large research efforts conducted all around the world in order to improve the insulating behavior and sustainability of SIR. However, the investigation on the effects of materials formulation and processing parameters towards the insulation performances of SIR are still scarce. In this work, materials and processing parameters of Alumina Trihydrate (ATH) (10–50pphr), Dicumyl Peroxide (0.5–1.5pphr), speed of mixer (40–70 rpm) and mixing period (5–10 mins) were varied accordingly as to evaluates their effects towards dependent response of surface resistivity. The inter-correlation and contribution between all four parameters with response studied and optimization of it were established by using the statistical Design of Experiment (DOE) of two level full factorial at 24 level using Design Expert v10 software. The model analysis is finalized with R2 value of 88.72% together with a suggested optimized solution of A: ATH=50 pphr, B: DCP = 0.50 pphr, C: Mixing Speed = 70 rpm and D: Mixing Time = 10 mins with overall 0.959 of desirability value. In overall, this study emphasizes that the materials and processing factor had a major impact in influencing the surface resistivity of SIR for high voltage insulation purposes.

Effects of viscosity of ester oils and different sizes of suspended cellulose particles on bridging phenomenon under non-uniform DC electric field

Petroleum-based mineral oils are insulating media that are typically used in the industry, particularly for high voltage (HV) applications. In recent years, however, there is growing interest among researchers to formulate novel dielectric liquids in replacement of petroleum-based mineral oils since mineral oils are non-biodegradable and highly flammable. In addition, the dielectric performance of mineral oils is somewhat limited and therefore, there is a need to develop alternative insulation oils with superior dielectric performance in order to fulfil the demanding requirements of dielectric liquids. One of the promising substitutes for mineral oils is ester oils. In this regard, this research investigates the bridging phenomenon in two types of ester oils with different values of viscosity, i.e. natural and synthetic esters under the influence of direct current (DC) electric field. Three different sizes of contaminants are used, i.e. 100, 300 and 500 μm. The results show that both the size of particles and oil viscosity play important roles in the formation of cellulose bridge and breakdown behaviour.