Fault Identification of In-Service Power Transformer using Depolarization Current Analysis

Preventive diagnostic testing of in-service power transformers require system outage and expert’s knowledge and experiences in interpreting the measurement results. The chemical oil analysis may cause significant variance to measurement results due to the different practices in oil sampling, storage, handling and transportation. Thus, a cost effective measuring technique by means of a simpler method that is able provide an accurate measurement results is highly required. The extended application of Polarization and Depolarization Current (PDC) measurement for characterization of different faults conditions on in-service power transformer has been presented in this paper. The oil sample from in-service power transformers with normal and 3 different faults type conditions were sampled and tested for Dissolved Gases Analysis (DGA) and PDC measurement. The DGA results was used to confirm type of faults inside the transformer while the PDC pattern of oil with normal, partial discharge, overheating and arcing were correlated to the oil sample conditions. The analysis result shows that depolarization current provides significant information to defferenciate fault types in power transformer. Thus this finding provides a new alternative in identifying incipient faults and such knowledge can be used to avoid catastrophic failures of power transformers

Pengaruh Return on Investment (ROI), Earning Per Share (EPS), Net Profit Margin (NPM), dan Market Value Added (MVA) Terhadap Return Saham

e capital market has a fairly strong role in increasing economic stability in a country, because the capital market is used as a means of business funding and as a means for the public to invest. This study aims to determine the partial and simultaneous effect of Return on Investment (ROI), Earning Per Share (EPS), Net Profit Margin (NPM), and Market Value Added (MVA) on Stock Returns in Banking Companies listed on the Indonesia Stock Exchange. (IDX). This type of research uses a quantitative approach. The population in this study are banking companies listed on the Indonesia Stock Exchange (IDX) for the 2015-2019 period, namely 44 companies. Sampling using purposive sampling method, and obtained a sample of 12 companies. Data collection techniques were carried out by means of documentation studies and literature studies. The data analysis technique used in this study is descriptive statistical analysis, classical assumption test, and multiple linear regression analysis techniques. The results of the study show: partially Return on Investment (ROI) and Market Value Added (MVA) have a positive and significant effect on Stock Returns, Earning Per Share (EPS) has no effect on Stock Returns, and Net Profit Margin (NPM) has a negative and significant to Stock Return. Meanwhile, simultaneously Return on Investment (ROI), Earning Per Share (EPS), Net Profit Margin (NPM), and Market Value Added (MVA) have no effect on Stock Returns

Moisture Absorption Analysis of Linear-Low-Density-Polyethyelene Natural-Rubber Nanocomposite for HV Insulation

Insulation for high voltage (HV) application such as cable subjected to several types of degradation. These degradation can lead to premature breakdown and when its happen cost to replace or repair equipment will be higher. Many research was done to improve the insulation properties and currently nanocomposite material get serious attention due to their abilities to enhance electrical performance by addition of nanofiller into the based material. In this paper, water absorption of Linear-Low-Density-Polyethyelene (LLDPE) with different amount of nanofiller composition is studied. This study is necessary to be conducted since polymer based material is the most common insulation material used in HV cable. The HV cable normally will be continuously exposed in uncontrolled environment. Because of this, the cable will exposed to watery condition and it is crucially needed for the insulation to remain dry to the cable performance. Three types of nanofillers at different weight percentage (%wt) added into LLDPE, was used in this study are: Silicon dioxide (SiO2), Titanium dioxide (TiO2) and Monmorillonite (MMT). Percentage absorption of water was measured according to BS 6470 until the samples reaches saturation level. Experimental result demonstrate that SiO2 absorb less water than other filler while, the MMT has hydrophilic properties which it absorb more water compare to another sample. By used appropriate composition and type of nanofiller, a good insulator that are resistant to environmental influence can be produce

Insulation characteristic analysis of coconut oil and palm oil as liquid insulating material

The paper presents a study which has been carried out to use coconut oil as insulation in transformers. In transformer, oil is used as a coolant and also as an insulator. Nowadays, petroleum based oil is widely used in the transformer as it meets the requirements to be the best insulator. It is a fact that petroleum based oil will not be available for future generation used. Hence, further studies discovered that the coconut oil and refined, bleached, deodorized palm oil (RBDPO) has a great potential to be used a liquid insulation in transformer. An electrical test which using the breakdown voltage method was conducted for the coconut oil and refined, bleached, deodorized palm oil (RBDPO). The coconut oil and palm oil which have different heat effect were measured and compared to each other. The results shows that the coconut oil have high breakdown voltage compared to RBDPO. The result of the coconut oil and refined, bleached, deodorized palm oil (RBDPO) show that the samples have good insulation characteristic as liquid insulating material

The physicochemical properties and thermal behaviour of rice husk for dust explosion study

Combustible dust is present in a great variety of industries. It is estimated there are about 13 million workers in the manufacturing industry and thousands of these may be at risk of injury related to combustible dust. In order to reduce dust explosion in this industry, a study on the physicochemical properties thermal behaviour on explosion characteristic of rice husk is carried out with range size of rice husk is 63μm - 355μm. Thermal gravimetric analyzer (TGA) which is used to test the present of moisture content, rice husk ash, volatility and fixed carbon shows that the value is 15.55%, 0.17%,50.19% and 34.05% accordingly. Decreasing of moisture content and increasing of volatile matter were tend to increase the explosion hazard which mean can lead to explosion as the moisture content of a sample may act as a prevention or mitigation factor for dust explosions while high volatile content may increase the maximum rate of pressure rise. Meanwhile, four size of rice husk samples; 63μm, 106μm, 125μm and 355μm were analysed along with the elemental identification by scanning electron microscopy with energy dispersive x-ray (SEM-EDX) analysis. The size of the sample may influence the ignition and severity of a combustible dust explosion

Breakdown characteristic of LLDPE-NR nanocomposite using high voltage direct current (HVDC) test

Polymer nanocomposite has attracted many researchers’ recently in which the materials were applied as insulation material since 21st century. Polymer nanocomposite was given more attention because of the material properties that can be drastically improved by adding a few percent of nano-sized filler. SiO2 and TiO2 these filler are listed as the main nanofiller commonly used in electrical engineering due to the increase of effective activation energy. Natural Rubber (NR) is used because it develops several interphases with Linear Low-Density Polyethylene (LLDPE) matrix. This paper primarily concern the outcome of the most effective performance of breakdown voltage between SiO2 and TiO2 nanofiller as solid insulation and the best percentage among 1 wt%, 3 wt%, 5 wt%, and 7 wt%. LLDPE-NR with the ratio composition of 80:20 was selected as the base polymer and has been conduct by using High Voltage Direct Current (HVDC) testing

Flexural behaviour of the two-way spanning reinforced concrete slab using spherical plastic bubble balls

The use of conventional reinforced concrete in the construction industry increases each year, especially in developing countries. However, the concrete content, particularly cement production contributed to the greenhouse gas emission subsequently increase to climate change. Thus, the reinforced concrete slab containing high-density polyethene (HDPE) hollow spherical plastic bubble balls also known as bubble deck slabs were introduced for sustainable construction. This type of slab forms a slab that has less concrete volume compared to the normal solid reinforced concrete slab. Although this unique system can facilitate up to a 50% longer span compared to the conventional reinforced concrete solid slab, yet, it can cause the performance of the slab structure such as flexural and shear capacity may be affected due to the thirty to forty per cent of fewer concrete volumes. Hence, this paper studies the comparison of the performance of the two-way supported slabs; reinforced bubble deck slab and normal solid reinforced concrete slab after being subjected to the area loading. The square slabs are 1200mm by 1200mm in width and length with a thickness of 235mm. The investigations of the experiments included flexural strength, bending stiffness and load-deflection behaviour due to the impact of the area loading. Also, the crack propagation and crack pattern which differs also was shown for each type of slab system, especially in shear strength

Performance of Hybrid Rice Husk and Kapok Fiber as Alternative Liner Materials in Landfill

Generation of waste from agricultural activities like rice husk (RH) and kapok fiber (KF) is on the rise annually. Some of the arising issues are landfill limitation and air pollution because of burning activities. This paper presented a potential application of agricultural waste as an alternative material in landfill. A series of standard tests were conducted such as hydraulic conductivity test (falling head method), batch adsorption test (COD, TSS and heavy metals testing). These tests were conducted in the ratio of 1:1 and 1:2 of hybrid RH:KF. The results yielded that the hydraulic conductivity of the hybrid RH:KF in the ratio of 1:1 was lesser than 10-9 m/s, satisfying the requirement of landfill liner. The hybrid arrangement (RH:KF) for 1:1 ratio as adsorption media was able to reduce at least 45% of the bulk parameter (COD) whereas for 1:2, ratio, about 43.5% of heavy metal (Zn) was reduced in leachate. The proposed hybrid arrangement (RH:KF) is a green material for the landfill (bulk parameters and heavy metal adsorption capacity) that improves landfill workability, minimizing manpower on site and cost

Development of Two-Stage Network Data Envelopment Analysis (DEA) Model to Measure Production Line’s Performance: Combination of Automation and Labor

Nowadays, the growth of industry can be seen as a nature of the world. Each company race again each other to increase productivity to produce new, high quality and product that fulfil customer demand. One can achieve the Key Performance Indicator (KPI) or targeted goal but without considering the cost, manpower, time or others elements is inefficient toward productivity. Upgrade production line in manufacturing industry needs huge investment to come out with good performance. The company can receive Return of Investment (ROI) and save more money from paying labor salary and increase productivity. However, the company also may have the risk of losing their money from the investment done. In this research, we studied the effectiveness of production line that equipped with automation usage to determine the productivity and quality of the product produced. We apply Data Envelopment Analysis (DEA) to measure efficiencies of the production line where DEA is one of an excellent tool that can evaluate efficiencies and have been using widely in many sectors. The model that will be used in this study is Two-Stage Network DEA. As a case study, this research focuses on the production line that producing a product with a high and continues demand to observe how the investment on automation can give good return or otherwise