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Condition Monitoring and Diagnosis (CMD), 2012 International Conference on

Date 23-27 Sept. 2012

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Displaying Results 1 - 25 of 292
  • Development of asset management support tools for electric power equipment

    Publication Year: 2012 , Page(s): 1 - 8
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3524 KB) |  | HTML iconHTML  

    To establish maintenance strategies to reduce costs is one of the crucial issues of electric power industry. So asset management support tools are expected to be developed. The authors have developed support tools for asset management of several kinds of electric power equipment, such as transformers, gas-insulated switchgears, overhead transmission lines. In this report, some of the tools are explained and some important points to develop those tools based on the authors experiences during development processes of those tools. Those tools are aimed to give the minimum maintenance cost over target time interval such as 30 years based on the maintenance cost data. The authors also develop an evaluation model for typical maintenance methods, CM (corrective maintenance), TBM (time based maintenance) and CBM (condition based maintenance) which utilizes several input information, such as equipment age distribution, life time probability density distribution and accuracy of life time diagnosis. This model can evaluates annual and average maintenance cost during operation period of equipment, and these maintenance methods are compared each other. View full abstract»

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  • Modern insulation condition assessment for instrument transformers

    Publication Year: 2012 , Page(s): 52 - 55
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (339 KB) |  | HTML iconHTML  

    Instrument transformers in service are exposed to the harming effects of water and ageing. The increasing age is leading to a higher risk of explosions, which can damage surrounding parts and cause high follow-up costs. This paper introduces a new approach to use the dielectric response analysis for condition assessment of instrument transformers. The measurement of the dielectric response in a wide frequency range provides information about the insulation condition and especially for oil-paper/pressboard insulations about the water content in the solid insulation. The measured curve is formed by the superposition of the dielectric response of the cellulosic material and the oil. The curve can be used for the assessment of the insulation condition in various ways. Qualitative comparisons, e.g. between instrument transformers of the same type and age, might give general information which of these is in better condition. The dissipation factor and the capacitance trend can also deliver valuable data. Furthermore the water content in the solid insulation can be assessed using an automatic analysis algorithm. To confirm the validity of this assessment, measurements on several instrument transformers in service were performed. Dielectric response curves and the trend of the capacitances for new and aged instrument transformers with different water contents are discussed. Selected examples presented in this paper show, that the dielectric response is well modeled, the water content can be derived and ageing effects can be observed. View full abstract»

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  • Degradation of insulating polymer materials exposed to partial discharge under NOx environment

    Publication Year: 2012 , Page(s): 417 - 420
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (270 KB) |  | HTML iconHTML  

    The purpose of this study is to investigate the effects of humidity and NOx on partial discharge by insulating polymer materials degradation. Insulating polymer materials were used for the low density polyethylene (LDPE). The accelerated testing of these insulating materials was conducted. Experimental conditions are air atmosphere mixed with NO concentration of 600 ppm, and relative humidity was varied to 0, 25, 50, and 75 %. The quantity of partial discharge pulses can be evaluated with number of pulses, average pulses, maximum of pulses, and summation of pulses during 20 ms. The degradation factor of each sample was compared and examined from this quantity of partial discharge pulses. View full abstract»

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  • Simulation of electro-thermal aging based on the generic life-expression

    Publication Year: 2012 , Page(s): 421 - 424
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (282 KB) |  | HTML iconHTML  

    Simulations in polymeric aging models have been performed on the DMM life model in terms of generic aging features. These simulations were carried out on polyethylene-terephthalate (PET) samples with a thickness of 1mm, under DC fields of 40 and 20 MV/m and temperatures of 110 and 180 oC. Representation of the work was performed in 2-D to demonstrate the evolution of damage structures during aging process in insulating polymers. Susceptible sites in isolated regions will be produced during the aging process. Therefore, failure bonds will be initiated at a high energy concentration sites which leads to create a breakdown path between electrodes. Life-time was taken in the simulations by varying either the susceptibilities of the damage sites parameter or the concentration of the stored energies in the moieties parameter. This paper will provide the inverse relationship between the insulation life and the increasing of the thicknesses. The relation will be based on the Weibull statistical analysis. Simulations based on the generic life-expression are used to support this relation and investigate the validity of the model for various thicknesses. View full abstract»

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  • Time lag in CM-II electrode system attributed to dielectric surface conditioning

    Publication Year: 2012 , Page(s): 425 - 428
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1643 KB) |  | HTML iconHTML  

    This paper deals with a digest on discharge time lag characteristics in a cylindrical void bounded polymethyl-methacrylate (PMMA) and metal using the CIGRE method II (CM-II) electrode system. The specimens were treated by plasma irradiations (0, 3, 6, 11, 16, 21 seconds) simulating material ageing in service which are very difficult to measure. It was found that, under room temperature, the longer plasma irradiation to the void surface will result in higher degree of surface roughness indicated by the increase of surface protrusion sizes. The statistical discharge time lag (SDTL) has been studied using square pulse voltage with rising time 40 μs, through 64 pulses. The SDTL value is inversely proportional to the surface conditioning. For a particular time period of plasma irradiation (3 s), the specimens seem to recover its insulating property after given recovery time of 20, 60, and 180 minutes compared to that of without recovery time. View full abstract»

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  • Diagnosing winding and core condition of power transformer by vibration signal analysis

    Publication Year: 2012 , Page(s): 429 - 432
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (687 KB) |  | HTML iconHTML  

    The ability to diagnose the integrity of the transformer windings and core through online diagnostic method would be useful for electric utilities who are concerned about the availability and reliability of power transformer. This paper presents results of a study to identify the condition of power transformer windings and core by measuring the vibration signal of outdoor transformer in normal operating conditions. The obtained vibration signal which is recorded from various places on the transformer tank is analyzed by matching the signal frequency spectrum with transformer load. From this study, mechanical integrity of windings and core inside the transformer is determined by comparing the correlation between each main frequency of vibration signal and the load among similar transformer. View full abstract»

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  • Study on the Online Dissolved Gas Analysis Monitor based on the Photoacoustic Spectroscopy

    Publication Year: 2012 , Page(s): 433 - 436
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (420 KB) |  | HTML iconHTML  

    According to the principle of Photoacoustic Spectroscopy, HPAS-1000 Online Dissolved Gas Analysis Monitor is developed to monitor the dissolved gas in the power transformers online, which can directly extract the oil sample from the running transformer and measure the content of Hydrogen, Acetylene, Ethylene, Methane, Ethane, Carbon monoxide and Carbon dioxide dissolved in the oil sample in real time. Field Gas Monitor-INNOVA 1412 module is employed for it only takes a few milliliters of gas to achieve the measurement and the sensitivity of Acetylene, Ethylene, Methane, Carbon monoxide can reach to less than 0.5ppm. In order to separate the gas from the transformer oil a vacuum pump is used in the degassing module with TEFLON AF 2400 polymer membrane. For every fault gas has cross-interferences with each other including water vapor when measuring, INNOVA 1412 module should be calibrated by the fault gases of known standard concentrations before it can be used for measuring. Then several experiments were designed in order to study the characteristics of capillary negative pressure oil gas degassing system, and found the most efficient way of degassing. The experimental results show that, under the same conditions, the longer the degassing time, the higher the degassing efficiency; the greater the pressure difference, the higher the degassing efficiency; as the flow rate increases, the degassing efficiency increases first and then decreases, and the optimum flow rate is between 20ml/min and 30ml/min. Based on these results, the performance of HPAS-1000 Online Dissolved Gas Analysis Monitor is optimized, thus it subsequently passed the certification of CEPRI successfully and installed in the substations. View full abstract»

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  • Low-cost frequency response analyzer for transformer diagnosis

    Publication Year: 2012 , Page(s): 437 - 441
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (925 KB) |  | HTML iconHTML  

    Frequency response analysis (FRA) is a powerful and sensitive tool to assess the core, windings and clamping structures within power transformer. In this paper, it represents a Low-Cost Frequency Response Analyzer (LCFRA). The developed LCFRA was composed of digital oscilloscope, function generator and Labview software. In this paper, the measured sampling was 22kV/400V 250kVA 3phase transformer. Then, the frequency response of transformer measured by the LCFRA was compared with that from commercial SFRA (DOBLE M5300). The results of LCFRA were similar to that of the commercial SFRA. This relation was proved by the cross correlation coefficients (CCF) which had the minimum value at 0.9976. This CCF value showed a good match relation between those two results. View full abstract»

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  • Investigating the partial discharge electromagnetic wave propagation in power transformers considering active part characteristics

    Publication Year: 2012 , Page(s): 442 - 445
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (329 KB) |  | HTML iconHTML  

    UHF partial discharge localization in power transformers is getting more interests. One of the great advantages is the immunity of the measurements from external noises due to transformer tank electromagnetic shielding. The time delay of arriving signals to two or more UHF antennas installed in different locations at transformer tank is the key parameter for accurate localization algorithms. Due to presence of active part and transformer tank, unfortunately sometimes there is not a direct path for PD electromagnetic waves to propagate from defect site to antennas positions. Through the propagation path, these waves would be reflected and attenuated striking different materials inside transformer. Some materials like core did not allow the wave to propagate through them. Some parts like windings and dielectric boards impose attenuations to wave energy. Such attenuations in some cases might be so high that energy of the parallel long paths may be stronger than the shortest path and this would result in inaccurate localization. Propagating the wave along such paths are mainly caused by reflecting the waves by transformer tank and other components. In this paper using the CST software, the effects of these issues on PD UHF wave propagation in transformers are studied. View full abstract»

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  • Characterization of transformer FRA signature under various winding faults

    Publication Year: 2012 , Page(s): 446 - 449
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1051 KB) |  | HTML iconHTML  

    Frequency response analysis (FRA) is gaining global popularity in detecting power transformer winding and core deformations due to the development of FRA test equipment. However, because FRA relies on graphical analysis, interpretation of its signatures is still a very specialized area that calls for skillful personnel to detect the sort and likely place of the fault as so far, there is no reliable standard code for FRA signature classification and quantification. This paper aims to initiate the establishment of standard codes for FRA signature interpretation through comprehensive simulation analysis on a detailed transformer distributed parameters-based model. Various mechanical faults such as axial displacement, buckling stress, disk space variation and bushing fault are simulated on the model to study its impact on the FRA signature. The main contribution of this paper is the comprehensive table it presents for FRA signature sensitivity to winding and core deformations that can be used for classification and quantification of the transformer FRA signature. View full abstract»

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  • The application of FRA-SCR in the diagnosis of transformer coil deformation

    Publication Year: 2012 , Page(s): 450 - 453
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (262 KB) |  | HTML iconHTML  

    Failures of transformers can cause serious problems in electric power system, and the rate of transformer failures caused directly or indirectly by the winding deformation remains high, therefore, the study on detecting the transformer winding deformation is of great significance to avoid unexpected accidents and improve the reliability of the operation in electric power system. In this paper, by the use of ANSYS, a three-phase model of the transformer is established and the distributed capacitance and inductance parameters of windings under both normal and fault states caused by different kinds of deformation of the windings are calculated and summarized. A equivalent model of transformer windings(phase A) is also simulated using ATP, by adjusting the related inductance and capacitance parameters, the characteristic trans-admittance(I( )/U ( )) are investigated variations of the sweep frequency response curves of quantitatively under a sweep frequency voltage source of 100V in intermediate frequencies(0.5kHz-1MHz), and some preliminary conclusions are drawn here. This investigation has some degree of guiding significance in predicting structural faults of windings and is the basis for further experimental study. View full abstract»

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  • Developing norm for SF6 quality of tropical GIS

    Publication Year: 2012 , Page(s): 454 - 457
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (210 KB) |  | HTML iconHTML  

    The climate of Indonesia is almost entirely tropical. The uniformly warm waters that make up 81 % of Indonesia's area ensure that temperatures on land remain fairly constant, with the coastal plains averaging 28°C, the inland and mountain areas averaging 26 °C, and the higher mountain regions, 23 °C. It is huge difference between tropical weather compared to subtropical weather conditions. To identify the level of SF6 quality we use SF6 gas norm of the restriction of range value CIGRE. Data obtained from the test results over five years by using 30 samples. The method used used to obtain norm is a statistical method. View full abstract»

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  • New diagnosis method of aging degradation for insulating paper in power transformers by measuring the refractive index of cellulose fibers

    Publication Year: 2012 , Page(s): 56 - 59
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (386 KB) |  | HTML iconHTML  

    This paper proposes a new diagnosis method for aging degradation of insulating paper in power transformers. We took notice of cellulose fibers that suspended in insulating oil in transformers as useful samples for estimating degradation of insulating paper in transformers. The Mahalanobis-Taguchi System was applied for investigating the relationship between degradation and refractive indices of cellulose fibers measured. It was found that aging degradation of cellulose fibers on insulating paper accompanies a change of dispersion color. This result shows that it is capable to estimate degradation of the paper in oil-immersed power transformers by measuring dispersion color of fibers suspended in insulating oil. View full abstract»

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  • Application of MV GIS partial discharge measurement and location

    Publication Year: 2012 , Page(s): 462 - 465
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (391 KB) |  | HTML iconHTML  

    While the demand of electric power increases and the installation space of power equipment is fixed in a factory, the gas insulated switchgear (GIS) is gradually applied to medium voltage system due to its small size and easy maintenance. However, it also takes longer time for the repair of GIS accident. Therefore, the preventive maintenance (PDM) is very important and the most effective method is partial discharge measurement. Unfortunately, the metal-cladded GIS usually makes PDM inconvenient, especially for the partial discharge location. This paper provides a fast and easy method for the location of partial discharge in GIS, it can locate the defect quickly and effectively, and the related strategy can be made in advance. View full abstract»

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  • Noise discrimination from PD signal in pre-breakdown discharge detection test

    Publication Year: 2012 , Page(s): 466 - 469
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (556 KB) |  | HTML iconHTML  

    In Japan, 22-77 kV cross-linked polyethylene (XLPE) cables have been put into practical use for about 40 years, and some of them have been in operation for more than 30 years, which exceeds their expected lifespans of 30 years. At these voltage levels, the degradation of the insulation of XLPE cables is due mainly to the water tree. Central Research Institute of Electric Power Industry (CRIEPI) has studied the dielectric strength of XLPE cables and the various aspects of water tree degradation using a pre-breakdown discharge detection (PBPD test). This test's success rate of whether to find the water tree of weakest point in cable specimen depends on a method that distinguishes small partial discharge (PD) signals caused by water trees from noises in noisy environments of the test field. It also determines the likelihood of establishing a robust PBPD test that incorporates the developed method for the discrimination of PD signals from noises. View full abstract»

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  • Influences of different absorbents on the detection of SF6 gas decomposition products

    Publication Year: 2012 , Page(s): 470 - 475
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (451 KB) |  | HTML iconHTML  

    After the setup of detection system based on gas chromatography, typical gas decomposition products of corona and spark discharge in needle-to-plate defect model were detected. Modeling the practical regulations, absorbents with one tenth the quality of filled SF6 gas were added in the gas cell. Focusing on the concentrations of SO2F2 and SO2, gas decomposition on the sole existence of silica gel and four types of molecular sieve- KDHF-03, F-03, 4A and 5A were compared. Moreover, influences of absorbents with different numbers of use on detection results were analyzed. It is clear that influences of absorbents added in practical SF6 insulated apparatus on gas chromatography detection are not fatal. As for absorbent performance evaluation, comparing with molecular sieve, silica gel is not recommended. Among the molecular sieve investigated, while 4A is obviously worse than the other three, with lower SO2 concentration but higher SO2F2 concentration than the compare group. KDHF-03 is best with comprehensively lower concentrations of gas decomposition products. View full abstract»

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  • Minimizing the potential of SF6 gas emission

    Publication Year: 2012 , Page(s): 476 - 479
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (394 KB) |  | HTML iconHTML  

    PLN P3B Jawa Bali (JB) has been operating GIS installations for years wherein SF6 gas is applied as the insulating material. Despite of its superior well-known characteristics (colorless, odorless, tasteless, non-toxic and having density of five times of air), SF6 might be inhaled and causing reduction of oxygen content in human blood. According to Kyoto Protocol, an international consensus to preserve ozone layer sponsored by the United Nations Framework Conference of Clime Change in 1998 in Japan, SF6 is one of six gases which cause greenhouse effect. It has the highest global warming potential (GWP) which is 23,900 times of that of CO2 and lasts for 3,200 years in atmosphere without any chemical reaction with other gases or compounds. Because in Indonesia GIS installation primary problem is gas leakage, which might end with SF6 deterioration, the possibility of SF6 release is quite high. Thus, PLN P3B Jawa Bali which is committed to conduct operational with friendly environmental needs to minimize the potential of SF6 emission. This paper will describe about how PLN P3B Jawa Bali deals with this issue. View full abstract»

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  • Surface trapping parameters of solid dielectrics: Novel measurement method and insulation condition characterization

    Publication Year: 2012 , Page(s): 480 - 484
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (995 KB) |  | HTML iconHTML  

    Charge traps greatly affect the charge transport, trapping and recombination in solid dielectrics such as ceramics and polymers. This paper presents a novel method of measuring the surface trapping parameters such as trapping density and energy level of insulating materials. Based on the isothermal relaxation current (IRC) theory, the trap measurement and calculation formula is deduced and a non-contact measurement setup is specially designed, and electron or hole trap parameters can be determined by choosing negative or positive charging, respectively. Two kinds of materials are selected as the samples, i.e., high temperature vulcanized (HTV) silicone rubber and machinable ceramics (MCs). Experimental results indicate that, with extending duration of aging time, electron and hole trap density both increase, and gradually saturate. SEM and XPS analyses reflect that specimens after aging process appear many physical defects as holes and flaws and chemical defects as strong polar groups, which causes significant influence on surface trap characteristics. It is shown that the glass phase on the surface of MCs greatly influences the existing shallow traps, which in turn degrade the fla-shover characteristics. Removing the glass phase with HF treatment reduces the concentration of shallow traps and stabilizes the flashover voltage. It is considered that charge trap is expected to be as a novel indicator for effective evaluation of aging status and electric withstanding strength of insulating materials. View full abstract»

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  • On-load tap changer diagnosis with dynamic resistance measurements

    Publication Year: 2012 , Page(s): 485 - 488
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (342 KB) |  | HTML iconHTML  

    A modern tendency is to perform condition-based rather than time-based maintenance on power transformers. This requires the use of diagnostic measurements to know the condition of the tap changer and to determine when and what kind of maintenance is necessary. In addition, diagnostic measurements on OLTCs can be used for the pre-failure detection of defects not seen during maintenance and to assess the condition of parts that are not easily accessible. A number of diagnostic tests can be performed and utilities combine different tests to determine its need for maintenance. Several utilities apply dynamic resistance measurement (DRM) to OLTCs during regular maintenance. Results showed that DRM is sensitive to major degradation mechanisms in on-load tap changers. View full abstract»

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  • Characteristics of partial discharge by AC and DC

    Publication Year: 2012 , Page(s): 489 - 492
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (523 KB) |  | HTML iconHTML  

    Partial discharge(PD) characteristics by AC and DC voltage were studied using the laboratory models. PPLP butt gap in oil, void in solid insulation, surface discharge in solid/air interface, and corona were adopted as the artificial PD models. Using these models, PD pulse wave shapes and the time sequential characteristics were investigated according to the AC and DC voltage application. View full abstract»

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  • Monitoring of SF6 gas admixtures in gas-insulated electrical equipment

    Publication Year: 2012 , Page(s): 493 - 496
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (533 KB) |  | HTML iconHTML  

    Mixtures of SF6 and N2 are used in gas-insulated lines to reduce the amount of SF6 in use and thus minimize environmental impact. Outdoor-installed electrical equipment operating in low-temperature regions currently also entails the use of mixtures of SF6 gas with N2 or CF4. The dielectric strength of SF6 mixtures depends on the density and the mixing ratio which can change as a result of leakage events, condensation, adsorption or decomposition. A general leak can be detected when the total density drops, but no information on the mixing ratio can be obtained. We have designed and experimentally verified a straightforward and easily implementable solution to this problem. Measurement of pressure, temperature and density allows the calculation of the partial pressures and hence of the mixing ratio of a two-component gas. The determined ratio can be processed analogously to today's density tracking, enabling early detection of faults in which one gas is lost preferentially. We report on the performance of such a sensor system in the laboratory. View full abstract»

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  • Investigating partial discharge UHF electromagnetic waves propagation in transformers using FDTD technique and 3D simulation

    Publication Year: 2012 , Page(s): 497 - 500
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (364 KB)  

    On-line partial discharge (PD) measurement in power transformers has become increasingly popular in recent years. Measuring PD signals at ultra high frequency (UHF) range have many advantages. So, numerical methods have been implemented to model the propagation of electromagnetic (EM) wave in power transformers. Utilizing conventional softwares, such as CST to simulate EM wave propagation in power transformers need tremendous amount of time and memory. So such packages are difficult to be used in these fields of study. In this paper we will verify the program written in C++ environment to simulate UHF wave propagation using the results obtained from CST package in small scale. Using the proposed FDTD code, it is possible to simulate EM wave propagation inside large power transformer. This task cannot be accomplished by CST software in a simple PC. To ensure the validity of the proposed codes, results of simulating EM wave propagation in small volumes such as distribution transformer is compared with CST software package results. After validation, these codes are used to model larger transformers. Finally, the characteristics of PD source are investigated using simulated PD signals detected at different sensor locations. View full abstract»

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  • Dielectric properties measurements of oil immersed pressboard

    Publication Year: 2012 , Page(s): 60 - 63
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (611 KB) |  | HTML iconHTML  

    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 electrode's 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 immers- d pressboard in compliment with IEC 60093 and IEC 60250. View full abstract»

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  • Adapting frequency domain spectroscopy as an online monitoring tool for the insulation of power transformers

    Publication Year: 2012 , Page(s): 501 - 504
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (442 KB) |  | HTML iconHTML  

    This paper investigates the possibilities and limitations of the FDS method as an on-line monitoring method for the oil-impregnated-paper insulation of power transformers. Bushing taps and the earthed tank are used as feed-in and measuring points for the perturbing voltage signal and its corresponding current response respectively. All possible capacitances of a transformer (HV-LV, HV-Tank, LV-Tank, Bushings) are considered in this investigation. Special guarding configurations which are important for the FDS method especially under simulated on-line conditions were also investigated. The proposed method was first simulated using equivalent circuit models and then measurements were performed on a transformer under online conditions. The results were then compared with conventional off-line FDS measurements which showed good agreement with each other, hence verifying the feasibility of this method. Our initial investigations show that the proposed FDS method could be adapted as an on-line measuring tool to continuously monitor the insulation of a power transformer. View full abstract»

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  • Integrated assessment model of GIS operating under tropical conditions

    Publication Year: 2012 , Page(s): 505 - 508
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (316 KB) |  | HTML iconHTML  

    For the past two decades, electricity utilities have struggled to provide high quality electrical power to their customers while keeping on spending effectively the expenses for operating and maintaining the power system. Unfortunately, under tropical conditions, operation circumstances affect the equipment so that either its lifetime is cut shorter or its failure rate is higher. One of the affected equipment is GIS installations. This paper focuses on the assessment model of a GIS operating under tropical conditions which consists of condition, lifetime and risk assessment. The condition assessment model is used to assess the health index of a GIS while the lifetime assessment measures the GIS degradation level. The risk assessment model is used to prioritize work delivery. The model is developed based on the understanding of how the tropical circumstances influence GIS long term performance. In this paper, the elaboration of the long-term performance focuses on the insulating system because this causes a major share of fatal failures. This knowledge is hence applied to develop a maintenance methodology for these circumstances to enable better tropical GIS performance. View full abstract»

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