Development of a moisture-in-solid-insulation sensor for power transformers

Moisture is an important variable that must be kept under control to guarantee a safe operation of power transformers. Because of the hydrophilic character of cellulose, water mainly remains in the solid insulation, while just a few parts per million are dissolved in oil. The distribution of moisture between paper and oil is not static, but varies depending on the insulation temperature, and thus, water migration processes take place continuously during transformers operation. In this work, a sensor is presented that allows the determination of the moisture content of the transformer solid insulation in the steady state and during the moisture migration processes. The main objective of the design is that the electrodes of the sensor should not obstruct the movement of water from the solid insulation to the oil, so the proposed prototype uses a metallic-mesh electrode to do the measurements. The measurement setup is based on the characterization of the insulation dielectric response by means of the frequency dielectric spectroscopy (FDS) method. The sensitivity of the proposed sensor has been tested on samples with a moisture content within 1% to 5%, demonstrating the good sensitivity and repeatability of the measurements.This work has been supported by the Spanish Government under Contract DPI2012-35819

UHF diagnostic monitoring techniques for power transformers

This paper initially gives an introduction to ultra-high frequency (UHF) partial discharge monitoring techniques and their application to gas insulated substations. Recent advances in the technique, covering its application to power transformers, are then discussed and illustrated by means of four site trials. Mounting and installation of the UHF sensors is described and measurements of electrical discharges inside transformers are presented in a range of formats, demonstrating the potential of the UHF method. A procedure for locating sources of electrical discharge is described and demonstrated by means of a practical example where a source of sparking on a tap changer lead was located to within 15 cm. Progress with the development of a prototype on-line monitoring and diagnostic system is reviewed and possible approaches to its utilization are discussed. New concepts for enhancing the capabilities of the UHF technique are presented, including the possibility of monitoring the internal mechanical integrity of plant. The research presented provides sufficient evidence to justify the installation of robust UHF sensors on transformer tanks to facilitate their monitoring if and when required during the service lifetime

Pendekatan psikologi dakwah menangani histeria remaja muslim di Selangor

Gejala histeria dalam kalangan remaja di Malaysia merupakan epidemik sosial yang telah lama berlaku dalam masyarakat. Kejadian tersebut mengganggu proses pengajaran dan pembelajaran, psikologi, jasmani dan spiritual remaja. Pelbagai pendekatan pencegahan dilakukan oleh remaja dan pihak sekolah dalam menangani gejala yang berlaku, namun tidak menunjukkan pengurangannya. Oleh itu kajian ini bertujuan mengenal pasti konsep histeria, menganalisis faktor dan simptom histeria remaja, mengenal pasti pendekatan psikologi dakwah untuk menangani histeria, mengkaji kaedah pencegahan yang dilakukan remaja terhadap gejala histeria serta menganalisis hubungan antara faktor, simptom dan langkah pencegahan. Reka bentuk kajian adalah kajian tinjauan dengan menggunakan instrumen soal selidik dan temu bual. Seramai 122 orang responden yang mengalami histeria dari 10 buah sekolah di Selangor dipilih secara persampelan kelompok dan seramai 9 orang pelajar yang mengalami histeria ditemu bual. Temu bual turut dijalankan terhadap kaunselor, pakar psikiatri dan perawat perubatan Islam bagi menyokong dapatan kajian. Hasil kajian mendapati terdapat lima faktor histeria dalam kalangan remaja Muslim iaitu faktor psikologi, tekanan keluarga dan persekitaran, kepercayaan dan kebudayaan dan amalan keagamaan. Manakala dari aspek simptom, terdapat tiga bentuk simptom iaitu simptom gangguan emosi, psikiatri dan gangguan makhluk halus. Dari sudut pencegahan, remaja yang mengalami histeria kerap menggunakan pencegahan secara tazkiyah al-nafs, perawatan Islam dan psikiatri. Hasil analisis hubungan antara faktor dan simptom histeria mendapati faktor yang berhubung secara signifikan dengan ketiga-tiga simptom histeria adalah faktor psikologi, tekanan persekitaran dan kepercayaan dan kebudayaan. Manakala dari aspek pencegahan terdapat hubungan yang signifikan antara pencegahan tazkiyah al-nafs dan perawatan Islam dengan simptom gangguan emosi. Implikasi kajian dapat membantu pelbagai pihak dalam menangani punca dan simptom histeria remaja dengan menggunakan pendekatan psikologi 3 dakwah

Optical sensor for determining the degree of polymerization of the insulation paper inside transformers

Effective lifetime and maintenance management of a transformer fleet requires precise monitoring of the electrical insulation conditions of each transformer. Currently, the condition assessment of the insulating paper of transformers in operation is done indirectly, by oil samples and evaluation of aging markers in the liquid with only limited accuracy. In fact, sampling of the paper for direct analysis of insulation paper quality is only possible when the transformer is under maintenance or decommissioned. In this paper, the methodology and product development of a novel patented optical sensor is presented, which provides a possibility to determine the degree of polymerization (DP) of insulating paper online and in real-time with high precision via optical spectroscopy inside operating transformers. The measurement is carried out non-destructively and within seconds by a specific evaluation of the reflection spectrum of the insulating paper inside the oil or ester filled environment. The investigation has shown that measurement under strongly aged insulating oil is possible, and the medium surrounding the paper has no influence on the determination of the DP-value. Product development involves materials and technologies to ensure long-time accuracy under mechanical, vibrational, chemical, thermal, and electromagnetic challenges of the transformer environment. This novel, innovative sensor is designed to enable online monitoring of the quality of insulating paper in the transformer at various points, like the hotspot, in order to improve operational safety and economical operation. The optical measuring method provides very high reliability and high accuracy. Deviation analysis shows higher accuracy for lower DP-values, which supports the determination of the end-of-life DP-values

Condition monitoring of power transformer as part of power plant maintenance process

Power transformer is one of the most critical components for electrical network in power plants. This means that dependability has a big role. At the moment end users allocate resources to power transformer maintenance. Resources for on-line condition monitoring on the other hand are not very significant. Reason for this is that transformers are reliable and long life components. However, failure costs might be very significant and online monitoring is justified from that point of view. This thesis focuses on power transformer online condition monitoring. The goal is to find cost-effective and integrated solution which provides good-enough transformer monitoring. The subject has been studied quite a lot which tells about increasing interest towards the subject and might indicate possible markets for transformer monitoring services. In the beginning research will focus on describing maintenance and condition monitoring related terms. Also goals are defined for different stakeholders applying the Delphi method. The middle part of the work focus on power transformer structure, fault statistics, condition monitoring methods and measurement devices. Also possibilities of condition monitoring are covered. Research results are divided into two different categories. First part of the results will be related to requirements defined for power transformer condition monitoring. Results include requirements for three different ranges of transformer monitoring. Second part of the results contains a specification for pilot project to test power transformer condition monitoring methods and devices.fi=Opinnäytetyö kokotekstinä PDF-muodossa.|en=Thesis fulltext in PDF format.|sv=Lärdomsprov tillgängligt som fulltext i PDF-format

Recent Trends in Power Transformer Fault Diagnosis and Condition Assessment

Power transformers are interface between different voltage levels of essential importance. Because of the long manufacturing processes, transformers are one of the most critical and expensive equipment and so this is one of the reasons why condition monitoring becomes more popular. Monitoring systems as basis for diagnostics open the possibility for expanding the operating time, reducing the risk of expensive failures and allows several maintenance strategies. With different monitoring techniques, detailed informations about the transformer condition can be received and helps to minimize the probability of an unexpected outage. In this paper a methodology has been developed to use information derived from condition monitoring and diagnostics for rehabilitation purposes of transformers. The interpretation and understanding of the test data are obtained from the International Standards

Utilisation of transformer condition monitoring data

Electricity grids are getting older and demand of electricity is rising. The critical com-ponents in electricity transmission systems should be monitored for assessing the need for maintenance. The electricity grid works more reliable when the condition infor-mation of important components are available continuously and thus larger catastrophic failures are preventable. Transformers are one of the critical components in electricity transmission. It is im-portant that they operate continuously. Transformers are reliable and long life compo-nents but the older the transformer is, the more sensitive it is about to fail. Condition monitoring provides improved data on the condition of transformer. With on-line condi-tion monitoring it is possible to detect developing failures and then a corrective action can be made in time. This study focuses on the utilization of transformer condition monitoring system in tra-ditional grid and in upcoming smart grid. The aim is to find out, where the condition monitoring data is needed in electricity transmission and distribution system manage-ment and how it is possible to carry the information to right place. This thesis introduces first the basics of a power system, the construction of a trans-former, transformer condition monitoring methods and condition monitoring data pro-cess. After that the management of a power system within traditional and smart grid is analyzed. The asset management process of both type power systems is explored through case study of transformer failure situations. In traditional power system the transformer maintenance bases mostly on time scheduled inspections. In smart grid the management is all time aware on the condition information of transformers which al-lows using of better fault prevention strategies.fi=Opinnäytetyö kokotekstinä PDF-muodossa.|en=Thesis fulltext in PDF format.|sv=Lärdomsprov tillgängligt som fulltext i PDF-format

Dissolved gas analysis equipment for online monitoring of transformer oil: A review

Power transformers are the most important assets of electric power substations. The reliability in the operation of electric power transmission and distribution is due to the correct operation and maintenance of power transformers. The parameters that are most used to assess the health status of power transformers are dissolved gas analysis (DGA), oil quality analysis (OQA) and content of furfuraldehydes (FFA) in oil. The parameter that currently allows for simple online monitoring in an energized transformer is the DGA. Although most of the DGA continues to be done in the laboratory, the trend is online DGA monitoring, since it allows for detection or diagnosis of the faults throughout the life of the power transformers. This study presents a review of the main DGA monitors, single- or multi-gas, their most important specifications, accuracy, repeatability and measurement range, the types of installation, valve or closed loop, and number of analogue inputs and outputs. This review shows the differences between the main existing DGA monitors and aims to help in the selection of the most suitable DGA monitoring approach according to the needs of each case.This research was funded by the EU Regional Development Fund (FEDER) and the Spanish Government under RETOS-COLABORACIÓN RTC-2017-6782-3 and by the University of Cantabria Industrial Doctorate 19.DI12.649