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Electrical Insulation Magazine, IEEE

Issue 4 • Date July-August 2012

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  • Table of contents

    Publication Year: 2012 , Page(s): 1 - 2
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  • IEEE Electrical Insulation Magazine

    Publication Year: 2012 , Page(s): 3
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  • Editorial

    Publication Year: 2012 , Page(s): 4 - 5
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  • From the editors' desk

    Publication Year: 2012 , Page(s): 6 - 7
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  • A review of electrical winding failures in wind turbine generators

    Publication Year: 2012 , Page(s): 8 - 13
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1854 KB) |  | HTML iconHTML  

    Since its commercial beginnings in the early 1990s, wind energy has grown to be a significant factor in the electrical generation industry, representing 9.6% of the installed capacity in Europe [1] and nearing 3.5% in North America [2]. Almost 25% of the US-based turbines are in Texas, supplying 8% of that state's annual energy requirements and peaking at almost 25% of grid demand on occasion [3]. As with any new industry, there are learning curves in nearly all aspects, but the industry is maturing and coming to terms with some of the technical shortcomings of the early generations of turbines. Although most drive train issues are related to gearbox component failures, failure of and damage to the generators are the second most common cause of lost production. As reported by George Gao and William Chen at the Electrical Insulation Conference in 2009 [4], several common failure modes have been identified, many of which can be traced to identifiable root causes. However, many failures remain difficult to trace because minor failures can lead to catastrophic electrical failures not directly related to the root cause [5]. Understanding the types of failures and how often they might occur in a fleet of turbines is instrumental to developing a proper maintenance procedure and testing regimen. By reviewing the failures of more than 1200 generators, we have been able to isolate the failures of electrical materials from the pure mechanical failures. Here, we address their occurrences and present some general suggestions for both the generator design engineers and the operating companies responsible for maintaining the wind turbine performance. View full abstract»

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  • A step forward in the characterization of the partial discharge phenomenon and the degradation of insulating materials through nonlinear analysis of time series

    Publication Year: 2012 , Page(s): 14 - 21
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    The partial discharge (PD) phenomenon is an electrical discharge that affects only part of a dielectric connecting two conductors [1]. This process may occur in the vacuoles of solid insulation, in gas bubbles in insulating liquids, or between dielectric layers. PDs can also occur on spikes or sharp edges of metal surfaces. Generally, the PDs affect the insulator integrity only if it persists for a long time. However, the continuous release of small amounts of energy may cause a slow and progressive deterioration of the dielectric that can lead to its final breakdown [2], [3]. The degradation rate depends more or less on the microscopic structure of the dielectric, the production process, the types of electrical stresses, and other operating conditions [4]. At the beginning of the 20th century, the problem was not even recognized. However, after the middle of the century, along with the introduction of new dielectrics, the development of more compact insulators, and a general increase in the operating voltages, diagnostics of PDs have become a primary issue in electrical engineering [5]. Today, measuring PDs is a common practice even in operational medium- and high-voltage devices. The data gathered are useful to determine the weak points of the components before irreversible damage occurs. Thus, PD detection and recognition have become important tools for the evaluation of insulating degradation in large power devices. The phase φ, the apparent charge q, and the occurrence n have generally been accepted as the basic parameters for the pattern recognition of PDs by means of the standardized algorithm termed phase-resolved PD analysis (PRPDA) [6]. View full abstract»

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  • The use of MIL-PRF-87257 hydraulic fluid as a switching medium for a high-power microwave switch

    Publication Year: 2012 , Page(s): 22 - 28
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    The article investigates the use of synthetic polyalphaolefin-based MIL-PRF-87257 hydraulic fluid as a switching dielectric medium in gigawatt-class repetitive pulsed power applications. View full abstract»

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  • Measurement of leakage current for monitoring the performance of outdoor insulators in polluted environments

    Publication Year: 2012 , Page(s): 29 - 34
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1007 KB) |  | HTML iconHTML  

    Monitoring of leakage currents on various types of insulators, in the field and in laboratory tests, has provided a much broader perspective on the performance of outdoor insulators in various pollution zones. The technique can be effective for corrective maintenance of transmission lines, provided the type of pollutant and the critical leakage currents are analyzed periodically. A leakage current that is continuous, periodic, or increasing with time is one consideration in the performance of insulators in pollution zones, whereas the maximum permissible levels of leakage current at flashover, which is considerably different for each insulator profile, is another consideration. What this means is that insulators showing lower leakage currents will not necessarily have the best operating performance. The insulator profile affects the accumulation of pollutants, which defines their pollution performance, and control of the leakage current by the insulator design depends largely on the type of pollutant. As a result, there is no unique solution, and leakage current values with flashover risk from laboratory tests for various types of insulators must be determined by using the type of pollutant in the field. This combination of strategies will provide an effective means of ensuring reliable transmission line operation in pollution zones. View full abstract»

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  • Comparison between conventional and nanofilled enamels under different environmental conditions

    Publication Year: 2012 , Page(s): 35 - 41
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (921 KB) |  | HTML iconHTML  

    The article describes a study aimed at understanding the behaviour of both conventional and nanocomposite organic enamels in the presence of partial discharge as influenced by relative humidity. View full abstract»

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  • In memoriam [Dr. George Sidney Eager]

    Publication Year: 2012 , Page(s): 42
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  • Obituary [Professor John Tanaka]

    Publication Year: 2012 , Page(s): 43 - 44
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  • D&EI folks

    Publication Year: 2012 , Page(s): 45
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  • Call for proposals

    Publication Year: 2012 , Page(s): 46
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  • News from Japan

    Publication Year: 2012 , Page(s): 47 - 49
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  • Book reviews [7 books reviewed]

    Publication Year: 2012 , Page(s): 50 - 54
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  • IEEE media advertising sales offices

    Publication Year: 2012 , Page(s): 55
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  • Meetings calendar

    Publication Year: 2012 , Page(s): 56
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  • IEEE Electrical Insulation Magazine - Front cover

    Publication Year: 2012 , Page(s): c1
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  • Author's guide

    Publication Year: 2012 , Page(s): c3
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  • IEEE Global History Network [advertisement]

    Publication Year: 2012 , Page(s): c4
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Aims & Scope

The EI Magazine is specifically concerned with publishing articles in the development and characterization of the dielectric, chemical, mechanical, and environmental properties of all vacuum, gaseous, liquid, and solid electrical insulation, and with utilization of these materials in circuits and systems under conditions of use.

Full Aims & Scope

Meet Our Editors

Co-Editor-in-Chief
Edward Cherney

Co-Editor-in-Chief
Robert Fleming