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The Megger technical library provides access to a range of additional content and resources such as technical guides, application notes and more. Use the filters to browse specific content (e.g. application notes) or refine your search to a particular electrical application area. 

 

If you would like to see the content we have available on a particular subject or need to locate some software, simply enter a search below. Please note, you will need to create an account to access some resources.

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    Showing item(s) 1 - 10 of 38 in total
Transformer Turns Ratio Test: Some Unknown Facts
Megger’s article “Transformer Turn Ratio Test: Some Unknown Facts” was presented at the 2020 NETA PowerTest Conference in Chicago, Il.  This article takes an in-depth look at the transformer turns ratio test, some of the challenges associated with interpreting test results, and unknown facts related to test variables.  Article Brief:Transformer Turns Ratio (TTR) is one of the most common test used to assess the condition of the transformer’s windings and core.  It is performed as a part of acceptance and maintenance test procedure to determine any problems due to poor design, assembly, handling, overloading, fault conditions or poor maintenance. TTR results are compared against the nameplate ratings to determine any possible insulation deterioration, shorted turns, core heating or any other winding or core abnormalities. TTR is a simple and easy test to perform that is often taken for granted without fully understanding the principle and basis of the test. In cases when measurements are not within expected limits, it becomes a challenging task to determine the root cause and resolve the problem. This paper will focus on some of the unknown facts associated with the TTR test. The paper covers in detail the effect of applied test voltage, comparative analysis of step up vs step down excitation, different vector configurations, differences between nameplate ratio, voltage ratio and turns ratio, sources of ratio and phase angle errors, comparison of per phase testing vs true three phase testing, extreme tap ratios being out of tolerance for On Load Tap Changers (OLTC), and TTR test correlation with other electrical tests. The paper also provides field test results and case examples to explain the above-mentioned unknown facts. Click below to download the full article.
Published: 28 April 2020
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HV and EHV OIP Bushing Condition Assessment based on Advanced Non-intrusive Diagnostic Techniques
This article describes the application of DFR and HV DFR as a preventive method to evaluate the condition and prioritize maintenance activities on HV and EHV bushings and relates some case studies. 
Published: 12 November 2019
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IEEE guide for dielectric frequency response test advancements in industry
The  Institute  of  Electrical  and  Electronic  Engineers  (IEEE)  Standards  Association recently approved the publication of IEEE Std. C57.161–2018, Guide for Dielectric Frequency Response Test. The work was developed within the IEEE Transformers Committee and the Dielectrics Subcommittee. The industry needed a document to better understand the field application of a non-intrusive and non-destructive method to assess the condition of oil-paper insulation in power and distribution transformers.
Published: 1 October 2019
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Expanding the Diagnostic Impact of Power Factor Testing - Interpretation of Narrow Band Dielectric Frequency Response
The Narrow Band Dielectric Frequen-cy Response (NBDFR) test method consists of a series of power factor measurements ranging from 1 to 1000 hertz. This aggregate of the CHL (pri-mary to secondary) measurements constitutes the dielectric response of the test specimen. The subsequent evaluation consists of a geometric analysis of a plot where the mea-sured power factors and correspond-ing frequencies are graphed. As an insulation system ages, the response migrates towards the high frequency end of the plot. When the frequency corresponding to the lowest magni-tude within the response (the trough) is used as a reference point, the move-ment of the response may be quanti-fied; enabling the transformer may be classified in terms of condition.
Published: 15 August 2019
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Power swing detection/trip testing in IEDs using smart testing methodology
Power swing which is principally caused by an oscillation in active and reactive power of transmission line, consequent to an enormous disruption in power system, which if not blocked, could cause wrong operation to the distance relay which may lead to tripping the healthy part of the transmission line. In the absence of power swing function it may result in severe damage to the machines or cascading tripping in the grid resulting in blackouts. To prevent such scenarios, intelligent electronic devices (IEDs) have power swing block (PSB) detection and trip logics incorporated with distance schemes. 
Published: 12 July 2019
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End to End testing of Transformer protection IEDs using Smart Testing Philosophy
Transformers are critical assets of power system network and their adequate protection is a matter of vital importance. Modern protection relays are usually defined as intelligent electronic device (IED) s, and they provide huge flexibility and enhanced protection features to assure correct operation of the equipment. Transformer protection IEDs are equipped with key features such as differential and restricted earth fault (REF) protection along with several other functionalities as per the guidelines of IEEE C37.91.
Published: 12 July 2019
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Protection of complicated bus arrangements using centralized low impedance intelligent electronic device
In this paper, protection of a complicated bus arrangement with dual bus coupler and bus sectionalizer using low impedance differential protection applicable for very high voltages like 220kV and 400kV is discussed. In many power generation stations, several operational procedures are implemented to utilize the transfer bus as main bus and to facilitate maintenance of circuit breakers and current transformers (in each section) without shutting down the bay(s). Owing to this fact, the complications in operational philosophy have thrown challenges for the bus bar protection implementation.
Published: 12 July 2019
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Transformer Life Enhancement Using Dynamic Switching Of 2nd Harmonic Feature in IEDs
Energization of a transformer results in sudden flow of current which is an effect of core magnetization. This current will be dominated by the presence of 2nd harmonic, which in turn is used to segregate fault and inrush current, thus guaranteeing proper operation of the relay. This additional security in the relay sometimes obstructs or delays differential protection in a specific scenario, when the 2nd harmonic content was present during a genuine fault. This kind of scenario can result in isolation of the transformer by Buchholz and pressure release valve (PRV) protection, which is acted when fault creates more damage in transformer. 
Published: 12 July 2019
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Standardization of Transformer Protection testing using Smart Testing Equipment
Transformers are critical assets of power system network and their adequate protection is a matter of vital importance. Modern protection relays are usually defined as intelligent electronic device (IED) s, and they provide huge flexibility and enhanced protection features to assure correct operation of the equipment. Transformer protection IEDs are equipped with key features such as differential and restricted earth fault (REF) protection along with several other functionalities as per the guidelines of IEEE C37.91. These functions are available with enhanced facilities such that it can incorporate the difference in phase angle based on vector rotation, ratio correction of current transformers used, interposing CT corrections etc… The increase in flexibility of the IED has also increased the complexity of programming it where a trivial error in the configuration will result in unwarranted operation causing loss of power and reduction of equipment life. 
Published: 12 July 2019
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Testing of complicated bus bar protection using smart testing methodologies
In this paper, protection of a complicated bus arrangement with dual bus coupler and bus sectionalizer using low impedance differential protection applicable for very high voltages like 220kV and 400kV is discussed. In many power generation stations, several operational procedures are implemented to utilize the transfer bus as main bus and to facilitate maintenance of circuit breakers and current transformers (in each section) without shutting down the bay(s).
Published: 12 July 2019
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  • Showing item(s) 1 - 10 of 38 in total