Journal Articles

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Subject: search.filters.subject.Insulation

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    A fast and effective method for assessing insulation condition based on time domain spectroscopy data /
    (IEEE, 2022-01-21) Mishra, D.
    A novel methodology is suggested to predict the condition of Oil-paper Insulation (OPI), popularly used in power transformers. The proposed method is based on transient measurement of polarization current data from laboratory samples. Initially, complete polarization current profile is used to formulate an insulation model and then find the rise time of the system. After that, a relation is provided between rise time and measured performance parameters like moisture content(%pm). Further, another relation is suggested between rise time and the initial decay rate of recorded data. Hence, just by knowing the value of the initial decay rate, the value of crucial parameters like %pm can be evaluated using the proposed relationship.
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    Condition assessment of power transformer insulation using short-duration time-domain dielectric spectroscopy measurement data
    (IEEE, 2019-10-14) Mishra, Deepak; Baral, Arijit; Haque, Nasirul; Chakravorti
    Utilities prefer noninvasive methods for assessing the condition of power transformer insulation. Analysis of polarization-depolarization current (PDC) is one such popular method. One such analysis involves the estimation of trapped charge released from the interfacial region of oil-paper insulation. The literature shows that such charges can be reliably used for the diagnosis of transformer insulation. However, such analysis requires a complete profile of PDC. PDC measurement (an offline technique) takes a large amount of time (several hours) to complete. The magnitude of PDC data for a larger value of time is also sensitive to changes in environmental conditions and field noise as its magnitude is low. Hence, a reliable estimation of detrapped charge may require numerous PDC measurements. This situation is not convenient for utilities as it prolongs shut down time. In this article, a method has been proposed which is capable of estimating detrapping charge using PDC data measured for a short span of time. The proposed method is tested on data collected from several real-life in-service transformers.