Diagnostic testing and condition monitoring of transformer bushings

Venkatesh, R.; Kannan, Sivasundari

doi:10.1109/ceidp.2002.1048936

Cited by 5 publications

(3 citation statements)

References 4 publications

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“…Taking into account (1), (2), (3) and (4), the variation of capacitance C tap can be written as: (7) Since we are interested in measuring just the variation of C tap due to those of C 1 and C 2 , the following condition shall be verified: (8) In other terms: (9) with an arbitrary constant k much greater than 1.…”

Section: Methods Feasibility and Accuracymentioning

confidence: 99%

“…When considering the AC mains frequency, typical values of the bushing parameters are some hundreds of picofarads for the capacitances and few gigaohms for the resistances. At higher frequencies it can be shown that the capacitance values are basically the same, while the resistance values change considerably [9], [10] and [11]. In particular at 1 MHz the resistances are some tens of kiloohms.…”

Section: A Bushingmentioning

confidence: 95%

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On-line analysis of power transformer bushings

Faifer

Ottoboni

Cristaldi

et al. 2011

2011 IEEE International Instrumentation and Measurement Technology Conference

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The approach to the maintenance of devices and systems has strongly changed in the last years, thanks to the availability of more and more sophisticated technologies. In particular, when the servicing involves very critical processes, a new interesting strategy is represented by the Condition Based Maintenance (CBM). It is based on the continuous observation of some physical parameters which permits to infer the status of the system and thus to detect the need to service it. In this paper a novel monitoring method is proposed. It allows the application of CBM techniques to one of the least reliable components in HV and MV systems: the transformer bushing. Starting from some theoretical and practical considerations, it will be shown that it is possible to measure the capacitance and the power factor of transformer bushing, without putting the plant out of order. It is known that these two parameters are particularly useful to schedule the maintenance activity. This goal can be achieved by superimposing a high frequency sinusoidal voltage between the bushing tap and the ground. Some considerations prove that having chosen a proper frequency, the consequent current is much more sensitive to the bushing capacitance than to the other impedances. Finally the architecture of a measurement system is also presented

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Section: Methods Feasibility and Accuracymentioning

confidence: 99%

Section: A Bushingmentioning

confidence: 95%

On-line analysis of power transformer bushings

Faifer

Ottoboni

Cristaldi

et al. 2011

2011 IEEE International Instrumentation and Measurement Technology Conference

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“…On the other hand, a modification has been made in the elementary circuit of the dielectric material by adding an equivalent series resistance (ESR) [37], [38]. This series resistive element represents the energy losses through the heating generated by current.…”

Section: Model Improvement Elementsmentioning

confidence: 99%

High Frequency Model of Power Transformer Bushing for Very Fast Transient Studies

Messadi,

Zouaghi,

Ferdjallah-Kherkhachi

et al. 2023

IEEE Access

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Fast and very fast transient overvoltages generally appear during switching operations within electrical substations. The oscillatory nature of such phenomena with frequencies that can reach several tens of megahertz tends to degrade the lifetime of high voltage equipment such as bushings and transformers, inducing partial discharges activity or breakdown of the insulation system. According to several case studies, bushings are one of the most sensitive parts to such overvoltages, indeed, a failure in a bushing will in most cases lead to a failure of the transformer, often catastrophically. Generating such overvoltages with a very high frequency character and considerable amplitude can be very difficult, moreover, studying the effect of such overvoltages on the insulated bushings is not easy, even experimentally. Therefore, a simulation of the fast transients in the system can be very useful to understand the consequences of such phenomena. In this context, this document aims to propose a model of high voltage capacitive graded oil impregnated paper (OIP) bushing based on a distributed electrical circuit. The equivalent circuit is constructed based on the geometric design and electrical properties of the materials. The model was developed and implemented using Matlab/Simulink® software, and was validated with experimental measurements based on impedance sweep frequency analysis. The modeling results are in a good agreement with the experimental ones. INDEX TERMSBushing, distributed circuit model, high voltage, high frequency, impedance analysis, numerical modeling, overvoltage, power transformer, very fast transient.

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Monitoring of power transformer bushings in high voltage substations

Cristaldi

Faifer

Laurano

et al. 2015

2015 IEEE International Workshop on Applied Measurements for Power Systems (AMPS)

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Power transformer bushings are among the least reliable components in high voltage systems, therefore the knowledge of their wear condition is very important for a proper network management. The aim of this work is to study the limits of applicability of an on-line monitoring method for transformer bushings previously presented by the authors. The technique allows to continuously estimate the variation of the bushing capacitance and its dissipation factor, without requiring to disconnect the bushing itself from the network. The method is based on a high frequency impedance measurement at the bushing tap. It is clear that its value is not only related to the bushing, but it also depends on the other substation devices. For this reason, it is vital to discriminate the variations of the parameters due to the bushing from those due to the rest of the components. In order to understand these dependencies and to evaluate the applicability of the monitoring method, a high-frequency equivalent model of the substation is required. In this work, a typical substation has been modeled considering a frequency around 1 MHz. Through proper simulations, the applicability of the method has been investigated, in particular the impact of the high voltage transmission lines has been studied

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Diagnostic testing and condition monitoring of transformer bushings

Cited by 5 publications

References 4 publications

On-line analysis of power transformer bushings

On-line analysis of power transformer bushings

High Frequency Model of Power Transformer Bushing for Very Fast Transient Studies

Monitoring of power transformer bushings in high voltage substations

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