Measurement and modeling of dielectric response of composite oil/paper insulation

Frimpong, G.; Gäfvert, U.; Fuhr, J.

doi:10.1109/icpadm.1997.617534

Cited by 43 publications

(34 citation statements)

References 2 publications

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“…Over the last few years, several researchers [1][2][3][4][9][10][11][12][13][14] have proposed a number of equivalent circuits for modelling the transformer oil/paper insulation system for better understanding of the dielectric response. In essence, all the models proposed so far have been derived from an extended Debye approach based on a linear RC-model.…”

Section: Frequency Domain Polarization Measurementsmentioning

confidence: 99%

Correlation between time and frequency domain polarisation measurements for transformer moisture assessment

Saha¹,

Middleton²,

Thomas³

2005

Australian Journal of Electrical and Electronics Engineering

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Preventative diagnosis and maintenance of transformers has become more popular in recent times in order to improve the reliability of electric power systems. A number of transformers have recently been tested using Return Voltage (RV) and Dielectric Dissipation Factor (tanδ) measurements in the time and frequency domain, respectively. This paper outlines a circuit model which describes the dielectric behaviour of the transformer insulation system and has been parameterised from the frequency domain data. This model was then used to simulate RV and Polarisation-Depolarisation current (PDC) results. Some recommendations about the diagnosis of the transformers have been proposed.

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Section: Frequency Domain Polarization Measurementsmentioning

confidence: 99%

Correlation between time and frequency domain polarisation measurements for transformer moisture assessment

Saha¹,

Middleton²,

Thomas³

2005

Australian Journal of Electrical and Electronics Engineering

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“…This method based on polarization and depolarization currents, generally named PDC method, has been used by several authors [9,11,[18][19][20][21]. One of these new methods is based on a recovery voltage phenomenon occurring after voltage application followed by a short circuit.…”

Section: Introductionmentioning

confidence: 99%

“…Therefore, the decision to continue or to stop the transformer exploitation is closely dependent on a perfect knowledge of the moisture levels [7][8][9][10][11][12][13]. Because of the effect of moisture on the insulation's global behavior several researchers undertook studies on the subject.…”

Section: Introductionmentioning

confidence: 99%

A Recovery Voltage as non-Destructive Tool for Moisture Appreciation of Oil Impregnated Pressboard: An Approach for Power Transformers Testing

Bitam-Megherbi¹,

Megherbi²,

Mammeri³

2013

ijeei

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This paper is devoted to recovery voltage as a diagnostic non destructive method for an assessment of an insulating state of power transformers. The insulating pressboard used in power transformers is tested for different moisture levels. Experiments were carried out with samples from the same material intended to power transformers building. A charge and discharge of a capacitor having pressboard paper as dielectric is a suitable tool for an appreciation of the polarization and relaxation processes. The polar character of the water's molecules has an influence on the permittivity. Then the polarization of the paper will be affected by a moisture presence. Time evolution of the recovery voltage for different durations of the charges was examined. An increase of the recovery voltage with the moisture content was observed. The maximum of recovery voltage occurs much later starting from the moment of the opening of the circuit for higher moisture for all examined levels. Thus, the time separating the short circuit and the maximum's occurring can be considered like an important parameter allowing an appreciation of the moisture state of oil impregnated paper.

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“…The Polarisation and Depolarisation Current (PDC) analysis is a non-destructive dielectric testing method for determining the conductivity and moisture content of insulation materials in a transformer [2][3][4][5]. PDC can provide information about the Response Function of the dielectric and the conductivities of oil and paper.…”

Section: Introductionmentioning

confidence: 99%

“…[11]. It is thus evident that unless the temperature is stable and the oil-paper has attained equilibrium, any dielectric test done in-between will not reflect the true condition of the insulation.It has been reported by [2][3][4][5][6][7][8] and several other researchers that the relaxation currents are very sensitive to the temperature. This phenomenon has been attributed to the increased mobility of the charge carriers during the polarisation/depolarisation process at elevated temperatures.…”

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confidence: 99%

Some precautions for the field users of PDC measurement for transformer insulation condition assessment

Saha

Purkait

2003 IEEE Power Engineering Society General Meeting (IEEE Cat. No.03CH37491)

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Abstract--The need for economic, reliable and effective delivery of electric power has lead to the search for new, efficient and effective methods for diagnosing the insulation of the HV equipments in the industries all over the world. One of the methods currently being investigated as a potential nondestructive diagnostic tool for condition monitoring of the oilpaper insulation of power transformers is the Polarisation and Depolarisation Current (PDC) measurement. This paper starts with a theoretical and physical description of the PDC technique. Several practical aspects of the technique have been discussed in the paper along with corresponding experimental and field test results. These physical considerations can be used as 'precautions' for the potential field users of the PDC technique for insulation condition assessment of transformers. Index Terms-Condition I. INTRODUCTIONOISTURE and ageing strongly influence the dielectric properties of oil/paper insulation system of power transformer. To assess the reliability of insulation it is necessary to know the condition of the oil and the paper separately.In recent years, new methods to assess insulation systems have been promoted in addition to the classical insulation resistance and power frequency loss factor measurements. Dielectric diagnostic measurements based on polarisation and depolarisation current measurements and return voltage measurements have gained significant importance over the last several years [1].The Polarisation and Depolarisation Current (PDC) analysis is a non-destructive dielectric testing method for determining the conductivity and moisture content of insulation materials in a transformer [2][3][4][5]. PDC can provide information about the Response Function of the dielectric and the conductivities of oil and paper. On the basis of this analysis it is possible to take further actions like oilrefurbishment or drying or replacement of the transformer. This paper presents a description of the PDC technique with the physical and mathematical explanations. The different physical parameters and practical considerations of the technique are discussed along with supporting experimental and field test results on transformers. These parameters have been identified by the authors from their experience with the actual on-site measurements over the years. It is recommended that the field-users of the PDC technique should carefully address these issues while conducting the test and also during analysis of the results. II. PDC MEASUREMENT A. Theoretical BackgroundWhen a step voltage of magnitude U 0 is applied to an initially discharged dielectric, the polarisation current flowing through it is given by (1). The process is summarised in Fig.1. (1)Where σ is the DC conductivity, ε 0 is the permittivity of vacuum, f(t) is the response function and C 0 is the geometric capacitance (measured capacitance divided by relative permittivity) of the dielectric material.Once the step voltage is replaced by a short circuit, a depolarisation current is built up. ...

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Measurement and modeling of dielectric response of composite oil/paper insulation

Cited by 43 publications

References 2 publications

Correlation between time and frequency domain polarisation measurements for transformer moisture assessment

Correlation between time and frequency domain polarisation measurements for transformer moisture assessment

A Recovery Voltage as non-Destructive Tool for Moisture Appreciation of Oil Impregnated Pressboard: An Approach for Power Transformers Testing

Some precautions for the field users of PDC measurement for transformer insulation condition assessment

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