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 diel...

The oil/paper insulation system in a transformer degrades under various chemical, thermal and electromechanical stresses during its operation. Dielectric response measurements like the Return Voltage Measurement (RVM) and Polarisation and Depolarisation Current (PDC) measurement are currently being used for condition assessment of the insulation. In the current research project, the ageing cond...

The emission anisotropy (EA) of 4-Dimethyl-amino-4'nitrostilbene (DNS), 4-Amino-4'-nitrostilbene (ANS) and 2,5-Di(4-biphenylyl)oxazole (BBO) was observed to be decreasing with increasing dielectric constant e of the solvent. The effect is interpreted as an influence of the Onsager reaction field on the volume of the solvent shell, which in the excited state is smaller in solvents with larger e....

This paper describes an accelerated ageing experiment of transformer oil/paper insulation with preset moisture levels. These samples were tested with return voltage and polarisation/depolarisation measurements. Molecular weight has also been measured with Gel Permeation Chromatography (GPC). Results suggested the impact of moisture on the ageing of oil/paper insulation. An attempt has been made...

The aim of this study is to propose simple and reliable techniques to assess the condition of metal oxide arrester based on the dielectric response techniques. A number of modern electrical diagnostics for Metal Oxide Surge Arrester (MOSA) are discussed in this paper. The techniques included return voltage, decay voltage and polarisation/depolarisation current measurement. The single and multip...

Dielectric characterisation of polarisable particles, and prediction of the forces and torques exerted upon them, relies on the knowledge of the effective, induced dipole moment. In turn, through the mechanism of depolarisation, the induced dipole moment of a particle is strongly dependent upon its shape. Since realistic shapes create modelling difficulties, the ‘spherical particle’ approximati...