M. A. R. M. Fernando

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This paper presents the possibility of using Frequency Domain Dielectric Spectroscopy (FDS) measurement as a condition monitoring tool for Current Transformers (CT). A 132 kV live tank type CT was thermally aged in the laboratory for 840 hours by injecting twice the rated current from the CT's secondary side. The FDS responses were periodically measured and(More)
This paper presents the experimental results of a study, which has been carried out to analyze the insulation characteristics of coconut oil in order to check the suitability as the liquid insulation in power transformers. In this study dielectric response measurements were carried out in frequency domain at temperatures of 25degC, 50degC, 80degC. In(More)
The 400/230 V low voltage systems are usually affected by lightning mainly due to surges coming through the distribution transformers. The lightning surges appear at the transformer primary due to direct strikes or induced voltages in the MV lines and then transfer to the secondary side and to the LV system. This paper presents a broad investigation of the(More)
This paper presents analysis of leakage currents on high voltage insulators in frequency and time-frequency domains. Leakage currents were measured on five silicone rubber insulators under salt fog conditions and recorded over 1000 hours. Different types of leakage current patterns were identified and were grouped according to their levels and the shapes.(More)
This paper presents the condition assessment of generator stator winding due to moisture ingress in their asphalt, polyester and epoxy mica insulations. The work has two parts i.e. laboratory and field investigations. In the laboratory investigations, two naturally wetted asphalt mica and two dry (polyester and epoxy mica one each) spare stator windings(More)
This paper presents variation of dielectric properties of aged and wet asphalt mica winding samples using frequency dielectric spectroscopy measurements. The test procedure consisted of three phases: drying, wetting and electrical ageing. During drying, naturally wet samples were dried inside an oven at 70°C for 168 hrs. During wetting, dried samples(More)
This paper presents laboratory investigation of treated coconut oil as alternative to liquid insulation of power transformers. Thirteen different virgin and treated coconut oil samples consisting three different brands were used for the investigation. Frequency Dielectric Spectroscopy measurements were conducted on the samples at room temperature and at(More)
Transformer oil is one of the essential insulation medium used in power transformers. During transformer operation oil may expose to various stresses such as electrical, thermal, chemical etc. As a result electrical properties of the oil may be degraded and hence leads to transformer failures. This study aims at monitoring condition of field aged oil and(More)
This paper proposes a method of condition assessment of generator stator winding insulation by simultaneously fitting time variation of Insulation Resistance (IR) and DC Ramped voltage plots. The insulation conductivity (σ), permittivity (ε) and response function (f(t)) was used for the assessment. A novel model which derived starting from the(More)
A new configuration to replace the Thyristor Controlled Reactor (TCR) of a Static VAR Compensator (SVC) by a DC link voltage controlled inductor is proposed in this paper. In this proposed technique, the reactor current contribution is regulated by controlling the peak current through the reactor which conducts for a complete cycle. This is in-contrast with(More)