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Polarization and Depolarization Current (PDC) testing is a non-destructive dielectric testing method to determine the conductivity and moisture content of transformer insulations. This research was carried out to find the dielectric responsive function and maximum conductivities of biodegradable and mineral transformer oils for comparative analysis. Each insulation oil with different moisture levels...
Partial discharge (PD) is a phenomenon that commonly occurs in the insulation of power system equipment. In this paper, PDs occurring in a single void and multi-voids were investigated. Air voids at atmospheric pressure were injected into cylindrical epoxy resin blocks to create test samples with single void and multi-voids. PDs from the samples were recorded and further analyzed using phase resolved...
The ultra high frequency (UHF) detection method of partial discharge (PD) is presented in this paper. The log spiral and conical sensors were developed and used with a spectrum analyzer to detect PDs. Measurements of signals produced by two artificial PD defects were carried out in both broad and narrow band frequency ranges. The effectiveness of the sensors was compared and shown in this paper. Both...
Electrical treeing is an electrical prebreakdown phenomenon commonly found in solid dielectrics. It is a damaging process due to partial discharge (PD) and progresses through the stressed insulation by chemical degradation whose path resembles the form of a tree root. The characteristics of PDs due to electrical treeing before the insulation breakdown are discussed in this paper. Several point to...
Due to environmental concerns regarding the use of mineral oil, biodegradable oil was commercially introduced as an alternative for transformer insulation in 1999. Since then, the usage of this oil in the power industry has steadily increased and a lot of researches have been in progress to make biodegradable oil as compatible as mineral oil. This paper presents results of experimental tests performed...
This paper presents results of experimental tests performed on laboratory models of transformer windings immersed in bio-degradable oil. The investigations covered three common types of transformer faults: partial discharge (PD), arcing and overheating. Dissolved hydro-carbon gas products generated by these three fault types in bio-degradable oil are analyzed and compared with existing dissolved gas...
The use of traditional maintenance scheme such as corrective maintenance and preventative maintenance are insufficient to prevent costly events triggered by failure of power system equipment. On-line condition monitoring is increasingly becoming popular. It is non-destructive and cost-saving as it can be carried out with the equipment kept in-service. The on-line monitoring of partial discharges (PD)...
The inner insulation system is a critical component of a power transformer. Its degradation may cause the device to fail while in service. If deterioration of the insulation system caused by Partial Discharge (PD) activity can be detected at an early stage, preventive maintenance measures can be taken. Due to the complex structure of power transformers, accurate locating of PD is not an easy task...
This paper presents results of experiments performed on laboratory to simulate overheating fault on bio-degradable transformer insulation oil. Dissolved hydrocarbon gas products generated by such a fault in three oil conditions (normal, dried and wet) and with and without presence of pressboard are analyzed. For comparison, the tests are also performed on conventional mineral. Results obtained indicate...
The insulation lifetime of XLPE power cables is determined by several factors. One of the most important of these is the occurrences of partial discharge (PD) in the dielectric. The ability to detect and locate the PD sources is limited by attenuation and distortion of the high frequency PD pulses as they propagate through the cable. This paper presents the results of measurements of PD pulses that...
This paper presents the measurements results of simulated partial discharge propagation on a compact three phase XLPE cable, and shows how the high frequency signal on one phase of the cable is induced on the other two phases. A frequency dependent three phase cable model is employed to simulate this phenomena.
This paper presents the development of an on-line partial discharge monitoring system and its application on distribution cables at rated voltages from 11 kV to 132 kV. The system has been used on various in-service applications with different cable types and configurations. Measurement sensitivity of ~100 pC is achievable. The practical issues of noise and interference, and techniques to overcome...
Partial discharge (PD) is a common phenomenon which occurs in insulation of high voltage equipments such as transformers and has a damaging effect to the insulation. In this paper, the application of descriptive data mining on PD occuring in insulating system is shown. Experiments were set up to create three basic types of PD: corona, surface discharges and internal discharges. Partial discharge data...
This paper uses generic three phase models to illustrate how the frequency response analysis (FRA) data of distribution transformers with different vector group numbers will be effected by inductive disparity. The inductive disparity of a three phase transformer is a well documented property due to variation in the observed core reluctance of transformer windings on different phases. At low frequency...
This paper investigates the partial discharge activity and characteristics in mineral oil and bio-degradable oil. Both types of oils tested are commercial products and commonly used in transformers. Tests were done on laboratory models using paper insulated conductor sections to simulate transformer windings and needle-plane configuration to simulate corona in transformer. The laboratory models are...
Bio-degradable oil was commercially introduced as transformer insulation oil in 1999. Since then, the usage of this oil in the power industry has steadily increased and a lot of researches have been in progress to make bio-degradable oil as compatible as mineral oil. This paper presents results of experimental tests performed on laboratory models of transformer windings immersed in bio-degradable...
Lifetime of power cable is influenced by the several factors. One of the most important factors is the occurrence of partial discharge (PD) at the dielectric. The ability to detect and locate a PD source is limited by attenuation of the high frequency PD pulses as they propagating through the cable. Attenuation is the result a range of phenomena, including: dielectric loss of the insulation and the...
This investigation details the results of an investigation of different techniques for modeling high frequency electromagnetic wave propagation in power cables. ATP is probably the most widely used simulation tool for modeling transient phenomena in electrical systems, including power cables. However, ATP is not able to include complex geometries and material physical constants such. However the finite...
This paper proposes the use of a narrowband high frequency based distributed transformer model for estimating partial discharge location within the winding of an interleaved power transformer. At high frequencies, the residual inductance within a transformer winding becomes significant This inductive interaction generates its own characteristic response which, due to its distributed nature, can be...
Continuous on-line monitoring of partial discharge (PD) activities involves recording large amounts of data and a challenging task is to extract useful information from them. Thus, data mining plays a very important role. In this paper, data of PD in power cables are obtained from on-site monitoring and from laboratory test. The PD patterns in terms of the univariate phase-resolved distributions are...
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