Major drawbacks to high voltage insulator especially on electrical aging process have been an issue for decades. The internal electric field distribution due to the presence of local space charge will distort, which in turn may cause the... more
Major drawbacks to high voltage insulator especially on electrical aging process have been an issue for decades. The internal electric field distribution due to the presence of local space charge will distort, which in turn may cause the insulating material to degrade and finally can lead to accelerated aging and electrical breakdown. Comprehension of space charge buildup in solid insulator is crucial to determine how aging occurs, thus enabling the prediction of insulator lifetime. Space charge measurement has been extensively researched in recent years and has become a common method of investigating solid insulator properties. Pressure Wave Propagation (PWP) and Pulsed Electro-Acoustic (PEA) are non-destructive dielectric testing methods used to determine the space charge distribution within the insulation. This paper presents the basic principles, typical measurement setup and comparison of results from several published papers on application of PWP and PEA methods to investigate space charge accumulation. The space charge distribution in the sample is measured as current and voltage signals obtained from PWP and PEA methods respectively. Judging from extracted results of other research, both methods show the capability to detect premature aging activities in the insulator, which is necessary for condition monitoring of high voltage insulators.
In this paper a novel approach to model partial discharges (PD) activity taking place inside a spherical void in epoxy resin system has been traced. The approach is based on a time varying conductance of the inner void, subjected to... more
In this paper a novel approach to model partial discharges (PD) activity taking place inside a spherical void in epoxy resin system has been traced. The approach is based on a time varying conductance of the inner void, subjected to multistress conditions: voltage, temperature and pressure. A simple lumped circuit macro-model simulates the global effects of PD activity: the different parameters influencing the discharge phenomenon in the void are taking into account by using a physical approach resulting in a time varying conductance inside the circuit. The evaluated PD activity has been compared with experimental and simulated one for the accessible and inaccessible part of the system. A discussion on the observed changes in PD activity has been reported.
In this paper, effects of lead doping on the lattice response and phase transitions of Sr1KxPbxBi2Nb2O9 (x=0.0–0.5 in steps of 0.1) ferroelectric ceramics are reported. It is observed that structure attains more tetragonality with doping... more
In this paper, effects of lead doping on the lattice response and phase transitions of Sr1KxPbxBi2Nb2O9 (x=0.0–0.5 in steps of 0.1) ferroelectric ceramics are reported. It is observed that structure attains more tetragonality with doping of lead up to 40%. Increased orthorhombic distortion is observed for undoped SBN and 50 at.% lead substituted SBN. Phase transitions for all samples were studied using Curie temperature measurements and are explained in terms of lattice response of these ceramics. Sample with x=0.5 shows decreased tetragonal strain and Curie temperature. Relationship of polarization with lattice response is discussed.
