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Comparing with porcelain and glass insulator, polymeric one has some advantages like as good insulating performance, lighter weight and low price etc. Flashover mechanism on a surface of the polymeric insulator is different from that of porcelain or glass ones. It suggests that lots of studies are required to understand the flashover mechanism on the surface of the polymeric insulators and to use...
Polymers are extensively used as insulating material in high voltage devices, such as underground power cables, power capacitors and transformers. During normal operation the polymeric insulation of a power device is not only subjected to electrical stresses, but could also be subjected to thermal, mechanical and environmental stresses. These stresses either acting singly or in combination can cause...
Partial discharge (PD) endurance of epoxy/SiC nanocomposite was investigated in comparison with that of epoxy/silica (SiO2) nanocomposite. Filler contents were 1 wt%, 2 wt%, 3 wt%, 4 wt% and 5 wt% in epoxy/silicon carbide (SiC) nanocomposite. Evaluation was made by erosion depth and eroded cross sectional area in its profile measured with the laser surface profilometory. It was confirmed that epoxy...
Electrical wiring and interconnected systems (EWIS) have become a major area of research and development for variety of industries. A variety of factors lead to catastrophic failure described. Here partial discharge (PD) analysis methods for diagnosing aircraft wiring faults are explored since PD signals are strongly correlated with the defects that produce them and form an ideal part for prognostic...
Laboratory tests on field aged and unaged cables were performed using DC depolarization current measurements. Aged cables with water trees showed high dielectric losses and depolarization currents as compared with the reference, unaged cable. Both the area under the depolarization current waveform and dielectric loss factor, tandelta, increased with DC poling and the applied AC voltage, respectively...
The electrical degradation of cable insulation in distribution lines is due to the electrical stress caused by switching surges. During the operation, the insulation of power cables will be placed under high electrical stress, including overvoltages caused by switching. The status of power cable insulation aging is evaluated by the measurement of partial discharge level and AC breakdown voltage. The...
Several degradation mechanisms may affect polymeric insulation system reliability. Some authors postulate that, even in a perfect dielectric, nanoscale cavities can enlarge due to various mechanisms (from mechanical fatigue to lowering of the degradation reaction energy barrier) up to a point where highly energetic phenomena, which bring about breakdown, can be incepted. Other authors are more focused...
Several examples of terahertz (THz) spectroscopic measurement results carried out for dielectric solids are reviewed, including THz time-domain spectra of polyamide-6 composites with nm-sized clay fillers obtained by the authors. For polyamide nanocomposites, it has become clear that the dielectric loss factor shows two peaks at around 1.9 THz and 2.7 to 3.1 THz. By referring to X-ray diffraction...
The topic of nanodielectrics is one that has grown enormously in importance since Lewis first introduced the concept of a nanodielectric in 1994. However, while nanodielectrics exhibit great promise, changes in macroscopic physical properties are determined by dispersion, and therefore it is imperative that reliable methods are available for the cost-effective determination of the dispersion state...
This paper presents results from laboratory experiments performed in order to evaluate different methods for quality control of polymeric insulated HVDC cables. In this work, we have investigated the effect of short term (24 h) DC stress followed by rapid grounding of the cable. This is comparable to a voltage step of -U0 at the point of grounding ,and depending upon the cable length, a step of up...
Saudi electric Company (SEC), and Petrochemical industries in Saudi Arabia and other plants provide the utilizing location and testing, and also some of the raw insulation materials for cable industries. Major petrochemical producers are striving to improve the quality of the plastic raw materials. On the other hand, cable industry has also made noticeable progress in the production of distribution...
Corrosion on grounding rod can significantly increase the grounding resistance and compromise the safety of the power system. Silicone rubber used in outdoor insulation area for its long life in adverse environments. This paper proposes a kind of conductive RTV silicone coating suitable for grounding systems. Conductive nano-particles such as carbon black and carbon fiber are added to reduce the resistivity...
Insulation liquids are mainly used in oil filled transformers for their cooling and insulating properties. Besides a testing of electrical properties, there is also important to monitor oxidation stability and activation energy as the factors which can decide on an application possibility of the insulating liquid. The main aim of this paper is to describe the influence of temperature aging on the...
Short circuit of a stator winding is one of the most probable faults of induction motors, resulting in huge economical loss by stopping of production lines in industrial plants and factories. Establishment of an easy and effective fault diagnosis method has been strongly required to assure motors for operation with high reliability. This paper reports the results of analysis of current waveforms of...
The differences between AC and DC aging are pointed out and are partly due to the different dissipated energy under the two types of field and partly due to the fatigue induced by the alternating stress. In addition to these effects, the sample size has also a considerable impact on both aging and breakdown. It is shown, from well known existing data, that the aging characteristics of polyethylene...
Tracking of a cord plug is attributed to one of the main causes of fire accident, which is caused by surface leakage current flowing between its electrodes when dust is accumulated in the space between the plug and the outlet and wetted for example by dew condensation. This paper reports two novel detection methods of cord plug tracking. One is to detect the existence of the surface leakage current...
Multistress aging of outdoor composite polymeric insulators continues to be a topic of interest for power transmission research community. Aging due to dry conditions alone at elevated temperatures and electric stress in the presence of UV radiation environment probably has not been explored. This paper deals with long-term accelerated multistress aging under the above conditions on full-scale 11...
The dissipation current waveform observation method is considered one of possible way as a diagnostic method for the un-bridged water tree on the high-voltage class power cable. In this paper, in order to clarify the time variations with the un-bridged water tree growth, by using the special chamber and setup, the dissipation current waveforms monitoring under the high voltage application test of...
Power transformers are vital parts of electric energy transmission and generation systems. Numerous power transformers in the European power grid have reached an age of 30 years or even more and are possibly close to their end of life. Because of economic reasons it is demanded to keep current assets as long as possible in service without taking the risk of a failure. The DP (degree of polymerization)...
An atypical enhancement of both the dielectric properties and the static (dc) conductivity in polyimide (PI) films has been observed using isothermal dielectric relaxation spectroscopy at 300degC under air atmosphere during short-term thermal aging (up to 200h). Simultaneously, an increase of the dielectric strength of PI is observed. Despite a close similarity with the typical electrical signature...
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