HARMONIC ANALYSIS OF LEAKAGE CURRENT OF SILICON RUBBER INSULATORS IN CLEAN-FOG AND SALT-FOG

International audienceEnvironmental and electrical stresses have deterioration effects on Silicon Rubber (SIR) insulators. In coastal areas due to high amount of salt, humidity and dust suspended in the air, the deterioration process is intensive. In this paper, based on IEC 60507 the leakage current (LC) of 20kV SIR insulators has been investigated in clean-fog and salt-fog with and without artificial pollution. Tests have been executed with six similar SIR insulators. A pair of polluted and clean SIR insulators is subjected to clean-fog; other two pairs are subjected to salt-fog with 5 and 10 kg/m 3 salinity respectively. Results show that combination of pollution and salt-fog is more destructive than clean-fog, where the main reason may be the increase of conductivity. Dry band arcing makes insulator perform nonlinearly and some LC waveform harmonic growth. The Fast Fourier Transform (FFT) method, used to find the harmonic spectrum of the LC. Results, also illustrate the coordination between the 3 rd and 5 th harmonic components of the LC and insulators surface condition

A STUDY ON THE RELATION BETWEEN LEAKAGE CURRENT AND SPECIFIC CREEPAGE DISTANCE

International audienceThe usage of polymeric insulators is common due to their advantages in comparison with porcelain insulators. Environmental and electrical stresses have got deteriorating effects on polymeric insulators. Thus, knowing about behaviour of these types of insulators under various stresses is necessary. Till now, various electrical tests have been performed on polymeric insulators to investigate their performance in different situations and to provide a solution for predicting their effective lifetime. Also some standards for testing polymeric insulators have been proposed e.g. IEC62217. In this paper, three pairs of similar 63kV and three pairs of similar 132kV polymeric insulators have been selected for studying the relation between leakage current of polymeric insulators and their specific creepage distance based on IEC62217 standard. The specimens have been tested in three different creepage distances which are proportion of overall creepage distance. The Fast Fourier Transform analysis has been used to find the harmonic spectrum of the leakage current. The results showed that the amplitude of harmonic components for 63kV insulators in all three cases is mostly equal to each other and similarly for 132kV insulators

Experimental investigation of dielectric barrier impact on breakdown voltage enhancement of copper wire-plane electrode systems

Non-pressurized air is extensively used as basic insulation media in medium / high voltage equipments. An inherent property of air-insulated designs is that the systems tend to become physically large. Application of Dielectric barrier can increase the breakdown voltage and therefore decrease the size of the equipments. In this paper, the impact of dielectric barrier on breakdown voltage enhancement of a copper wire-plane system is investigated. For this purpose, the copper wire is covered with different dielectric materials. Depending on the air gap and dielectric strength of the barrier the breakdown can be initiated in the solid or gas dielectric. Theoretically, free charges are affected by the electric field between the electrodes and accumulated at the dielectric surface, this leads to the reduction of electric field in air gap and enhancement of the ifield in the dielectric layer. Therefore, with appropriate selection of the barrier thickness and material, it is possible to increase the breakdown voltage of the insulation system. The influence of different parameters like inter-electrode spacing, and dielectric material on the break-down voltage is investigated for applied 50 Hz AC and DC voltages. The results indicate that up to 240% increase of the breakdown voltage can be achieved

Experimental investigation of dielectric barrier impact on breakdown voltage enhancement of copper wire-plane electrode systems

Non-pressurized air is extensively used as basic insulation media in medium / high voltage equipments. An inherent property of air-insulated designs is that the systems tend to become physically large. Application of Dielectric barrier can increase the breakdown voltage and therefore decrease the size of the equipments. In this paper, the impact of dielectric barrier on breakdown voltage enhancement of a copper wire-plane system is investigated. For this purpose, the copper wire is covered with different dielectric materials. Depending on the air gap and dielectric strength of the barrier the breakdown can be initiated in the solid or gas dielectric. Theoretically, free charges are affected by the electric field between the electrodes and accumulated at the dielectric surface, this leads to the reduction of electric field in air gap and enhancement of the ifield in the dielectric layer. Therefore, with appropriate selection of the barrier thickness and material, it is possible to increase the breakdown voltage of the insulation system. The influence of different parameters like inter-electrode spacing, and dielectric material on the break-down voltage is investigated for applied 50 Hz AC and DC voltages. The results indicate that up to 240% increase of the breakdown voltage can be achieved

Electromagnetic fields near transmission lines - problems and solutions

Nowadays, people are highly concerned about the effects of high voltage transmission lines on their health. Probable risk for leukemia, breast cancer, neuropsychological disorders and reproductive outcomes has been reported due to this exposure. In this study, several measurements around different areas such as overhead transmission lines, GIS compartments and some appliances have been conducted and compared with the standard tolerances. The emphasis of this research is on high voltage substations and publics. Field magnitudes above 10kV/m have been measured under wires. Results show that there is no serious concern for the people living near the transmission lines but for the individuals who are beneath those lines for long. Recent achievements about electric fields′ effect on human health are reviewed in the present paper. In a case study, three types of 230kV structures are analyzed and the best phase arrangement for reducing the electric and magnetic fields is determined (the circular arrangement). It is concluded that the most effective solution is for the governments to use the best phase arrangement and replace outdoor substations with GIS to reduce the radiations and for the people to be near the high voltage overhead lines as rarely as possible

Solid-State High-Voltage Pulse Generator for Low Temperature Plasma Ion Mobility Spectrometry

Low-temperature plasma ion mobility spectrometry (LTP-IMS) is the method to identify some materials by measuring concentration of gas phase ions. IMS used in a wide range of laboratory-based biomedical research studies. A nanosecond pulse generator is necessary for LTP-IMS apparatus to enable direct analysis of various chemical compounds without having to evaporate the analyte or seek a solvent or any reagent. In this paper, a dual Marx pulsed generator for LTP-IMS Ionization power supply is proposed based on a new combination of some solid-state switches including insulated gate bipolar transistor (IGBT) and avalanche bipolar junction transistors (BJTs). The compact dual Marx generator is composed of a series of avalanche BJTs and an IGBT as the trigger switch, where its rise time is reduced from 100 to 5 ns by using an avalanche BJT in its command circuit. In this way, a controllable high-voltage pulse generator has designed, built, and tested. The proposed circuit can be used to generate the repetitive high-voltage pulses necessary for low temperature ionization in advanced IMS apparatus. The output voltage has an amplitude of up to 6 kV with pulse widths in the range of 40-1000 ns and pulse repetition rates up to 2 kHz, having rise time and fall time less than 10 ns independent of the load specifications

Optimized High Frequency Lumped Parameters Model of Induction Motor Using Genetic Algorithm (GA)

Abstract: In this paper an optimized high frequency lumped model of Induction motor is presented. Model parameters are identified and optimized using Genetic Algorithm (GA). A novel model and approach in an improved high frequency based on GA for parameter identification are used. At first, parameters are limited and then fitted using GA for best fitting. The proposed model considered accurate simulation of both differential and common mode behavior in the EMI-frequency range from 100 Hz to 30MHz. Model parameters which extracted from GA are compared with experimental data in both magnitude and phase at the same time and results show a good accordance between the experimental results and simulation results of the proposed model. A least mean square (LMS) method was used with a GA optimization method to solve the identification problem. The proposed model is suitable to obtain the simulation models to predict high frequency conducted Electromagnetic Interference (EMI), over voltage on terminated motor and common mode current in cable fed induction motor

Impact of Surface Morphology on Arcing Induced Erosion of CuW Contacts in Gas Circuit Breakers

In this paper, the impact of surface morphology of contacts, in particular different microstructural parameters like size and distribution of contact ingredients, on contact erosion in high voltage gas circuit breaker is investigated. It is demonstrated that the size and contiguity of copper and tungsten zones play a key role in contact erosion so that the mass loss in one specific contact after interruption of the rated short-circuit current is 2.5 times higher than that of another one, with the same dimensions and material composition. It is shown that the arc roots tend to be formed on larger copper zones and if the zones are not confined by tungsten area, the arc cross section expands resulting in a higher evaporation rate of copper areas. In addition, it is emphasized that ejection of tungsten particles after evaporation of surrounding copper areas is another mechanism leading to more contact erosion, which has to be taken into consideration in contact erosion modeling along with molten contact splash and vaporization