Mechanism of saline deposition and surface flashover on high-voltage insulators near shoreline:mathematical models and experimental validations

This paper deals with sea salt transportation and deposition mechanisms and discusses the serious issue of degradation of outdoor insulators resulting from various environmental stresses and severe saline contaminant accumulation near the shoreline. The deterioration rate of outdoor insulators near the shoreline depends on the concentration of saline in the atmosphere, the influence of wind speed on the production of saline water droplets, moisture diffusion and saline penetration on the insulator surface. This paper consists of three parts: first a model of saline transportation and deposition, as well as saline penetration and moisture diffusion on outdoor insulators, is presented; second, dry-band initiation and formation modelling and characterization under various types of contamination distribution are proposed; finally, modelling of dry-band arcing validated by experimental investigation was carried out. The tests were performed on a rectangular surface of silicone rubber specimens (12 cm × 4 cm × 8 cm). The visualization of the dry-band formation and arcing was performed by an infrared camera. The experimental results show that the surface strength and arc length mainly depend upon the leakage distance and contamination distribution. Therefore, the model can be used to investigate insulator flashover near coastal areas and for mitigating saline flashover incidents.</p

Different characteristics of artificially polluted high voltage composite insulators

Characteristics of leakage current, electrical field and surface resistivity of artificially polluted high voltage composite insulators for different composite materials in their structure, equivalent salt deposit density, electrolyte flow-rate and hydrophobicity are discussed, analyzed and presented in this paper. All these parameters are compared with conventional non composite insulators, too. Relativity of leakage current, applied electric field, electrolyte flow-rate and electrolyte conductivity to the environmental conditions are presented by the results of artificial pollution tests. Waveform, frequency spectrum and magnitude-phase diagram of leakage current of polluted insulators with different pollution densities and durations and applied voltages are presented. Surface resistivity of different insulators is compared regarding different kinds and densities of pollution. Electrical field causing flashover for polluted insulators as a function of the insulators' surface hydrophobicity and salt deposit density is also presented. Through the study, investigating the life time of being used insulators is achieved by measuring their leakage current, salt deposit density and surface resistivity and comparing with the test results

Feasibility Study on Electrical Properties of 20 kV Polymeric Insulator Dry Test and Rainwater Test

Insulator is a very important equipment in an electric power system. Ceramic insulators have been widely used to support conductors in 20 kV power lines. The problem of ceramic insulators is that they are heavy, easily contaminated on the surface and require a lot of energy in the manufacturing process. Therefore, polymer insulators were developed. This paper presents the design of an epoxy resin polymer insulator with Titanium Dioxide (TiO2) as a nanofiller. The leakage current test was carried out in a high voltage laboratory by applying an AC high voltage of 50 Hz to the insulator dry conditions and the insulator wetted by rainwater contaminants. The results of the leakage current test in dry conditions are 487.6 μA, rainwater contaminated conditions are 594.93 μA, insulation resistance in dry conditions is 2.07 G-Ohms, and contaminated conditions are 1.41 G-Ohms. Based on the test results show that the insulator leakage current increases up to 22% when the surface of the insulator is contaminated with rainwater. Meanwhile, the insulation resistance decreased by up to 32% in conditions contaminated with rainwater. The value of leakage current and insulation resistance indicates that the epoxy resin insulator with TiO2 as filler is electrically feasible to use

LaF3 insulators for MIS structures

Thin films of Laf3 deposited on Si or GaAs substrates have been observed to form blocking contacts with very high capacitances. This results in comparatively‐hysteresis‐free and sharpC‐V (capacitance‐voltage) characteristics for MIS structures. Such structures have been used to study the interface states of GaAs with increased resolution and to construct improved photocapacitive infrared detectors

IMPLEMENTATION OF THE PUSH-OUT TEST FOR IMPROVING OF COMPOSITE INSULATOR END FITTING PERFORMANCE

Destructive push-out test of composite rod joint was prepared in order to estimate ultimate load capacity of composite insulators end fitting joint. Plane strain and axisymmetric finite element models were developed. Imperfect interface with large allowed slipping and Coulomb friction was analysed. Experimental results were preliminary processed and ultimate load criteria chosen for appropriate manipulation and comparison. Results show that composite joints with contact pressures higher than the radial strength do not obey Coulomb friction law due to partial damage effect on the composite rod surface. However, for joints with limited contact pressure good agreement with classical friction model was obtained. Generalised relation between ultimate axial stress and contact pressure was also presented

Faulty sensor detection using data correlation of multivariant sensor reading in smart agriculture with IOT

The Internet of Things (IoT), the idea of getting real-world objects connected with each other, will change the ways we organize, obtain and consume information radically. Through sensor networks, agriculture can be connected to the IoT, which allows us to create connections among agronomists, farmers and crops regardless of their geographical differences. On the other hand, Sensor fault is critical in smart grids, where controllers rely on healthy measurements from different sensors to determine all kinds of operations. However, when sensor fault happens, missing data and/or bad data can flow into control and management systems, which may lead to potential malfunction or even system failures. This brings the need for Sensor Fault Detection and eliminate this potential fault. This thesis proposes to design a Faulty Sensor Detection Mechanism using the data correlation method of multivariate sensors. This method will be applied to the smart agriculture which uses multi-variate sensors such as moisture sensor, temperature sensor and water sensor in IoT. The data are collected and received by a microcontroller which also can be linked to the internet. According to the algorithm, which applied on the smart agriculture, in case, the system gives No FAULT when the correlation value between (temperature, moisture) and (temperature, water) are negative and positive for (Water, moisture). In other cases. The system has a fault in a sensor when the correlation values between sensors are changed. Also, when the sensor gives a constant reading for a long time the system has got a fault in this sensor. The system got No FAULT when was different in sensors reading and the correlation value between (temperature, moisture) is (-0.33), between (temperature, water) is (-0.16) and (moisture, water) is (0.36). In addition, this system will be connected to the internet through the ESP8266 module. In order to surveillance the system at anytime and anywhere, this system is connected with the cloud (Things board) by using an ESP8266 WiFi network connection. This would allow the system to be more efficient and more reliable in detecting and monitoring the system’s parameters such as the state of sensors. The accuracy of the algorithm for data correlation may be changing depending on the application that wants to detect the faulty sensor in the system and according to how many data that income to the microcontroller per minute and how many data should take to calculate the correlation coefficient. Therefore, for the smart agriculture which it's used in this project, the period is adjusted to give a good diagnose for the sensor as soon as possible

Seismic Standards Qualification of Instrument Transformers by Shake Table Test and Linear FEM Analysis

Power grids are widely recognized as vital components of modern infrastructure. In today\u27s society, nearly every aspect of daily life comes to a halt without electricity. Therefore, it is crucial to design power grids and their components to withstand various natural disasters. In this context, special attention is given to earthquakes and the need to enhance equipment resilience against this highly unpredictable event, which significantly impacts power grids. Instrument transformers could be the critical component in substations due to their slender design. Having this in mind, it is necessary to carry out further research and encourage development in order to reduce the impact of earthquakes on substations. Seismic qualifications are one of the means to achieve that goal. The primary objective of this paper is to share insights and experiences related to the preparation, implementation, and supervision of seismic tests conducted on a shake table. The FEM analysis, conducted as a crucial step in transformer design preparation and shake table testing, strictly adhered to the standards set by IEEE 693. IEEE 693 is widely recognized as the most demanding seismic standard regarding the substation equipment. Furthermore, the latest version of IEEE 693 was compared to other relevant standards, including IEC 61869 (current draft 38/652/CD), ETGI 1.020, and IEC 62271-300, to gain a comprehensive perspective. FEM analysis is characterized not only as a tool for design preparation and pre-test analysis but also as a valid tool for performing seismic qualifications, based on the comparison with the actual shake table tests. The paper extensively utilized the findings from seismic tests conducted on two distinct transformers, each employing different materials for critical components, in various test laboratories. These findings formed the basis for detailed analysis and conclusive insights, aligning with different versions of IEEE 693. This article aims to offer a comprehensive understanding of the seismic qualification process, providing valuable insights for substation designers, seismic specialists, and end users