Electric Field Distribution Of Insulator Research Articles

Optimized Design of Shed Parameters for Polluted Hollow Porcelain Insulators at High Altitude

The pollution flashover problem of hollow insulators, one of the primary faults in substations, can be improved by optimizing the shed parameters. Combining the artificial pollution test and electric field simulation, this paper studies the optimal shed parameters for 220 kV hollow porcelain insulators at high altitudes. The AC artificial pollution flashover test was conducted by solid-layer and up-and-down methods in the artificial climate chamber to analyze the pollution flashover characteristics of the 220 kV hollow porcelain insulator at various altitudes and pollution degrees. After the validity of the artificial pollution flashover test and the direction of optimization of the shed parameters were clarified, electric field simulation was implemented on a two-dimensional axisymmetric model to analyze the effects of shed spacing and large shed overhang on the electric field distribution of the insulator. Based on the pollution flashover characteristics and the simulation analysis results, we find that appropriately increasing the shed spacing and reducing the large shed overhang can improve the surface electric field distribution of the hollow porcelain insulator, thereby improving its pollution flashover characteristics.

Research on Electric Field Detection of Degraded Insulators Based on a Sensitive Detection Method under Complex Operating Conditions

Insulators are the basis of the stable operation of transmission lines, and it is particularly important to regularly detect the insulation performance of insulators. After several years of research, contactless space electric field detection technology for degraded insulators, based on an unmanned aerial vehicles (UAV) platform, has developed rapidly. However, the existing technology is only limited to the typical vertical/horizontal state research category and cannot apply to complex operating conditions such as attitude disturbance and path tilt. This paper builds a simulation model of insulators at a voltage level of 220 kV by COMSOL finite element software and analyzes the space electric field distribution characteristics of degraded insulators and the influence of different surface conditions, attitude disturbance, path tilt, etc., on the space electric field distribution of insulators. To reduce the error of UAV detection under complex operating conditions of insulators, a method for detecting the electric field of degraded insulators based on sensitive insulators is proposed and verified by experiments. According to the research results, surface conditions of insulators have little influence on their space electric field, while the attitude disturbance and path tilt of UAVs have a great influence on the electric field of insulators. Sensitive insulators at a level of voltage below 220 kV are generally located at the low-voltage end. The principles of sensitive insulators are combined with the space electric field measurement method to measure the space electric field distribution, thus effectively judging whether there are degraded insulators in the string. The method specified in the paper greatly improves the accuracy and detection efficiency of the contactless electric field detection of insulators, which is of great significance for the promotion of the electric field detection method of insulators in practical applications.

Three‐dimensional electric field simulation and flashover path analysis of ice‐covered suspension insulators

Flashover of ice-covered insulators seriously affects the safe operation of transmission lines. It is necessary to study the electric field distribution for flashover analysis of ice-covered insulators. The electric field of ice-covered insulators was mostly calculated by a two-dimensional (2D) axisymmetric model that cannot be well corresponded to actual icing situations. In this study, a 3D electric field simulation model of ice-covered suspension insulators under moderate icing condition with applied DC voltage was established. Two characteristic parameters, Eav and Emax were proposed to measure electric field distortion degree. Based on the simulation results, the effects of water film conductivity, icicle length, icicle deviation angle, and icicle distribution on Eav and Emax were studied. The results showed that icicles have a significant influence on the electric field distribution of insulators. Eav increases with the increase of icicle length and decreases with the increase of icicle deviation angle. Emax increases with the increase of the icicle length, icicle spacing and adjacent icicle length difference. When the icicle deviation angle is 45°, Emax is the largest. Lastly, the possible flashover paths were analysed based on the simulation results, which would provide a theoretical basis for building a flashover model of ice-covered insulators.

Overview of development, design, testing and application of compact gas-insulated DC systems up to ± 550 kV

The development of high-voltage direct current gas-insulated switchgear assemblies (DC GIS) of rated voltages up to ±550 kV has been completed. DC GIS provide a compact technical solution with a high functional density, optimized for projects with limited space as in offshore HVDC converter platforms, onshore HVDC converter stations and transition stations between different transmission media. Up to now, no standards for testing of gas-insulated DC systems are available, although pre-standardization work is in progress within CIGRE. Some tests can be performed as required in AC GIS standards. Special aspects of DC voltage stress, like the electric field distribution of insulators influenced by the accumulation of electrical charge carriers and the operation-related inhomogeneous temperature distribution, must be considered by additional electric and thermoelectric tests. For DC GIS, the experience of long-term performance is limited today. Although ageing is expected to be of lower importance, tests are recommended. This contribution summarizes the physical and technical background to design and develop compact DC switchgear assemblies using gas-insulated technology. It explains the developed modules of the substation and gives an overview of the performed tests. Furthermore, it provides an insight in the on-going standardization activities and describes applications in converter and transition stations, showing its space-saving characteristics.

Contamination effects on charge distribution measurement of high voltage glass insulator string

Abstract It is certain that accumulated charge greatly enhances the local electric field distribution of insulator and may lead to breakdown even under nominal voltage. Although research on charge distribution has gained worldwide attention for the past few decades, yet the study of charge distribution on its surface is still insufficient. Therefore, this paper presents the charge distributions measurement on the surfaces of glass insulators string without grading ring subject to clean and contaminated conditions. The experimental results revealed that the distribution of charge for glass insulator recently removed from service has negative distribution pattern and this is further supported by the simulation work results. Charge injection and extraction occurring at the metal-dielectric interface greatly affects the charge amplitude of the adjacent insulators. This study also revealed that the presence of contamination affect the charge distribution of the insulator located near to ground electrode.

Stress conditions in HVDC equipment and routes to in service failure

High voltage equipment designed for DC applications is stressed differently from ac equipment. Most notably, the load conditions of the equipment play a major role in determining the electric field distribution in insulation under dc, due to the temperature dependence of conductivity. Additionally, polarization and space charge phenomena impose a time dependent behavior on the stress distribution. This has major consequences for the way in which degradation of the insulation under dc stress takes place. The nature of the stresses under dc may lead to accelerated degradation processes which could result in early breakdown of the insulation. This paper provides an overview of the stress conditions specific for dc application and highlights via which routes they may lead to failure. The stress distributions in converter transformers and dc cable systems will serve as typical examples.