Experimental investigation of cf3i-co2 gas mixtures on the breakdown characteristics in uniform and nonuniform field configurations

This thesis is concerned with the investigation of trifluoroiodomethane (CF3I) gas mixtures as an alternative for an insulation medium in high voltage applications. The work has involved a broad review of literature, followed by developing a test rig for carrying out experimental investigations, extensive computational modelling and simulation studies as well as extensive laboratory tests on CF3I gas and its gas mixtures. The literature survey reviewed the current trend of efforts taken by researchers to find solutions for minimizing the usage of sulphur hexafluoride (SF6) as a gas insulator, focusing on CF3I and its mixtures. The physical properties of CF3I are investigated, along with thermal and electrical properties. A new test rig has been designed and constructed specifically to be used for gas insulation research. The test rig is integrated with wireless temperature and humidity sensors, as well as an electrode gap length control system. The test rig is completed with a gas recovery system to ensure proper gas handling is carried out after each test. Extensive laboratory experimental investigations on CF3I mixtures have been completed, focusing on the mixture of CF3I-CO2 gas with a ratio of 30%-70%. Standard lightning impulse of 1.2/50 has been used, with both positive and negative polarity. The effects of electrode configuration, impulse polarity, electrode gap length, gas pressure, and CF3I content have been investigated. Insulation properties such as 50% breakdown voltage (U50) and V-t characteristics for each test condition are investigated and presented, as well as the electric field behaviour. Finite element method (FEM) has been used to determine the electric field behaviour of a given test condition. This study revealed that CF3I gas mixtures perform better under more uniform field condition. It was also found that an increase in gas pressure will increase the insulation strength and an increase in CF3I content is more likely to give benefit in conditions with a more uniform field when compared to less uniform field conditions. Also, relation between liquefaction temperatures of a CF3I-CO2 mixture with varying CF3I content has been developed for various pressures based on literature. Observations on solid by-products of CF3I have also been carried out. It has been found that iodine particles are deposited on both high voltage and ground electrodes, which can affect the insulation properties of CF3I and its mixtures

Breakdown of CF3I Gas and its Mixtures under Lightning Impulse in Coaxial-GIL Geometry

SF6 is widely used in modern transmission and distribution networks because of its outstanding dual qualities: arc quenching and dielectric insulation. As a gas medium, SF6 is chemically inert, non-toxic, and non-flammable, which makes possible the construction of compact SF6 switchgear. One major known disadvantage of the gas is that it has a global warming potential which is 23,900 times higher than CO2. This has led to research into alternative gases with a much lower environmental impact, and one of the emerging candidates is CF3I. The high boiling temperature of CF3I means that it has to be used as part of a mixture inside gas-insulated equipment. To carry out the investigation on CF3I, a scaled-down coaxial system that replicates the maximum electric field of a 400 kV GIL system was designed and fabricated. The insulation performances of CF3I/CO2 and CF3I/N2 gas mixtures were then examined by measuring the 50% breakdown voltage, U50, using a standard lightning impulse waveform (1.2/50) under absolute pressures of 1 to 4 bar. The experimental results show that CF3I gas mixtures have promising potential as an insulation medium for application in gasinsulated lines

CF3I Gas Mixtures: Breakdown Characteristics and Potential for Electrical Insulation

SF6 is a potent greenhouse gas, and there has been research into more environmentally friendly alternative gases with the aim of replacing the use of SF6 gas in high-voltage equipment. So far, the research into alternative gases has shown that CF3I gas mixtures have promising dielectric properties comparable to those of SF6. This paper provides an overview of research into CF3I gas and its mixtures, and gives an insight into its key properties. These include laboratory tests on the gas mixtures and initial applications to electrical power equipment. The insulation capability makes CF3I a feasible alternative to SF6 as an insulation medium where arc quenching is not required. On the other hand, iodine deposition after electrical discharge means CF3I may not be a suitable arc quenching gas for switchgear applications that require high current interruption unless a solution is found for controlled capture of the iodine

Characteristics of grounding performance at Taman Bukit Perdana

Grounding system is one of the important part during installation of power systems. The function of grounding system is to enable protection to the power system in case of any current leakage or lightning strike. A grounding system will disconnect the circuit as soon as the fault current flows through the earth [1]. Every potential connection or equipment that may cause the current leakage must be grounded. In a simple way, it can be defined as the system to protect and stabilize the operation for human and equipment during fault conditions

Breakdown Characteristics of Unused Transformer Oil and Olive Oil under AC and DC Voltages at Different Temperature Rate

This project aim is to investigate the breakdown characteristics of unused transformer oil and olive oil under AC and DC voltage at different temperature rate. HVAC and HVDC breakdown tests are carried out alongside with the hemisphere electrode arrangements. The high voltage test is done in order to observe the performances of the oil samples to attain the highest breakdown AC and DC voltages. In addition, this project needs to be done to see if olive oil as one of the vegetable oil can be an alternative for the conventional transformer oil. Commonly used transformer oil is made from mineral oil and it is declining day by day as its use increases. So as a precaution studies are done with vegetable oils to replace the mineral oil-based transformer insulation fluid. In this study, each oil sample is tested at different temperature rate and has recorded different value of breakdown voltage from the experiment. The gap distance between electrodes is constant and oil samples are heated at different temperature ranges. More voltage is needed to breakdown at higher temperature rate. Both the unused transformer oil and olive oil have linearly increased AC and DC breakdown voltages when subjected to higher temperatures. However, it is found that the highest AC and DC breakdown voltages are recorded at the highest temperature range and when the insulating medium used is olive oil. Moreover, the obtained AC and DC voltages are then be used to study the electric field in FEMM softwar

Development Of Test Vessel For Gas Insulation Breakdown Test

This paper discusses a new test vessel developed to investigate the breakdown test performance of gas insulation. The test vessel is equipped with certain specialty including pressure chamber and control measures. Through help from a steering, it is provide of controlling the gap length of the electrodes without the need of removing the gas. Other control measures include humidity, temperature, and pressure readings. The humidity and temperature are read wirelessly and from the readings, the necessary atmospheric corrections can be made according to standards. The developed vessel is then tested with AC breakdown test using air with various gap lengths and various electrode configurations. There are two types of electrode configuration used in this project i.e., rod (R0.5)-plane and plane-plan

Potential of CF3I gas mixture as an insulation medium in gas-insulated equipment

SF6 is a widely used gas medium in gas-insulated equipment. Due to the high global warming potential and long atmospheric lifetime of SF6 , there has been research into a new environmentally friendly replacement gas. This paper describes the research carried out at Cardiff University on CF3I gas and its mixture as a substitute insulation medium for SF6 in gas-insulated lines (GIL). A reduced-scale coaxial test system having the electric field properties of a full-scale 400 kV GIL system was fabricated. The design of the reduced-scale coaxial test system was simulated to ensure that the highest electric field would be along the center of the conductor. The coaxial prototype was then tested under a standard lightning impulse (1.2/50) in order to determine the 50% breakdown voltage for such a system when insulated with CF3I gas mixture. It was found that CF3I has the potential to replace SF6 as an insulation medium in GIL. A full-scale short length GIL demonstrator is being assembled in the laboratory to evaluate further the feasibility of using a CF3I gas mixture as an insulation medium

Finite Element Analysis Of Maximum Electric Field For Air Breakdown Under Various Electrode Configurations

This paper describes the electric field behavior of air breakdown under various electrode configurations and gap length.By using COMSOL Multiphysics,a Finite Element Method (FEM) software,the values of maximum electric field can be determined based on the air breakdown voltage data obtained from the experiment under AC stress.The results show that R0.5-plane configuration provides a very high electric field upon breakdown, compared to R6-plane,R48-plane and plane-plane configurations.In addition,the comparison between the analytical and simulation results of maximum electrical field gives almost identical results for each electrode configuration except for R6-plane