Breakdown behavior of a 10 mm point-sphere gap is investigated for R12, R12 (Dichlorodifluoromethane, CCL2F2), air mixtures for pressures of up to 60psi. It is shown that at high gas pressures, mixtures containing high R12 content can have breakdown voltages higher than the corresponding values in air. Furthermore, these voltages are compared with the SF6. And make a comparison of R12 and SF6 in different scenarios i.e. GWP, cost, dielectric strength. Then Ac voltage breakdown characteristics of various combinations of insulating filler in transformer oil for use in transformers were investigated, with the aim of reducing the amount of oil and thus the cost. Tests were conducted on a sphere–sphere electrode in a horizontal arrangement and a sphere–plane electrode in a vertical arrangement. The Breakdown characteristics were also investigated in a modal in which Nomex paper was inserted between filler and the high-voltage electrode. Based on the experiments, optimum conditions are proposed for the application of transformer oil to transformers. Detailed results of investigations of both gas and composite insulating oil are described and discussed in this paper.
Table of Contents
1. INTRODUCTION
1.1 Gas
1.2 Composite liquid
2. EXPERIMENTAL ARRANGEMENTS AND PROCEDURES
2.1 Gas
2.2 Composite liquid
3. EXPERIMENTAL RESULTS
3.1 Gas
3.2 Composite liquid
Research Objectives and Topics
The primary objective of this research is to evaluate R12 gas and composite insulating liquids as environmentally friendly and cost-effective alternatives to SF6 gas and standard transformer oil. The study investigates the breakdown behavior of R12-Air mixtures and the impact of adding insulating fillers to transformer oil to reduce overall volume and costs.
- Breakdown characteristics of R12 and R12-Air gas mixtures.
- Environmental impact and dielectric comparison of R12 versus SF6.
- Performance of composite insulating liquids using glass beads and Nomex paper.
- Optimization of insulation assemblies to reduce transformer oil usage.
Excerpt from the Book
3.2 Composite liquid
The BDV characteristics of the vertical arrangement are as follows.
The BDV decreases from the grounding electrode (h/d=0.0) until just before the glass beads touches the high-voltage electrode (h/d<1.00). When the glass beads approaches the high-voltage electrode (h/d=0.84), the BDV decreases by only about 20% from the normal value when h/d=0. If the glass beads touches the upper spherical electrode of the high electric field, i.e. the high-voltage electrode (h/d≥ 1.00), the BDV decreases significantly to about 46% from the normal value.
The BDV did not changes until the glass beads touches the lower side of the high-voltage and grounded electrodes (h/d≥ 1.00), and decrease by only 10% compared to the normal value when h/d=0. When the glass beads. If h/d=1.52, the high-voltage electrode is covered by the glass beads, BDV falls to 50% of the normal value when h/d=0.
By inserting a Nomex paper between the high voltage electrode and glass beads, the BDV increases by 60% of the normal value.
By further increasing the no of Nomex papers there was no significant change in BDV found.
Summary of Chapters
1. INTRODUCTION: Outlines the environmental concerns associated with SF6 gas and the motivation to develop cost-effective, safer alternatives for high-voltage insulation.
2. EXPERIMENTAL ARRANGEMENTS AND PROCEDURES: Describes the pressure vessel configurations, electrode setups, and the specific materials used to test gas mixtures and composite insulating liquids.
3. EXPERIMENTAL RESULTS: Presents the measured breakdown voltages, spark formation observations, and the impact of filler materials on dielectric strength.
Keywords
High Voltage, R12 Gas, SF6 Gas, Insulation, Transformer, Nomex Paper, Glass Beads, Breakdown Voltage, Dielectric Strength, Global Warming Potential, Electric Power Apparatus, Gas Mixtures, Spark Discharge
Frequently Asked Questions
What is the primary focus of this research paper?
The paper examines the breakdown behavior of R12-air gas mixtures and the performance of composite insulating liquids in transformers to find viable, cost-effective, and eco-friendly alternatives to traditional SF6 and transformer oil systems.
What are the main thematic areas discussed?
The study covers high-voltage insulation, refrigerant gas applications, dielectric material testing, and the optimization of insulation geometries for power apparatus.
What is the core research objective?
The goal is to develop an insulating medium that is technically competitive with SF6 while reducing global warming potential and minimizing transformer oil consumption through the use of composite fillers.
Which scientific methodology was employed?
The researchers conducted experimental testing using pressure vessels for gas analysis and various electrode arrangements (sphere-sphere, sphere-plane) with composite fillers to measure breakdown voltage (BDV) characteristics.
What topics are covered in the main section?
The main sections detail experimental setups, provide empirical results regarding breakdown curves for R12-air and composite liquids, and discuss the impact of adding Nomex paper to the assembly.
Which keywords characterize this work?
Key terms include High Voltage, R12 Gas, SF6 Gas, Insulation, Transformer, Nomex Paper, and Dielectric Strength.
How does R12 compare to SF6 in terms of insulation performance?
The research indicates that R12 offers a breakdown strength approximately 99.6% as high as SF6, while simultaneously being 49% cheaper and possessing 65% less global warming potential.
What effect does the addition of glass beads have on transformer oil insulation?
The study finds that while glass beads act as a filler, their interaction with the high-voltage electrode is critical; specifically, if the beads touch the electrode, the insulating property is negatively influenced due to decreased oil volume and increased material non-homogeneity.
What role does Nomex paper play in the proposed composite liquid?
The insertion of Nomex paper between the high-voltage electrode and the glass beads acts as a barrier that improves the breakdown voltage by up to 60%.
What specific by-products were identified after R12 decomposition?
Following high-voltage testing, the researchers identified carbon monoxide, carbon dioxide, hydrogen fluoride, and hydrogen chloride as decomposition by-products, with visible carbon deposits remaining on the electrodes.
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- Muhammad Junaid (Autor), Mehran Tahir (Autor), Muhammad Aamir (Autor), 2013, HVAC Breakdown of R12, R12 – Air Mixtures in Sphere gap Electrodes and Proposed Composite insulating Liquid to Reduce the Amount of Transformer Oil In Transformers, Múnich, GRIN Verlag, https://www.grin.com/document/229763
