This book describes the state-of-the-art use of biological insulating liquids in detail. In recent years, more and more transformers filled with esters have been put into operation. This is because people recognize the benefits of ester liquids in terms of their fire safety (high flash and fire points) and environmental characteristics, judging from their biodegradability, their low CO2 footprint (only valid for natural ester) and their beneficial interactions with solid insulation, etc. One of the main reasons is that the water adsorption and absorption characteristics of these liquids are excellent and very different compared to mineral oil. The today’s discussion about climate change and global warming is an additional driver for using natural ester. Another advantage is that transformers filled with biological insulating liquids can operate with an overload of up to 150%. This is advantageous in the case of volatile energy generation from wind and solar power and in the supply of electrical energy for electromobility. Liquid inside electrical equipment is the lifeblood that serves both as a dielectric and a cooling medium. Some properties of these liquids differ from mineral oil, which had to be considered in the transformer design. The dielectric liquid is always in direct contact with transformer materials; therefore, the interaction should be very well understood, especially when retrofilling an existing mineral oil filled device. There are several natural ester fluids derived from various seeds and fruits on the market, and their properties may differ more or less. In the book, the most important properties of the different biological insulating fluids and mineral oil are compared. Ester fluids have already found their way into various standards. The condition of the device can be verified very well from the contents of the insulating liquids. For analysis and testing, the same equipment and devices that are commonly used for mineral oil are used for ester liquid. The chemical and physical behaviors of ester fluids compared to mineral oil are different. This must always be considered when interpreting test results stemming from ester fluids. The book is a guideline for students, original equipment manufacturers, users, laboratories and authorities in the use of biological insulating liquids.
Author(s): Ernst Peter Pagger, Norasage Pattanadech, Frank Uhlig, Michael Muhr
Publisher: Springer
Year: 2023
Language: English
Pages: 328
City: Cham
Preface
Contents
1 Introduction
References
2 Dielectric Insulating Liquids
2.1 Mineral Oil
2.2 Bio-based Hydrocarbon Insulating Liquid
2.3 Ester Liquids
2.3.1 Synthetic Ester
2.3.2 Natural Ester (Vegetable Oil)
2.4 Silicon Oil
2.5 Iodine Number of Different Insulating Liquids
2.6 Content of Halogens of Different Insulating Liquids
2.7 Additives
2.7.1 Antioxidants
2.7.2 Pour Point Depressant
2.7.3 Passivator
References
3 Production Process of Dielectric Liquids
3.1 Mineral Oil
3.2 Ester Liquids
3.2.1 Synthetic Ester
3.2.2 Biological Insulating Liquids (Natural Esters)
3.2.3 Methyl Ester Liquids Stemming from Vegetable Oils
3.3 Bio-based Hydrocarbon Liquids
3.4 Silicone Oil
References
4 Properties of New Insulating Liquids and Main Differences
4.1 Chemical Properties
4.1.1 Neutralization Number
4.1.2 Aging Stability
4.1.3 Gassing Tendency
4.1.4 Gas Solubility
4.2 Physical Properties
4.2.1 Density
4.2.2 Viscosity
4.2.3 Interfacial–Surface Tension
4.2.4 Water Absorptive Capacity
4.2.5 Miscibility of Alternative Insulating Liquids
4.3 Thermal Properties
4.3.1 Flash Point—Test Method
4.3.2 Fire Point—Test Method
4.3.3 Heating Value—Test Method
4.3.4 Specific Heat Capacity and Thermal Conductivity
4.3.5 Decomposition Products in Technical Use
4.3.6 Pour Point
4.4 Electrical Properties
4.4.1 Dielectric Constant and Refractivity
4.4.2 Breakdown Voltage
4.4.3 Dielectric Breakdown Voltage Under Impulse Condition
4.4.4 Dielectric Dissipation and Power Factor
4.4.5 Volume Resistivity
4.4.6 Partial Discharge Behavior
4.4.7 Electrostatic Charging Tendency (ECT)
4.5 Environmental Properties
4.5.1 Biological Properties
4.5.2 Ecological Properties
4.6 Interaction with Transformer Materials
4.6.1 Corrosive Sulfur Contamination
References
5 Application of New Insulating Liquid in High Voltage Equipment
5.1 General
5.2 Interaction with Other Transformer Materials
5.2.1 Interaction Between Solid and Liquid Insulation
5.2.2 Electrical Charging Tendency
5.3 Degradation Mechanism of Insulation Systems
5.4 Transformer Design
5.4.1 Risk Analysis
5.4.2 Temperature Monitoring
5.4.3 Biological Liquids—Accompanied Tests
5.4.4 Oxidation Stability
5.4.5 Accelerated Aging
5.4.6 Transport of Lost Energy (Heat Transfer)
5.4.7 Cold Temperature Behavior
5.4.8 Electrical Stress
5.4.9 Switching Technology
5.4.10 Dielectric Response Measurement
5.4.11 Sustainable Peak Load Transformers
5.5 Condition Monitoring and Diagnosis
5.5.1 Measurement Accuracy
5.5.2 Insulting Liquid Sampling
5.5.3 Color
5.5.4 Acid Number
5.5.5 Interfacial Tension
5.5.6 Pour Point
5.5.7 Viscosity
5.5.8 Water Content
5.5.9 Dissipation Factor
5.5.10 Volume Resistivity
5.5.11 Dissolved Gas Analyzes
5.5.12 Degree of Polymerization
5.5.13 Vibro-Acoustic Measurement
5.6 Passivators
5.7 Transformer Dielectric Liquid Regeneration
5.7.1 Reconditioning, Regeneration-Reclamation Process
5.8 Economic and Ecological Consideration
References
6 Advanced Research in the Field of Biological Insulting Liquids
6.1 Corrosion Caused by the Insulating Liquid (Corrosive Sulfur)
6.1.1 Sample Treatment with Air and Nitrogen
6.1.2 Sample Treatment with Sulfur Compounds
6.1.3 Degradation of Dibenzyl Disulfide (DBDS) Through Thermal Treatment
6.2 Interaction with the Solid Insulation (Paper) During an Aging Test
6.2.1 Furans Production Due to Aging
6.2.2 Furans Transport and Distribution Due to Aging
6.2.3 Change of Total Acid Number Due to Aging
6.2.4 Modifications in IR Spectrum Due to Aging Test
6.2.5 Change of Degree of Polymerization Due to Aging Test
6.2.6 Change of Breakdown Voltage Due to Aging Test
6.2.7 Change in Interfacial Tension Due to the Aging Test
6.2.8 Change in Viscosity Due to the Aging Test
6.3 Moisture Transport Between Insulating Liquid and Solid Insulation
6.3.1 Impregnation of the Solid Insulation
6.3.2 Preparing and Treatment of Samples After Impregnation for Moisture Transport
6.3.3 Results of Moisture Tests
6.4 Vibration and Noise
6.5 The Effect of Nanoparticles in Biological Insulating Liquids
6.5.1 Effects on AC Breakdown and Resistivity
6.5.2 Effects on Partial Discharge Characteristics
6.6 Dielectric Behavior of the Liquid Board Insulation Under Direct Voltage Stress
6.6.1 Electrical Conductivity in Liquid Immersed Cellulose Insulation System
6.6.2 Measurement of Electrical Conductivity
6.7 Operation of Equipment with Biological Insulating Liquids
6.7.1 Sustainable Peak Load Transformer
6.8 Examination of Electrically Stressed Insulating Liquids
6.8.1 Streamer Propagation in Case of Lightning Impulse
6.8.2 DGA from Switching and Lightning Impulse Test
6.8.3 AC Breakdown Tests with Palm Oil
6.8.4 Electrical Tests of Natural Ester Impregnated Pressboards
6.8.5 Breakdown Voltage Tests Under Cold Condition
6.8.6 Dissolved Gas Analyzes of Electrical Fault Simulation of Natural Ester Insulating Liquids
6.9 Comparing the Dielectric Behavior of Different Insulating Liquids in Solid Insulation
6.9.1 DC Conductivity of Solid Impregnated with Ester Fluids
6.10 Retrofill of Mineral Oil Filled Equipment with Biological Insulating Liquids
6.10.1 Transformer Selection for Retrofilling
6.11 Advantages of Biological Insulating Liquids
References
7 Standardization
References
8 Conclusion
8.1 Advantages When Using Biological Insulating Liquids (Summary)
8.2 Disadvantages When Using Biological Insulating Liquids (Summary)
8.3 Comparison of Applicability Performance of Different Insulating Liquids
