Polymer Insulation for Superconductive Application

With the research and development of high temperature superconducting technology, superconducting insulating materials under liquid helium and nitrogen temperature have been gradually taken seriously. Considering the unique operating environment, epoxy resin and PI face the challenge of low temperature. Electrical tree is one of the aging failure phenomena occurring in solid dielectrics. These imperfections could cause the field concentration with the application of high voltage, which results in partial discharges (PD). PD testing is an important quality check for the insulation of HTS cable. This chapter presents a study aimed at clarifying the influence of low temperature, pulse frequency and pulse duration on the electrical tree characteristics in epoxy resin, as well as PD characterization of PI film in LN2. The results show that the number of discharges and the discharge quantity in PI films increase with the increasing of the applied voltage and the defect size. The PD inception voltage decreases when the void defect diameter in PI enlarged and it is higher in LN2 than that at room temperature.

Oil and Paper Insulation for DC Converter Transformer

Transformer oil and oil-impregnated paper, serve as the essential parts of converter transformer, suffering various electric fields. The accumulation of surface charge on the paper would lead to flashover. When the power flow of the HVDC system is reversed, the charge field will easily lead to discharge. Direct-fluorination is a method which could affect the material property without alternating the bulk property. Besides, a new type of nano-modified transformer oil is a method to improve properties. This chapter presents a study of the effect of fluorination on surface charge behavior, the effect of polarity reversal voltages on interface charge behavior and the effect of Boron nitride (BN) nanoparticles on the high thermal conductivity of transformer oil. Results show that fluorination had an influence on the chemical property of the paper and BN nanoparticles has improvements in heat transfer process. In the polarity reversal test, the dissipation rate becomes smaller as the reversal time gets longer.

HVDC Cable Accessory Insulation

HVDC cables have shown great advantages for long-distance, high-power underground or underwater transmission. The performance of cable accessories, as an essential part of the HVDC networks, is a great concern to the reliability of the system. However, Cable accessories made of ethylene-propylene-diene terpolymer (EPDM), which are considered to be the weakest part of HVDC cable system, have to face the problem of space charge accumulation. Nanosized particles have been proved as an effective method to suppress the space charge accumulation in dielectric composites. This chapter presents a study aimed at clarifying the effect of nanoparticles and direct-fluorination on space charge behaviors for HVDC cable accessory insulation. Obtained results show that the dielectric properties and DC conduction for HVDC cable accessory insulation are significantly influenced and the interface charge density can be effectively suppressed by doped fillers.

SiR Insulation for Outdoor Insulator

Silicone rubber (SiR) insulators were employed in power system due to its light weight, high electrical strength and excellent contamination performance. Much attention has been paid on the accurate evaluation of the insulator hydrophobicity. In this chapter, the acoustic characteristics of surface discharge were investigated to evaluate the hydrophobic properties of SiR insulator at different ageing degrees. The obtained results indicate that the acoustic characteristic of discharge is sensitive to the hydrophobic properties in the laboratory tests, which can be applied as a non-contact method for hydrophobicity evaluation of SiR insulator. Besides, the surface charge behaviors considering the hydrophobic properties of SiR insulator were discussed. The droplet experiment was carried out to investigate the maximum value, cumulative charge and energy eigenvector of discharge current. Finally, considering the strong airflow for SiR insulators employed in high-speed railway, the hydrophobic properties and corona discharge properties were investigated in this chapter.

Epoxy Resin for GIS Disc-Type Insulator

Epoxy resin is widely used in disc-type spacers of gas insulated switchgear (GIS), such as disc-type insulator, post insulator and so on. While surface flashover related to the existence of surface charge and tracking failure often occur on the spacer, which is a great threat to the application of GIS and the safety of entire grid. This chapter presents a study aimed at clarifying surface charge behaviors, surface flashover and tracking resistance of EX and EX/ Al2O3 composites. It is indicated that surface charge behaviors of EX charged by AC and positive pulse voltage are totally different from that charged by AC and negative pulse. And it can be concluded that the characteristics of surface charge behaviors are changed by adding nanoparticles. With increasing the filler content from 0 to 5 wt%, the relative discharge intensity, weight loss and pattern area of the specimens decrease, the last time of the tracking process increases.

Polypropylene Insulation for Cables

Cable insulation made of polypropylene is of great prospective since it is recyclable to some degree. There are many problem the cable insulation need to deal with in HV system. The tree properties of polypropylene with repetitive pulse voltage at low temperature is discussed firstly. At different temperature, the pattern and length of electrical tree are shown in our results. This research analyzed the influence of temperature on the grow speed of electrical tree. The effects of mechanical stretching on space charge behaviors of pp/poe blend is also included in this chapter. This part presents the influence of stretching rate on electric properties. Finally, this chapter also provided some research of PP/POE/ZnO nanocomposites for HVDC cables. This part includes the space charge behavior analysis considering nano fillers.

Polyimide Film for Generator Winding

Polyimide film is widely used in different areas due to its brilliant chemical and electrical properties. This chapter discusses effect of direct fluorination on surface charge and surface partial discharge of polyimide films. The influences of different fluorination time and voltage frequency are studied. The trap properties of polyimide film are analyzed. It is clear that the fluorination has changed the micro structure of the sample so that the trap property and the dissipation time are different. Further research focuses on the effects of water absorption on surface charge and dielectric breakdown of nanocomposite. The polyimide/Al2O3 film is selected as sample and the relation between water absorption and surface charge and breakdown voltage is discussed.

Polymer Insulation in Nuclear Power Station

Nuclear power is giving an increasing share of power resource in China since it produces much less air pollution compared with power plant consuming fossil fuel. The power system insulation in nuclear power plant takes the risk of radiation. This chapter provides some basic research on the effect of radiation on different materials. The gamma-ray irradiation inhibiting surface charge accumulation on polyethylene is shown in this chapter. The quantity of surface charge is relative with the direction and the magnitude of voltage. Another interesting study presents the effects of atmospheric pressure on tracking failure of gamma-ray irradiated polymer insulating materials. Finally this chapter puts forward a research revealing that the Magnetic could influence the field tracking failure of gamma-ray irradiated polybutylene polymers.

High Thermal Conductivity Polymer Insulation

In this chapter, a range of silicone rubber (SiR), polypropylene (PP) and polyethylene (PE) based composites filled with micro or nano sized boron nitride (BN) particles at different loadings were manufactured to investigate effects of thermal conductivity. The study of SiR attempts to clarify whether the addition of boron nitride (BN) particles can improve the resistance to tracking and erosion of SiR by increasing its thermal conductivity. For PP, in addition to measuring thermal conductivity of various samples, thermal dissipation was also discussed to analyze the relationship between them. Meanwhile, in order to evaluate tracking failure (a kind of surface dielectric breakdown) resistance of the manufactured samples, time to failure, erosion depth and weight loss of the test samples were measured through tracking test. As for PE, Thermal conductivity and relative permittivity were measured to characterize the basic properties of various samples. Obtained results show that several properties of the filled specimens are obviously improved.

Introduction for Topics in Polymer Insulation

Polymer dielectrics have been used as insulation for long. Many Properties have drawn researches' attention in different occasions. Generally, these topics are usually interdisciplinary while requiring necessary professional knowledge of electrical system. Potential readers may find some ideas and methods mentioned in this book hard to understand if they are not quite into the modern high voltage power system. People may want to learn some basic principles and concepts in the area of polymer insulation. To this end, this chapter provides the introduction of methods and concepts which concern with the content of this book. It is hard to be all-sided, but the introduction is sure to be helpful to understand these topics better.