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Transformer is one of the most important equipment in the power system, assuming the voltage conversion, distribution, transmission of electrical energy mandate in power network, which is an important prerequisite for safe and stable operation of power system. Once the transformer fault, it may lead to blackouts, and even the collapse of the power network, causing huge economic losses. From the point...
Cross-linked polyethylene (XLPE) insulation cable is the main type of cable in use now. Its main insulation is aging with the increasing of service years. Two methods are used to diagnose the condition of the cable insulation-polarization/depolarization current (PDC) and frequency domain spectroscopy (FDS). The PDC is a time domain method, while the FDS is frequency domain. In this paper, we put forward...
As cable insulation failure usually started with PD activity, a PD detection system based on pulse current was built to study the PD characteristics of typical defects in XLPE cable. To facilitate the test, the oil cup test terminal was used. Considering the installation procedure, three different kinds of insulation defects in cable accessory samples were made, which were knife incision defect, metal...
Cross-linked polyethylene (XLPE) insulation cable is the main type of cable in use now. Its main insulation is aging with the increasing of service years. This problem seriously affects the stability of the power system, particularly for the distribution cables. Therefore, the diagnosis of XLPE insulation cables has important social and economic significance. Polarization and depolarization current...
The inner temperature of power transformers is one of the major factors of the life of insulation life and the load operation mode in transformers. So it's of great significance to predict and calculate the inner temperature of transformers precisely in different loads and ambient temperature, which could be used to assess the surplus useful life and the safety performance of transformers. When the...
With the pace of construction of electrical grid, more districts are likely to be influenced by galloping of overhead transmission lines in winter. The galloping of overhead transmission lines may cause mechanical damages to metal fittings, insulators and transmission line towers. So it's of great significance to monitor the state and movement of overhead transmission lines. In transmission line galloping...
Studies discovered that Low temperature plasma (LTP) could promote wound healing. However, the detailed mechanisms in the cellular and molecular levels are still not fully understood. In this study, an atmospheric pressure discharge plasma jet in flowing argon by means of dielectric barrier discharge (DBD) was used to treat murine fibroblasts cultured in vitro, in order to explore the molecular mechanism...
Cross-linked polyethylene (XLPE) insulation cable is widely used in distribution power system, so it is important to reasonably estimate cable insulation status. Cable insulation is mainly affected by high temperature and water tree. Therefore, in this paper, we use PDC method to evaluate cable insulation, which is non-destructive due to its low voltage. In order to find out the relationship between...
The degradation of oil-paper caused by thermal aging seriously affects the lifetime of power equipment such as transformers. In order to investigate the relationship between partial discharge (PD) and degradation of oil-paper insulation, PD characteristics and trap parameters of the paper are measured. In this work, we fabricate oil-paper model with cavity discharge, and the adopted oil-immersed paper...
This paper presents a systematic discussion on the principal factors which influence the grain production through fuzzy clustering analysis method and multiple linear regression. Then, the proportion of all the factors are obtained though fuzzy comprehensive evaluation method, which provides a reliable theoretical basis to how to improve grain production.
In order to understand effects of oil thermal aged state on space charge behaviors in oil-paper insulation further, transformer oil with different aged states is prepared by accelerated thermal aging. What's more analysis on physical and chemical properties of oil is made. The samples are made of new kraft paper which is dried in vacuum and oil with different thermal aged states. The pulsed electro-acoustic...
Synthetic plastic materials were used in the new guardrail considering the shortcoming of the current highway guardrail such as high cost, easy to corrosion and so on. In addition the “sandwich” structure was used to enhance the crashworthiness of the new guardrail. A finite element simulation crash model of highway buses and semi-rigid guardrail was established in Hypermesh and Ls-dyna software....
This paper describes partial discharge (PD) location through electromagnetic (EM) waves in ultra-high frequency (UHF: 300MHz–3GHz) band leaked from the insulating spacers in a T-shaped branch of gas insulated switchgear (GIS). The propagation of EM waves in GIS and the leakage through spacers were simulated by using the finite difference time domain (FDTD) method. The time difference of arrival (TDOA)...
Reliability of large oil-immersed power transformers is attracting more and more attention by the power system, and a lot of new test methods are being under research. In this paper, the dielectric response for oil-immersed transformer insulation condition and ageing diagnosis is introduced; a 220 kV transformer was measured utilizing frequency domain spectroscopy in China. The tan delta-f curves...
Transformer oil-paper insulation system is continuously subjected to thermal stress which is a key factor inducing its deterioration. Dielectric response of oil-paper insulation in frequency domain is being gradually used by power utilities for assessing the condition of transformer oil-paper insulation system, and the Frequency Domain Spectroscopy (FDS) measurement is a promising method. It is important...
As well known, the secondary electron emission yield is one important factor for the flashover phenomena of solid materials under high electric field in vacuum. On the basis of the novel low melting temperature machinable glass ceramics for vacuum insulation system, which has excellent machinable performance and good electrical properties, different low SEE yield metal oxides including Cu2O and Cr...
La-doped BiFeO3 (BLFO) thin films have been deposited on Pt (111)/TiO2/SiO2/Si (100) substrates under different oxygen pressure of 5 mTorr - 50 mTorr by the pulsed-laser deposition (PLD). The effects of oxygen pressure on crystal structure and ferroelectric properties have been investigated. X-ray diffraction analysis shows that the BLFO thin films are of pure perovskite phase with tetragonal structure...
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