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The modeling of harmonic source based on harmonic measurement is put forward for the first time. Three-phase fundamental and harmonic models of the whole power system are built in the paper. Then, the power system harmonics penetration (PSHP) software package is developed on VC++ circumstance. Zhengzhou, Luoyang and Sanmengxia electric power system in Henan grid are studied, and the harmonics and...
Group-type transformer has poor ability withstand DC bias, which causes transformer local overheating, increases vibration, noise and other adverse reactions. The internal characteristics of group-type transformer DC bias are analyzed in this paper. Pointed out what it is increased with the increase of DC that harmonic of excitation current and frequency. With different DC bias current, the variation...
The computation of circulating currents between parallel conductors is a difficult problem in reactor and transformer design. A direct field-circuit coupling FEM model has been established to analyze the magnetic field of air core power reactor. And the circulating current losses has been calculated based on the magnetic field distribution.
This paper has summarized the history of the development of the state monitoring system of the power transformer and introduced the present situation in research, especially the multifold comparison on different methods to diagnose the trouble in transformer. This paper not only takes the comprehensive analysis on the extant online monitoring equipments, which is based on DGA, and methods of trouble...
Based on the dissolved gases analysis and grey relational theory, a fault diagnosis method for transformers is proposed. Fault diagnosis in transformers has several parameters such as the severity of fault and the kind of fault, a lot of typical fault samples are divided into several sets according to the fault type. The practical data are analyzed using grey relational analysis. The experiment showed...
Any failures in these equipments directly reduce network reliability and increase maintenance costs. Consequently, the preventive maintenance techniques are increasingly developed. In this regard, frequency response analysis is an appropriate method in order to diagnose any change which occurs in transformer physical construction. This contribution has been concentrated on fault diagnosis by use of...
1000kV/1000MVA UHV the scene of the transformer no-load test for the first time at home and abroad, in particular test voltage of 380V, Measuring mA current level, the corresponding test technology research is very difficult. In addition the transformer core remanence of the impact test results, effectively to demagnetizating UHV transformers is the key to the trial. In this study, using the method...
A power transformer operating in electric network is supplied by voltage source. When analyzing leakage flux and magnetic forces of the power transformer applied to windings, the field-circuit coupled 3D finite element method is needed because of the drawbacks of magnetic dipole model and 2D finite element method. The models were used for simulating and analyzing leakage flux and magnetic forces data...
The removal of a transformer in grid-connected PV systems can reduce size, weight and costs. When no transformer is used, a galvanic connection between the grid and PV panels exists and leakage current appears due to parasitic capacitance. In this paper, the principle of leakage current is analyzed from equivalent resonant circuit and an equation is derived to evaluate the current. It will be shown...
Acetylene always arises from the discharge faults of power transformers. A photoacoustic spectrometer was developed and it has been applied to the detection of acetylene using a properly designed photoacoustic cell on its first longitudinal mode. Experimental results show that the photoacoustic signal has a significant linear correlation with the gas content and the laser power under low gas content...
Cost minimization is one of the main goals in electric market so economic dispatch and load allocating, named as optimal power flow (OPF), are more interesting concerns. In this paper a Modified Genetic Algorithm (MGA) is presented for the solution of the OPF. The control variables are unit active power outputs, generator-bus voltages and discrete transformer-tap settings. To overcome the operating...
The mechanism of oil flow electrification in transformers was described in this paper. The mechanism of oil flow electrification in transformers could be understood from the effect of the oil flow's movement and the electromotive action of AC electric field. The electric polarity of oil flow and the insulating layer were mainly depended on the state of charged cations and anions in oil, while the...
Virtual Reality technology is new technology developed in recent years. Transformer overhaul of virtual reality simulation system is an important area of technology. In this paper, based on virtual reality simulation system for transformer overhaul and development process, this system development and design concept can also be applied to the circuit breaker, isolator and other electrical equipment.
Direct current through directly-grounded neutrals of nearby AC transformers may induce DC biases of transformers when high voltage direct current transmission (HVDC) system operates on ground return mode, thus producing negative impact on the AC system. This paper introduced the influence of DC bias to transformer and its research efforts. The suppression measures of DC bias were analyzed .
The operating experience of transformer in recent years show that oil-flow electrification have proved to be one of the crucial factors which impact the safe operation of large transformers. For the manufacturing process of extra high voltage transformer become more rigorous than the usual one, relatively, the operating conditions are more severe than before, therefore, effective measures should be...
In this paper, A transformer capacity and loss on-line detecting experimental system is presented. The on-line detecting methods used in this system are proposed based on the off-line detection research. Two components of the system, a data acquisition system and analysis software on PC, are designed and a simulated experiment platform is also set up. The on-line test of the capacity and loss of distribution...
Two experimental high temperature superconducting transformers has been designed and built using Bi2223 HTS tape. The transformers are unique in that the magnetic circuit is comprised of air and a silicon steel partial core. The first transformer failed during a full load endurance run and an investigation was carried out to determine the cause of the failure. The cause was believed to be from operating...
Details regarding performance can be obtained by detecting the important parameters of transformer. One of the important parameters of transformer is the capacity. The transformer load can be adjusted in time according to the real capacity. Off-line measures are mainly taken in power industry, however, these methods have many disadvantages. In this study, we proposed an on-line capacity detection...
As the power transformer has been to the direction of high voltage and large capacity. Therefore, the calculation of major insulation and longitudinal insulation has been played a more and more important role in transformer design. Use the simplified equivalent circuit as the calculated model. The calculation software for wave process of power transformer winding is developed with Matlab language...
Transformers are set underground and embedded in pit for a long time, so heat problem is very prominent. In this paper, the DGSR11-H-315/10 transformer was directly buried in pit, heat transfer models of embedding system (including embedding transformer, pit flow and soil medium) were established, and the numerical simulation was conducted for temperature and flow-field distribution. Comparison of...
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