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This paper studies and evaluates the effect of current transformer (CT) distortion parameters on its performance using various secondary current calculation methods according to IEC 44–1 & 44–6 like: magnitude (ratio) error, peak instantaneous error, phase error and composite error. These parameters include: multiple short circuit level (Isc/IR), secondary burden value & type, DC component...
In traction power supply system of China High-speed Railway, the transient process of EMU has a great difference between the state of passing by Phase-separation with electric load and passing by Phase-separation without electric load. The overvoltage caused by switch in with arc in the process will influence the correct operation of the common protection device. Based on the theoretical analysis...
In order to solve the fault transient signal extracting and analysis problem in aircraft power system, Hilbert-Huang Transform (HHT) is used in this paper. The complicated signal can be decomposed into a finite Intrinsic Mode Functions (IMF) by the Empirical Mode Decomposition (EMD), which makes the instantaneous frequency meaningful. Thus, the fault transient signal can be analyzed by instantaneous...
This paper sets up a simulating model of single-phase transformer under DC bias in MATLAB. Using MATLAB software, the magnetization characteristic curves and exciting currents under no-load condition are simulated and analyzed. The result shows that the magnetization characteristic curves do not shift up, but they are no longer symmetrical under DC bias. They get saturate at one side of X axis. The...
Based on existing domestic and international standards and norms, this paper conducts a preliminary study on the technical requirements as proposed from the perspective of grid on microgrids during their grid-connecting, grid-connection operation and islanding processes. The basic principles and grid-connecting norm of microgrid grid-connection is proposed, and the requirements of the access point,...
Distance relay is the main protection of power transmission lines and make an important role in power system stabilization if it operates selective and instantaneous. In this paper, the trajectory of the fault impedance is determined. It is shown that in the end of the first zone or in the middle of the second zone, distance relay could not make a correct decision for operating if the fault occurs...
In this paper, a new method is introduced which is based on the application of adaptive neuro fuzzy method to investigate transformer inrush current. This algorithm uses the second harmonic and the dead angle methods joint to each other utilizes the neuro fuzzy technique. In this method, an inrush detector is defined as an output of neuro fuzzy system. An eligible advantage of this method is evaluation...
The ageing of insulation denotes physical and chemical changes, which takes place as a result of electrical stresses in the power system network. In the modern days, a large use of nonlinear devices has resulted into increased distortion in load voltages. The current drawn by all such devices contains harmonics. The losses as well as insulation are more in the equipment at harmonic frequencies than...
The stability of HVDC system is under the influence of the strength of AC system, which is reflected as the AC and DC short-circuit ratio(SCR) on the converter stations. In this paper, a simulation study is carried out on the sending end of a certain HVDC system that has been put into operation under different SCR, using PSCAD/EMTDC. The simulation indicates that with the reduction of SCR, the recovery...
A phase angle comparison method for detection of current-transformer (CT) saturation and stability against mis-operation on heavy external faults in numerical current differential relay is presented in this paper. The proposed directional criterion is based on comparison of line currents phase angle of two sides of the power transformer. Defined criterion can differentiate saturation condition from...
Different control strategies for shunt active power filter (APF) are reported in literature several of them have satisfactory response under normal operating conditions, but there is still some confusion regarding the preferable controller for the shunt APF under normal and fault conditions. This paper evaluates the performance of shunt active filter for two different control strategies namely Hysteresis...
This paper presents a methodology for steady-state and transient harmonic analysis in electrical networks, the methodology is applied to transformer harmonic analysis. The method is based on the use of dynamic harmonic domain (DHD) and companion circuit models. The dynamic harmonic domain is a natural approach for conducting dynamic and steady-state studies of the evolution of harmonics in electrical...
With increased emphasis on reducing carbon footprints, many countries are moving towards generating power from distributed generation (DG) that can harness energy from renewable resources such as wind and solar generation. This paper discusses the electrical power system analysis and modeling required as part of the design process for a new-build township that will integrate generation based on solar...
Today the use of digital IEDs for protection, monitoring and recording systems brings questions about the management and analysis of fault and swing records. Basic questions include: "what is the difference in between records captured from DFRs versus relays?", "do I need a DFR in my system, and why?", and "is my fault information good enough for complete fault and disturbance...
Increase of dispersed generation in medium-voltage-grids and lack of practical experience with new standards form dangerous impacts on current control- and protection functions that are part of substation automation systems. To overcome these problems a simulator proposed, that supports the development of new protection systems and provides practical training opportunities in terms of IEC 61850. Real...
This paper studies the effects of using compact fluorescent lamps (CFLs) on the power distribution system elements on both the generation and the consumption sides. Previously, we presented a comprehensive analysis of how the harmonic distortion is generated in the CFLs and how it affects the distribution system wave shape. Here we study the technical and practical issues of mass utilization of CFLs...
This paper is a theoretical study of the magnetizing current components. Three conditions were investigated: 1. Sinusoidal voltage supply. 2. Sinusoidal voltage with dc bias. 3. Sinusoidal voltage with sinusoidal bias. The magnetizing curve is approximated with the equation. The analysis leads to closed expressions that enable the quantitative evaluation of effects dependent on the core geometry and...
The used of non-linear loads nowadays in industrial system has increased accordance with the present technology. However, the used of non-linear loads supply more harmonic distortion into the distribution systems. Therefore, current transformer function as protection equipment in reducing the current that supplying to the loads. This paper aims to explore current transformer reaction with linear and...
In this paper, firstly, the principles of adaptive protection for feeder in traction power supply system are analyzed. Secondly, the feeder line's adaptive protection scheme is presented. Finally, the hardware and software of the device are designed. One CPU uses TMS320LF2407 as kernel realizing the protective functions. The other CPU uses ARM processor S3C4510B as kernel and focuses on the communication...
The high voltage variable frequency system has complicated structure and high power density. It comprises industrial frequency AC, DC and variable frequency AC. All of these bring new challenges to the system's protection and stability control. This paper considered the protection strategy in two aspects: device-level protection and system-level protection. Through improving the circuit structure...
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