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DC microgrid offers significant advantages such as control simplicity and less conversion stages for energy storage, renewables and electronic load integration. However, its implementation is highly restricted by the development of dc protection system. Especially, the series dc arc faults have been posing significant challenges due to low fault current level. This paper explores the impact of dc...
DC grids of system voltages above 20V demand different safety concepts compared to conventional AC grids. More elaborate protection devices have to be developed to detect not only high-power, but also low-power faults. The discrimination between faults and load variations can be supported by model-based machine learning methods. For this purpose, this contribution developes time-invariant and linearized...
With the development of microgrid technologies, the impacts brought by distributed generation (DG) on the distribution network protection has not been improved effectively. Therefore, this article analyzed the fault characteristics of IBDG (inverter-based distributed generations) and that of microgrid composed by IBDG; built the simulation model of IBDG with P-Q control and that of IBDG with U-F control,...
There is an increasing demand for more detailed and accurate modeling techniques for predicting transient response of power systems caused in particular by high impedance arcing faults (HIF). This is particularly so in relation to the design and development of improved equipment and new protection techniques. Accurate prediction of fault transients requires detailed and comprehensive representation...
This paper proposes a new method for line fault analysis of ungrounded distribution systems. The fault condition of a line fault is integrated into the nodal admittance matrix of the faulted line to be modeled. The zero-impedance branch is merged into adjacent impedance branches to be taken into account, and one of its terminal buses with zero neutral-to-ground voltage is chosen as a slave bus when...
This paper shows the influence of the load modeling in the behavior of voltage (V), current (I) and impedance (Z) measurements during pre-fault and fault steady states of power distribution systems. The test system is the 24.9 kV IEEE 34 nodes power distribution system, modeled by ATP software, considering load models as constant impedance, constant current, constant power and hybrid load composed...
A new electromagnetic loop with Voltage Class of 500kv and 220kv are constantly generated when 500kv power network is being constructed in China. Optimizing for the existing layering partition is of great significance to the safety and stably operation of the grid. The short circuit current calculation is crucial to the selection of grid's equipment and scheme for layering partition between electromagnetic...
Transformers are important electrical equipments in distribution network. Therefore, establishing the high-frequency model of them accurately is quite benefit for modeling and attenuation analysis of medium voltage power line carrier channel. The model of transformers under power frequency is well known, while their high-frequency model is quite different. This paper introduces two common high-frequency...
Complex fault diagnosis is one of the most important areas of power system analysis. Currently the power supply system is complicated, the causal relationship for or logic of general unstick quantitative which determined by the structure exists between the input and output in a Complex fault system. Therefore, the mapping one-to-one simple relationship does not exist between the fault and sign, which...
A deep research on the contact line (T)-negative feeder(F) short-circuit impedance is made in this paper on the basis of analyzing the advantages and disadvantages of all existing parallel AT power supply system fault location methods . Then, the simulation model of the all parallel AT traction power supply system is established and the characteristic of system impedance under T-F short-circuit condition...
In order to improve characteristics of pilot protection, a new pilot differential protection based on parameter identification is proposed. In this new approach, the transmission line is dealt as PI model. As we know, the simplified PI model can only match physical lines within limited frequency band, which is defined as suitable frequency band (SFB). In order to apply the new approach, it is important...
High impedance fault has always been difficult for distribution network fault identification due to its unobvious fault signature and difficult detection. This paper decomposed the transient signal in multi-scale by utilizing the good localization performance of the wavelet in both time domain and frequency domain, reconstructed the wavelet coefficients under each scale, took the wavelet reconstruction...
This paper investigates the fault behaviour of inverter-interfaced distributed generators in stand-alone networks. It is shown that the rapid transient response of the inverter control system allows its fault behaviour to be characterised by quasi steady-state equivalent fault models. The choice of inverter control strategy, control reference frame and the method of active current limiting dominate...
A concept named 'steady process in transient condition' is proposed for transmission line based on the transient expression of electromagnetic traveling wave. Considering the impact of distributed parameters and the characteristics of electro-magnetic wave, the transmission line model is built. Wave impedance factor is defined with line voltage fluctuation. The voltage equation is derived and the...
This article presents a range of possible values for the fault resistance in transmission power systems, considering six existing models for the arc resistance and a model for the grounding impedance of the towers. Resistance by possible additional objects in the path of the fault current was not considered. Known the short circuit level (without fault impedance), the fault resistance was calculated...
Double circuit lines, operated in parallel, have become popular in the Portuguese transmission network. When a new line is constructed between two substations, the towers are initially built to encompass two circuit lines even if only one bay is constructed at each substation line ends. The two circuits are operated in parallel having the advantage of postpone the cost of constructing new bays in...
Voltage sag is the major power quality problem, which could disrupt the operation of sensitive equipment. This paper presents the applications of instantaneous energy direction for voltage sag source detection. Simulations have been performed to provide the analysis for system with distributed generation units. The studies show that the presented method can effectively detect the location of the voltage...
This paper discusses the basic properties of thin-film inductors driven at high flux densities. We made inner-coil-type thin-film inductors, each with either a closed or an open magnetic circuit, and developed a technique for measuring the impedance of the inductors at high flux densities. We used this technique to reduce the multiple voltage reflections between amplifier and inductor. The impedance...
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