This paper analyzes the general process of power flow transferring and divides it into four parts: 1) the process of first phase selection after fault occurs; 2) the process of selective action at the first time; 3) t...
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This paper analyzes the general process of power flow transferring and divides it into four parts: 1) the process of first phase selection after fault occurs; 2) the process of selective action at the first time; 3) the process of second phase selection and status confirmation; 4) the process after status confirmation. It points out that the issue of asymmetrical flow transferring is a critical process which must be put emphasis on. Then it proposes a method to identify this process, and discuss different solution methods.
Fault locator for power distribution system with neutral non-effectively grounded should locate phase-to-phase fault and single-phase-to-ground fault respectively. For phase-to-phase fault, the point can be located by...
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Fault locator for power distribution system with neutral non-effectively grounded should locate phase-to-phase fault and single-phase-to-ground fault respectively. For phase-to-phase fault, the point can be located by power-frequency impedance. However, for single-phase-to-ground fault with limited power-frequency current not more than load current, a novel fault location technology should be developed. The paper will present a practical single-phase-to-ground fault location based on fault generated traveling waves acquired from one phase current transducer and zero sequence current transducer at first. Then implementation of the novel fault locator is proposed including hardware design and software flowchart. At last field tests will be made to verify the feasibility of the fault locator.
This paper studies the fault current frequency spectrum characteristics of single phase ground fault in ungrounded distribution networks, and the fault location method based on it. Firstly, it analyzes the production ...
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This paper studies the fault current frequency spectrum characteristics of single phase ground fault in ungrounded distribution networks, and the fault location method based on it. Firstly, it analyzes the production mechanism of 2 nd major frequency component, and the relationship between the 2 nd major frequency component and series resonance frequency of the faulted line. Secondly, from the perspectives of lumped-parameter circuit, the relationship between 2 nd major frequency component and fault location is deduced. simulation cases are used to confirm the relationship. Last, the impact of load and initial fault phase angle on the 2 nd major frequency component are researched. simulation research proves the feasibility of the fault detection and location method based on frequency domain characteristics.
Aimed at power system large-scale blackouts, the paper firstly analyzes the existing problems of current protective relaying and emergency control in power grid. A novel system protection based on local information, p...
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Aimed at power system large-scale blackouts, the paper firstly analyzes the existing problems of current protective relaying and emergency control in power grid. A novel system protection based on local information, protecting both the equipment and power system secure is then proposed, which scheme consists of: identification of fault flow transferring identification, adaptive overload protection and active load shedding strategy. The processes and system structure are introduced, and the following research points are also discussed in this paper.
Smart substation is the base of smart grid and it is made up of a lot of IEDs (intelligent electric device). Synchronized phasor measurement unit (PMU) plays a very important role in the smart grid, and a great deal o...
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Smart substation is the base of smart grid and it is made up of a lot of IEDs (intelligent electric device). Synchronized phasor measurement unit (PMU) plays a very important role in the smart grid, and a great deal of PMUs have been installed in China. The requirement of PMU in the smart substation is different from traditional substation. This paper introduces that the PMU is suitable for smart substation, there are several details that need to be complemented in IEC 61850 standards, and the paper gives some suggestion to improve it.
Smart substation is the base of smart grid and it is made up of a lot of IEDs (intelligent electric device). Synchronized phasor measurement unit (PMU) plays a very important role in the smart grid, and a great deal o...
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This paper focuses on the modeling and analysis of the basic composition, characteristic and the interactions with grid for megawatt (MW)-level large scale grid-connected photovoltaic (PV) plants. For a MW-level PV pl...
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This paper focuses on the modeling and analysis of the basic composition, characteristic and the interactions with grid for megawatt (MW)-level large scale grid-connected photovoltaic (PV) plants. For a MW-level PV plant, numbers of inverters with relatively smaller capacity are employed to operated in parallel. When the irradiance on the large area of PV array is not equal, the output power verses the voltage of the PV array will have several peak values and affect the maximal power tracking. LCL filters are adopted for filtering the harmonics generated by inverters, but due to its inherent resonance character, additional damping strategy is required. The power quantity of harmonics and voltage fluctuation may occur when one MW-level PV plant is connected to grid. For these characteristics, with the modeling and simulation of a real MW-level PV plant, this paper proposed and verified a novel method toward MPPT of large area PV arrays. The parallel running of inverters and grid voltage fluctuation are also simulated. Finally, the interaction with the grid voltage fluctuation is explored in detail.
The development of digital substation provides new opportunity for integrated protection. However, the realization of integrated protection is constrained by serial communication between process level and bay level. B...
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On the basis of analyzing the composition of losses in high-efficient high-voltage asynchronous motors, the approaches of increasing the efficiency of the motors is investigated in this paper. The approaches concern w...
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On the basis of analyzing the composition of losses in high-efficient high-voltage asynchronous motors, the approaches of increasing the efficiency of the motors is investigated in this paper. The approaches concern with the improvement of material, winding, fan, magnetic groove and so on. By taking the economy and efficiency into account synthetically, the design of the YKK series induction motors is carried on, and it is realized by software simulation.
Lightning is a major cause of power interruptions in power transmission *** the Leader Progression Model is an advanced method to evaluate the shielding failure probability of transmission *** the surface electric fie...
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Lightning is a major cause of power interruptions in power transmission *** the Leader Progression Model is an advanced method to evaluate the shielding failure probability of transmission *** the surface electric field on phase conductors and ground wires precisely is important, because the surface electric field has great effect on the upward leader *** this paper, the influence of lightning current and some other factors on surface electric field were analyzed.
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