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Construction of UHV power grid is the fundamental guarantee to the growing demands of electricity in the future. Six phase transmission lines can evidently improve power transmission density, and many countries pay attention to it. A new method of fault location and phase selection on six-phase transmission lines was analyzed in this paper. The six sequence variables method to analyze the electrical...
Voltage sag has became the most concerned about power quality problems. Voltage sag source detection for power quality fault detection, diagnosis and to ease the formulation of strategy is necessary. This paper proposes a new method about voltage sag disturbance source location based on real current component. The product of the RMS current and the power factor angle at the monitoring point is employed...
It is very desirable to achieve high accuracy in fault location due to the increasing demands of fast detection and clearance of fault of transmission line. Most fault location algorithms incorporated in the fault recorders are based on the lumped parameter single-ended circuit model. Therefore, their accuracy is not satisfactory in many scenarios. A new revising scheme which can improve the accuracy...
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...
Bayesian Networks is used to study and deal with the reasoning under uncertainty in the power system fault process. Data mining method can find useful information for decision-making from massive history data. Therefore, an Augmented Naive Bayesian power network fault diagnosis method based on data mining is proposed to diagnose faults in power network. The status information of protections and circuit...
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...
A novel wide area backup protection based on multi-agent technique for series compensated lines is proposed in this paper. The principle of conventional distance protection could be remained normally, and the operating procedure of relaying devices in adjacent substations would be coordinated by each agent within protected area. The simulation tests of practical series compensation project based on...
This paper presents modeling of the 500 kV transmission line located between Bang-Saphan 2 (BSP2) and Chom-Bung (CBG) substations, Thailand. The network is modeled based on the transient simulation program- PSCAD/EMTDC. The equivalent circuit of BSP2 and CBG is obtained from the actual parameters. The initial condition parameters are verified by PSS/E, an electrical simulation program. After the modeling...
Load model has great uncertainty characteristic due to the time-variation of load. As a consequent, it is essential to analyze the influence of load model on power system stability. The effect of load model structure and parameter on Yunnan power grid transient stability is researched in this paper. Simulation results indicate that load model has great influence on Yunnan power great transient stability...
The mechanism of Emergency DC Power Support (EDCPS) is analyzed based on a model in which two AC systems are connected by a HVDC Link. This model can be considered as an equivalent two-machine power system, and it is demonstrated that stepping up (or stepping down) DC power during the angle-swing-up (or angle-swing-back) course of the equivalent system can help absorb (or compensate) active power...
Rotor earth fault protection is used to detect earth faults in the excitation circuit of synchronous machines, ping pong type and injecting-step-voltage rotor earth fault protection are both used in Three Gorges Hydropower Plant. This article analyzes both the principle and application of the two types of protections, together with the operation on giant generating set, advantages and disadvantages...
A new fault isolation and restoration technique for distribution automation, which employs local Ethernet network, is presented. It can isolate all short circuit faults in the loop within 300ms and restore the supply of healthy sections in less than 1.2 seconds. A reliable fault location method for isolating the single phase to ground fault in the non-effectively earthed network, which makes use of...
A new on-line fault location method is proposed based on the voltage sag characteristics resulted by different faults in the power systems. Only the voltage sag measured at single end is used to locate the fault. For a given distribution system, construct a simulation model to obtain faulted section locating function and fault distance calculating function of the network. When a real short circuit...
The 100 Hz protection function in an HVDC system is a backup protection for the ac system. The misoperation of the 100 Hz protection has severe effect on the safe and stable operation of the power system. Based on the proposed sequence switching-function model of the HVDC converter, and combined with the short circuit calculation program for the ac system, a practical method of calculation and Identification...
The fault ride-through ability of doubly fed wind generators (DFIG) has got more and more attention. New grid codes for interconnection of wind turbines required that wind turbines remain connected to the grid and actively contribute to the system stability during and after grid faults. Uninterrupted excitation of DFIG can both avoid running over-speed of wind turbines during grid faults and accelerate...
Present single-phase reclosure in ultra-high-voltage (UHV) and extra-high-voltage (EHV) transmission lines normally using a dead reclosing time may aggravate severe damage to the system and equipments, for unsuccessful reclosure in permanent fault or insufficient transient fault. Thus, it is important to study on the single-phase permanent detection technique aiming to lower unsuccessful reclosing...
This paper proposes a new partition principle based on bus sequence voltage distribution characteristic for wide area protection system. The influence of short lines, multiple fault and high resistance ground faults are analyzed. Information from multiple points within wide area network is supervised by central station of protection system. Then, suspected faulty zone can be detected according to...
This paper presents an improved current differential protective principle. Marti model of the transmission line is applied in this principle, which place emphasis on solving frequency-dependent line parameters. The operating current expressions for an internal fault are also deduced in frequency domain. Finally, simulating comparison have been carried out between the proposed protective principle...
This paper analyses the advantages and disadvantages of fault line detection methods for neutral un-effectual grounded system at home and abroad, proposes a novel fault line detection algorithm based on morphological operator and rough set theory. Using rough set theory to amplify weak signal and morphological operator to identify the polarity of the fault zero sequence current's first wave, it can...
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 .
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