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Self-adaptive system islanding refers to the separation of an interconnected power system into electrically isolated islands automatically based on the identification of unstable mode. A fast searching algorithm for self-adaptive power system islanding, which is called multilevel reduced graph partitioning (MLRGP) algorithm, is presented in this paper. The aim of this algorithm is that the generation...
Recent blackouts have fully presented the damage of the cascading overload trip. The basic reason for cascading overload trip is poor global superiority of the back-up protection and existing auto-mechanisms which only focus on action behavior of themselves to cut component, but don't consider the damage of power transferring and the change of network. This paper first illustrates the meaning of transmission...
Transformers are required to demonstrate the ability to withstand short circuit currents. Over currents due to short circuit can cause winding deformation. A novel method for monitoring the state of transformer windings by identifying parameter of leakage inductance of transformer windings is presented in this paper, using least square techniques based on the equivalent circuit equation of transformer...
This paper bring forward new algorithms that integrate on-line detecting winding deformation into transformer, which is based on Equivalent Circuit Equation (ECE) of transformer. Firstly, the protection algorithm based on ECE is presented, and the criterion functions are derived for single-phase and three-phase transformer. The leakage inductance is the key parameter in ECE, which is not available...
From the viewpoint of risk the power system security and reliability under the environment of electricity market were researched. Because in competitive electricity market the power generation companies, power grid companies and load service entities belong to different economic bodies respectively, so that in the system operation, planning and design the consideration of the factors impacting system...
Economics is the first goal pursued by all the participants in power market environment. The security and reliability of power system should be subordinate to this goal. The economic equivalent of security and reliability measure is based on the difference of the economic profits brought by the security and reliability measure and the cost needed by the implementation of the security and reliability...
With the application of APMU (angle & phase measurement unit) based on GPS (global position system) in power system, online system trajectory prediction that is of great significance to transient stability emergent control becomes feasible. Based on normal form (NF) analysis at the instant of removal of the fault, a predictive algorithm for complex exponential time series is proposed in this paper,...
This paper introduces a new concept for EHV transmission line protection, the boundary protection, which can instantly discriminate faults at any point of the protected line relying on only single-ended measurement of the fault induced transient information. Part I of the paper introduces the time-frequency spectrum characteristics of fault-induced transients. The spectrum analyses show that: (i)...
To avoid the adverse effect of current transform (CT) transient saturation, this paper studies a novel bus protection based on transient current traveling-waves. Firstly the paper presents the differential traveling-wave (DTW) for each phase of circuits connected to the protected bus. The DTW fault features are analyzed. Then in order to distinguish more sensitively between faults internal and external...
The application of ultra-high-speed protection based on traveling-waves or transient components suffers mal-operation in case of lightning strokes on transmission lines. This paper analyzes the spectra and traveling-wave waveforms of current transient components to find the differences in energy distribution and waveform. The characteristics are as follows: the signal energy of short-circuit faults...
The objective of this paper is to find ways to determine the splitting surface to calm down angles swing to prevent collapse of the whole system. First, generators of the disturbed power system is set in several groups according to the prediction of the critical unstable mode of electric power system in this paper. The hookup of electric power system is turned to non-directed graph with weighted nodes...
The mutual flux calculated from the equivalent circuit equation of the primary and second winding is equal during normal operation conditions, magnetizing inrush and external fault. It differs during an internal winding fault, ground fault and phase fault. A new transformer protection algorithm based on the equivalent circuit equation of the primary and secondary winding mutual flux is described in...
In the operation of distribution system, if the tap of transformer and capacitors regulators was frequently changed, these devices would be easily damaged. So it is necessary to lower the tap-changing and capacitors regulators times. The solution algorithm developed for this problem is based on a phase1-phase2 feasible directions approach. A new optimization algorithm, that can obtain the optimal...
Because in competitive electricity market the power generation companies, power grid companies and load service entities belong to different economic bodies respectively, so that in the system operation, planning and design the consideration of the factors impacting system security and reliability is obviously different from those in traditional power systems. The economic equivalent of security and...
With the application of APMU (angle & phase measurement unit) based on GPS (global position system) in power system, online system transient instability detection becomes feasible. It is of great significance to transient stability emergent control that out-of-step condition is as soon as possible detected. This paper is concerned with faster transient instability detection for online application...
Through analyzing the principle of micro-current sensor and the shortage of "zero-flux" micro-current sensor, a new on-line monitoring method of dielectric tangent of loss angle (tandelta) based on passive micro-current sensor technology is presented. This method can not only overcome difficulties existing in the manufacturing sensors of the high precision relative scale difference and the...
To minimize insecurity and instability of rapid developing power systems, the ultra-high-speed protection schemes are demanded. However, the application of the ultra-high-speed protection techniques suffers relatively low reliability and feasibility by its limitations such as lack of effective signal processing tools. The advent of the wavelet transform (WT) method, which possesses capabilities of...
A new approach is proposed in this paper to calculate the critical unstable trajectory of disturbed electric power system based on a non-time referenced variable. The critical unstable trajectory is obtained by calculating the unstable manifolds on CUEP through special linear and nonlinear transformation on a post-fault power system. The important thing is that there is no poly-value problem by the...
This paper describes a new algorithm of fast distance relay based on the conception of phaselets. The principle is proposed by means of directly comparing phase difference between the operating voltage phaselet and the polarizing phaselet on the basis of new phaselet equation of transmission line and new definition of operating voltage. Additionally, the exponential decaying DC component matches the...
This paper presents the discriminative criterions of the boundary protection for EHV transmission lines. The boundary protection relay consists of three parts, the start unit, the direction unit and the boundary unit. The fault discriminative criterions of the relay are based on the single-ended transient information extracted by the wavelet transform. The tests using EMTP simulations and recorded...
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