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Aiming at the problem of transient saturation of P class current transformer (TA) in power system, this paper simulates the working condition of TA in 330/110kV short circuit system. The transient saturation characteristics of TA are discussed and demonstrated in the form of exploratory test at transient currents up to 48kA. For the application level of transient saturation, the maloperation of relay...
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...
At present, the electricity rate in China varies from plant to plant. This paper has presented a power-exchanging transaction model. Based on the assumption that the interest of individual plants will not be affected and the average on-grid electricity rate among the plants not be increased, and with the help of Pratt optimization, the model gives the solution which guarantees the minimum loss in...
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...
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...
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...
This paper proposes a novel ultra-high-speed directional protection scheme for EHV transmission lines using the wavelet transform. The wavelet transform technique extracts high-frequency transient components from two composite relaying signals, forward and backward traveling-waves, which are derived from the fault-induced voltage and current wave propagating along transmission lines and the wavelet...
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