Short-window power frequency component extraction algorithm used in transient saturation calculation of current transformer

A technology for current transformers and power frequency components is applied in the field of short-window power frequency component extraction algorithms, which can solve the problems of deviation of calculation results, difficulty in accurately measuring initial magnetic flux and saturation magnetic flux, and many samples.

Inactive Publication Date: 2014-04-02
XI AN JIAOTONG UNIV +1
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Problems solved by technology

The compensation method uses the excitation current to compensate the distorted secondary current to obtain the primary current. It is difficult to accurately measure the initial magnetic flux and saturation magnetic flux, which will affect the calculation results.
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  • Short-window power frequency component extraction algorithm used in transient saturation calculation of current transformer
  • Short-window power frequency component extraction algorithm used in transient saturation calculation of current transformer
  • Short-window power frequency component extraction algorithm used in transient saturation calculation of current transformer

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Embodiment Construction

[0055] The present invention will be described in further detail below in conjunction with the accompanying drawings and specific embodiments.

[0056] Such as figure 1 Shown is the test waveform of the transient saturation transfer characteristic of the current transformer. The sampling rate of the oscilloscope is 25kHz (500 points / cycle), and the data length of the unsaturated segment is greater than 5ms, so a 5ms (125 sampling points) data window is selected for calculation. The data in Table 1 are experimental data, which are compared with the calculated results as standard values.

[0057] Table 1 primary current parameters

[0058]

[0059] (1) Effective order determination and reasonable selection of sampling rate

[0060] In the first step, the upper limit of the order is selected to be 45 according to formula (3).

[0061] The second step is to construct the sample matrix and perform singular value decomposition. Each singular value takes a logarithmic value. F...

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Abstract

The invention provides a short-window power frequency component extraction algorithm used in transient saturation calculation of a current transformer. The algorithm comprises the following steps that 1. an effective order number is determined, and a sampling rate is calculated: a control system estimates an order number upper limit value Lmax according to an experience formula in the time sequence analysis, in addition, a sample matrix R is constructed according to the Lmax, the sample matrix R is subjected to SVD (singular value decomposition) to obtain a singular value Sigma i, the log koc of the singular value Sigma i is taken, and the control system judges the effective order number value p and selects the sampling rate used for calculation; 2. the fault current power frequency component is calculated: the control system forms each element of an augmented sample matrix according to a new sampling sequence xD after the frequency division, in addition, an augmented sample matrix equation and a feature equation are constructed, and the control system calculates the vibration amplitude Ai, the phase theta i, the attenuation factor alpha I and the frequency fi of each component. The algorithm provided by the invention has the advantages that non-saturation section data after transient saturation of the current transformer can be utilized in a shorter data window for fast extracting the amplitude value and the phase of the power frequency component in the fault current.

Description

technical field [0001] The invention belongs to the technical field of transient saturation calculation of a current transformer (TA), and in particular relates to a short-window power frequency component extraction algorithm used in the transient saturation calculation of a current transformer. Background technique [0002] The current transformer is an important component of the relay protection system, and its accurate transmission and transformation of the primary current is the first prerequisite for the correct operation of the relay protection. The P-level TA widely used in the power grid is only selected according to the maximum steady-state short-circuit current during configuration, and the transient saturation problem is not considered. The previous grid structure was simple, the short-circuit current was small, and the problem of TA transient saturation was not prominent. With the rapid growth of the grid scale, the short-circuit current increases sharply, and t...

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Application Information

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IPC IPC(8): G01R35/02
Inventor 郝治国王小立张保会任龙飞刘志远温靖华
Owner XI AN JIAOTONG UNIV
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