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Method for judging voltage sag reason

A technology of voltage sag and causes, applied in the electric power field, can solve the problems of large amount of calculation and limited application scope of supervision and judgment methods, and achieve the effect of simple calculation and accurate supervision and judgment.

Inactive Publication Date: 2011-05-25
NORTH CHINA ELECTRIC POWER UNIV (BAODING)
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  • Abstract
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Problems solved by technology

Therefore, the main disadvantage of the existing method for monitoring and judging the cause of voltage sags is that the amount of calculation is too large, the scope of application of the monitoring method is limited, and it is difficult to realize the monitoring and judgment of the actual data with a limited amount of data

Method used

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  • Method for judging voltage sag reason

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Embodiment Construction

[0029] figure 1 In this method, the three-phase voltages ua(t), ub(t), and uc(t) of the monitoring point are collected first, and the effective value of a cycle width centered on the point is calculated for each point of the sampling signal by using the point-by-point sliding method. Get the initial waveform uao(t), ubo(t), uco(t) of the effective value of the ABC three-phase voltage. Perform calculations on the beginning and end half cycles of the initial waveform of the effective value to form voltage effective value calculation waveforms uax(t), ubx(t), and ucx(t). Assuming the acquisition time of the three-phase voltage at the monitoring point is Ts, and the period of the voltage signal is T, the voltage RMS operation waveforms uax(t), ubx(t), and ucx(t) are calculated according to the following formula.

[0030]

[0031]

[0032]

[0033] Define the voltage sag amplitude as the minimum value of the voltage RMS waveform divided by the nominal voltage and multipli...

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Abstract

The invention relates to a method for judging voltage sag reason. The method comprises the following steps: calculating the active value initial waveform of each phase voltage by using a point-by-point sliding method according to three-phase voltage for actually measured public connection point, and calculating the voltage active value operation waveform by using the voltage active value initial waveform; selecting a phase with the minimum value of voltage sage scale in the three-phase voltage active value operation waveform, calculating to obtain the voltage active value pretreatment waveform sequence and an inverted order waveform sequence thereof; taking the two waveform sequences as an input for calculating waveform relative coefficients, calculating the waveform relative coefficients; and finally judging that the reason causing the voltage sag is one of line fault, transformer commissioning and induction motor start. The method for judging voltage sag reason is accurate and reliable in judgment, and simple in calculation, which facilitates the actual measurement execution.

Description

technical field [0001] The invention relates to a method capable of supervising and judging the causes of voltage sags in power distribution networks, which belongs to the technical field of electric power. Background technique [0002] With the rapid development of the economy, complex electronic devices have been widely used in various power consumption departments, and many of these devices are sensitive to short-term voltage changes. When events such as short-circuit faults, induction motor startup, lightning strikes, switch operations, switching of transformers and capacitor banks occur in the transmission and distribution system, voltage sags may be caused. The characteristics of voltage sag caused by different reasons are different, and the control measures taken are also different. Therefore, accurately distinguishing the cause of voltage sag is the premise of evaluating the regional system and determining the control measures, and is the basis for coordinating power...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01R19/02G01R19/165G01R31/00
Inventor 贾秀芳赵成勇龙文
Owner NORTH CHINA ELECTRIC POWER UNIV (BAODING)
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