A method for estimating the frequency of voltage sags caused by transformer commissioning
A voltage sag, transformer technology, used in transformer testing, measuring current/voltage, instruments, etc.
Active Publication Date: 2021-01-29
SICHUAN UNIV
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Problems solved by technology
[0026] The technical problem to be solved by the present invention is to provide a method for estimating the frequency of voltage sags caused by transformer operation, objectively estimate the remanence of the transformer and the closing angle to calculate the voltage sags, and use the proposed method of counting the frequency of subsections to solve the problem of The overestimation problem of this kind of non-rectangular sag, and finally get the estimation result of grid voltage sag frequency that is more realistic
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Embodiment Construction
[0092] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.
[0093] The invention includes the steps of establishing the magnetization curve of the transformer, determining the probability distribution of the closing angle and residual magnetism, calculating the voltage sag caused by the no-load closing of the transformer, and evaluating the frequency of the voltage sag caused by the transformer being put into operation, wherein each large The steps and their sub-steps are elaborated as follows:
[0094] First, establish the magnetization curve of the transformer
[0095] Transformer excitation inrush current can be calculated by core flux and magnetization curve Φ-i. The magnetization curve of a transformer is a highly nonlinear curve reflecting the magnetization characteristics of the iron core, which cannot be directly measured. Although a more accurate transformer magnetization curve can b...
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The invention discloses a method for estimating the frequency of voltage sags caused by transformer commissioning, which includes establishing the magnetization curve of the transformer, determining the probability distribution of the switching angle and residual magnetism, calculating the voltage sag caused by the no-load switching of the transformer, and evaluating the voltage sag caused by the transformer switching on and off. The frequency of voltage sags caused by this operation; the present invention uses the principle of maximum entropy, and utilizes the relationship between the transformer closing angle, residual magnetism and the maximum instantaneous magnetic flux to objectively and accurately evaluate the probability distribution of transformer residual magnetism, and overcomes the traditional method The unreliability of residual magnetism is estimated according to experience; the non-rectangular sag caused by the transformer is used for equivalent frequency statistics by using the multi-segment amplitude-duration function, which avoids the overestimation of this type of sag by traditional frequency statistical methods.
Description
technical field [0001] The invention relates to the technical field of voltage sags, in particular to a method for estimating the frequency of voltage sags caused by transformer operation. Background technique [0002] The causes of voltage sag mainly include short circuit (including lightning strike) and switching of large-capacity equipment, such as transformer operation. In previous assessments of the frequency of voltage sags, regardless of factors such as the distribution of fault locations and the coordination of relay protection, the frequency of voltage sags caused by short circuits was only evaluated, and the voltage caused by transformer operation was usually ignored. Pause. Theoretical research and monitoring data show that a huge inrush current is generated when the transformer is switched on without load, and the voltage sag caused by this current to the busbars with a short distance cannot be ignored. [0003] Secondly, the operating principle of the three-ph...
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IPC IPC(8): G01R31/62G01R19/00
CPCG01R19/0053G01R31/62
Inventor 汪颖李顺祎肖先勇
Owner SICHUAN UNIV