A cvt capacitance online monitoring method based on cvt secondary voltage monitoring

Abstract

The invention discloses a CVT capacitor online monitoring method based on CVT secondary voltage monitoring, and the method comprises the steps: S10, carrying out the parallel reading of at least one CVT secondary voltage value and a change speed through a plant station monitoring system, and setting a reference voltage; S20, carrying out the statistics of the duration time of all CVT secondary voltage changes, carrying out the filtering of the secondary voltages of all CVTs, and switching to step S30 if the secondary voltage change speed of one CVT is greater than a set change speed; S30, calculating the difference between the CVT secondary voltage value and the reference voltage: judging that the secondary voltage of the CVT is abnormal if the difference is greater than or equal to a first voltage threshold value or the duration time exceeds the set time, and switching to step S40; S40, judging whether the difference between the CVT secondary voltage value and the reference voltage is located between the first voltage threshold value and a second voltage threshold value nor not: judging the capacitor breakdown of the CVT if the difference is located between the first voltage threshold value and the second voltage threshold value. Through the CVT secondary voltage, the method can accurately judge the operation condition of a CVT capacitor, carries out deep processing through employing the data of the plant station monitoring system, does not need to add equipment, and improves the reliability.

Description

technical field [0001] The invention relates to the technical field of electric power on-line detection, in particular to an on-line monitoring method of CVT capacitance based on CVT secondary voltage monitoring. Background technique [0002] The existing pre-test inspection cannot find the capacitive breakdown defect of the capacitor voltage transformer (abbreviated as CVT in English): the current pre-test regulations have no requirements for the transformation ratio error and angle difference test, while the "National Metrology Verification Regulations of the People's Republic of China ——Power Transformer” requires that the reference error of the voltage transformer be measured every four years, but the bus CVT is not connected to the measurement, so the error test project has not been carried out before the bus CVT. [0003] It is difficult to carry out the error test of CVT, which requires corresponding qualifications, and the test equipment is relatively large, and the ...

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Problems solved by technology

[0002] The existing pre-test inspection cannot find the capacitive breakdown defect of the capacitor voltage transformer (abbreviated as CVT in English): the current pre-test regulations have no requirements for the transformation ratio error and angle difference test, while the "National Metrology Verification Regulations of the People's Republic of China ——Power Transformer requires that the reference error of the voltage transformer be measured every four years, but the bus CVT is not connected to the measurement, so the error test project has not been carried out before the bus CVT

Therefore, according to the existing pre-test procedures for capacitance and dielectric loss requirements, it is impossible to detect the problem of excessive ratio error caused by capacitance breakdown

However, the existing CVT online monitoring devices, such as the "CVT online monitoring system" with application number 201110003819. Hidden dangers such as capacitor breakdown, and capacitor breakdown will lead to unqualified CVT ratio error, resulting in measurement data errors

[0005] The accuracy of the existing dielectric loss tester for measuring capacitance and dielectric loss is generally 1% or 0.5%, and it is impossible to test the transformation ratio error with an accuracy of 0.5%.

For example, multiple CVT capacitive elements in a 500kV substation had breakdown, but the results were within the acceptable range during the pre-test. Therefore, the existing online monitoring device and pre-test inspection for power failure could not find the breakdown of CVT capacitors. However, due to the large capacitance of the CVT, the ratio error test has higher requirements on the capacity of the instrument, and it is difficult to carry out the ratio error test

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