Current transformer remanence measurement system and method

Abstract

The invention discloses current transformer remanence measurement system and method. An upper computer receives current transformer data signals transmitted by a data unit. Related data processing is performed to calculate remanence coefficient. Operation states of an operating unit are automatically judged during measurement, and on and off of a relay are controlled. When the primary side of a current transformer is open, the secondary side is sequentially subjected to positive charging, discharging and revere charging until the current transformer is saturated. Flux variations in positive charging process, discharging process and revere charging process are obtained by calculation. The three flux variations are then calculated to obtain accurate remanence coefficient. Therefore, errors in remanence coefficient measurement caused when initial core flux of the current transformer is not zero are eliminated, accuracy in remanence coefficient measurement for the current transformer is increased, and fairness in electric energy measurement and trade settlement for the current transformer is guaranteed. The current transformer remanence measurement system and method have promising application prospect.

Description

technical field [0001] The invention relates to a current transformer residual magnetism measurement system and a measurement method, belonging to the technical field of electric energy parameter measurement. Background technique [0002] The DC residual magnetism in the current transformer will affect the error of the transformer, thereby affecting the measurement and protection performance. The manufacturer can only ensure that the current transformer has no residual magnetism before leaving the factory, and the resulting error influence is limited within a qualified range. If the current signal is taken from a current transformer that is seriously affected by DC residual magnetism, it will lead to an increase in the error during actual operation. After the current transformer produces residual magnetism, it will have a significant impact on the measurement characteristics, and the error will increase by more than double the normal condition, or even serious. Out of tolera...

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Problems solved by technology

[0005] There are deficiencies: the AC method does not take into account the fact that the initial magnetic flux of the current transformer is not zero; the value of the DC resistance of the secondary winding cannot be directly obtained during the test, and the test process is cumbersome; if the inductance of the secondary winding coil is large , the excitation voltage required to reach saturation will be very high, which will have a certain impact on the difficulty of measurement and safe operation

[0008] There are deficiencies: the first DC method does not take into account the fact that the initial magnetic flux of the transformer is not zero; if the inductance of the secondary winding coil is small, the charging process is very short, which is not conducive to the accurate collection of current and voltage data

[0011] There are deficiencies: the fact that the initial magnetic flux of the current transformer is not zero is not considered; the measurement process is cumbersome and the operation is complicated

[0014] There are deficiencies: the capacitance discharge method does not take into account the fact that the initial magnetic flux of the transformer is not zero; the measurement process is cumbersome and the operation is complicated

[0015] Areas for improvement: by figure 1 It can be known from the test curve of the traditional method that when the initial magnetic flux of the current transformer is not zero, φs measurement=φs-φ(0), similarly φr measurement=φr-φ(0), when calculating the remanence coefficient, Kr=φr measurement / φs measurement=(φr-φ(0)) / (φs-φ(0)), so the larger the φ(0), the greater the error of the remanence coefficient Kr. The above four methods, due to Neglecting the fact that the initial magnetic flux of the current transformer is not zero, there is an error in measuring the remanence coefficient, so in the new measurement method, it is necessary to consider the situation that the initial magnetic flux of the current transformer is not zero

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