Analysis of the influence of miniature transformer on measurement error of electric energy meter

In practical applications, due to the influence of some factors, it will cause certain errors in the electric energy meter. Among them, the miniature transformer will also have a certain impact on the measurement accuracy of the electronic electric energy meter. In recent years, with the development of smart grids, the metering accuracy requirements of electric energy meters have become higher and higher. There are many factors that affect the measurement accuracy of electric energy meters, and the miniature current transformer used for current sampling is a very critical factor.

So do you know what factors will affect the measurement error of the electric energy meter? In general, the measurement error of the electric energy meter is mainly caused by the error of voltage sampling and current sampling. Voltage sampling generally uses high-precision resistor divider, and current sampling generally uses miniature transformers. Both voltage and current sampling can achieve a certain accuracy through calibration.

It should be noted that with the change of the phase angle, the angle difference of the miniature transformer will also change to a certain extent, and it is nonlinear, so it will affect the error of the electric energy meter under different phase angles. The voltage sampling of the resistor divider will not change with the change of the phase angle, so the measurement error of the electric energy meter is mainly caused by the angle difference of the transformer. Suppose the voltage and current of the electric energy meter are U1 and I1 respectively, and the power factor is cosφ; assuming that the sampling is ideal, the voltage and current sampling of the electric energy meter are respectively: U2=KuU1, I2=KiIi. Among them, KU is the voltage sampling coefficient, and KI is the current sampling coefficient.

Analyzed in conjunction with relevant data, when the power factor is 1.0, even a 0.2S-class electric energy meter, the angular difference of the miniature transformer is required to be more than 200 minutes, and the angular difference of the transformer is generally within 15 minutes. When the power factor is 1.0, the transformer has little effect on the error of the electric energy meter.

Especially with the decrease of the power factor, the angular difference of the miniature transformer has an increasing influence on the error of the electric energy meter. At the normal check point, when the power factor is 0.25L, the change of the angular difference of the transformer will affect the error of the electric energy meter. The influence of, that is, the requirements for the angular difference of the transformer are the most stringent.