The working principle of zero line current transformer is the same as that of ordinary current transformer used by people, but its accuracy and error requirements are particularly high, and its measurement error is no more than 1%, which is not sold in the general electrical market. This is a means for the State Grid to monitor large and medium-sized enterprises and power users in real time in order to adapt to the smart grid and intelligent terminal equipment.
Due to the large load of large and medium-sized power users, the "zero line current transformer" is installed in the zero line busbar in the low-voltage distribution panel to detect the current of three-phase load flowing through the zero line, and then the collected current signal is sent to the special electric energy metering chip for data analysis and statistics. At the same time, the voltage signal is also sent to the electric energy metering chip. The data is processed by the microprocessor and fed back to the server of the power supply company in time by carrier communication. The following is the working principle structure diagram of intelligent anti-theft and metering of a power supply company.
The intelligent metering device adopts microprocessor and chip specially used for electric energy metering. It has the characteristics of perfect function and high measurement accuracy. For single-phase 220V power users, the current intelligent watt hour meter has been installed with "zero line current transformer" in its internal structure. In order to improve the technical protection ability of the intelligent electric energy meter, it can detect the current in the zero line loop of the electric energy meter when the incoming and outgoing phase lines of the power supply are short circuited. Moreover, the State Grid clearly puts forward in the requirements of technical specifications that all smart meters must be equipped with the functions of zero line current transformer measurement and recording. See the figure below
In Electrotechnics, it is pointed out that for single-phase load (i.e. phase line and zero line), the incoming phase line current is consistent with the outgoing zero line current. According to this principle, a current transformer (as shown in Figure 2 above) can be connected in series in the zero line circuit of intelligent watt hour meter for current sampling, and then sent to the microprocessor for data comparison and analysis, By comparing the current unbalance of phase line and zero line, the service state or working condition of intelligent watt hour meter can be judged, and the load switch in the watt hour meter can be tripped remotely if necessary.
Do not underestimate the role of this zero line current transformer. In the current intelligent watt hour meter, through the self detection of the watt hour meter, if there is a serious imbalance between the phase line and zero line current, and through the preset settings inside the watt hour meter, you can judge whether the single-phase user uses electricity illegally, and generate an alarm signal to prompt the user or automatically control to stop the power supply inside the watt hour meter. The above is the working principle and function of zero line current transformer.
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