Three-phase four-wire electric energy metering device having null line missing detection function

Abstract

The invention relates to the technical field of electrical measurement and more particularly to a three-phase four-wire electric energy metering device having a null line missing detection function. The three-phase four-wire electric energy metering device comprises a three-phase four-wire energy metering processing circuit, a null line current sensor, a null line missing signal processing circuit, and a three-phase four-wire power supply circuit. The three-phase four-wire electric energy metering processing circuit samples a three-phase input voltage signal and a three-phase input current signal and calculates a grid parameter. The null line missing signal processing circuit samples the output signal of the null line current sensor and calculates the null line current of the three-phase four-wire power supply circuit. When the null line current of the three-phase four-wire power supply circuit is smaller than a set null line missing current threshold value, the null line missing signal processing circuit outputs a null line missing signal. Compared with the prior art, the three-phase four-wire electric energy metering device eliminates an influence of the installation of an null line current transformer on the measurement accuracy of the grid parameter of the three-phase four-wire energy metering device.

Description

technical field [0001] The invention relates to the technical field of electrical measurement, in particular to a three-phase four-wire electric energy metering device with the function of detecting missing neutral wires. Background technique [0002] In the existing three-phase four-wire system power supply system, a three-phase four-wire electric energy metering device is used to measure the electricity consumption used by power users. The three-phase voltage line terminal of the power supply system is connected to the neutral line terminal, and the three-phase current input terminal of the three-phase four-wire electric energy metering device is connected to the output terminal of the power current transformer for measuring the three-phase four-wire power supply system. The three-phase four-wire electric energy metering device measures the three-phase four-wire power supply system and calculates the effective value of the three-phase voltage, the effective value of the th...

AI Technical Summary

Problems solved by technology

[0003] Chinese patent CN100588977C "a zero-missing detection method and device for a three-phase circuit" provides a zero-missing detection circuit and a detection method for a three-phase four-wire smart electric energy meter, such as figure 1 As shown, including optocoupler, neutral current transformer and signal processing circuit, the circuit diagram when applying this patented technical solution to detect whether the three-phase four-wire electric energy metering device is missing the neutral line is as follows figure 2 As shown, the zero line current transformer is connected in series with the zero line current of the three-phase four-wire electric energy metering device, and the signal processing circuit determines whether the three-phase four-wire electric energy metering device has a missing zero line by detecting whether there is current on the zero line , a small signal voltage will be generated at the primary end of the neutral line current transformer, so that the zero line of the three-phase four-wire electric energy metering device will have a small electric displacement, and the measurement of the grid parameters of the three-phase four-wire electric energy metering device Accuracy affects

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