Method and system for detecting zero line lacking function of three-phase four-wire electric energy meter

Abstract

The invention discloses a method and a system for detecting a zero line lacking function of a three-phase four-wire electric energy meter. The detection method comprises the steps of identifying whether more than two phases of voltages exist in the three-phase four-wire electric energy meter based on a system power-on state; when identifying that more than two phases of voltage exist in the three-phase four-wire electric energy meter, detecting whether current passes through a null line based on a null line metering circuit; under the condition that no current is detected on a zero line, loading the voltage of more than two phases on a zero line lack function detection circuit to obtain an output waveform; and detecting the output waveform under the action of the interruption frequency, and judging the zero line state of the three-phase four-wire electric energy meter according to the detection result. According to the detection method, under the condition of ensuring accurate meteringof the three-phase four-wire electric energy meter, the accuracy of null line lack function detection is greatly improved.

Description

technical field [0001] The invention relates to the field of zero line detection of electric energy meters, in particular to a function detection method and system for missing zero line of three-phase four-wire electric energy meters. Background technique [0002] In the three-phase four-wire power supply system, when the load is a three-phase load under normal conditions, the three-phase line is in a balanced state, but in terms of domestic power supply, the load is all a single-phase load, resulting in a three-phase line sent by the transformer. In the case of unbalanced load, the three-phase neutral point shifts. Therefore, in the three-phase four-wire watt-hour meter, the zero line enters the meter, and the zero line is used as a reference point. When the meter measures the line voltage of each phase, the accurate line voltage value of each phase can be obtained, even if there is any When the phase voltage is disconnected, the other two-phase voltages are still measured...

AI Technical Summary

Problems solved by technology

However, this detection method also has some disadvantages

The withstand voltage value of the solid state relay is only 400V, and it is vulnerable to lightning strikes and surges during field use, which makes the reference point of the three-phase four-wire electric energy meter with normal wiring disconnected from the neutral line for a long time. At this time, the electric energy The measurement accuracy of the meter is inaccurate, which seriously affects the customer's measurement charges

In addition, because the CTR value of the photocoupler is easily affected by the ambient temperature, resulting in abnormal output waveforms, when the software detects the output waveforms, there will be misjudgment of the zero line status of the three-phase four-wire electric energy meter

Therefore, while detecting whether the zero wire is entering the meter, considering the problem of field application, the existing technology cannot guarantee the accuracy of the meter measurement

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