Electric energy meter and terminal relay contact on-line monitoring device and method based on double frequency difference method

Abstract

This invention discloses an online monitoring device and method for electricity meters and terminal relay contacts based on the dual-frequency difference method, belonging to the field of electrical variable measurement technology. The device includes a high-frequency constant current source, a power frequency current acquisition module, a voltage acquisition module, a separation module, and a calculation and judgment module. It simultaneously injects power frequency current and a constant high-frequency current into the line segment where the relay contacts are located, acquires the mixed voltage, separates the power frequency and high-frequency components, calculates the power frequency impedance and high-frequency impedance respectively, and then obtains the magnitude of the difference between the two. The method includes injection, acquisition, separation, calculation, and judgment steps. This invention compensates for interference from parameters such as the inherent resistance of the line by calculating the dual-frequency impedance difference. The magnitude of the difference is only related to the contact resistance and contact capacitance of the contacts themselves, realizing online, real-time, and quantitative monitoring of the contact state of the relay contacts, and accurately identifying early deterioration faults such as contact oxidation and wear.

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