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Why does the Photovoltaic Inverter Generate Leakage Current?

Update time : 2022-07-07 11:18:44

The leakage current of the photovoltaic system, also known as the residual current of the square array, is essentially a common-mode current, which is caused by the existence of parasitic capacitance between the photovoltaic system and the ground. The voltage will create a common mode current on the parasitic capacitance. When a power frequency transformer is installed in the photovoltaic system, since the parasitic capacitance impedance between the transformer windings in the loop is relatively large, the common mode current generated by the common mode voltage in the loop can be suppressed to a certain extent. However, in a photovoltaic system without transformer, the loop impedance is relatively small, and the common mode voltage will form a large common mode current on the parasitic capacitance between the photovoltaic system and the ground, that is, leakage current.

For photovoltaic high-frequency inverter systems, there are two forms of leakage current: resistive leakage and capacitive leakage. As shown in the figure above, the capacitor is formed by insulating material between conductors A and B. The larger the area of A and B, the larger the capacitance. In wet and rainy days, the electric charge of the plate is prone to form resistive leakage to the ground. When the high-frequency inverter is working, there is mainly a high-frequency common-mode leakage current.

The leakage current in the photovoltaic system, including the DC part and the AC part, if connected to the grid, will cause problems such as grid-connected current distortion and electromagnetic interference, which will affect the operation of the equipment in the grid; the leakage current may also make the inverter shell live, posing a threat to personal safety. In order to avoid harm, it is necessary to detect leakage current and prevent accidents. HANGZHI RIT series leakage current sensor can closely monitor the leakage current in the photovoltaic system according to the requirements of photovoltaic standards.

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