Method for processing direct current electric arc and apparatus

An apparatus for detecting a direct current electric arc, comprising an electric arc fault processing module, and a first sampling module and a second sampling module that are connected to the processing module, wherein

• the first sampling module is disposed on a detected direct current cable connected to a photovoltaic cell panel of a photovoltaic cell system, and is configured to perform sampling on the direct current cable, to obtain a first current (x);
• and the second sampling module is disposed on a direct current cable on a direct current port side of an inverter of the photovoltaic cell system or on an alternating current cable on an alternating current port side of the inverter, and is configured to perform sampling on the direct current cable on the direct current port side of the inverter or the alternating current cable on the alternating current port side of the inverter, to obtain a second current (y);
• after receiving the first current and the second current, the electric arc fault processing module obtains a frequency domain component of the first current based on the first current, and is further configured to:
• obtain a frequency domain component of the second current based on the second current, and calculate a correlation coefficient (rxy) between the frequency domain component of the first current and the frequency domain component of the second current, wherein the frequency domain component is a frequency value of a current within a preset frequency band in frequency domain, and the correlation coefficient reflects a degree of correlation between the frequency domain component of the first current and the frequency domain component of the second current;
• and
• when the electric arc fault processing module determines that the first current meets an electric arc occurrence condition and the correlation coefficient is greater than or equal to a preset coefficient threshold, the electric arc fault processing module does not send a direct current electric arc fault alarm, wherein that the electric arc fault processing module determines that the first current meets an electric arc occurrence condition comprises:
• performing frequency domain decomposition on the first current to obtain a first frequency range, wherein the first frequency range is a frequency band in which electric arc noise occurs;
• calculating a standard deviation of a current frequency value in the first frequency range;
• and
• obtaining a quantity N of times that the standard deviation is greater than a first threshold in a preset time period, and when N is greater than a second threshold, determining that the first current meets the electric arc occurrence condition, wherein N is an integer that is greater than or equal to 0.

A method for processing a direct current electric arc, applied to a photovoltaic cell system, comprising:

• obtaining a first current (x), wherein the first current is a direct current input current of a direct current cable connected to a photovoltaic cell panel of the photovoltaic cell system;
• obtaining a second current (y), wherein the second current is a direct current common mode current of a direct current cable on a direct current port side of an inverter of the photovoltaic cell system or an alternating current common mode current of an alternating current cable on an alternating current port side of the inverter;
• obtaining a correlation coefficient (rxy) between a frequency domain component of the first current and a frequency domain component of the second current, wherein the frequency domain component is a frequency value of a current within a preset frequency band in frequency domain, and the correlation coefficient reflects a degree of correlation between the frequency domain component of the first current and the frequency domain component of the second current;
• and
• when determining that the first current meets an electric arc occurrence condition and the correlation coefficient is greater than or equal to a preset coefficient threshold, skipping sending a direct current electric arc fault alarm, wherein the calculating a correlation coefficient between a frequency domain component of the first current and a frequency domain component of the second current comprises:
• separately calculating a standard deviation (sx) of the frequency domain component of the first current and a standard deviation (sy) of the frequency domain component of the second current;
• calculating a covariance (sxy) between the frequency domain component of the first current and the frequency domain component of the second current;
• and
• calculating the correlation coefficient between the frequency domain component of the first current and the frequency domain component of the second current based on the standard deviations and the covariance.