Method for processing a current transformer signal

A residual current operation protection device, comprising:

• a current transformer;
• a trip unit;
• and
• a processing unit configured to process a current transformer signal and control the trip unit based on the processed current transformer signal, wherein the processing unit is configured to process the current transformer signal according to a method comprising:
• obtaining the current transformer signal with a cycle;
• in each cycle of the current transformer signal:
• for each time point, calculating a ratio between an amplitude of the current transformer signal at the time point and an amplitude at a previous time point;
• determining that a tailing exists in the current transformer signal based on the ratio being equal to a tailing threshold and lasting for a threshold time;
• and
• removing the tailing.

A computer-readable storage medium having computer-executable instructions stored thereon, when executed by a processing unit, the instructions are used to implement a method comprising:

• obtaining the current transformer signal with a cycle;
• in each cycle of the current transformer signal:
• for each time point, calculating a ratio between an amplitude of the current transformer signal at the time point and an amplitude at a previous time point;
• determining that a tailing exists in the current transformer signal based on the ratio being equal to a tailing threshold and lasting for a threshold time;
• and
• removing the tailing.