Process for current measurement comprising a digital recombination of a low-frequency current signal and at least one high frequency current signal

A process for current measurement, comprising a digital recombination of a low frequency current signal ILF coming from a low frequency current sensor and at least one high-frequency current signal IHF coming from a high-frequency sensor measured on a single electrical line, where a parasitic continuous offset is added to said high-frequency current, the process comprising the steps of:

• a. digitally amplifying said high-frequency signal with an amplifier having gain G which produces an amplified high-frequency signal:
• G·IHF+G·offset;
• b. first filtering of said high-frequency signal by means of a digital low-pass filter with a cutoff frequency fc to get a filtered amplified high-frequency signal Ihf+G·offset:
• c. second filtering of said low-frequency current signal ILF with a digital low-pass filter provided with said cutoff frequency fc in order to get a filtered low-frequency signal:
• Ilf;
• d. first summing of the filtered amplified high-frequency signal Ihf+G·offset with the filtered low-frequency current Ilf and filtering of the sum of said signals at frequency fc resulting in a signal:
• Ilf+Ihf+G·offset;
• e. third filtering of said signal Ilf+Ihf+G·offset resulting in a signal Ilf+G·offset from which the Ihf component is deleted;
• f. multiplying the signal Ilf by two resulting in a signal:
• 2 Ilf;
• and
• g. adding/subtracting signals:
• 2 Ilf+(Ihf+G·offset)−(Ilf+G·offset).