System and method for calibration of data in an electric power monitoring system

A system for compensating for errors introduced into electric power monitoring systems by a data acquisition section thereof, which in operation is responsive to analog quantities from an electric power line to produce sampled digital signals which are used in a monitoring algorithm, the system comprising:

• a test unit for applying a sinusoidal test input signal to a front end portion of the data acquisition section;
• a processing module to which the test input signal is also applied for converting the test signal to a module output signal having falling and rising edges corresponding to transitions between positive and negative portions of the sinusoidal test signal;
• means for determining a zero crossing of the sampled digital signal and for determining the time difference between an edge of the module output signal and said zero crossing of the sampled digital signal, wherein said time difference is representative of the phase shift produced by the data acquisition section;
• and
• a compensation circuit for phase adjusting the sampled digital signals in accordance with said time difference.