Abstract: The adaptive notch's performance is analyzed when it is used in a real system. It is discovered that there are several elements that effect its performance and the performance will be much better if the input signals are frequency down-converted and processed in low frequency. A low-frequency plan based on this result is presented. The comparison between the low-frequency and high-frequency plan is made by computer simulations and hardware experiments. It is shown that the low-frequency plan has a much better performance than the high-frequency plan:the speed request for iC chips can be lowered, the range of input signal's amplitude is 25 times larger and the tracking range of signal's frequency is larger than the high-frequency plan, too.

Key words: adaptive notch, low-frequency plan, single frequency tracking (SFT), Wiener solutions, high-frequency plan, relay protection device