Abstract: Electronic instrument transformer has excellent characteristics compared with traditional electromagnetic one, but the AD sampler is separated with measurement, observation and control and protective device, and this leads that synchronized sampling became an important question influencing measuring accuracy. A survey algorithm without frequency tracking was put forward in this paper. The algorithm does not require entire station synchronization sampling, the electronic instrument transformer can operate at the standard fixed sampling period, its design can be simplified and the cost can be lowered greatly. the survey algorithm is to seek the data array characteristic obtained from analyzed message, then compute every demanded electric quantity, and the effective values of voltage and current by means of its peak to peak values detection, thus accomplish the power computation by zero point detecting to measure the frequency and phase difference.

Key words: Electronic instrument transformer, measurement, frequency tracking