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This paper presents a novel and reliable technique for estimation of a distorted signal frequency. Unlike the other available techniques, the proposed algorithm does not need linearization to the signal voltage and or current. The proposed technique uses the samples available for the voltage and or current signal in the relay location to estimate the signal fundamental frequency. The frequency of the signal is calculated from the arccosine of two successive samples for a pure sinusoidal. The least errors square algorithm is used to minimize the signal errors, noise and harmonics. The frequency is estimated from a closed formula that easily can be programmed on the microprocessor based frequency estimation. Different simulated examples are offered within the text and different critical parameters that affect the performance of the proposed algorithm are discussed.