Patent ID: 8024143

Claim:
A method for ascertaining a mains frequency in a voltage signal using a mains analyzer, the method comprising: stipulating a sample frequency f s for a sample oscillation in the mains analyzer; polling a voltage signal, using a pair of connections of the mains analyzer, at N equidistant times in X periods of the sample oscillation, where X=5, 6, 7, . . . , to obtain N sample values x n , with n=0, 1, . . . , N−1; ascertaining, in the mains analyzer, a first phase φ 1 (X) on the basis of the formula φ 1 ⁡ ( X ) = arc ⁢ ⁢ tan [ ∑ n = 0 N - l - 1 ⁢ ( x n + l ⁢ cos ⁡ ( X × 2 ⁢ π × n N ) × w ⁡ ( n ) ) ∑ n = 0 N - l - 1 ⁢ ( x n + l ⁢ sin ⁡ ( X × 2 ⁢ π × n N ) × w ⁡ ( n ) ) ] where 1=0, 1, . . . and w (n) is a window function; ascertaining, in the mains analyzer, a second phase φ 2 (X) on the basis of the formula φ 2 ⁡ ( X ) = arc ⁢ ⁢ tan [ ∑ n = 0 N - m ⁢ ( x n + m ⁢ cos ⁡ ( X × 2 ⁢ π × n N ) × w ⁡ ( n ) ) ∑ n = 0 N - m ⁢ ( x n + m ⁢ sin ⁡ ( X × 2 ⁢ π × n N ) × w ⁡ ( n ) ) ] where m=1, 2, 3, . . . , with m>1; and ascertaining, in the mains analyzer, a frequency f on the basis of the formula f = f s ×  φ 2 ⁡ ( X ) - φ 1 ⁡ ( X )  2 ⁢ π ⁡ ( m - l ) as the mains frequency.