POWER SYSTEM STATE ESTIMATION - IIT Mandi

(Cont.,)• The degrees of freedom k, represents the number ofindependent variables in the sum of squares.• Now, let us consider the function f(x), written in terms of themeasurement errors:2m m m1 2 eN2if (x) Rii ei eiRi 1 i 1 ii i 1• where e is thethi measurement error, R ii is the diagonal entry ofthe measurement error covariance matrix and m is the totalnumber of measurements.• Then, f(x) will have a chi-square distribution with at most (m -n) degrees of freedom.where, m is number of measurements.n is number of state variables.