As the most commonly used state estimator in power industry, WLS based SE is essentially an average estimator, and therefore, the influence of a bad data is shared (or hidden) by the neighbor buses around the location of bad data. This feature of WLS based SE makes the bad data detection very hard, if not impossible.
Considering WLS is essentially an average estimator, if the average value go beyond the stop criterion due to the huge inconsistence caused by the bad data, the state estimator will definitely diverge.
The difficulty of bad data detection lies in the following aspects:
1) Measurements and System Data
Power utility companies have low measurement redundancy ratio and
high percentage of bad data.
Weighted Least Square based state estimator forces the
influence of bad data shared by its neighbor buses, which makes the
bad data detection very hard, especially the nonlinearity of
power grids raising a big challenge to residual-based bad data detection
which fully depends on linearization.
Unlike WLS based SE, the NDSE can obtain a feasible voltage estimate ones the system is solvable with the following characteristics:
1) No human involvement. Examples of human involvement: adjusting
the measurement weights to make it convergent; changing the
measurement values or system data, etc.
2) The voltage estimate completely depends on the given measurements
and system data/parameters.
3) NDSE can help largely improve the data accuracy of power system
4) NDSE is robust because it is Not sensitive to bad data.