This paper presents different types of robust state estimators and introduces original formulations that allow solutions to be obtained using general-purpose mathematical programming algorithms. Different set up of bad measurements and bad leverage measurements are introduced to evaluate the performance of these estimators. Independent and confirming bad measurements are considered. The performance of the different estimators is evaluated by comparing the summation of the absolute residuals between the estimated and the actual values. The IEEE 14-bus DC example is used to illustrate the properties of these estimators.