With integration of a larger amount of clean power sources and power electronic equipment

operation and dynamic characteristics of the power grid are becoming more and more complicated and stochastic. Therefore

it is necessary and urgent to obtain accurate real-time states

which is difficult from traditional state estimation. This paper systematically develops a phasor measurement unit (PMU) based real-time state estimator for a realistic large-scale power grid for the first time. The estimator mainly relies on three refined algorithms

i.e.

an improved linear state estimation algorithm

a practical bad data identification method and a distributed topology check technique. Furthermore

a novel system architecture is designed and implemented for the China Southern Power Grid. Numerical simulations and extensive field operation results of the state estimator recorded under both normal and abnormal situations are presented. All the tests and field results demonstrate the advantages of the proposed algorithms in terms of online system monitoring and feasibility of refreshing the states of the whole system at intervals of tens of milliseconds.