BC Hydro approach to load modeling in state estimation

Modeling of loads in energy management system (EMS) impacts significantly the robustness and quality of state estimator solution. Loads are traditionally used as pseudo measurements to fill in for unavailable real-time analog telemetry in order to provide required observability for state estimator to solve. The quality of load model also directly impacts the quality of state estimator and power flow solution. There are several important factors to consider when modeling for real-time applications in EMS. Those include (i) the granularity of load model i.e. whether loads are lumped for the entre station bus or each individual feeder in a substation is represented as a separate load, (ii) load voltage sensitivity which describes the variations of real and reactive loads with changes of bus voltage, (iii) load frequency sensitivity which emulates impacts of frequency deviations on loads and (iv) load accuracy model that assigns accuracy class to loads to be used by state estimator. In addition, the aspects of load model such as load allocation in real-time as well as modeling of loads in the external system also need to be addressed. The objective of this paper is to discuss the load model that BC Hydro has implemented in the network model in EMS to support the state estimator and other EMS advanced applications in real-time.