Distribution Automation Applications And Their Status Estimation

Distribution Automation is one of the advanced techniques in the domestic and overseas, and it has been a general trend to develop and construct the Distribution Automation System step by step, especially for today when the power is put into markets and the information technology is developing rapidly. Advanced Application Software is an important component of Distribution Automation System that plays great role in guaranteeing the safe and economical operation of the system. State Estimation is an important component of PAS. It uses breaker state (change), measurements data and pseudo-measurement data provided by load forecasting to detect and identify bad data, and then estimate completed, consistent and believable real-time network state. Afterwards State Estimation provides reliable and comprehensive real-time operation mode to other application software of PAS.Distribution Sate Estimation has already many different algorithms today, but these algorithms all have shortcomings such as complex programming, weak in dealing with measurements or being bad in convergence. This paper presents a new modified approach for distribution state estimation. This approach uses Bus Load Distribution technology to account for current magnitude measurements, solving the problem that the branch-power-based state estimation method for distribution systems cannot deal with current magnitude measurements. At first, we get power factor by voltage magnitude and power-injection of root node in the network topology, and then use current measurements of outlets and voltage magnitude, power factor of root node to obtain active power and reactive power of outlets; afterwards, distribute the obtained P and Q to every load node on basis of the static load values on each load node to obtain the first modified load values; after this, by acquiring a modified coefficient of load through the load of nodes with load measurements, we get thesecond modified load values on each load node; finally, by completing correlative calculations to branches with current magnitude measurements we obtain the last modified values through the second modified values. Eventually, the last modified load values are introduced into the branch-power-based state estimation method for distribution systems.The distribution network has a remarkable characteristic: insufficient measurements and current magnitude measurements in the majority, thus the shortcoming influences convergence and precision of the branch-power-based state estimation method for distribution systems. Because the modified approach can deal with current magnitude measurements, it obtains good convergency and precision. This improvement is efficacious that is proved by testing with IEEE 13,34 nodes systems.This paper realizes the power flow and network topology to test the modified approach better. Power flow adopts Newton-Raphson method that is superior in solving large-scale distribution power flow. Network topology adopts the breadth first search based on branch layering, and uses the chain technology to form the nodes chain, branches chain and layers chain to store topology information, providing the data structure to programming of power flow calculation and state estimation.