Automatic detection of tap changes on an electricity grid

Demand side management (DSM) is a key concept for smart grid. In order to achieve DSM, network stress information needs to be provided to the users, which normally requires two-way communication between users and an upper level control centre. Implementing such communication in large scale power networks will be both costly and introduces problems with security and privacy of data. On-load tap changes (OLTC) are used to adjust the voltage at the users' side in response to network conditions. By detecting tap changes, an indication of the level of network stress can be provided to users without communicating with a control centre, which provides an economical and efficient measure for network stress. This paper presents a tap change detection algorithm based on Hilbert-transform phase-locked loops, Q-R decomposition windowed recursive least square algorithm and a hypothesis test, which can distinguish tap changes made by an OLTC transformer from the fluctuation in voltage caused by changes in loads. In this paper, the tap change detection algorithm is illustrated and the results for both simulated input and real-time data are presented and discussed.