Power Quality Measurement In Digital Substation

With the wide application of power electronic devices in power system, power quality problems have already become the focus to which both suppliers and users of electricity have paid close attention. To improve power quality, a monitoring and analyzing system must be established to detect, estimate and classify different disturbances.Digital substation came to us in the end of 20th century as its several merits such as: improving reliability of system, IEDS with Interoperability, easy to maintenance and refresh the IEDS, reducing time to put into operation, improving work efficiency and so on. As a new substation system, it's very important to study how to establish power quality detection system. Based on the deeply study of communication system in digital substation, several new problems which came up in the study of power quality detection in digital substation are presented in this paper and then we find a solution by analyzing them, at last a software is made up to achieve several functions.Firstly, power quality phenomena and its theoretical foundation are introduced briefly. The classification, definition, characteristic and causation of all kinds of power quality are also presented. Then several popular methods of calculation of power quality are introduced and compared.Secondly, IEC61850 protocol is studied deeply. Through the research on IEC61850-9-1, the transmission Model of sample values during Process layer in digital substation is build; the communication stack composition of the analog sample value during transmission is identifiedLast, based on Visual Studio 2005, software is developed which can detect power quality online. The software realizes the purpose of obtaining sample value data from Merging Unit; analyzes the data; calculate the power quality indicators of sample value by FFT (Fast Fourier Transform); and then shows them in screen.The contents of this paper is the detection method of the power quality in digital substation which is a big help to improve the level of power quality and on-demand power indicator in digital substation, and is also a valuable exploration to improve the communication system in digital substation.