An automatic transient detection system which can be incorporated into an algorithm to accurately determine the fault level in networks with DG

The use of distributed generation is on the increase within the United Kingdom and the Distribution Network Operators (DNO's) require a novel approach of assessing potential fault levels in near “real-time” to assist with network planning and design. The short circuit current is the current expected to flow into a short circuit fault at a known point on the system, and therefore, the fault level is the product of the open circuit voltage and short circuit current. Recent techniques used by the industry involve power system software that calculates the fault level in accordance with BS EN 60909, however, this frequently provides a conservative answer and possibly this will be a factor restricting future connections of distributed generation. This paper will describe the initial stages of the development of an algorithm which can be used alongside a digital signal controller (a Texas Instruments TMS320F28335) to calculate in near “real-time” the fault level at a specified point on the distribution network. Matlab & Simulink are utilised to both simulate source faults and to create the initial elements of the algorithm which are analysed utilsing the test program. The implementation of a Short Time Fourier Transform (STFT) to determine when a fault occurs is discussed. Finally the results from these simulations are examined and presented alongside a discussion of future work.