Model-based analysis of protection system performance

Following a power system fault, protection engineers have to analyse the scheme activity to ensure correct operation. To aid them in this task, data gathering systems are increasingly being fitted to the power system. However, during extreme operating conditions the volume of data made available by these systems can be overwhelming. To help overcome this, knowledge-based systems have been developed and installed at ScottishPower's corporate headquarters to extract the relevant 'information' from the Supervisory Control and Data Acquisition (SCADA) system 'data'. The paper reports on the next stage of decision support for the protection engineers which builds upon the diagnosis provided by the knowledge-based systems. This enhanced support is provided by a model-based diagnostic system which provides automatic analysis of the available fault recorder data. This system utilises the most appropriate techniques employed by existing model-based diagnostic systems. A novel approach for handling tolerances associated with the operating times of protection scheme components is introduced, thus enabling modelling and measurement inaccuracies to be dealt with.