Power quality issues-a distribution company perspective

Scottish Power supplies electricity to a customer base of three million in the south of Scotland and Manweb. A high proportion of the manufacturing and process industries in Scotland are involved in semiconductor production, requiring a consistent and high quality power supply. The quality of supply is therefore important to both customers and Scottish Power in terms of attracting and keeping new industry and business. This paper discusses why power quality is such an important issue and then discusses Scottish Power´s company strategy to improve power quality. The strategy is chiefly based on the classification of voltage dips as a quality of supply indicator. The voltage dips are detected by digital fault recorders (DFRs) installed across the Scottish Power distribution system. This strategy enables Scottish Power to provide industrial and commercial customers with tangible system performance reporting and feedback. This method of network assessment also promotes practical dialogue between Scottish Power and the customer during the specification of new customer loads to ensure that the subsequent load characteristics do not degrade the performance of the load or the network. Two case studies are examined.