Building an ontology for flexible power quality querying

Electrical power quality (PQ) is measured as a set of PQ parameters, such as frequency, flicker, and harmonics, obtained from electrical transmission and distribution systems. The domain of electrical PQ suffers from the lack of a common vocabulary to be shared by the involved parties. There exist several systems of varying complexities to measure PQ parameters, yet no ontology development effort for PQ data has been reported in the literature. In this paper, a novel and generic domain ontology for electrical PQ is presented. During the ontology development process, relevant standards as well as experiences gained during the development of two distinct large-scale systems for nationwide PQ monitoring have been used. Among these monitoring systems, one is a mobile measurement system which has collected sample PQ data of considerable size all over the Turkish Electricity Transmission System to detect problematic locations. The second system, which aims to perform on line PQ monitoring with permanent monitors, is the successor of the previous one and has recently started to collect data at several problematic points in the transmission system. The PQ ontology is especially important for its being the first attempt to create a common vocabulary for the domain and hence to make differing PQ monitoring systems interoperable. The proposed ontology is utilized to develop a natural language based interface for querying the PQ data collected through mobile measurement system, in a flexible way. The implementation details of the interface is presented with a query example on the PQ data. The future work will include the extension of this natural language based interface into a speech recognition engine to get spoken queries into the system and enhance the interface to handle queries in Turkish.