Application of Devices and Systems Designed for Power Quality Monitoring and Assessment

Abstract

The paper presents the problems associated with increasing demands on the equipment and systems for power quality assessment (PQ), installed at power substations. Difficulties are signaled due to current lack of standards defining the test methodology of measuring devices. The necessary device properties and the structure of a large system operated in real time and designed to assess the PQ are discussed. The usefulness of multi-channel analyzers featuring the identification and registration of transients is pointed out. The desirability of synchrophasor assessment implementation and device integration by standard PN-EN 61850 with other SAS devices is also justified. DOI: 10.12736/issn.2300-3022.2014102 1. Growing importance of power quality assessment 1.1. Impact of deregulation in the energy sector In Europe, the standardisation of electricity characteristics has long been associated with a wide-ranging deregulation of the energy sector. In 1989 issues of power quality assessment (PQA) were reflected in EU Directive No. 89/336 relating to electromagnetic compatibility. The Directive was intended to formulate the conditions which would have to be meet by supply grids and electrical equipment placed on the market to fulfil compatibility requirements. The Directive, together with many accompanying standards, laid down specific guidelines for equipment manufacturers and electricity distribution companies. On the other hand, it justified member States’ development of instruments to discipline electricity consumers, suppliers, and producers, somehow forced to continually respect standards, and thus to care for appropriate electricity characteristics. In Poland, the debate over the electricity characteristics standardisation gradually grew in relevance in connection with harmonisation processes related to accession to the European Union. Originally it was thought that the issue of PQA assessment would concern large consumers, such as major industrial plants, sensitive to energy supply disturbances, while potentially disrupting the supply. It was assumed that over time the PQA would cover smaller consumers, such as craft workshops and small stores. Ultimately, the need was seen to install appropriate analyzers, even at locations of individual consumer, who would seek compensation from the electricity supplier for the damage and losses caused by failure to adhere to proper parameters. The offering of devices available on the market matched these needs. It consisted of relatively simple devices, often designed for fixed panel mounting in switchboards, identifying only some PQA characteristics. Their measurement archiving capabilities were limited and data transmission capabilities very poor and based on proprietary non-standardised protocols. Another group of offered equipment was expensive portable devices, with a very complex design, intended for temporary installation and recording of possible disturbance in the power grid. The change factor was deregulation processes in the power industry, which for good strengthened in Poland in 2005–2007, and have resulted in a number of area distribution companies. Electricity was not perceived as a common good anymore. Energy has become a commodity purchased by distribution companies from a grid company, and further sold to consumers. Conceptually, this commodity, at least in part, would have to be traded at stock exchanges. It was assumed that energy trading would be regulated by contracts, which would stipulate not only the quantity but also the quality. At the same time a business entity appeared, a large distribution company, somehow naturally interested in maintaining appropriate parameters of the purchased and sold energy. During this period, in important points of energy intake and output the installation of equipment for continuous measurement of PQA parameters and evaluation began. In practically all distribution companies pilot R&D projects were conducted, and the equipment properties were discussed. It soon became W. Gil, P. Wronek | Acta Energetica 1/18 (2014) | 18–23