A new restructuring and regulatory process is taking place all over the world in the electrical sector. Special attention is being paid to power quality. Customers are becoming more sensitive to power quality problems and new commercial opportunities are arising associated with power quality solutions. Distribution companies are responsible to ensure adequate quality levels to their customers. Voltage quality problems related to voltage disturbances, such as harmonics, flicker, dips, etc, not only depend on operation and maintenance of distribution networkds but also on voltage disturbances injected by customers themselves. To be able to ensure power quality disturbance levels, distribution companies should monitor and control existing customers and evaluate the connection of new potentially disturbing customer installations. In this paper, a method to share the acceptable disturbance injection level to the network between all customers, based on the network available supply capacity and the requested power of each customer, is presented. The distribution company follows a process to determine if each connected customer installation complies with the required disturbance injection limits. First, the proposed method evaluates the disturbance injection from the customer based on a questionnaire on the type of equipment installed and their characteristics. Disturbance injections are estimated based on simple equipment data. Different types of equipment used by industrial and commercial customers have been standardised to simplify the calculation from normally available data. Second, the customer is assigned a maximum disturbance injection limit based on its total requested power and on the network supply capacity at its point of common coupling. Both valures, the estimated and the limit disturbance injections, are compared to determine if the customer meet the required quality criteria. Additionally, a set of corective remedial actions are proposed in case that the customer injection exceeds the allowed limit. The evaluation method is being implemented in a computer program that would be operated by commercial staff of distribution companies. This program is designed to be very user friendly, even for non technical users. The modular design will allow adding new types of equipment with its associated disturbance injection calculations. The voltage disturbances initially evaluated by this program are flicker and harmonics. This research project is leaded by the distribution companies Unión Fenosa and Iberdrola with the collaboration of Universidad Pontificia Comillas (IIT) and Universidad Politécnica de Valencia and is funded by a national research program (PIE program, project nº 132.357). The results oabtained and the software developed will be available to be used by Spanish distribution companies.
Keywords: Power quality regulation, distribution systems, flicker, harmonics, voltage quality, disturbance injection.
DistribuTECH Europe DA/DSM & Power Delivery Europe’99 Conference, Madrid, Spain, 28-30 Septiembre 1999.
Published: September 1999.