Study of a cement plant experiencing power quality problems in Uruguay

UTE is the Uruguayan electrical utility involving generation, transmission and distribution. Power quality is an important activity developed by its distribution department. Since 1995, they started to study the international standards referred to this topic. As a result of this, company standards were written and approved. Tolerances were defined to RMS voltage, unbalance, harmonics, flicker and frequency. Meanwhile, they served some customers with sensitive equipment. One of those customers is an important cement industry fed at 60 kV with 7 MW. Voltage sags were the main cause of the power quality problems. This paper includes a description of the study that was made in order to predict the number of voltage sags, before the connection of the customer to the network. It also describes how the actual power quality was measured. The registered events are matched with the kind of the network faults and the consequence into the industrial process caused by its depth. The customer is more sensitive than what was specified in the supply application form. The most frequent sags are the least deep ones and make only a small portion of the plant power to trip. Finally, some pieces of advice that were given to the customer, in order to desensitize the plant of part of it, are included