Paper Presentations

Power Quality Analysis in Substation Automation Systems
Alexander Apostolov, AREVA T&D Automation

Power quality monitoring devices are designed to detect and record different power quality events and report to the user their characteristics. However, using specialized devices in many cases is limited by the fact that they are an additional peace of equipment that needs to be purchased, installed, commissioned and maintained. At the same time, multifunctional protection or disturbance recording devices operate during system events and record the waveforms or profiles of the system parameters measured by the device.

The availability of this data allows the development of a substation level power quality analysis system. The paper analyses the architecture of such a system. It considers the recording capabilities of protection relays and compares them with disturbance recording devices. Requirements for time-synchronization of all Intelligent Electronic Devices used to record the power quality events are described. Automatic disturbance records extraction of available records from the IEDs is one of the essential functions of the system. Combining and aligning the records from the different devices in a data base builds the foundation of the analysis module of the system. Based on a user-defined period of time the analysis module determines the parameters of the individual power quality events that occurred. It generates reports for individual events or performs statistical analysis. The results from the analysis can be presented as reports or as different charts as required by the power quality standard used.

Total Clean Power
Simon Walton, Vectek Electronics Ltd

The "Clean Power" concept is to analysis a company's susceptibility to disturbances originating in the utility distribution system. Define the level of risk, segregate the areas of criticality and provide individual protection of each level of plant using the latest inverter based technology and alternative energy sources.

Four categories are typically identified, i.e. critical plant, essential services, sensitive processes and standard unconditioned power. The "Clean Power" system then utilizes conventional power sources such as lead acid batteries and a diesel electric generator to provide the system alternative options, but also provides the capability to accommodate the new emerging technologies of super capacitors and fuel cells to maintain the independent loads.

Some of the significant features of this "Clean Power" concept is that the system is a totally integrated package, but also that the diesel electric generator is not a conventional alternator but rather an ordinary AC squirrel cage induction motor, driven by the diesel. This allows the system to operate at variable engine speeds. The alternative energy sources can be low voltage (<50Vdc), high current fuel cells supplying energy over a considerable time, but also medium voltage (>100Vdc but <750Vdc)very high current super caps, available only for very short term energy bursts.

Feeder Overcurrent Protection Design Tools for Power Quality Improvement
Thomas E. McDermott, EnerNex

The utility can sometimes improve its power quality by changes to the overcurrent protection system, but usually lacks the design tools to make such changes. The existing software tools were designed mainly to coordinate the protective devices and settings. They can also serve for power quality analysis, if they can output the voltages at all buses, and the times between each device operation, for a specific fault event. A systematic simulation of faults on the distribution system will then produce a set of predicted power quality indices due to sags and interruptions, such as the SARFI series. These predicted indices might be benchmarked against monitored data, but they can also be used to make relative power quality comparisons of different feeder designs. An IEEE tutorial feeder for overcurrent protection is analyzed with an available software package to illustrate the process, showing the effect of different reclosing and fusing practices on the predicted SARFI indices at various load points. Many power quality performance contracts are based on similar indices, so this method can be used to rigorously investigate potential improvements for those situations.