Ternes, Elisete; Lopes, Sergio; Philip, William
FURB
Accuracy in fault location is a very important issue for power systems. While this has been successfully accomplished for transmission systems through the application of the traveling wave theory, it still represents a challenge for power distribution networks due to the greater complexity of the latter. After all, when a fault occurs in a distribution feeder, voltage and current waves originating in the fault travel to the substation carrying information on the fault point, but this information becomes rapidly distorted due to successive reflections on the many discontinuities of the system, including power transformers. Thus, in order to locate the fault point with the same accuracy as in a transmission system, a device must be able to record the first front of waves traveling from the fault that manage to reach the substation. Additionally, the traveling waves must be recorded at other points of the network in order to secure accurate location.
However, installing very fast transducers capable of measuring transient surges of both current and voltage at several points of a distribution network can be a very expensive proposition. Therefore, the aim of this work is to present the experimental results of a very fast transducer that records the derivative of both the transient current and voltage.
Due to its derivative nature, the proposed transducer has an elevated sensitivity. Its measuring system for transient current is based on the Rogowski coil principle, while for transient voltage it is based on the principle of the passive RC differentiator. Besides its considerably high sensitivity to easily detect transient surges, the conception of the transducer is the simplicity, which allows it to be produced at low cost. For its turn, these characteristics imply into the viability of its installation in several points along the network of power distribution systems, which is a requirement for the better location of fault points in power distribution systems. Thus, in this work is demonstrated how this development results in a much better performance than any another device used to capture with fidelity transient waves in transmission systems, especially those yielded from a fault. For example, the developed transducer allows for the calculation of the surge impedance, which can be an extremely meaningful data. Furthermore, it points to the viable development of a fault locator based on traveling wave theory that can be used for distribution systems at relatively low cost. The practical results of this study were obtained using test equipment that was installed on a distribution line of Celesc´s power network, located in the city of Blumenau, Brazil.
