Fault Locator Approach for High-Impedance Grounded or Ungrounded Distribution Systems using Synchrophasors

Fault Locators in general are designed for HV solidly grounded systems because of the importance of fault location detection in the overhead transmission lines. In distribution line fault location there are some developments that are based again on the impedance measurement from one end. Accurate fault location in distribution systems is more difficult to achieve because of the existence of multiple branches and also because system neutral point is usually grounded through the high impedance or is ungrounded. In these conditions, fault current is low and with a high capacitive component. The other problem is fault resistance. Since the grounding point impedance is fixed and usually known, the fault resistance always depends on fault conditions. In these cases, the use of the impedance measurement criteria from one end is not enough to assure an adequate accuracy for the operational purposes. There are several other methods that overcome the classical impedance measurement method weaknesses, but majority are still based on the single end measurement, which are inherently limited because of the limited information available from the network. In order to overcome these limitations, a new approach based on synchrophasors and using information from different sources, is proposed. Solution is composed by several algorithms that are using measurements from different sources complementing each other to overcome their own inherent weakness in the fault location determination and providing a better accuracy than the one using a single-ended algorithm from the single measuring point. The solution has been tested in Real Time Digital Simulator (RTDS) with a focus to the ungrounded systems with a fault resistances values up to 500 Ohms. A description of the algorithms used for fault locator purposes is provided and also its implementation in a Phasor Data Concentrator device (PDC) is discussed.