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Identification of the faulted line using controlled grounding

For neutrally ungrounded systems, it is very difficult to identify the line experiencing single-phase to ground fault. This is due to the fact that the non-effectively grounded system produces a very small fault current. This paper presents a novel method that can help to overcome this difficulty. The idea is to convert the ungrounded system into a grounded system temporarily through a judicially controlled grounding of the system neutral. A controllable ground fault current that is large enough for identifying the faulted line and yet small enough not to cause system problems is extracted by subtraction method. The criterion to distinguish the faulted and unfaulted line short-circuit impulse is established through spectral analysis and the sensitivity of the proposed method is analysed on the criterion, The effectiveness of the proposed method is proved by the lab experiment finally. The proposed method may be solve the problem of faulted line identification completely.