Controlled Closing of PT Delta Winding for Identifying Faulted Lines

It is very difficult to identify the line experiencing a single-phase to ground fault in ungrounded and resonant grounded systems. This paper presents a scheme for faulted line identification based on the concept of converting the ungrounded system into a grounded system in a controlled manner. This conversion or controlled grounding is done through the delta-winding of the potential transformers commonly available in substations. The delta-winding is inserted with a pair of SCRs and the controlled conduction of the SCRs results in a temporarily closed delta and thus creating a temporarily grounded system. This scheme is very easy to implement and does not involve high voltage components. Results of theoretical analysis, computer simulation and lab experiments have confirmed the effectiveness of the proposed method.