This paper presents an innovative two-terminal traveling wave (TW)-based fault location formulation. It depends only on the time difference between the first incident TW and the successive reflection from the fault point, at both line ends. Thereby, the proposed formulation requires neither data synchronization nor line parameters, which are sources of error that usually affect TW-based fault location schemes. Several faults on a typical 500 kV line were simulated to compare the proposed formulation performance with that of a classical twoend approach. The obtained results attest that the proposed formulation is able to accurately locate faults on transmission lines, even when data synchronism errors and uncertainties in the monitored line parameters exist.

In the few years, wavelet-based methodologies have been proposed as a good alternative for real-time fault detection. However, these methodologies usually fail to detect faults with overdamped transients and they are highly influenced by the choice of the mother wavelet, presenting time delay in the real-time analysis. By using the discrete wavelet transform (DWT) or the maximal overlap discrete wavelet transform (MODWT), the wavelet coefficient energy has been also used for fault analysis and presents the same drawbacks of the wavelet coefficient analysis. However, this paper presents a novel wavelet-based methodology for real-time detection of fault-induced transients in transmission lines, where the wavelet coefficient energy takes into account the border effects of the sliding windows. As a consequence, the performance of the proposed energy analysis is not affected by the choice of the mother wavelet, presenting no time delay in real-time fault detection, and the fault detection is scarcely influenced to the fault inception angle, fault resistance, and fault location, even if in critical situations where there are no fault-induced transients. The performance of the proposed methodology was assessed by using actual and simulated data. Some records were reproduced to be analyzed in real time with a digital signal processor.

The development of modern protection functions is a challenge in the emerging environment of smart grids because the current protection system technology still has several limitations, such as the reliable high-impedance fault (HIF) detection in multigrounded distribution networks, which poses a danger to the public when the protection system fails. This paper presents the wavelet coefficient energy with border distortions of a one-cycle sliding window designed for the real-time detection of transients induced by HIFs. By using the border distortions, the proposed wavelet-based methodology presents a reliable detection of transients generated by HIFs with no time delay and energy peaks scarcely affected by the choice of the mother wavelet. The signatures of different HIFs are presented in both time and wavelet domains. The performance of the proposed wavelet-based method was assessed with compact and long mother wavelets by using data from staged HIFs on an actual energized power system, taking into account different fault surfaces, as well as simulated HIFs. The proposed method presented a more reliable and accurate performance than other evaluated wavelet-based algorithms.

In this paper, a new two-terminal traveling-wave-based fault-location algorithm is proposed. Its main advantage over similar two-terminal algorithms lies in the fact it does not require the data from both line terminals to be synchronized. In order to do so, the algorithm is applied in real time, and a communication system is used, whose data-transmission latency is taken into account in the proposed formulation. The fault locator routines were implemented using the real-time digital simulator (RTDS), such that a wide variety of fault scenarios in a 230-kV transmission line 200 km long was evaluated in real time, considering communication systems with different latency variability levels. The obtained results indicate the proposed algorithm is able to locate faults using either synchronized or unsynchronized two-terminal data, whereas classical methods work properly for synchronized measurements only.

The current transformer (CT) saturation phenomenon has been one of the main problems for the power transformer differential protection, leading to incorrect current measurements and relay misoperation. This paper proposes a fast and efficient transformer differential protection scheme with additional differential CT saturation and cross-country fault detection modules after the external fault detection, all of them based on the differential wavelet coefficient energy with border distortions in order to stabilize the relay during external faults and distinguish accurately CT saturation from cross-country internal faults. The proposed method was assessed by using representative simulations of internal faults, transformer energizations, and external faults with CT saturation followed by cross-country internal faults, and good results were achieved.

Currently, the differential function is the most used for the power transformer protection, leading to a reliable discrimination between internal faults and other events. However, the conventional phasor-based differential protection function presents difficulties in the detection of some internal faults and its performance depends on the harmonic restraint and blocking functions in order to avoid relay misoperation during inrush currents. However, internal faults and other disturbances present transient, which can be properly detected by using the wavelet transform. This paper recreates the phase current and the negative-sequence current differential elements by means of the boundary wavelet coefficient energy. The proposed method was evaluated by using representative simulations of internal faults, external faults, and transformer energizations in two different power systems. By using the boundary wavelet coefficient energy instead of phasor estimation, the proposed method was quite fast, accurate, was not affected by inrush currents in transformer energizations and fault clearance, and could be used in a real-time application with low computational burden. In addition, the proposed method presented no failure in fault with overdamped transients, was scarcely affected by the choice of the mother wavelet, presented no time delay associated with the wavelet filtering, and was not affected by typical noise.