Felipe V. Lopes

Settings-Free Traveling-Wave-Based Earth Fault Location Using Unsynchronized Two-Terminal Data

This letter presents a two-terminal traveling-wave (TW)-based earth fault-location algorithm. It works using unsynchronized data and does not require information about the line parameters. Evaluated signals are decoupled into aerial and ground modes and, then, only the incident TWs of each mode are detected at the line ends. Earth fault case studies are carried out to attest the proposed algorithm feasibility, comparing its performance with those of one- and two-terminal approaches reported in the literature. Obtained results reveal that the proposed algorithm is straightforward and quite reliable.

A Wavelet-Based Busbar Differential Protection

This paper presents a new wavelet-based busbar differential protection algorithm, named as 87BW function. The instantaneous current-based differential protection fundamentals are taken into account and the well-known 1-out-of-1 and 2-out-of-2 tripping logics are mapped into the wavelet domain. Operating and restraint wavelet coefficients energy of currents are computed, regarding station configuration and bus zones boundaries. Thereby, the proposed 87BW function can be properly used in both static and dynamic busbar configuration. Its performance was evaluated through EMTP-based simulations of faults in a 230 kV power substation with double bus single breaker configuration. The obtained results reveal it provides ultra-high-fast trip for internal and evolving external-to-internal faults, guaranteeing security for normal through-load and external faults as well, even in the case of early and severe current transformer (CT) saturation.

Methodology for Protection Performance Evaluation on Power Transmission Networks

An innovative methodology for protection performance evaluation on transmission networks is presented in this paper. It was developed to overcome difficulties faced by the Brazilian utility Companhia Hidro Elétrica do São Francisco (CHESF) during the preparation of short-circuit reports that must be sent to regulatory organizations whenever transmission-line faults occur. In the proposed methodology, a combination of several algorithms is used to extract from oscillographic records relevant information about short circuits and performance of protection functions. Aiming toward practical applications in CHESF, a software named disturbance analysis and protection performance evaluation has been developed in order to execute the proposed methodology functions, providing reports about the short-circuit characteristics and protection operation. To validate the proposed methodology, digital fault simulations in the Alternative Transients Program (ATP) and in Computer-Aided Protection Engineering (CAPE) software were carried out. Furthermore, real-world fault cases were also analyzed by assessing actual oscillographic fault records provided by CHESF. The obtained results show that the proposed methodology is reliable and quite useful for short-circuit analysis and protection performance evaluation procedures.

Performance evaluation of the phase comparison transmission line protection

In this paper, the performance of the phase comparison (PC) transmission line protection is evaluated, considering fault scenarios which are not readily analyzed in the literature on the subject. In order to do so, several faults in a 500 kV/60 Hz transmission line 200 km long were simulated using the Alternative Transients Program (ATP). Different values of power system loading, fault parameters and system-to-line impedance ratio (SIR) were taken into account. In each case, both phase and sequence elements, with and without charging current effect removal, were analyzed. The obtained results reveal the sensitivity limits of the studied PC protection algorithms, highlighting the differences on their performances when the line capacitive effect is removed from the measured currents.