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This paper revisits the generalized alpha plane (GAP) formulation applied to differential protection of multi-terminal apparatus. The GAP formulation is improved by aiming for three main goals: 1) control over the internal fault settlement region (FSR); 2) enabling a simple operation characteristic instead of a restraint characteristic; and, 3) The adjustments are not dependent to the device type. For this purpose, the GAP formulation is redefined in terms of two settings, which transform the FSR into a circumference with a controllable center and radius. Thereby, a circular operation characteristic with an adjustable radius is enabled around the FSR, for to improve security. To validate and test the performance of the improved GAP, numerous computer simulations have been carried out using Alternative Transients Program on different multi-terminal equipment (i.e., busbars, transmission lines, and power transformers). Furthermore, massive data analysis is held as a means to highlight the GAP's sensibility. The obtained results demonstrate a well-stable pre-fault point, a consistent circular FSR, and the effectiveness of the improved GAP even under severe conditions. [ABSTRACT FROM AUTHOR]

This paper presents a new method for busbar differential protection based on the instantaneous power concept. In order to do so, the instantaneous power per phase of each network element connected to the busbar is computed by using the instantaneous current values and a voltage memory action strategy. The performance of the proposed technique is compared to one of the traditional instantaneous-current-based differential protection algorithms, which is widely used by manufacturers of commercial relays. Both internal and external faults, as well as evolving external-to-internal faults, were simulated in a power substation with double-bus single-breaker configuration using the software ATPDraw. The obtained results reveal that the proposed algorithm is twice or more faster than the traditional instantaneous-current-based algorithm for most of the internal and evolving external-to-internal faults, while ensuring secure operation for external ones even when severe current transformer (CT) saturation takes place, through a new harmonic power restraint strategy. Also, since the proposed method provides faster fault detection time, the requirements for CT time to saturate may be alleviated, guaranteeing correct operation even in the case of early CT saturation. [ABSTRACT FROM AUTHOR]