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A novel, fast unblocking scheme for distance protection to identify symmetrical faults occurring during power swings has been proposed in this paper. First of all, the change rate of three-phase active power and reactive power being the cosine function and the sine function with respect to the phase difference between the two power systems during power(More)
To deal with the maloperation of distance protection in the case of power swings, the criterion of “concentric circle” was widely used. This criterion is implemented based on the time difference that the apparent impedance locus passes through boundaries of these two impedance circles. In many cases (e.g., a very fast power swing), it will(More)
This paper discusses the set up of a mathematical model of the powerformer, a new type of salient-pole synchronous machine, for analyzing internal phase and ground faults in stator windings. The method employs a direct-phase representation considering the cable capacitance. To effectively implement the internal fault simulation, the magnetic axis locations(More)
A new criterion to detect the stator single phase-to-ground fault for Powerformer is proposed in this paper, which is based on the direction of zero-sequence compositive power flow. By virtue of the analysis of new fault characteristics of Powerformer and the comparison with conventional methods, a novel identification scheme is put forward. The proposed(More)
In this paper, a new principle of stator single-phase ground fault protection for powerformers is proposed, based on the energy function of the fault component. Different from the traditional protection schemes, which need measurements of the zero-sequence fundamental frequency voltage and the zero-sequence third-harmonic voltage at both the neutral and the(More)
This paper analyses the reality of traditional three phase AC contactless switch, and points out the inherence break time is over 10ms. It puts forward using IGBT as the main component of solid state circuit breaker for the transformer neutral point's contactless switch. This enables that the operating time of ultra-high-speed short circuit protection is(More)
Single phase-to-ground faults are the most frequent faults likely to occur in power distribution networks. The fault current of the faulty feeder is quite low when a single-phase earth fault occurs on a neutral non-effectively grounded grid. As for the safety of the system, such faults should be quickly distinguished and the faulty feeder should be(More)
A novel criterion for exactly identifying the machine leading to overvoltage of the common bus among the machines working in parallel is developed. Lose of selectivity of existing schemes in some cases is discussed. Correspondingly, an improved scheme is proposed. The change of nonload electromotive force (EMF) of generator is used to design a correction(More)
Compressed sensing (CS) aims to reconstruct signals and images from significantly fewer measurements than the traditional necessary. The step of reconstructing image is equivalent to find the sparse coefficients of image in a proper basis by solving a l<sub>1</sub> problem. This article implements the compressed sensing system using the sparse prior of(More)
Based on the analysis of the relationship between the terminal voltages and the reactive power of a generator, the shortcomings of the available scheme to protect generators in parallel from overvoltage have been pointed out, and a novel overvoltage protection scheme is put forward. For machines connected directly to busbars, especially for powerformers, a(More)