Abstract
In view of the difficulties in coordination between reliability and sensitivity of conventional generator differential protection, this paper presents a novel generator differential protection scheme based on a new braking method. On the basis of the mathematical model of the field-circuit coupling method and the electrical network cascade characteristics, the stator windings were combined and decoupled by the improved six-sequence component method to eliminate electromagnetic coupling between winding coils. In accordance with the basic characteristics of longitudinal impedance, the function of sub-item discrimination was realized. Numerous simulations and the up-to-date dynamic experiments showed that the proposed method has good state discrimination ability and can effectively resist the influence of current transformer saturation. Thus, it has an excellent prospect for engineering promotion.
Highlights
Aiming at problems of traditional generator differential protection, a more comat the problems traditional generator protection, plete, large-scale, Aiming turbo-generator model of was established, and a differential new type of braking a more complete, large-scale, model was established, and a between new type of braking method for generator differentialturbo-generator protection is proposed by using the difference method for generator differential is proposed bymethod using the between the current characteristics of the healthy phase protection and the fault phase
This is difference based the current characteristics of the healthy phase and the fault phase. This method is based on the protection characteristics of longitudinal impedance: on the protection characteristics of longitudinal impedance: For external fault, the current sum at both ends of the winding stator winding is conFor ratio external fault, the current sum at both ends of winding the winding stator winding is constantly less than the of the voltage phasor difference to the impedance, stantly less than the ratio of the voltage phasor difference to the winding which which is significantly less than the set value, so the protection is reliable and doesimpedance, not is significantly less than the set value, so the protection is reliable and does not operate
According to the simulations and the up-to-date dynamic experiments under differfault conditions, this model took into account the influence of the mutual inductance ent fault conditions, this model took into account the influence of the mutual inductance between the internal windings of the generator and made use of the stator winding method between the internal windings of the generator and made use of the stator winding to improve the model parameters
Summary
New energy power generation has been developed on a large scale in China. The proportion of new energy power generation installed capacity exceeded 50% for the first time in 2017, and the intermittent and randomness of its output brings challenges to the stability of the power system [1,2]. The wide application of new power electronic technologies, such as large-scale DC transmission and flexible AC/DC transmission, makes the operating characteristics of the power system more complex and changeable [3,4]. An in-depth investigation of the change rule of each electrical quantity after an internal fault, which occurs in the generator, is conducive to the research of new generator protection algorithms and further improves the effectiveness of generator operation.
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