Faulty phase selection method based on long wire model

Abstract

The invention provides a long line model fault phase selection method, which relates to the power system relay protection technical field, and aims to solve the technical problem of the fault phase selection method for long line models. The fault phase selection method refers to a method of utilizing the characteristic that the compensating voltage changes at two points of a fault phase are more than that during normal operation to carry out fault phase selection when a long line has a short circuit. When the compensating voltage change at one point is not obvious, the compensating voltage change at the other point is obvious certainly, and the two points are substituted for each other. In order to allow the method to be applicable to short line models at the same time, one of the voltages at two compensating points is taken as Uy1 at the position of 0.8ZL, and the other of the voltages is taken as the Uy2 at the position of 0.3ZL. The fault phase selection method of the invention canbe simultaneously applicable to the fault phase selection for long lines and short lines, can improve the accuracy and sensitivity of phase selection under the conditions of different load currents, different fault positions and different transition resistance, and has the characteristics of reliability, sensitivity, accuracy and strong adaptability.

Description

technical field [0001] The invention relates to the relay protection technology of the power system, in particular to a long-line model fault phase selection technology based on compensation voltage calculation and discrimination for high-voltage transmission line fault phase selection. Background technique [0002] Fault phase selection of high-voltage transmission lines is an important link in line protection, especially distance protection. The correctness of phase selection results directly affects the correctness of protection action outlets. Among the many phase selection schemes, the combination of low-voltage phase selection based on steady-state quantity and single-point compensation voltage phase selection scheme is a relatively comprehensive one, but it is only suitable for faults of shorter lines, and in the event of When it comes to the long-line model, when a nearby fault occurs on the line, the fault phase voltage at the protection installation will not drop m...

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Problems solved by technology

[0004] 1) Current phase selection element: Determine the maximum value of the three-phase current, then the phase is the fault phase, and the amplitude of other phase currents exceeds 0.5 times it is also considered as the fault phase. The disadvantage is that it is affected by the load current and transition resistance. Greater impact

[0005] 2) Voltage phase selection element: Three-phase voltage is used for ground faults, and the criterion is: For phase-to-phase faults, three phase-to-phase voltages are used to distinguish, which can improve the sensitivity of phase selection for long-term end faults, but the sensitivity to high-resistance grounding faults is still insufficient

[0006] 3) Impedance phase selection element: using impedance relay without zero-sequence current compensation for phase selection, the sensitivity to high-impedance faults is still insufficient

[0008] 5) Sudden current phase selection element: for example, the phase selection element of phase current difference sudden change and the comprehensive sudden change reflecting current and voltage used on the weak power supply side meet the criteria, etc. The advantage is that it is very sensitive to nearby faults and is not subject to load Current influence, but not reflective of transitional faults

[0028] But as the line model becomes longer, Z S / Z L When the short circuit occurs in the positive direction of the line, the voltage U at the protective installation of the faulty phase will drop less and less, and the original low voltage phase selection range is gradually replaced by the compensation voltage phase selection, but at 0.8Z L faults within the figure 2 It can be seen that the compensation voltage is always on the extension line of the fault point, when Z S / Z L When it decreases, it is inevitable that the voltage U at the protection installation of the fault phase will not drop much, and it is impossible to rely on low voltage for phase selection, and at the same time, the compensation point voltage U y There is little or no drop, but its amplitude has increased, so it is not possible to rely on the characteristics of the drop in fault phase compensation voltage for phase selection

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