Pilot protection method suitable for T-type wiring transmission line

Abstract

The invention discloses a pilot protection method suitable for a T-type wiring transmission line, which is characterized in that: (1) a fast start element: the absolute value of the difference of ik, i<k-N> is more than the sum of the product of Ks and the absolute value of the difference of i<k-N>, i<k-2N> and Imk, wherein N is the number of sampling points of each period, and Imk is a fixed threshold, when any phase in the three-end current of the T-type wiring transmission line meets the conditions, the fast start element acts; and (2) protection action judgment conditions: the absolute value of delta Ucd is less than the product of Krel, Zc and the absolute value of delta Icd; and the absolute value of Icd is more than Iset, wherein delta Ucd is equal to the sum of delta Um, delta Un and delta Up; delta Icd is equal to the sum of delta Im, delta In and delta Ip, Icd is equal to the sum of Im, In and Ip; the delta Um, delta Un and delta Up and delta Im, delta In and delta Ip are the failure voltage component and the failure current component at the m, n, p buses of the T-type wiring transmission line; Im, In and Ip are the steady-state current passing through the m, n and p buses, Krel is a reliability coefficient, ZC is the equivalent capacitance of the line, Iset is a current set value, and Icd is the steady-state differential current of the three-end transmission line. Through the method, the pilot protection sensitivity of the T-type wiring transmission line is not affected by the fault current and through current, and the sensitivity is improved.

Description

technical field [0001] The invention relates to a longitudinal protection method suitable for T-connection transmission lines, which belongs to the field of electricity. Background technique [0002] The principle of current differential protection was proposed at the beginning of this century. Because of its simple principle and reliable performance, it is widely used as the main protection of components such as generators, transformers, busbars and large motors in power systems. The application of the principle of current differential protection on power lines is the traditional guide line protection at the earliest. It can be used as the full-line fast-moving main protection for short-distance lines in high- and medium-voltage power grids. For medium and long-distance transmission lines, it is difficult to measure The current at the opposite end of the line, and for a long time, it is difficult to apply the principle of current differential protection. [0003] With the ...

AI Technical Summary

Problems solved by technology

Since the load current is introduced into the differential protection criterion of the full-current phasor differential protection, the sensitivity of faults in the area is reduced, and the protection may refuse to operate when a high-resistance fault is accompanied by a large load; and based on the fault component current The differential protection method of the T-connection line is in the case of an internal fault in the three-terminal system and a fault current flows out on one side, due to the influence of the through current, compared with the case of no fault current flowing out when the internal fault occurs, although the action amount remains the same, but the amount of braking has increased, and in this case the protection may also refuse to move

At present, the phase-separated current differential protection of transmission lines does not consider the influence of distributed capacitive currents and some defects in the differential protection method of T-connection transmission lines.

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