Single-phase-to-earth fault distance protection method for overload, anti-misoperation and high-resistance lines

Abstract

The invention discloses a single-phase grounding fault distance protection method for a line overloaded and resistant to maloperation and high impedance. The method uses a fault phase voltage, a fault phase current, a fault phase negative sequence current and a zero sequence current on a protected installation place of a transmission line to calculate the line distance between the setting protection range of the transmission line and a single-phase grounding fault point, and then whether the line distance between the setting protection range of the transmission line and the single-phase grounding fault point is greater than zero is judged. If the line distance is greater than zero, the single-phase grounding fault point is determined to be located within the setting protecting range of the transmission line, an action tripping signal is sent, and circuit breakers on both ends of the transmission line trip. The method eliminates the influence of transition resistance on protection action performance in principle, and the method has the strong ability to resist the influence of the transition resistance.

Description

technical field [0001] The invention relates to the technical field of electric power system relay protection, in particular to a single-phase grounding fault distance protection method for overload prevention, high resistance and resistance to high resistance. Background technique [0002] Since distance protection is less affected by power system operation mode and structural changes, it can selectively remove various faults in transmission lines instantly, and has been widely used in power system transmission line protection. The distance protection on the high-voltage transmission line is used as the main protection of the transmission line, and the distance protection on the EHV / UHV AC transmission line is used as the backup protection of the transmission line. At present, the distance protection widely used in power system transmission lines mainly includes power frequency variation distance protection and impedance distance protection. [0003] The power frequency va...

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Problems solved by technology

[0005] However, the action performance of impedance distance protection is seriously affected by the transition resistance. The main performance is that if the additional impedance generated by the transition resistance is resistive and inductive, it is easy to cause the impedance distance protection to refuse to operate when there is a fault in the protection zone of the transmission line; if the additional impedance generated by the transition resistance If it is resistive and capacitive, it is easy to cause the impedance distance protection action to exceed when there is a fault outside the protection zone of the transmission line.

[0006] Over / extreme voltage AC transmission lines are often also heavy-duty transmission lines. Heavy-load currents will cause impedance distance protection to malfunction or refuse to operate. The impact of heavy-load current on the performance of impedance distance protection cannot be ignored.

Under the condition of overload transmission, the transmission line has no faults. The measured impedance of the traditional distance protection will seriously deviate from the actual measured impedance due to the influence of the overload current, which will easily lead to the misoperation of the traditional distance protection, which will cause the power grid to expand the scope of power outages, and even cause large load transfers to threaten other transmissions. The normal operation of the line has brought huge potential safety hazards to the safety of the power grid

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