Method for eliminating resonance of power distribution station

Abstract

The present invention relates to a method for eliminating resonance of a power distribution station, and a first resonance elimination device and a second resonance elimination device cooperate mutually for using. The method includes the steps as follows: 1) determining system parameters Omega C and Omega L, and determining a model of a computer resonance elimination device; 2) selecting a damping resistance value according to a neutral point serial resistance R0>=0.056 Omega L, and setting a resonance elimination value according to an open delta connecting damping resistance Rdelta<=0.32 Ohm; 3) completing an installation of the neutral point resistance, and completing an installation of the computer resonance elimination device. According to the method, the mutual cooperation of the first resonance elimination device and the second resonance elimination device has a complementary advantage, reduces a dead zone due to only one resonance elimination method, improves a reliability and a coverage area of resonance elimination without an obviously increased cost, and does no influence on a power grid at implementing. The method can be widely applied and popularized.

Description

technical field [0001] The invention belongs to the field of distribution network technology, in particular to a method for eliminating harmonics of a distribution station. Background technique [0002] In the 10kV neutral point ungrounded system, the electromagnetic voltage transformer (PT) on the bus usually needs to ground the neutral point. The nonlinear characteristics of the inductance will form a parameter match with the capacitance of the system to ground, which will cause ferromagnetic resonance, resulting in overvoltage in the system and overcurrent in the PT. Not only may the PT high-voltage fuse be blown, the PT may be burned or exploded, but even the lightning arrester may explode, the weak insulation flashover, and the grounding line selection device may malfunction, which seriously affects the safe operation of the system. [0003] In order to prevent the occurrence of ferromagnetic resonance as much as possible, in recent decades, experts at home and abroad ...

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Problems solved by technology

[0005] The device has two functions of eliminating PT saturation resonance and limiting inrush current, but there are limitations in application: 1) It can only limit the resonance of this PT, and it is invalid for other PTs in the grid (only one-to-one effective); 2) When a single-phase ground fault occurs, the measurement value of the PT zero-sequence voltage has errors, so it is not suitable for use in occasions that require high precision in the amplitude and angle of the zero-sequence voltage; 3) The thermal capacity of the device itself is limited, even if the thermal capacity is relatively high Under the excitation of large intermittent arc grounding overvoltage, the device can still be damaged

In this way, under the condition that the power frequency displacement voltage is not very high (such as the closing of the empty bus), the device will not be able to operate, and the fuse of some PTs with poor excitation characteristics and easy saturation of the iron core may be blown.

Moreover, when the capacitance of the power grid to the ground is large, this device is powerless to prevent the accident of fuse blown due to the instantaneous saturated inrush current of the transformer caused by intermittent grounding or grounding disappearance.

In addition, under the long-lasting intermittent arc overvoltage excitation, the current flowing through the PT high-voltage winding will increase significantly, and the PT may still be burned out.

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