Distribution network fault line selection method using non-power frequency transient state component

Abstract

The invention discloses a new method for performing fault line selection by using the characteristic of a non-power frequency transient state fault component for extracting single-phase fault zero-sequence current by using Hilbert-Huang transform (HHT). The method comprises the following steps: performing EMD decomposition on fault zero-sequence current of each feeder line by using the HHT to acquire an IMF component of the zero-sequence current of each feeder line; constructing a resolving signal according to Hilbert transform, solving instantaneous amplitude and frequency of the zero-sequence current of each feeder line, and eliminating a power frequency component in the instantaneous frequency of the zero-sequence current of each feeder line to acquire a non-power frequency fault component; and forming a line selection criterion according to the characteristics that the amplitude of the non-power frequency fault component of the fault line is greater than that of the non-fault line and the polarity of the fault line is opposite to that of the non-fault line. The line selection method is not affected by an arc suppression coil, and is applicable to non-grounded, arc suppression coil grounded and high-resistor grounded systems, overhead lines or cable lines and cable overhead mixed lines; and the line selection result shows that the method applied to low-current single-phase grounding fault line selection is accurate and reliable.

Description

technical field The invention relates to a fault line selection method of a distribution network, in particular to a method for selecting a fault line by using Hilbert-Huang transformation (HHT) to extract the zero-sequence current component of a non-power frequency transient fault. Background technique For a long time, the problem of low-current ground fault detection has been a major problem in power systems. Traditional line selection methods for small current grounding systems include amplitude comparison method, polarity comparison method, group ratio amplitude comparison method, zero sequence current reactive power direction method, etc. These methods can only basically meet the needs of small current ungrounded systems. Line selection requirements, not applicable to resonant grounding systems. At present, the line selection methods used in the resonant grounding system mainly include the active component comparison method and the harmonic comparison method. The act...

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Problems solved by technology

The active component comparison method mainly includes the amplitude and polarity comparison method of the active current component of the fault current, the active current direction comparison method, and the active power direction comparison method. The phase angle propagation error of the transformer and current transformer has a great influence, resulting in low reliability of this method, which cannot meet the reliability requirements of the current power supply network

The harmonic comparison method is greatly affected by the content of harmonic sources in the system and the location of the fault, the reliability of the method is relatively low, and it also fails to meet the practical requirements

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