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Instantaneous-power-based single phase ground fault line selection method of resonant grounded system

A single-phase-to-ground fault, instantaneous power technology, applied in the direction of electric power measurement, measurement devices, instruments, etc. through current/voltage, can solve the problems of difficult power theory, interpretation and description, and the effect is not very ideal, and achieve anti-interference ability. Strong, eliminate the large gap between the length of the line and the effect of high sensitivity

Inactive Publication Date: 2013-12-25
KUNMING UNIV OF SCI & TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

The effect is not very ideal. In the line selection method using the energy principle, when a single-phase ground fault occurs in the resonant grounding system, the energy transfer process on each line is not fully and clearly explained; Dissipated power and its components are used to describe the continuity of energy flow in the power grid, but for asymmetric power grids and power solutions in symmetric and asymmetric power grids, further research is needed
[0005] When a single-phase ground fault occurs in the resonant grounded power grid, besides the load current, there is also a fault transient current on the fault line. Composed of state inductance current, including capacitive power frequency steady-state quantity, capacitive high-frequency attenuation oscillation quantity, inductive power frequency steady-state quantity, inductive attenuation DC flow, etc.; coupled with the asymmetric component of the power grid generated by harmonic signals, it makes The transient fault signal exhibits non-sinusoidal characteristics. Under non-sinusoidal conditions, traditional power theory is usually difficult to correctly explain and describe it

Method used

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  • Instantaneous-power-based single phase ground fault line selection method of resonant grounded system
  • Instantaneous-power-based single phase ground fault line selection method of resonant grounded system
  • Instantaneous-power-based single phase ground fault line selection method of resonant grounded system

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0132] Embodiment 1: A cable hybrid resonance grounding system simulation model such as image 3 , in the figure, , , They are overhead lines with lengths of 9㎞, 15㎞ and 10㎞ respectively; , , are cables, the lengths are 4.3㎞, 6㎞ and 8㎞ respectively; The first 5㎞ is an overhead line, and the last 2㎞ is a cable; the load ranges from 0.2 to 1.5MVA, the power factor is 0.8, and the arc suppression coil is grounded through a Z-shaped transformer. set line A ground fault occurs at 4㎞ of B phase, the fault closing angle is 20°, and the transition resistance is 50 . The failure occurred at 0.04s, and the simulation time was 0.08s.

[0133] Due to space limitations, only sound lines are taken and the fault line for comparison.

[0134] (1) Instantaneous zero-sequence power comparison

[0135] 1) if Figure 4 Line l when the system shown is in normal operation 1 The instantaneous zero-sequence power waveform diagram; such as Figure 5 Line l when the system sh...

Embodiment 2

[0147] Example 2: Also for the simulation model such as image 3 , a bus ground fault occurs. At this time, the waveform diagrams of instantaneous zero-sequence power, instantaneous real power, and instantaneous virtual power of each line are similar, and the difference is not obvious. calculated for each line (p.u.) see table below:

[0148]

[0149] The top three lines with the largest variation are , and , its corresponding The values, in order of magnitude, are: =3.853p.u., =3.811p.u., =3.786 p.u.. dissatisfied , so it is determined to be a bus fault.

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Abstract

The invention relates to an instantaneous-power-based single phase ground fault line selection method of a resonant grounded system, which belongs to the technical field of small current fault line selection. According to the method, coordinate transformation is performed on the acquired line phase voltage and line current signals to calculate the instantaneous zero-sequence power, the instantaneous real power and the instantaneous virtual power. When a single phase ground fault occurs in the system, the fault line can be selected by a comprehensive algorithm formed according to the principle that the instantaneous energy variable quantity of the fault line is the largest before and after the fault. According to the method, the line voltage and line current signals are used for calculating the instantaneous power, which helps to discover subtle features in a fault ground transient process, and the sensitivity is high; also, the method adopts the principle of relativity, can help to eliminate the influence of large difference in the length of lines, unbalanced loads and arcing ground, and the anti-interference capability is strong.

Description

technical field [0001] The invention relates to a single-phase grounding fault line selection method for a resonant grounding system based on instantaneous power, belonging to the technical field of small current fault line selection Background technique [0002] The grounding of the neutral point through the arc suppression coil is widely used in the medium and low voltage distribution network at present. This grounding method has the advantage of high power supply reliability. The grounding system of the neutral point through the arc suppression coil is also called the resonant grounding system. Most of the faults in this system are single-phase grounding faults. When a single-phase ground fault occurs, no short-circuit loop is formed in the system, only a small zero-sequence current caused by the distributed capacitance of the system, and the voltage between the three phases is still symmetrical, which does not affect the normal operation of the system. my country's elect...

Claims

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Application Information

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IPC IPC(8): G01R31/02G01R21/06
Inventor 李斌束洪春
Owner KUNMING UNIV OF SCI & TECH
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