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Transition resistance calculation method for grounding fault of neutral point in combined grounding mode

A technology of transition resistance and grounding method, which is applied in the field of calculation of ground fault transition resistance of neutral point through combined grounding mode, to achieve the effect of improving accuracy and sensitivity

Pending Publication Date: 2021-06-18
NANJING NORMAL UNIVERSITY
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Problems solved by technology

[0006] In the existing neutral point combination grounding mode of the existing generator, the single-phase grounding protection of the external power supply does not consider the influence of the neutral point grounding transformer parameters. Therefore, in order to improve the single-phase grounding fault To further improve the accuracy of the fault resistance calculation, and to further improve the sensitivity of fault detection, it is necessary to consider the neutral point grounding transformer parameters when calculating the transition resistance

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  • Transition resistance calculation method for grounding fault of neutral point in combined grounding mode

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Embodiment Construction

[0018] The specific implementation process of the present invention will be described in detail below in conjunction with the accompanying drawings.

[0019] The present invention proposes a method for calculating the ground fault transition resistance of the neutral point via combined grounding, such as figure 1 Shown is the T-type equivalent circuit considering the distribution transformer parameters when the neutral point of the hydro-generator is grounded through combination. In the figure, R 1 , L 1 It is the value converted from the leakage impedance of the primary winding to the secondary side at 20Hz; R 2 , L 2 is the leakage impedance of the secondary winding; R m , L m is the excitation impedance converted to the secondary side; R n , L n is the grounding resistance and inductance of the low-voltage side of the grounding transformer; E i For external 20Hz power supply; R i 20Hz power supply internal resistance; U s is the voltage across the transition resis...

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Abstract

The invention discloses a grounding fault transition resistance calculation method for a neutral point through a combined grounding mode. The method comprises steps that in a grounding mode that a neutral point of a hydraulic generator is connected with an inductor in parallel through a load resistor at the low-voltage side of a distribution transformer (a combined grounding mode for short), on the basis of single-phase grounding protection of an external 20Hz power supply type stator, grounding fault transition resistance is calculated by adopting an admittance criterion, the influence of equivalent parameters of a generator grounding device on calculation of a primary side grounding fault resistance value through current and voltage measured by a secondary side in the admittance criterion is analyzed, and the method for calculating the grounding fault transition resistance of the neutral point of the hydraulic generator in the combined grounding mode is obtained. According to the method, by correcting the admittance criterion, accuracy of fault resistance calculation can be improved, and sensitivity of fault detection is further improved.

Description

technical field [0001] The invention relates to the field of relay protection for generators, in particular to a calculation method for ground fault transition resistance in a neutral point combined grounding mode. Background technique [0002] As the capacity of hydro-generators continues to increase, the motor voltage and stator capacitance also continue to increase, and the grounding capacitor current increases continuously when the stator winding fails; and with the continuous promotion of the application of this type of neutral point grounding device, water The problem of significant neutral point drift of turbine generators has become increasingly prominent; in order to ensure the compensation of ground fault current and facilitate the application of stator ground protection, in recent years, some hydro-generators (such as the generators of Ertan and Tongjiezi hydropower stations) A compromise grounding scheme is applied, that is, an inductor is connected in parallel w...

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H02H1/00H02H7/06H02H7/26G01R31/52
CPCH02H1/0007H02H7/06H02H7/26G01R31/52
Inventor 丁树业周龙金子辰刘玲李争亮
Owner NANJING NORMAL UNIVERSITY
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