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A protection method for two-point grounding of different-named phases of multi-circuit parallel lines in an ungrounded system

A parallel line, grounding system technology, applied in emergency protection circuit devices, electrical components, etc., can solve the problems of inability to select lines and phases, inability to select phases, lines, etc., to achieve simple structure, easy processing, and simple logical judgment. Effect

Inactive Publication Date: 2016-09-14
KUNMING UNIV OF SCI & TECH
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  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0008] The invention provides a protection method for two-point grounding of different names and phases of multi-circuit parallel lines in an ungrounded system, which is used to overcome the problem in the prior art that only monitors whether the system is grounded but cannot select lines and phases, and line selection is affected by zero sequence. Current filter unbalanced current and the influence of capacitive current of the system, the lack of line selection but phase selection

Method used

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  • A protection method for two-point grounding of different-named phases of multi-circuit parallel lines in an ungrounded system
  • A protection method for two-point grounding of different-named phases of multi-circuit parallel lines in an ungrounded system
  • A protection method for two-point grounding of different-named phases of multi-circuit parallel lines in an ungrounded system

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Embodiment 1

[0040] Embodiment 1: as Figure 1-6 As shown, a protection method for two-point grounding of different names and phases of multiple parallel lines in an ungrounded system, the specific steps of the method are as follows:

[0041] A. Zero-sequence current transformers (1TA, 2TA, ..., nTA) 4 are installed on each parallel line (L1, L2, ..., Ln) 1 of the ungrounded system, and three-phase installed on the busbar 3 of the ungrounded system The voltage transformer TV2 senses the three phase-to-ground voltages of phase A, phase B and phase C on the bus;

[0042] B. Three-phase voltage transformer TV2 secondary side a, b, c small busbar output voltage is connected to negative sequence overvoltage relay U2> through negative sequence voltage filter; three-phase voltage transformer TV2 open triangle output voltage is connected to zero Sequence overvoltage relay U0> on;

[0043] C. Three-phase voltage transformer TV2 secondary side a, b, c small busbars take the relative ground voltage...

Embodiment 2

[0051] Embodiment 2: as Figure 1-6 As shown, a protection method for two-point grounding of different-named phases of multi-circuit parallel lines in an ungrounded system, the specific implementation steps of the method are as follows:

[0052] The ungrounded system has n parallel lines (L1, L2, ..., Ln), in which the A-phase of the L1 line is single-phase grounded, and the B-phase of the L2 line is single-phase grounded, such as figure 2 shown.

[0053] When the single-phase grounding of the A-phase of the L1 line and the single-phase grounding of the B-phase of the L2 line, the three-phase voltage transformer TV on the system bus will feel the negative sequence voltage and zero-sequence voltage, and the negative-sequence overvoltage relay U2> and the zero-sequence overvoltage relay U0>simultaneous action;

[0054] At the same time, the three-phase voltage transformer TV2 on the system bus feels the voltage drop of phase A and B relative to the ground, and the low-voltage ...

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Abstract

The invention relates to an ungrounded system multi-circuit parallel line different-phase two-point grounding protection method, and belongs to the field of ungrounded operation power system earth fault monitoring. When a negative-sequence overvoltage relay U2> and a zero-sequence overvoltage relay U0> work at the same time, it means that an asymmetric earth fault occurs, and meanwhile a low-voltage relay 1KV, a low-voltage relay 2KV and a low-voltage relay 3KV work and judge corresponding fault phases to be a phase A, a phase B and a phase C respectively; when the negative-sequence overvoltage relay U2> and the zero-sequence overvoltage relay U0> work at the same time, it means that the asymmetric earth fault occurs, and meanwhile zero-sequence current direction judgment components (1KP, 2Kp, ..., nKP) of parallel lines work to judge corresponding fault lines L1, L2,...,Ln respectively. The method overcomes the defects that in the prior art, it can only be monitored whether a system is grounded, lines and phases can not be selected, and line selection is influenced by unbalanced current of a zero-sequence current filter.

Description

technical field [0001] The invention relates to a protection method for two-point grounding of different names and phases of multi-circuit parallel lines in an ungrounded system, and belongs to the field of ground fault monitoring of an ungrounded operating power system. Background technique [0002] In the neutral point ungrounded system, when a single-phase ground fault occurs, the current at the fault point is very small, and the line voltage between the three phases remains symmetrical, which has no effect on the power supply of the load. It is allowed to continue to run for 1 to 2 hours without tripping immediately. [0003] However, when a single-phase ground fault occurs in the neutral point ungrounded system, the fault phase-to-ground voltage decreases, and the other two phase-to-ground voltages increase by 1.73 times. In order to prevent further expansion of the fault, a signal should be sent in time so that the operator can take measures. In particular, measures ...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H02H7/26
Inventor 黎敬霞李捷黎敬涛钱晶宋建马蕾晏妮
Owner KUNMING UNIV OF SCI & TECH
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