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Method for selecting wire after single-phase grounding of ungrounded system

A single-phase grounding and grounding system technology, applied in the direction of fault location, fault detection according to conductor type, etc., can solve problems such as TV fuse blown, bus short circuit, power cable explosion, etc. The method is simple and convenient, reduces faults, and improves fault detection efficiency effect

Inactive Publication Date: 2017-02-22
NANJING NENGDI ELECTRICAL TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, in actual operation, overvoltage may cause accidents such as power cable explosion, TV fuse blowout or even burnout, and bus short circuit. It is very important to quickly determine the system ground point and eliminate single-phase ground faults for the safe operation of the system. Therefore, it is necessary to develop a A new and simple way to solve existing problems

Method used

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  • Method for selecting wire after single-phase grounding of ungrounded system
  • Method for selecting wire after single-phase grounding of ungrounded system

Examples

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Effect test

Embodiment 1

[0021] The method for line selection after a single-phase grounding occurs in an ungrounded system of the present invention comprises the following steps:

[0022] A) In the substation system where the neutral point is not grounded, a control switch and a control switch are installed between the neutral point of the capacitor and the ground

[0023] A resistor with a resistance value of 100 ohms, in normal operation, the control switch is in the minute position;

[0024] B) According to the change of the bus voltage to judge whether there is a single-phase grounding of the line, the criterion is that the zero-sequence voltage is greater than 50V, and at the same time, when the voltage of a certain phase of the three-phase voltage drops less than 30V, and the voltage of the other two phases rises greater than 70V, It is judged that a single-phase ground fault has occurred;

[0025] C) After judging that it is single-phase grounding, close the control switch immediately and put...

Embodiment 2

[0029] The method for line selection after a single-phase grounding occurs in an ungrounded system of the present invention comprises the following steps:

[0030] A) In a substation system where the neutral point is not grounded, a control switch and a resistor with a resistance value of 100 ohms are installed between the neutral point of the capacitor and the ground. During normal operation, the control switch is in the position;

[0031] B) According to the change of the bus voltage to judge whether there is a single-phase grounding of the line, the criterion is that the zero-sequence voltage is greater than 50V, and at the same time, when the voltage of a certain phase of the three-phase voltage drops less than 30V, and the voltage of the other two phases rises greater than 70V, It is judged that a single-phase ground fault has occurred;

[0032] C) After judging that it is single-phase grounding, close the control switch immediately and put the resistor into it. At this t...

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Abstract

The invention discloses a method for selecting a wire after single-phase grounding of an underground system. By adopting the method, after single-phase grounding happens in the ungrounded system, a fault wire can be selected according to the change of zero sequence current after a neutral point of a capacitor bank is instantly grounded. The method comprises the following steps: A, additionally installing a control switch and a medium resistor between the neutral point of a capacitor and the ground, and keeping the control switch on the point position during normal operation; B, judging whether single-phase grounding happens in a circuit or not according to the voltage change of a bus bar, and judging that single-phase grounding failure happens when the criterion is that a zero sequence voltage is more than a certain value, a certain phase voltage in three-phase voltages is reduced, and voltages of other two phases rise; C, immediately closing the control switch and putting in a resistor after single-phase grounding is judged to ensure that the grounding mode of the system is turned into grounding through the resistor and the active component of the zero sequence current of the single-phase grounded circuit is greatly increased; and D, tripping the circuit switch to clear the failure after the single-phase grounded circuit is determined.

Description

technical field [0001] The invention relates to a method for line selection after a single-phase grounding occurs in an ungrounded system. Background technique [0002] In my country's 35kV and 10kV power systems, the neutral point of the transformer mostly adopts the non-direct grounding method (small current grounding system). The voltage drops to zero, and the non-fault phase voltage rises to the phase voltage times, but the line voltage between the three phases remains symmetrical and has no effect on the power supply load, so the regulations allow to continue to run for 1 to 2 hours. However, in actual operation, accidents such as power cable explosion, TV fuse blowout or even burnout, and bus short circuit may be caused by overvoltage. It is very important to quickly determine the system ground point and eliminate single-phase ground faults for the safe operation of the system. Therefore, it is necessary to develop a A new and simple way to solve an existing problem....

Claims

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Application Information

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IPC IPC(8): G01R31/08
CPCG01R31/085
Inventor 许平王剑
Owner NANJING NENGDI ELECTRICAL TECH
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