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Single-phase gruonded fault protecting method for distributing net

A ground protection and ground fault technology, applied in the direction of emergency protection circuit devices, electrical components, etc., can solve problems such as unfavorable applications, affecting power system safety and power quality, limited accuracy and operational reliability, etc.

Inactive Publication Date: 2005-07-27
CHANGSHA UNIVERSITY OF SCIENCE AND TECHNOLOGY
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AI Technical Summary

Problems solved by technology

When a single-phase ground fault occurs in the distribution network, an overvoltage is generated. If it is not cleared in time, it may cause cable explosion and other faults, affecting the safety of the power system and power quality.
In the distribution network, the traditional method of tentatively pulling the switch one by one to find the faulty line is a waste of manpower and material resources, and has long been unable to meet the needs of the automation development of the power system.
[0003] Due to the small single-phase ground fault current in the distribution network and the unstable grounding process caused by arc light, the problem of single-phase ground fault protection has been difficult to solve completely.
The ground fault protection method based on the negative sequence current variation has high sensitivity, but is easily affected by load changes
Application No. 200310117359.9 titled "Faulty Line Selection Method for Single-phase Grounding in Small Current Grounding System" Invention patent application discloses the comparison of transient current traveling waves of each outgoing line, and the line with the largest amplitude and opposite polarity to other lines is the faulty line method, which needs to measure the magnitude and polarity of the transient change signal of the traveling wave head, and the device is difficult to realize
Application No. 00126787.6 titled "Single-phase Grounding Protection Method for Small Current Grounding System" discloses a method of using the difference between the power frequency variation of any two-phase current and the power frequency variation of another phase current (or a constant value) to form a single-phase grounding protection for small current grounding systems. This method uses steady-state quantities for calculation and has poor protection against arcing grounding faults.
The accuracy and operational reliability of the existing grounding protection methods for small current grounding systems are limited. Most of the grounding protection methods need to compare the measured quantities of each outgoing line, which is difficult to implement on the field terminal unit FTU of power distribution automation, which is not conducive to the distribution system. Application in electric automation

Method used

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  • Single-phase gruonded fault protecting method for distributing net
  • Single-phase gruonded fault protecting method for distributing net
  • Single-phase gruonded fault protecting method for distributing net

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Embodiment Construction

[0092] This protection method needs to measure three-phase current, three-phase current and zero-sequence voltage, and is suitable for realization on a hardware platform such as a microcomputer line protection device or a distribution automation field terminal unit FTU.

[0093] image 3 It is an FTU device, provided by Ningbo Tianan Group, and implemented by digital signal processor TMS320F206. The hardware structure principle is as follows Figure 4shown. It adopts 14-bit AD conversion and collects analog quantities such as three-phase voltage, three-phase current, zero-sequence voltage and zero-sequence current at 32 points per power frequency cycle. Calculate the effective value of the zero-sequence voltage. When the zero-sequence voltage is greater than the set value (10% phase voltage), it is judged that a ground fault occurs in the distribution network. The moment of zero-sequence voltage mutation is the moment when the fault occurs. Calculate the change of the three-...

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Abstract

The method includes following steps: 1, the zero sequence voltage, phase voltage and three phase of feed line are monitored on line; 2, when the zero sequence voltage is more than a setting value, the system is determined in failure, and the protection judgment is started. 3, the sampling variance of three phase current between before and after the failure is calculated, and the phase to phase difference of current sampling variance is calculated. 4, after a period of time of failure, the absolute value of sampling variance of phase current is compared with the setting value; when the sampling numbers being more than the setting value exceeds a certain proportion, the line is determined to have earth failure.

Description

technical field [0001] The invention relates to a distribution network relay protection technology, in particular to a single-phase ground fault protection for a distribution network whose neutral point is not directly grounded and a generator. Background technique [0002] Most of my country's distribution network adopts the neutral point ungrounded or grounded through the arc suppression coil. When a single-phase ground fault occurs in the distribution network, overvoltage is generated. If it is not cleared in time, it may cause cable explosion and other faults, which will affect the safety and power quality of the power system. In the distribution network, the traditional method of tentatively pulling the switch one by one to find the faulty line is a waste of manpower and material resources, and has long been unable to meet the needs of the automation development of the power system. [0003] Due to the small single-phase ground fault current in distribution network and...

Claims

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Application Information

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IPC IPC(8): H02H7/26H02H7/28
Inventor 曾祥君李继洸苏胜穆大庆郭自刚曾祥淼
Owner CHANGSHA UNIVERSITY OF SCIENCE AND TECHNOLOGY
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