Single-phase gruonded fault protecting method for distributing net

A ground protection and ground fault technology, applied in emergency protection circuit devices, electrical components, etc., can solve problems affecting power system safety and power quality, limited accuracy and operational reliability, and poor arc ground fault protection capabilities

CN100418282CInactive Publication Date: 2008-09-10CHANGSHA UNIVERSITY OF SCIENCE AND TECHNOLOGY
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Patent Information

Authority / Receiving Office
CN · China
Patent Type
Patents(China)
Current Assignee / Owner
Publication Date
2008-09-10
Estimated Expiration
Not applicable · inactive patent

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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.
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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...

Examples

Embodiment Construction

[0093] 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.

[0094] 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 4 shown. 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...