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Direct-current power grid ground fault ultrahigh-speed non-unit protection method

A ground fault, DC power grid technology, applied in fault locations, power transmission AC networks, emergency protection circuit devices, etc. The effect of action speed and reliability

Inactive Publication Date: 2018-03-30
TIANJIN UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

The MMC DC power grid grounding method is mostly a small current grounding system, that is, the three phases on the AC side of the converter are grounded through a star reactor and then high-impedance grounding. When a single-pole grounding fault occurs on the DC line, the fault current is small, but it may be Cause the voltage of the system to ground to rise, which will threaten the safety of lines and equipment
In the traditional flexible DC transmission network, the main protection principle of the line usually adopts the longitudinal differential protection. The action speed of this protection principle is slow, and the failure of the communication device may cause the protection to malfunction or refuse to operate.
The high-voltage and large-capacity flexible DC power grid has higher requirements on the quickness and reliability of protection, and the protection principle based on communication is no longer applicable

Method used

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  • Direct-current power grid ground fault ultrahigh-speed non-unit protection method
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Embodiment Construction

[0023] The present invention will be described in further detail below in conjunction with accompanying drawing and example.

[0024] An obvious feature after a single pole ground fault is the ground pole current i of the converter station g increase. During normal operation and double-pole short-circuit fault i g are close to 0, and will increase by more than ten times or even dozens of times when a single-pole grounding fault occurs (considering the grounding electrode resistance is 1000Ω). When the protection detects a sudden increase in the grounding pole current, it can be judged that a single-pole grounding fault has occurred in the system. The fault occurrence and type criteria can be set as:

[0025]

[0026] In the formula, means i g The average value of N consecutive sampling values, k s is the sampling point at the moment of protection startup, Δ 2 Indicates the current threshold. when i g When the threshold is exceeded, the protection determines that a...

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Abstract

The invention belongs to the field of power system relay protection and automation, and particularly relates to a direct-current power grid ground fault ultrahigh-speed non-unit protection method. Themethod includes: considering that no ground fault occurs when current at a ground point on an alternating-current side of a system does not meet fault occurrence and type criteria; considering that there might be a ground fault when the current meets the fault occurrence and type criteria, sending a fault occurrence signal to a higher-level protection device, and sending fault type criteria to the higher-level protection device; measuring voltage at two ends of a current-limiting reactor in real time by each protection device, considering that a ground fault occurs within the protection rangewhen the voltage is greater than a voltage threshold value, and sending a fault positioning signal to the higher-level protection device. By the method, protection correctness when ground faults occur at different positions of the system can be ensured; compared with other protection methods, the method is higher in action speed, only needs to utilize non-unit information and does not depend on inter-station communication devices, so that protection reliability is improved.

Description

technical field [0001] The invention relates to the fields of relay protection and automation of power systems, in particular to a single-pole grounding fault protection method for a pseudo-bipolar wiring structure MMC DC power grid. Background technique [0002] In recent years, my country's wind power, photovoltaic power generation and other renewable energy installed capacity has continued to expand, making the power generation center far away from the load center. The high-voltage direct current transmission method has gained great attention and development because it is suitable for long-distance and large-capacity power transmission. At present, MMC converters with active and reactive power independent control properties are widely used in flexible direct current transmission projects, and have the advantages of high output voltage level, low switching loss and good output voltage waveform. [0003] It is of great value and research prospect to study the DC power grid...

Claims

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Application Information

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IPC IPC(8): H02H7/26H02H7/28G01R31/08H02J3/36
CPCG01R31/086H02H7/268H02H7/28H02J3/36Y02E60/60Y04S10/52
Inventor 薛士敏崔淼廉杰齐金龙范勃旸
Owner TIANJIN UNIV
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