WO2014135093A1 - 一种特高压交流输电线路单相接地故障类型诊断方法 - Google Patents

一种特高压交流输电线路单相接地故障类型诊断方法 Download PDF

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Publication number
WO2014135093A1
WO2014135093A1 PCT/CN2014/072955 CN2014072955W WO2014135093A1 WO 2014135093 A1 WO2014135093 A1 WO 2014135093A1 CN 2014072955 W CN2014072955 W CN 2014072955W WO 2014135093 A1 WO2014135093 A1 WO 2014135093A1
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transmission line
uhv
phase
fault
ground fault
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French (fr)
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曾惠敏
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State Grid Fujian Electric Power Co Ltd
Maintenance Branch of State Grid Fujian Electric Power Co Ltd
State Grid Corp of China SGCC
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State Grid Fujian Electric Power Co Ltd
Maintenance Branch of State Grid Fujian Electric Power Co Ltd
State Grid Corp of China SGCC
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    • GPHYSICS
    • G01MEASURING; TESTING
    • G01RMEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/08Locating faults in cables, transmission lines, or networks
    • G01R31/081Locating faults in cables, transmission lines, or networks according to type of conductors
    • G01R31/085Locating faults in cables, transmission lines, or networks according to type of conductors in power transmission or distribution lines, e.g. overhead
    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02HEMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H3/00Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
    • H02H3/16Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to fault current to earth, frame or mass
    • H02H3/162Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to fault current to earth, frame or mass for AC systems
    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02HEMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H3/00Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
    • H02H3/38Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to both voltage and current; responsive to phase angle between voltage and current
    • H02H3/387Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to both voltage and current; responsive to phase angle between voltage and current using phase-sequence analysing arrangements

Definitions

  • the invention relates to the technical field of power system relay protection, in particular to a single-phase ground fault type diagnosis method for an ultra-high voltage AC transmission line. Background technique
  • the transmission corridor of the UHV AC transmission line is wide and the operating environment is complex. There are many kinds of factors causing the single-phase grounding fault of the UHV AC transmission line. After the UHV AC transmission line fails, the relay protection device acts on the trip to connect it to the grid. isolation. Then, the line patrol personnel searched for the fault point to eliminate the fault, which caused the line troubleshooting task to be heavy, and the long time required for troubleshooting was not conducive to the rapid restoration of power supply, which had an impact on the social economy.
  • each relay protection device does not provide a method for effectively determining the type of low-medium-high-resistance ground fault of the UHV AC transmission line, which causes the power management department to have a heavy line troubleshooting task and a long troubleshooting time.
  • the object of the present invention is to overcome the deficiencies of the prior art and to provide a single phase ground fault type diagnostic method for an UHV AC transmission line.
  • the method can realize the effective discrimination function of the low, medium and high resistance ground fault types of the UHV AC transmission line.
  • the protection device measures the fault phase voltage ⁇ > 0 , the fault phase current, the fault phase negative sequence current ⁇ and the zero sequence current at the protection installation of the UHV AC transmission line.
  • ⁇ , ⁇ , C phase.
  • ⁇ , ⁇ , C phase, ⁇ .
  • the system zero-sequence equivalent impedance of the UHV AC transmission line protection installation, 1 ⁇ 4 is the positive sequence and zero-sequence propagation coefficient of the UHV AC transmission line, Z el and Z eQ are the positive sequence and zero of the UHV AC transmission line respectively.
  • the order wave impedance, ch(.) is a hyperbolic cosine function, which is a hyperbolic sine function and is a hyperbolic arctangent function.
  • the protection device calculates the phase angle of Z el ", calculates the angle of the leading 2 , calculates the ⁇
  • leads the angle of ⁇ 2 where 0 is the hyperbolic tangent function.
  • the amplitude of the ⁇ phase transmission line voltage during the line is the setting factor of the medium resistance ground fault.
  • the single-phase ground fault of the UHV AC transmission line is a medium-resistance ground fault; wherein, the high-resistance ground fault setting system
  • the single-phase ground fault of the UHV AC transmission line is a high-resistance ground fault.
  • the method of the invention is suitable for single-phase low-medium-high-resistance ground fault type diagnosis of the entire fault process of the UHV AC transmission line, and the diagnostic performance is not affected by factors such as transition resistance, load current, system operation mode and the like.
  • FIG. 1 is a schematic diagram of a power transmission system of an UHV AC transmission line to which the method of the present invention is applied.
  • the CVT is a voltage transformer and the CT is a current transformer.
  • the protection device samples the voltage of the voltage transformer CVT and the current waveform of the current transformer CT at the protection installation of the UHV AC transmission line to obtain the instantaneous value of the voltage and current, and uses the instantaneous value of the voltage and current collected by the Fourier.
  • the algorithm calculates the fault phase voltage t 0 , the fault phase current, the fault phase negative sequence current ⁇ and the zero sequence current / of the UHV AC transmission line protection installation.
  • ⁇ , ⁇ , C phase.
  • Protection device calculates ⁇ ⁇ ⁇ ⁇ leading angle calculating ⁇ ⁇ ⁇ + n.
  • the protection device calculates the phase angle of ⁇ , and calculates the angle of C 0 leading 02 , and calculates the angle ⁇ 2 + ⁇ 3 ) z o ⁇ ⁇ ⁇
  • the single-phase ground fault of the UHV AC transmission line is a low-resistance ground fault; where U is the normal operation of the UHV AC transmission line
  • the voltage amplitude of the phase transmission line The setting factor of the medium resistance ground fault.
  • the single-phase ground fault of the UHV AC transmission line is a medium-resistance ground fault
  • the single-phase ground fault of the UHV AC transmission line is a high-resistance ground fault.
  • the method of the invention is suitable for single-phase low-medium-high-resistance ground fault type diagnosis of the entire fault process of the UHV AC transmission line, and the diagnostic performance is not affected by factors such as transition resistance, load current, system operation mode and the like.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Emergency Protection Circuit Devices (AREA)

Abstract

一种特高压交流输电线路单相接地故障类型诊断方法。该方法首先利用集总参数模型建模,根据特高压交流输电线路保护安装处到单相接地故障点的电压降与故障距离呈线性关系计算故障距离,然后采用长线方程精确描述特高压交流输电线路电压、电流传输的物理特性,利用计算得到的故障距离计算输电线路补偿电流,进而利用特高压交流输电线路单相接地故障类型诊断判据对特高压交流输电线路单相接地故障类型进行精确诊断。该方法适用于特高压交流输电线路整个故障过程的单相低中高电阻接地故障类型诊断,诊断性能不受过渡电阻、负荷电流、系统运行方式等因素的影响。

Description

-种特高压交流输电线路单相接地故障类型诊断方法
技术领域
本发明涉及电力系统继电保护技术领域, 具体地说是涉及一种特高压交流输电线路单相接地故障类型 诊断方法。 背景技术
特高压交流输电线路的输电走廊宽、运行环境复杂, 引起特高压交流输电线路单相接地故障的因素种 类繁多, 特高压交流输电线路发生故障后, 由继电保护装置动作于跳闸将其与电网隔离。 然后由线路巡 线人员翻山越岭的寻找故障点以排除故障, 造成线路故障排除任务繁重, 且故障排除所需时间长, 不利 于快速恢复供电, 对社会经济造成影响。
特高压交流输电线路各种故障类型中单相接地故障占 90%以上, 引起特高压交流输电线路单相接地 故障的因素有漂浮物引起特高压交流输电线路低电阻单相接地故障、 绝缘子闪络引起特高压交流输电线 路中电阻接地故障、 火烧山引起特高压交流输电线路高电阻接地故障等。 然而, 目前各继电保护装置都 没有提供一种能有效判别特高压交流输电线路低中高电阻接地故障类型的方法, 造成电力管理部门的线 路故障排除任务繁重、 故障排除时间长。
发明内容
本发明的目的在于克服已有技术存在的不足, 提供一种特高压交流输电线路单相接地故障类型诊断方 法。 该方法可实现特高压交流输电线路低中高电阻接地故障类型的有效判别功能。
为完成上述目的, 本发明采用如下技术方案:
( 1 )保护装置测量特高压交流输电线路保护安装处的故障相电压 ί>0、 故障相电流 、故障相负序电 流^和零序电流 。; 其中, φ = Α、 Β、 C相。
(2 ) 保护装置计算 领先 的角度 , 计算 ζ /0 领先 ϊφ1的角度 ΘΊ, 计算单位长度特 高压交流输电线路正序阻抗 的相角 ; 其中, 为单位长度特高压交流输电线路正序阻抗, zQ为单位 长度特高压交流输电线路零序阻抗。
( 3 ) 保护装置计算特高压交流输电线路补偿电流 isei =
Figure imgf000004_0001
其中, φ = Α、 Β、 C相, Ζ。为特高压交流输电线路保护安装处的系统零序等值阻抗, 、 ¼分别 为特高压交流输电线路正序、零序传播系数, Zel、 ZeQ分别为特高压交流输电线路正序、零序波阻抗, ch(.) 为双曲余弦函数, 为双曲正弦函数, 为双曲反正切函数。
U,
(4 )保护装置计算 Zel 的相角《, 计算 领先 2的角度 , 计算 ζι
ζι 领先^ 2的角度 其中, 0为双曲正切函数。
( 5 ) 保护装置比较 是否成立, 若成立,
Figure imgf000004_0002
则判断特高压交流输电线路单相接地故障为低电阻接地故障; 其中, U 为特高压交流输电线路正常运
Figure imgf000004_0003
行时的 φ相输电线路电压幅值, 为中电阻接地故障整定系数。
U,
( 6 ) 保护装置比较 Ά - 是否成立,
Ιφ2 sm{a + r)
ζι 若成立, 则判断特高压交流输电线路单相接地故障为中电阻接地故障; 其中, 为高电阻接地故障整定系
( 7 ) 保护装置 是否成立, 若成立,
Figure imgf000004_0004
则判断特高压交流输电线路单相接地故障为高电阻接地故障。
本发明与现有技术相比较, 具有下列积极成果: 本发明方法适用于特高压交流输电线路整个故障过程的单相低中高电阻接地故障类型诊断, 诊断性能 不受过渡电阻、 负荷电流、 系统运行方式等因素的影响。
附图说明
图 1为应用本发明方法的特高压交流输电线路的输电系统示意图。
具体实施方式
下面结合实施例对本发明的技术方案做进一步详细表述。
图 1中 CVT为电压互感器、 CT为电流互感器。 保护装置对特高压交流输电线路保护安装处的电压互 感器 CVT的电压和电流互感器 CT的电流波形进行采样得到电压、 电流瞬时值, 并对其采集到的电压、 电 流瞬时值利用傅里叶算法计算特高压交流输电线路保护安装处的故障相电压 t 0、 故障相电流 、 故障相 负序电流 ^和零序电流 /。; 其中, φ = Α、 Β、 C相。 保护装置计算 ύφ领先 ϊφΊ的角度 , 计算 Ζι ϊφ +n 。 领先 ϊ 的角度 , 计算单位长度特高压交 流输电线路正序阻抗 的相角 θ3 ; 其中, 为单位长度特高压交流输电线路正序阻抗, ZQ为单位长度特 高压交流输电线路零序阻抗。
保护装置计算特高压交流输电线路补偿电流 isei =
Figure imgf000005_0001
保护装置计算 Ύν 的相角《, 计算 C 0领先 02的角度 , 计算 ^领 θ2 + θ3) zo― ζι
I0
zl 先^的角度 其中, φ = Α、 B、 C相, ZQ为特高压交流输电线路保护安装处的系统零序等值阻抗, ¼分别为特高压交流输电线路正序、 零序传播系数, Zd、 ZeQ分别为特高压交流输电线路正序、 零序波阻 抗, 为双曲余弦函数, 为双曲正弦函数, ct z (.)为双曲反正切函数, 为双曲正切函数。 保护装置比较 是否成立, 若成立, 则判
Figure imgf000006_0001
断特高压交流输电线路单相接地故障为低电阻接地故障; 其中, U 为特高压交流输电线路正常运行时
Figure imgf000006_0002
的^相输电线路电压幅值; 为中电阻接地故障整定系数。
保护装置比较 是否成立, 若成
Figure imgf000006_0003
立, 则判断特高压交流输电线路单相接地故障为中电阻接地故障; 其
保护装置比较 是否成立, 若成立, 则判
Figure imgf000006_0004
断特高压交流输电线路单相接地故障为高电阻接地故障。
本发明方法适用于特高压交流输电线路整个故障过程的单相低中高电阻接地故障类型诊断, 诊断性能 不受过渡电阻、 负荷电流、 系统运行方式等因素的影响。
以上所述仅为本发明的较佳具体实施例, 但本发明的保护范围并不局限于此, 任何熟悉本技术领域的 技术人员在本发明揭露的技术范围内, 可轻易想到的变化或替换, 都应涵盖在本发明的保护范围之内。

Claims

权 利 要 求 书
1、 一种特高压交流输电线路单相接地故障类型诊断方法, 包括下列步骤:
( 1 )保护装置测量特高压交流输电线路保护安装处的故障相电压 ί>0、 故障相电流 、故障相负序电 2和零序电流 。; 其中, φ = Α、 Β、 C相,
(2 ) 保护装置计算 领先 的角度 , 计算 Ζ: ζο - - l i0 领先 2的角度 , 计算单位长度特 高压交流输电线路正序阻抗 的相角 ; 其中, 为单位长度特高压交流输电线路正序阻抗, ZQ为单位 长度特高压交流输电线路零序阻抗,
( 3 ) 保护装置计算特高压交流输电线路补偿电流 isei =
Figure imgf000007_0001
其中, φ = Α、 B、 C相, ZQ为特高压交流输电线路保护安装处的系统零序等值阻抗, 、 ¼分别 为特高压交流输电线路正序、零序传播系数, Zel、 ZeQ分别为特高压交流输电线路正序、零序波阻抗, ch(.) 为双曲余弦函数, 为双曲正弦函数, 为双曲反正切函数,
U,
(4 )保护装置计算 Zel 的相角《, 计算 领先 2的角度 , 计算 ζι
ζι
^领先^ 2的角度 其中, 0为双曲正切函数,
(5 ) 保护装置比较 是否成立, 若成立,
则判断特高压交流输电线 特高压交流输电线路正常运
Figure imgf000007_0002
行时的 Φ相输电线路电压幅值, 为中电阻接地故障整定系数, U,
(6) 保护装置比较 是否成立,
Ιφ2 sm{a + r)
zi
若成立, 则判断特高压交流输电线路单相接地故障为中电阻接地故障; 其中, 为高电阻接地故障整定系 数,
(7) 保护装置 是否成立, 若成立,
Figure imgf000008_0001
则判断特高压交流输电线路单相接地故障为高电阻接地故障。
PCT/CN2014/072955 2013-03-06 2014-03-06 一种特高压交流输电线路单相接地故障类型诊断方法 Ceased WO2014135093A1 (zh)

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Families Citing this family (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103163413B (zh) * 2013-03-06 2015-07-01 福建省电力有限公司 一种特高压交流输电线路单相接地故障类型诊断方法
CN103762567B (zh) * 2014-02-18 2016-02-03 国家电网公司 基于故障位置因子的输电线路单相接地故障继电保护方法
CN104049182B (zh) * 2014-07-09 2016-08-24 国家电网公司 同杆并架双回线路单相接地故障类型诊断方法
CN105652156B (zh) * 2016-03-23 2018-11-06 国网福建省电力有限公司 特高压交流输电线路单相接地电压相位突变测距方法
CN105703339A (zh) * 2016-03-29 2016-06-22 国网福建省电力有限公司 特高压交流输电线路单相接地电压相位保护方法
CN112946534A (zh) * 2021-02-02 2021-06-11 长春工程学院 基于全线路检测的输电线路接地状态检测方法

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102200563A (zh) * 2011-01-20 2011-09-28 福建省电力有限公司福州超高压输变电局 一种基于定位函数幅值特性线路单相接地故障单端测距方法
CN102707197A (zh) * 2012-06-11 2012-10-03 福建省电力有限公司检修分公司 一种输电线路单相接地故障距离测定方法及故障类型诊断方法
CN103149493A (zh) * 2013-01-31 2013-06-12 福建省电力有限公司 一种输电线路单相接地故障类型诊断方法
CN103163413A (zh) * 2013-03-06 2013-06-19 福建省电力有限公司 一种特高压交流输电线路单相接地故障类型诊断方法

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FI108893B (fi) * 2000-09-22 2002-04-15 Abb Substation Automation Oy Menetelmä sähköverkon vikaantumassa olevan tai viallisen lähdön tai haaran ilmaisemiseksi
CN1349103A (zh) * 2000-10-18 2002-05-15 深圳市中兴通讯股份有限公司 一种配电网单相接地故障的判断方法
EP2113778B1 (en) * 2008-04-29 2017-12-06 ABB Schweiz AG System and method for determining location of phase-to-phase fault or three-phase fault
CN102331544B (zh) * 2011-07-28 2014-01-22 广东电网公司电力科学研究院 一种输电线路高阻接地与金属性接地故障的辨别方法
CN102520318B (zh) * 2012-01-04 2014-02-05 国家电网公司 一种输电线路故障识别方法

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102200563A (zh) * 2011-01-20 2011-09-28 福建省电力有限公司福州超高压输变电局 一种基于定位函数幅值特性线路单相接地故障单端测距方法
CN102707197A (zh) * 2012-06-11 2012-10-03 福建省电力有限公司检修分公司 一种输电线路单相接地故障距离测定方法及故障类型诊断方法
CN103149493A (zh) * 2013-01-31 2013-06-12 福建省电力有限公司 一种输电线路单相接地故障类型诊断方法
CN103163413A (zh) * 2013-03-06 2013-06-19 福建省电力有限公司 一种特高压交流输电线路单相接地故障类型诊断方法

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
MA, JING ET AL.: "Phase Distance Protection of Transmission Line Based on Distributed Parameter Model", ELECTRIC POWER AUTOMATION EQUIPENT, vol. 32, no. 5, 31 May 2012 (2012-05-31), pages 43 - 49 *
ZENG, HUIMIN ET AL.: "Distributed Parameter Based Distance Protection for Transmission Lines and Identification of Short-Circuit Faults Under Low-, Medium- and High Resistance at Fault Point", POWER SYSTEM TECHNOLOGY, vol. 38, no. 1, 31 January 2014 (2014-01-31), pages 262 - 268 *

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