WO2019105486A1 - 差动保护的判断方法 - Google Patents

差动保护的判断方法 Download PDF

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Publication number
WO2019105486A1
WO2019105486A1 PCT/CN2018/124261 CN2018124261W WO2019105486A1 WO 2019105486 A1 WO2019105486 A1 WO 2019105486A1 CN 2018124261 W CN2018124261 W CN 2018124261W WO 2019105486 A1 WO2019105486 A1 WO 2019105486A1
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Prior art keywords
phase
current
protection device
amplitude
currents
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PCT/CN2018/124261
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English (en)
French (fr)
Inventor
赵萍
何文其
张弛
沈一平
裘愉涛
徐华
徐晓春
李皓
郑远德
周再兵
黄镇
王康
吴坚
朱涛
谈浩
李奔
赵青春
朱晓彤
周晨
应国德
蒋旭
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Taizhou Power Supply Co of State Grid Zhejiang Electric Power Co Ltd
State Grid Corp of China SGCC
Original Assignee
Taizhou Power Supply Co of State Grid Zhejiang Electric Power Co Ltd
State Grid Corp of China SGCC
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Application filed by Taizhou Power Supply Co of State Grid Zhejiang Electric Power Co Ltd, State Grid Corp of China SGCC filed Critical Taizhou Power Supply Co of State Grid Zhejiang Electric Power Co Ltd
Priority to US16/761,022 priority Critical patent/US11764568B2/en
Publication of WO2019105486A1 publication Critical patent/WO2019105486A1/zh
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
    • H02H7/04—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for transformers
    • H02H7/045—Differential protection of transformers
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
    • H02H7/26—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/08—Locating faults in cables, transmission lines, or networks
    • G01R31/081—Locating faults in cables, transmission lines, or networks according to type of conductors
    • G01R31/085—Locating faults in cables, transmission lines, or networks according to type of conductors in power transmission or distribution lines, e.g. overhead
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
    • H02H3/26—Emergency 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 difference between voltages or between currents; responsive to phase angle between voltages or between currents
    • H02H3/28—Emergency 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 difference between voltages or between currents; responsive to phase angle between voltages or between currents involving comparison of the voltage or current values at two spaced portions of a single system, e.g. at opposite ends of one line, at input and output of apparatus
    • H02H3/30—Emergency 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 difference between voltages or between currents; responsive to phase angle between voltages or between currents involving comparison of the voltage or current values at two spaced portions of a single system, e.g. at opposite ends of one line, at input and output of apparatus using pilot wires or other signalling channel
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
    • H02H7/26—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured
    • H02H7/261—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured involving signal transmission between at least two stations
    • H02H7/263—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured involving signal transmission between at least two stations involving transmissions of measured values
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
    • H02H3/26—Emergency 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 difference between voltages or between currents; responsive to phase angle between voltages or between currents
    • H02H3/28—Emergency 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 difference between voltages or between currents; responsive to phase angle between voltages or between currents involving comparison of the voltage or current values at two spaced portions of a single system, e.g. at opposite ends of one line, at input and output of apparatus
    • H02H3/30—Emergency 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 difference between voltages or between currents; responsive to phase angle between voltages or between currents involving comparison of the voltage or current values at two spaced portions of a single system, e.g. at opposite ends of one line, at input and output of apparatus using pilot wires or other signalling channel
    • H02H3/307—Emergency 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 difference between voltages or between currents; responsive to phase angle between voltages or between currents involving comparison of the voltage or current values at two spaced portions of a single system, e.g. at opposite ends of one line, at input and output of apparatus using pilot wires or other signalling channel involving comparison of quantities derived from a plurality of phases, e.g. homopolar quantities; using mixing transformers

Definitions

  • This application belongs to the field of relay protection, for example, to a method for judging differential protection.
  • multi-terminal T-connected transmission lines are increasingly appearing in high-voltage transmission lines in terms of saving equipment investment and reducing land acquisition area.
  • the multi-point T-connection method is characterized in that different nodes T are connected to the same networked line, so the grid-connected line is more important, and the reliability and sensitivity of the protection are high.
  • any one end failure will affect the normal power transmission of other terminals, so in case of failure, rapid removal is required.
  • Due to the special nature of multi-terminal T-connected transmission lines distance protection and zero-sequence protection are difficult to meet the requirements of quick action and selectivity. Due to its simple principle, the current differential is hardly affected by many factors such as voltage transformer disconnection, series compensation or transmission line parallel rods, and is widely used in double-ended and three-terminal high-voltage transmission lines.
  • the embodiment of the present application provides a method for judging differential protection, which is applicable to a multi-terminal T-connected transmission line.
  • the method can select the value of the braking coefficient K according to the fault condition, thereby improving the sensitivity of the multi-terminal T-connected transmission line region. Improve the reliability of braking characteristics outside the zone.
  • the present application provides a method for judging differential protection, which is applicable to a multi-terminal T-connection transmission line
  • the multi-terminal T-connection transmission line includes a host protection device and a slave protection device
  • the host protection device is the multi-terminal T connection.
  • the determination method comprising: step 1, multiphase to the host protection device The current and the multi-phase current of the slave protection device are separately sampled, and the multi-phase current amplitude sampled by the slave protection device is transmitted to the host protection device; Step 2, the host protection device is Calculating the amplitudes of all phase currents sampled by the slave protection device and the step-by-step protection device, and obtaining the largest fault component current of each phase current amplitude of the total phase currents And calculating a differential current I cd per phase of the total phase currents, a brake current I res for each phase of the total phase currents, and removing all of the phase currents Vector sum of fault component currents Step 3: selecting a target phase current amplitude from the sampled all phase current amplitudes, and a maximum fault component current in the target phase current amplitude When it is greater than the threshold set value I max 0 , according to
  • I set is a current setting value, and if the target phase differential current I cd satisfies the above differential determination, it is determined that there is a fault in the region of the target phase.
  • the present application provides a method for judging differential protection applicable to a multi-terminal T-connection transmission line.
  • any end is determined as a host protection device, and the other ends are used as slave protection devices, as shown in FIG.
  • the judging method includes steps 1 to 5.
  • step 1 the multi-phase current of the host protection device on the multi-terminal T transmission line and the multi-phase current of the slave protection device are sampled, and the slave protection device transmits the sampled multi-phase current amplitude to the host protection device.
  • step 2 the host protection device calculates the amplitudes of all phase currents sampled by the slave protection device and the host protection device itself, and calculates the fault component current with the largest amplitude of each phase current in all phase currents. And calculate the differential current I cd for each phase in all phase currents, the brake current I res for each phase in all phase currents, and the removal of all phase currents.
  • Vector sum of fault component currents
  • step 3 the target phase current amplitude is selected from the sampled phase current amplitudes, and the maximum fault component current is in the target phase current amplitude. Greater than the threshold set value I max 0 , according to the maximum fault component current of the target phase current amplitude Phase angle and target phase current amplitude are removed Vector sum of fault component currents
  • the difference of the phase angles determines the target phase angle difference ⁇ 1
  • the target phase angle difference ⁇ 1 assigns the braking coefficient K
  • the fixed value K set of the braking coefficient K is determined.
  • step 4 the amplitude of each phase current in all of the phase currents is subjected to the processing as described in step 3, and the value of the braking coefficient K corresponding to the amplitude of each phase current is obtained.
  • step 5 according to the differential current I cd of each phase and the braking current I res of each phase, and the value of the braking coefficient K corresponding to the amplitude of each phase current obtained in step 4, the differential determination formula is used to perform the difference.
  • I set is a current setting value
  • the target phase difference current I cd satisfies the differential determination formula, and it is determined that there is a fault in the region of the target phase.
  • the current setting value is a parameter set in the differential protection device. That is to say, when the differential current is greater than the preset current setting value, the differential protection mode is entered.
  • the slave protection device transmits the sampled phase current to the host protection device; secondly, in order to obtain the braking coefficient K The value is calculated according to the amplitude of all phase currents sampled by the slave protection device and the self-sampling device, and the fault component current with the largest amplitude of each phase current is calculated. And all phase current removal Vector sum of fault component currents
  • the slave protection device and itself are sampled according to the host protection device. The amplitudes of all the phase currents are calculated. First, the differential current I cd of each phase in all phase currents and the braking current I res of each phase in all phase currents are calculated.
  • the value of the braking coefficient K is selected by itself, thereby improving the sensitivity of the outer region and simultaneously improving the reliability of the braking characteristics outside the region, first selecting the amplitudes of all the phase currents sampled.
  • Target phase current amplitude if the maximum fault component current in the target phase current amplitude Greater than the threshold set value I max 0 , the fault component current according to the target phase current amplitude is the largest Phase angle and target phase current amplitude are removed Vector sum of fault component currents
  • the difference of the phase angles determines the target phase angle difference ⁇ 1 , the target phase angle difference ⁇ 1 assigns a value to the braking coefficient K, and determines the set value K ⁇ of the braking coefficient K according to the phase difference ⁇ to be determined; or if the target phase current Maximum fault component current in amplitude Not more than the threshold set value I max 0 , a fixed value K set of the braking coefficient K is determined.
  • the differential current I cd and the braking current I res in the current amplitude of each phase are combined to obtain the amplitude corresponding to each phase current.
  • the value of the braking coefficient K is judged differentially according to the following formula:
  • I set is the current setting value
  • I cd satisfies the above differential judgment formula
  • the target phase differential current I cd does not satisfy the above differential judgment formula, it is determined that there is no fault in the region of the target phase.
  • the value of the braking coefficient K can be selected according to the fault condition, the braking coefficient K is small when the fault occurs in the region, and the braking coefficient K is large when the fault is outside the region, thereby improving the multi-terminal T connection. Sensitivity in the area of the transmission line also improves the reliability of the braking characteristics outside the area.
  • the calculating the fault component current with the largest amplitude of each phase current As shown in FIG. 2, steps 21 and 22 are included.
  • step 21 the amplitude of the fundamental phase wave of all phase fault components of the slave protection device and the host protection device is obtained, and the host protection device selects the amplitude of the target phase fault component current fundamental wave from the amplitude of the fundamental phase of all phase fault components.
  • the host protection device compares the amplitude of the fundamental phase wave of the target phase fault component, and selects the largest one from the continuous preset number of target phase fault component current fundamental amplitudes as the largest fault component current of the target phase current amplitude.
  • step 22 the process as described in step 21 is performed for each phase current fault component current fundamental amplitude to obtain the largest fault component current in each phase current amplitude.
  • the fault component current with the largest amplitude The selection method affects the value of the braking coefficient K, which in turn affects whether there is a fault in the judgment area.
  • the preset number of target phase fault component current fundamental wave amplitudes in this embodiment is usually 4-10.
  • step 21 the amplitude of the fundamental phase wave of all phase fault components of the slave protection device and the host protection device is obtained, and the host protection device selects the amplitude of the target phase fault component current fundamental wave from the amplitude of the phase fault of all phase fault components, and the host The protection device compares the amplitude of the fundamental phase wave of the target phase fault component, and selects the largest fault component current with the largest target phase current amplitude among the amplitudes of the four target phase fault component current fundamental waves.
  • step 22 operation step 21 is repeated until the fault component current with the largest amplitude of each phase current is obtained.
  • the calculation also calculates each phase differential current I cd of all phase currents, each phase phase braking current I res of all phase currents, and all phase currents are removed.
  • Vector sum of fault component currents Including: calculating the amplitudes of all phase currents of the host protection device and the slave protection device according to the full-circle Four-Frequency algorithm, and obtaining each phase differential current I cd of all phase currents according to Formula 1:
  • n The j-phase in-phase current value of the multi-terminal T transmission line, n is the sum of the number of the host protection devices and the number of the slave protection devices.
  • the differential current of each phase is obtained, and the differential current of each phase is the vector sum of the currents of the host protection device and the slave protection device in the amplitude of each phase current, and each phase is removed according to formula 2.
  • Vector sum of fault component currents According to the formula three, the braking current I res per phase, the braking current I res per phase is the maximum fault component current in the current amplitude of each phase. With removal Vector sum of fault component currents Vector and. These values are obtained to determine if there is a fault in the multiphase region.
  • the determining the set value K ⁇ of the braking coefficient K according to the phase difference ⁇ to be determined comprises: substituting the phase difference ⁇ to be determined into a phase angle difference function for calculation:
  • Table 1 the relationship between the set value K ⁇ and the phase difference ⁇ to be determined can also be quickly realized by means of table lookup, and no manual calculation is required.
  • the phase angle difference function is a monotonically increasing function, and when the phase difference ⁇ to be determined is 0°, the set value K ⁇ is K min .
  • the set value K ⁇ is K max .
  • the value of the set value K ⁇ is 0 ⁇ K min ⁇ K set ⁇ K max ⁇ 1.
  • the phase angle difference function is a monotonically increasing function, and the set value K ⁇ increases as the phase angle difference ⁇ to be determined increases.
  • the fixed value K set takes a value of 0.7.
  • the set value K ⁇ is determined as K min according to the look-up table, and the value of K min is 0.35.
  • the set value K ⁇ is K max , and the value of K max is 0.85. The value of the set value K ⁇ is determined to be 0. ⁇ K min ⁇ K set ⁇ K max ⁇ 1.
  • the present application provides a method for judging differential protection applicable to a multi-terminal T-connection transmission line.
  • the determination method includes: sampling and calculating all phase currents, and calculating a fault component current having the largest amplitude per phase current.
  • Differential current I cd per phase, brake current I res per phase, and removal per phase Vector sum of fault component currents Maximum fault component current in each phase current amplitude Compared with the threshold set value I max 0 , the value of the braking coefficient K corresponding to the amplitude of each phase current is determined according to the comparison result, and the differential current I cd and the braking current I res in the current amplitude of each phase are followed.
  • the differential protection formula performs differential determination: if the target phase differential current I cd satisfies the above differential determination, it is determined that there is a fault in the region of the target phase.
  • the value of the braking coefficient K can be selected according to the fault condition, thereby improving the sensitivity in the multi-terminal T-connected transmission line region and improving the reliability of the braking characteristics outside the region.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Emergency Protection Circuit Devices (AREA)

Abstract

本申请提供了差动保护的判断方法，适用于多端T接输电线路，判断方法包括：对全部相电流进行采样并计算，计算出每相电流幅值最大的故障分量电流Δİmax、每相差动电流Icd、每相制动电流Ires、以及全部相电流除去之外Δİmax的故障分量电流的矢量和ΔİΣ；将每相电流幅值中的最大故障分量电流Δİmax与门槛设定值Imax 0作比较，根据比较结果确定与每相电流幅值对应的制动系数K的数值，根据每相电流幅值中的差动电流I cd和制动电流Ires，按照差动判断公式进行差动判断：在目标相差动电流I cd满足上述差动判断公式时，判定目标相的区域内存在故障。

Description

差动保护的判断方法
本申请要求在2017年11月28日提交中国专利局、申请号为201711216771.4的中国专利申请的优先权，该申请的全部内容通过引用结合在本申请中。
技术领域
本申请属于继电器保护领域，例如涉及一种差动保护的判断方法。
背景技术
近年来，随着风电大量接入电网，出于节省设备投资和减少征地面积等方面考虑，多端T接输电线路越来越多地出现在高压输电线路中。多点T型接线方式的特点是不同的节点T接在同一条联网线路上，所以并网线路比较重要，对保护的可靠性、灵敏性要求高。多点T型接线方式中，任何一端发生故障都要影响到其他几端的正常送电，所以一旦出现故障就要求快速切除。由于多端T接输电线路的特殊性，距离保护和零序保护难以满足速动性和选择性的要求。电流差动由于其原理简单，几乎不受电压互感器断线、串联补偿或输电线路同杆并架等诸多因数影响，广泛用于双端和三端高压输电线路中。
相关技术中提出了一种适用于多端差动判断的方法，提出制动电流I res的计算方法中的制动系数K，依然是设定的固定制动系数，无法在提高多端T接输电线路区域内灵敏度的情况下，同时提高区域外制动特性的可靠性。
发明内容
以下是对本文详细描述的主题的概述。本概述并非是为了限制权利要求的保护范围。
本申请实施例提供了一种差动保护的判断方法，适用于多端T接输电线路，该方法可以根据故障情况自行选择制动系数K的数值，进而提高多端T接输电线路区域内灵敏度，同时提高区域外制动特性的可靠性。
本申请提供了一种差动保护的判断方法，适用于多端T接输电线路的，所述多端T接输电线路包括主机保护装置和从机保护装置，所述主机保护装置为所述多端T接输电线路上任意一端连接的保护装置，所述从机保护装置为除所 述任意一端之外的其它端连接的保护装置，所述判断方法包括：步骤1、对所述主机保护装置的多相电流和所述从机保护装置的多相电流分别进行采样，将所述从机保护装置采样到的多相电流幅值传输至所述主机保护装置；步骤2、所述主机保护装置对所述从机保护装置和所述逐级保护装置自身采样到的全部相电流幅值进行计算，得到所述全部相电流中的每相电流幅值中最大的故障分量电流
Figure PCTCN2018124261-appb-000001
并计算所述全部相电流中每相差动电流I cd、所述全部相电流中每相制动电流I res、以及所述全部相电流中除去所述
Figure PCTCN2018124261-appb-000002
之外的故障分量电流的矢量和
Figure PCTCN2018124261-appb-000003
步骤3、从采样到的所述全部相电流幅值中选取目标相电流幅值，在所述目标相电流幅值中最大故障分量电流
Figure PCTCN2018124261-appb-000004
大于门槛设定值I max 0时，根据所述目标相电流幅值中最大的故障分量电流
Figure PCTCN2018124261-appb-000005
的相角与所述目标相电流幅值中除去
Figure PCTCN2018124261-appb-000006
之外的故障分量电流的矢量和
Figure PCTCN2018124261-appb-000007
的相角之差确定目标相角差θ 1；所述目标相角差θ 1对制动系数K进行赋值，根据待定相角差θ确定所述制动系数K的设定值K θ；或者在所述目标相电流幅值中的最大故障分量电流
Figure PCTCN2018124261-appb-000008
不大于所述门槛设定值I max 0时，确定所述制动系数K的固定值K set；步骤4、对所述全部相电流中的每相电流幅值进行所述步骤3的处理，得到与所述每相电流幅值对应的制动系数K的数值；步骤5、将所述每相差动电流I cd、所述每相制动电流I res，以及结合所述步骤4中得到的与所述每相电流幅值对应的制动系数K的数值，根据以下公式进行差动判断：
Figure PCTCN2018124261-appb-000009
其中，I set为电流整定值，如果目标相差动电流I cd满足上述差动判断，则判定为目标相的区域内存在故障。
在阅读并理解了附图和详细描述后，可以明白其他方面。
附图说明
为了更清楚地说明本申请的技术方案，下面将对实施例描述中所需要使用的附图作简单地介绍。下面描述中的附图仅仅是本申请的一些实施例，对于本领域普通技术人员来讲还可以根据这些附图获得其他的附图。
图1是本申请提供的一种差动保护的判断方法的流程图；
图2是本申请提供的每相电流幅值最大的故障分量电流
Figure PCTCN2018124261-appb-000010
的流程图。
具体实施方式
下面将结合附图对本申请的结构作进一步地描述。
本申请提供了适用于多端T接输电线路的差动保护的判断方法，在多端T接输电线路中确定任意一端作为主机保护装置，其余各端作为从机保护装置，如图1所示，所述判断方法包括步骤1至步骤5。
在步骤1中，对多端T接输电线路上的主机保护装置的多相电流和从机保护装置的多相电流进行采样，从机保护装置将采样到的多相电流幅值传输至主机保护装置。
在步骤2中，主机保护装置对从机保护装置和主机保护装置自身采样到的全部相电流幅值进行计算，计算出全部相电流中的每相电流幅值最大的故障分量电流
Figure PCTCN2018124261-appb-000011
并计算全部相电流中的每相差动电流I cd、全部相电流中的每相制动电流I res、以及全部相电流中除去
Figure PCTCN2018124261-appb-000012
之外的故障分量电流的矢量和
Figure PCTCN2018124261-appb-000013
在步骤3中，从采样到的全部相电流幅值中选取目标相电流幅值，在目标相电流幅值中最大故障分量电流
Figure PCTCN2018124261-appb-000014
大于门槛设定值I max 0时，根据目标相电流幅值中最大的故障分量电流
Figure PCTCN2018124261-appb-000015
的相角与目标相电流幅值中除去
Figure PCTCN2018124261-appb-000016
之外的故障分量电流的矢量和
Figure PCTCN2018124261-appb-000017
的相角之差确定目标相角差θ 1，目标相角差θ1对制动系数K进行赋值，根据待定相角差θ确定制动系数K的设定值K θ；或者在目标相电流幅值中的最大故障分量电流
Figure PCTCN2018124261-appb-000018
不大于门槛设定值I max 0时，确定制动系数K的固定值K set。
在步骤4中，对全部相电流中的每相电流幅值进行如步骤3所述的处理，得到与每相电流幅值对应的制动系数K的数值。
在步骤5中，根据每相差动电流I cd和每相制动电流I res，以及步骤4中得到的与每相电流幅值对应的制动系数K的数值，按照以下差动判断公式进行差动判断：
Figure PCTCN2018124261-appb-000019
其中，I set为电流整定值，在目标相差动电流I cd满足所述差动判断公式，判定目标相的区域内存在故障。
电流整定值是差动保护装置中设置的参数。也就是说，当差动电流大于预先设置的电流整定值时，进入差动保护模式。
在实施中，首先采集多端T接输电线路上的主机保护装置和从保护装置的 相电流，从机保护装置将采样到的相电流传输至主机保护装置；其次，为了可以得到制动系数K的数值，根据主机保护装置对从机保护装置和自身采样到的全部相电流幅值进行计算，计算出每相电流幅值最大的故障分量电流
Figure PCTCN2018124261-appb-000020
以及全部相电流除去
Figure PCTCN2018124261-appb-000021
之外的故障分量电流的矢量和
Figure PCTCN2018124261-appb-000022
为了便于后续根据全部相电流中的每相差动电流I cd、全部相电流中的每相制动电流I res判断出全部相区域内是否存在故障，根据主机保护装置对从机保护装置和自身采样到的全部相电流幅值进行计算，先计算全部相电流中每相差动电流I cd、以及全部相电流中每相制动电流I res。
然后，根据每相故障情况自行选择制动系数K的数值，进而能提高全部相区域内灵敏度的情况下同时提高区域外制动特性的可靠性，先从采样到的全部相电流幅值中选取目标相电流幅值，如果目标相电流幅值中的最大故障分量电流
Figure PCTCN2018124261-appb-000023
大于门槛设定值I max 0，根据目标相电流幅值最大的故障分量电流
Figure PCTCN2018124261-appb-000024
的相角与目标相电流幅值中除去
Figure PCTCN2018124261-appb-000025
之外的故障分量电流的矢量和
Figure PCTCN2018124261-appb-000026
的相角之差确定目标相角差θ 1，目标相角差θ 1对制动系数K进行赋值，根据待定相角差θ确定制动系数K的设定值K θ；或如果目标相电流幅值中的最大故障分量电流
Figure PCTCN2018124261-appb-000027
不大于门槛设定值I max 0，确定制动系数K的固定值K set。
最后，直至得到与每相电流幅值对应的制动系数K的数值，将每相电流幅值中的差动电流I cd和制动电流I res，结合得到的与每相电流幅值对应的制动系数K的数值，根据以下公式进行差动判断：
Figure PCTCN2018124261-appb-000028
其中，I set为电流整定值，如果目标相差动电流I cd满足上述差动判断公式，判定目标相的区域内存在故障。
如果目标相差动电流I cd未满足上述差动判断公式，判定目标相的区域内不存在故障。
基于是上述的判断方法，可以根据故障情况自行选择制动系数K的数值，在区域内故障时制动系数K较小，在区域外故障时制动系数K较大，进而提高了多端T接输电线路区域内灵敏度同时提高区域外制动特性的可靠性。
在一实施例中，所述计算出每相电流幅值最大的故障分量电流
Figure PCTCN2018124261-appb-000029
如图2所示，包括步骤21和步骤22。
在步骤21中，获取从机保护装置和主机保护装置的全部相故障分量电流基波幅值，主机保护装置从全部相故障分量电流基波幅值中选取目标相故障分量电流基波幅值，主机保护装置对目标相故障分量电流基波幅值进行比较，从连续预设数量的目标相故障分量电流基波幅值中选取最大的一个，作为目标相电流幅值中最大的故障分量电流
Figure PCTCN2018124261-appb-000030
在步骤22中，针对每相电流故障分量电流基波幅值进行如步骤21所述的处理，得到每相电流幅值中最大的故障分量电流
Figure PCTCN2018124261-appb-000031
在实施例中，幅值最大的故障分量电流
Figure PCTCN2018124261-appb-000032
的选择方法影响着制动系数K的数值，进而影响着判断区域内是否存在故障。根据实验室测试，本实施例中预设数量的目标相故障分量电流基波幅值通常为4～10个。在步骤21中，获取从机保护装置和主机保护装置的全部相故障分量电流基波幅值，主机保护装置从全部相故障分量电流基波幅值选取目标相故障分量电流基波幅值，主机保护装置对目标相故障分量电流基波幅值进行比较，在连续4个目标相故障分量电流基波幅值中，选取最大的为目标相电流幅值最大的故障分量电流
Figure PCTCN2018124261-appb-000033
步骤22中，重复操作步骤21，直至获取每相电流幅值最大的故障分量电流
Figure PCTCN2018124261-appb-000034
在一实施例中，所述还计算全部相电流中的每相差动电流I cd、全部相电流中的每每相制动电流I res、以及全部相电流中除去
Figure PCTCN2018124261-appb-000035
之外的故障分量电流的矢量和 包括：根据全周傅式算法对主机保护装置和从机保护装置的全部相电流幅值进行计算，根据公式一得到全部相电流中的每相差动电流I cd：
Figure PCTCN2018124261-appb-000037
其中，
Figure PCTCN2018124261-appb-000038
为多端T接输电线路的第j侧同相电流值，n为主机保护装置的数目和从机保护装置的数目之和。
根据公式二得到全部相电流中除去
Figure PCTCN2018124261-appb-000039
之外的故障分量电流的矢量和
Figure PCTCN2018124261-appb-000040
Figure PCTCN2018124261-appb-000041
其中，
Figure PCTCN2018124261-appb-000042
为每相电流幅值中最大的故障分量电流。
根据公式三得到全部相电流中的每相制动电流I res：
Figure PCTCN2018124261-appb-000043
在实施中，根据公式一得到每相差动电流，每相差动电流为每相电流幅值 中主机保护装置和从机保护装置的电流的矢量和，根据公式二得到每相除去
Figure PCTCN2018124261-appb-000044
之外的故障分量电流的矢量和
Figure PCTCN2018124261-appb-000045
根据公式三得每相制动电流I res，每相制动电流I res为每相电流幅值中的最大故障分量电流
Figure PCTCN2018124261-appb-000046
与除去
Figure PCTCN2018124261-appb-000047
之外的故障分量电流的矢量和
Figure PCTCN2018124261-appb-000048
的矢量和。获取这些值为了用于判断多相区域内是否存在故障。
在一实施例中，所述根据待定相角差θ确定制动系数K的设定值K θ，包括：将待定相角差θ代入相角差函数进行计算：
K θ＝(asinθ/2+b)K set
其中，a、b为常数，待定相角差θ的取值范围为[0°，180°]；根据计算结果，确定制动系数K的设定值K θ。
在实施中，相角差函数为K θ＝(asinθ/2+b)K set，其中a、b为常数，待定相角差θ的取值范围为[0°，180°]；当目标相电流幅值中的最大的故障分量电流
Figure PCTCN2018124261-appb-000049
不大于门槛设定值I max 0时，制动系数K直接确定固定值K set，根据实验需求，本实施例的固定值K set取值为0.7；当目标相电流幅值中的最大的故障分量电流
Figure PCTCN2018124261-appb-000050
大于门槛设定值I max 0时，确定制动系数K为设定值K θ，将设定值K θ代入相角差函数为K θ＝(asinθ/2+b)K set，当a取值为0.7，b取值为0.5时，则相角差函数为K θ＝(0.7sinθ/2+0.5)K set，进而只要确定待定相角差θ的大小，再将相角差θ代入K θ＝(0.7sinθ/2+0.5)K set中就能计算出设定值K θ的数值，其中，设定值K θ是随着待定相角差θ的变化而变化。如表1所示，确定设定值K θ与待定相角差θ的关系还可以通过查表的方式快速实现，就不需要进行人工计算。
Figure PCTCN2018124261-appb-000051
表1
在一实施例中，所述相角差函数为单调递增函数，当待定相角差θ为0°时，设定值K θ为K min。
当待定相角差θ为180°时，设定值K θ为K max。
其中，设定值K θ的取值为0＜K min＜K set＜K max＜1。
在实施中，相角差函数为单调递增函数，设定值K θ随着待定相角差θ增加而增加。根据上述可知，固定值K set取值为0.7，当目标区域内故障时，确定待定相角差θ为0°，根据查表方式确定设定值K θ为K min，K min取值为0.35，当目标区域外故障时，确定待定相角差θ为180°，根据查表方式定设定值K θ为K max，K max取值为0.85，确定设定值K θ的取值为0＜K min＜K set＜K max＜1。
本申请提供了适用于多端T接输电线路的差动保护的判断方法，判断方法包括：对全部相电流进行采样并计算，计算出每相电流幅值最大的故障分量电流
Figure PCTCN2018124261-appb-000052
每相差动电流I cd、每相制动电流I res、以及每相除去
Figure PCTCN2018124261-appb-000053
之外的故障分量电流的矢量和
Figure PCTCN2018124261-appb-000054
将每相电流幅值中的最大故障分量电流
Figure PCTCN2018124261-appb-000055
与门槛设定值I max 0作比较，根据比较结果确定与每相电流幅值对应的制动系数K的数值，将每相电流幅值中的差动电流I cd和制动电流I res按照差动保护公式进行差动判断：如果目标相差动电流I cd满足上述差动判断，则判定目标相的区域内存在故障。通过所述判断方法，可以根据故障情况自行选择制动系数K的数值，进而提高了多端T接输电线路区域内灵敏度同时提高区域外制动特性的可靠性。
上述实施例中的各个序号仅仅为了描述，不代表各部件的组装或使用过程中的先后顺序。

Claims (5)

  1. 一种差动保护的判断方法，所述判断方法适用于多端T接输电线路，所述多端T接输电线路包括主机保护装置和从机保护装置，所述主机保护装置为所述多端T接输电线路上任意一端连接的保护装置，所述从机保护装置为除所述任意一端之外的其它端连接的保护装置，所述判断方法包括：
    步骤1、对所述主机保护装置的多相电流和所述从机保护装置的多相电流分别进行采样，将所述从机保护装置采样到的多相电流幅值传输至所述主机保护装置；
    步骤2、所述主机保护装置对所述从机保护装置和所述主机保护装置自身采样到的全部相电流的幅值进行计算，得到所述全部相电流中的每相电流幅值中最大的故障分量电流
    Figure PCTCN2018124261-appb-100001
    并计算所述全部相电流中每相差动电流I cd、所述全部相电流中每相制动电流I res、以及所述全部相电流中除去所述
    Figure PCTCN2018124261-appb-100002
    之外的故障分量电流的矢量和
    Figure PCTCN2018124261-appb-100003
    步骤3、从采样到的所述全部相电流幅值中选取目标相电流幅值，在所述目标相电流幅值中最大故障分量电流
    Figure PCTCN2018124261-appb-100004
    大于门槛设定值I max 0时，根据所述目标相电流幅值中最大的故障分量电流
    Figure PCTCN2018124261-appb-100005
    的相角与所述目标相电流幅值中除去
    Figure PCTCN2018124261-appb-100006
    之外的故障分量电流的矢量和
    Figure PCTCN2018124261-appb-100007
    的相角之差确定目标相角差θ 1；所述目标相角差θ 1对制动系数K进行赋值，根据待定相角差θ确定所述制动系数K的设定值K θ；或者在所述目标相电流幅值中的最大故障分量电流
    Figure PCTCN2018124261-appb-100008
    不大于所述门槛设定值I max 0时，确定所述制动系数K的固定值K set；
    步骤4、对所述全部相电流中的每相电流幅值进行如步骤3所述的处理，得到与所述每相电流幅值对应的制动系数K的数值；
    步骤5、根据所述每相差动电流I cd、所述每相制动电流I res，以及所述步骤4中得到的所述与每相电流幅值对应的制动系数K的数值，按照以下差动判断公式进行差动判断：
    Figure PCTCN2018124261-appb-100009
    其中，I set为电流整定值，在所述目标相的所述差动电流I cd满足所述差动判断公式时，判定所述目标相的区域内存在故障。
  2. 根据权利要求1所述的方法，其中，所述得到每相电流幅值最大的故障分量电流
    Figure PCTCN2018124261-appb-100010
    包括：
    步骤21，获取所述从机保护装置和所述主机保护装置的全部相故障分量电流基波幅值，所述主机保护装置从所述全部相故障分量电流基波幅值中选取目 标相故障分量电流基波幅值，所述主机保护装置对所述目标相故障分量电流基波幅值进行比较，从连续预设数量的所述目标相故障分量电流基波幅值中选取最大的一个，作为目标相电流幅值中最大的故障分量电流
    Figure PCTCN2018124261-appb-100011
    步骤22，对每相电流故障分量电流基波幅值进行如所述步骤21所述的处理，得到所述每相电流幅值中最大的故障分量电流
    Figure PCTCN2018124261-appb-100012
  3. 根据权利要求1所述的方法，其中，所述并计算所述全部相电流中每相差动电流I cd、所述全部相电流中每相制动电流I res、以及所述全部相电流中除去所述
    Figure PCTCN2018124261-appb-100013
    之外的故障分量电流的矢量和
    Figure PCTCN2018124261-appb-100014
    包括：
    根据全周傅式算法对所述主机保护装置和所述从机保护装置的所述全部相电流幅值进行计算，根据公式一得到所述全部相电流中每相差动电流I cd：
    Figure PCTCN2018124261-appb-100015
    其中，
    Figure PCTCN2018124261-appb-100016
    为所述多端T接输电线路的第j侧同相电流值，n为所述主机保护装置的数目和所述从机保护装置的数目之和；
    根据公式二得到所述全部相电流中除去所述
    Figure PCTCN2018124261-appb-100017
    之外的故障分量电流的矢量和
    Figure PCTCN2018124261-appb-100018
    Figure PCTCN2018124261-appb-100019
    其中，
    Figure PCTCN2018124261-appb-100020
    为所述每相电流幅值中最大的故障分量电流；
    根据公式三得到所述全部相电流中每相制动电流I res：
    Figure PCTCN2018124261-appb-100021
  4. 根据权利要求1所述的方法，其中，所述根据待定相角差θ确定所述制动系数K的设定值K θ，包括：
    将所述待定相角差θ代入相角差函数进行计算：
    K θ＝(a sin θ/2+b)K set
    其中，a、b为常数，所述待定相角差θ的取值范围为[0°，180°]；
    根据计算结果，确定所述制动系数K的设定值K θ。
  5. 根据权利要求4所述的方法，其中，所述相角差函数为单调递增函数，当所述待定相角差θ为0°时，所述制动系数K的设定值K θ为K min；
    当所述待定相角差θ为180°时，所述制动系数K的设定值K θ为K max；
    其中，所述制动系数K的设定值K θ的取值为：0＜K min＜K set＜K max＜1。
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