WO2020192156A1 - Distributed fault detection method for power distribution system having resonant grounding - Google Patents

Distributed fault detection method for power distribution system having resonant grounding Download PDF

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WO2020192156A1
WO2020192156A1 PCT/CN2019/120481 CN2019120481W WO2020192156A1 WO 2020192156 A1 WO2020192156 A1 WO 2020192156A1 CN 2019120481 W CN2019120481 W CN 2019120481W WO 2020192156 A1 WO2020192156 A1 WO 2020192156A1
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fault
voltage
ground voltage
phase
neutral point
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陈力
应强
周劭亮
沈健
张敏
唐凯
刘辉
孙建萍
张琼
沈宇龙
汤一鑫
殷垚
蔡可苏
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国电南瑞科技股份有限公司
国电南瑞南京控制系统有限公司
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
    • G01R19/165—Indicating that current or voltage is either above or below a predetermined value or within or outside a predetermined range of values
    • G01R19/16533—Indicating that current or voltage is either above or below a predetermined value or within or outside a predetermined range of values characterised by the application
    • G01R19/16538—Indicating that current or voltage is either above or below a predetermined value or within or outside a predetermined range of values characterised by the application in AC or DC supplies
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
    • G01R19/165—Indicating that current or voltage is either above or below a predetermined value or within or outside a predetermined range of values
    • G01R19/16566—Circuits and arrangements for comparing voltage or current with one or several thresholds and for indicating the result not covered by subgroups G01R19/16504, G01R19/16528, G01R19/16533
    • G01R19/16576—Circuits and arrangements for comparing voltage or current with one or several thresholds and for indicating the result not covered by subgroups G01R19/16504, G01R19/16528, G01R19/16533 comparing DC or AC voltage with one threshold
    • 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
    • G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections

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Abstract

Disclosed is a distributed fault detection method for a power distribution system having resonant grounding, which belongs to the technical field of electric power automation. The invention comprises: detecting a fault according to a shift in neutral-to-earth voltage; using pre-fault and post-fault voltages (relatively) to identify a fault phase; and identifying a faulty feeder (and a fault region of a long feeder) according to the relationship between an initial transient of a zero-sequence current and a fault phase voltage after the occurrence of the fault. The invention uses voltage signals and current signals from corresponding voltage transformers and current transformers, such that protection devices in the same or different feeders do not need to communicate with each other to identify a faulty feeder.

Description

一种具有谐振接地的配电系统分散式故障检测方法A distributed fault detection method for power distribution system with resonance grounding 技术领域Technical field
本发明涉及一种具有谐振接地的配电系统分散式故障检测方法，属于电力系统故障检测技术领域。The invention relates to a distributed fault detection method for a power distribution system with resonance grounding, and belongs to the technical field of power system fault detection.
背景技术Background technique
故障检测是电力系统安全、可靠、避免事故、设备损坏和意外停电的重要问题。电力系统中可能出现的故障类型有：单相接地(SPG)故障、相间故障、双相接地故障和三相接地故障。在这些故障中，SPG故障是最常见的一种，需要对其进行检测，以便尽快隔离故障段。公用设施最常见的做法是使用过流继电器检测配电系统中的故障，配电系统跟踪馈线电流，如果电流高于预定阈值，则指示故障。过电流阈值继电器取决于负载电流。通常，阈值被设置为略高于馈线的正常负载电流。然而，这种技术不适用于故障电流非常低的故障，因为这些故障的馈线电流处于阈值水平以下。另一方面，由于配电网接地故障而导致的故障电流大小取决于配电变电所变压器接地实践，为了安全起见，要求故障电流非常低。变电站变压器的中性点可以是通过各种方式接地，例如牢固接地、电阻接地、不接地(隔离)和谐振接地(RG)在这些接地实践中，基于RG的技术可以快速降低故障电流，由于单相接地故障，故障电流(通常为三次循环)减小到一个非常小的水平，所以需要在三个周期内识别出来，在这情况下，故障电流接地故障很小，常规过电流继电器不工作。因此，需要一种新的改进方法检测SPG故障并识别RG的故障类型。Fault detection is an important issue for power system safety, reliability, avoidance of accidents, equipment damage and unexpected power outages. The types of faults that may occur in the power system are: single-phase grounding (SPG) faults, phase-to-phase faults, two-phase grounding faults, and three-phase grounding faults. Among these faults, the SPG fault is the most common one, which needs to be detected in order to isolate the fault segment as soon as possible. The most common practice in utilities is to use overcurrent relays to detect faults in the power distribution system. The power distribution system tracks the feeder current and indicates the fault if the current is higher than a predetermined threshold. The overcurrent threshold relay depends on the load current. Usually, the threshold is set to be slightly higher than the normal load current of the feeder. However, this technique is not suitable for faults with very low fault currents because the feeder currents of these faults are below the threshold level. On the other hand, the magnitude of the fault current caused by the ground fault of the distribution network depends on the grounding practice of the transformer in the distribution substation. For safety reasons, the fault current is required to be very low. The neutral point of the substation transformer can be grounded in various ways, such as solid grounding, resistance grounding, ungrounded (isolated) and resonant grounding (RG). In these grounding practices, RG-based technology can quickly reduce the fault current. For a phase-to-ground fault, the fault current (usually three cycles) is reduced to a very small level, so it needs to be identified within three cycles. In this case, the fault current to ground fault is very small, and the conventional overcurrent relay does not work. Therefore, a new and improved method is needed to detect SPG failure and identify the type of RG failure.
发明内容Summary of the invention
本发明提供一种具有谐振接地的配电系统分散式故障检测方法，用以检测谐振接地(RG)的配电系统中的单相接地(SPG)故障。The present invention provides a distributed fault detection method for a power distribution system with resonance grounding, which is used to detect single-phase grounding (SPG) faults in a power distribution system with resonance grounding (RG).
为了实现上述目的，本发明是采取以下的技术方案来实现的：In order to achieve the above objectives, the present invention adopts the following technical solutions to achieve:
一种具有谐振接地的配电系统分散式故障检测方法，包括以下步骤：A distributed fault detection method for power distribution system with resonance grounding includes the following steps:
1)测量故障馈线上的电压和零序电流，计算中性点对地电压及中性点对地电压斜率；1) Measure the voltage and zero sequence current on the faulted feeder, and calculate the neutral point-to-ground voltage and the neutral point-to-ground voltage slope;
2)将中性点对地电压与设定的电压阈值进行比较，检测故障；2) Compare the neutral point to ground voltage with the set voltage threshold to detect faults;
3)估计故障发生时间；3) Estimate the time of failure;
4)将延时一段时间后的中性点对地电压与设定的电压阈值进行比较，识别故障类型；4) Compare the neutral-to-ground voltage after a delay of a period of time with the set voltage threshold to identify the fault type;
5)基于相地电压的均方根值偏差识别故障相位；5) Identify the fault phase based on the root mean square deviation of the phase-to-ground voltage;
6)基于故障发生时刻的开关分合操作零序电流识别故障馈线。6) The faulty feeder is identified based on the zero sequence current of the switch opening and closing operation at the time the fault occurs.
前述的步骤2)中，检测故障分为初步检测和二次检测；In the aforementioned step 2), the detection failure is divided into preliminary detection and secondary detection;
所述初步检测是指，将中性点对地电压V n与设定的电压阈值V th进行比较，如果中性点对地电压V n大于电压阈值V th，则系统被识别为故障系统； The preliminary detection refers to comparing the neutral point-to-ground voltage V n with a set voltage threshold V th . If the neutral point-to-ground voltage V n is greater than the voltage threshold V th , the system is identified as a faulty system;
所述二次检测是指，对于中性点对地电压V n小于等于电压阈值V th的情况，将中性点对地电压的斜率dV n与设定的斜率阈值dV th进行比较，如果dV n<dV th，则表示系统正常，否则，将当前时间记录为t l，在Δt 0的持续时间内持续检查dV n和V n，如果在Δt 0期间中性点对地电压的斜率dV n的平均值大于dV th，且在Δt 0期间中性点对地电压V n的平均值大于V th，则识别为故障系统。 The second detection refers to comparing the slope dV n of the neutral point-to-ground voltage with the set slope threshold dV th in the case that the neutral point-to-ground voltage V n is less than or equal to the voltage threshold V th , if dV n <dV th, then the system is normal, otherwise, the current time is recorded as t l, and continuously checks dV V n in the n-duration Δt 0, if the slope of the ground voltage dV at the neutral point period Δt 0 n The average value of is greater than dV th , and the average value of the neutral point-to-ground voltage V n is greater than V th during Δt 0 , it is identified as a faulty system.
前述的中性点对地电压V n计算如下： The aforementioned neutral point-to-ground voltage V n is calculated as follows:
Figure PCTCN2019120481-appb-000001
Figure PCTCN2019120481-appb-000001
其中，Z ASC是通过消弧线圈的阻抗，Z l和Z c分别是配电线路的电感和电容阻抗，Z f是系统故障阻抗，V pn是相间电压。 Among them, Z ASC is the impedance through the arc suppression coil, Z l and Z c are the inductance and capacitance impedance of the distribution line, respectively, Z f is the system fault impedance, and V pn is the phase-to-phase voltage.
前述的步骤3)中，故障发生时间为：t f＝min[t，t l]，其中，t f为故障发生时间，t l为中性点对地电压的斜率大于斜率阈值的起始点，t为当前时间。 In the foregoing step 3), the fault occurrence time is: t f =min[t, t l ], where t f is the fault occurrence time, and t l is the starting point where the slope of the neutral-to-ground voltage is greater than the slope threshold, t is the current time.
前述的步骤4)中，识别故障类型分为初步识别和二次识别，In the foregoing step 4), the identification of the fault type is divided into preliminary identification and secondary identification.
所述初步识别为，设定延时Δt c，在Δt c延时后，比较中性点对地电压V n与设定的电压阈值V th，如果中性点对地电压V n大于电压阈值V th，则系统被识别为永久性故障； The preliminary identification is, set the delay Δt c, after a delay Δt c, compare the neutral point voltage to the threshold voltage V th and V n is set, if the neutral-to-ground voltage is greater than the voltage threshold V n V th , the system is identified as a permanent fault;
所述二次识别为，对于中性点对地电压V n小于等于电压阈值V th的情况，设定二次延时Δt h，比较t f+Δt c到t f+Δt c+Δt h期间内中性点对地电压V n的平均值与设定的电压阈值，如果V n的平均值超过电压阈值，则识别为永久性故障，否则识别为暂时故障。 The secondary identification is, for the case where the neutral point-to-ground voltage V n is less than or equal to the voltage threshold V th , set the secondary delay Δt h , and compare the period from t f +Δt c to t f +Δt c +Δt h The average value of the internal neutral point-to-ground voltage V n and the set voltage threshold. If the average value of V n exceeds the voltage threshold, it is recognized as a permanent fault, otherwise it is recognized as a temporary fault.
前述的步骤5)中，相地电压的均方根值偏差计算如下：In the foregoing step 5), the root mean square value deviation of the phase-to-ground voltage is calculated as follows:
Figure PCTCN2019120481-appb-000002
Figure PCTCN2019120481-appb-000002
其中，ΔV p为相地电压故障前后的均方根值偏差，
Figure PCTCN2019120481-appb-000003
和
Figure PCTCN2019120481-appb-000004
分别为相地电压故障前和故障后的均方根值，
Figure PCTCN2019120481-appb-000005
和
Figure PCTCN2019120481-appb-000006
通过保护电压互感器获取，
Figure PCTCN2019120481-appb-000007
和
Figure PCTCN2019120481-appb-000008
为故障发生前和发生后时刻； Among them, ΔV p is the deviation of the root mean square value before and after the phase-to-ground voltage fault,
Figure PCTCN2019120481-appb-000003
with
Figure PCTCN2019120481-appb-000004
Are the root-mean-square values of the phase-to-ground voltage before and after the fault,
Figure PCTCN2019120481-appb-000005
with
Figure PCTCN2019120481-appb-000006
Obtained by protecting voltage transformer,
Figure PCTCN2019120481-appb-000007
with
Figure PCTCN2019120481-appb-000008
Is the time before and after the failure;
如果ΔV p值为负则为故障相，如果ΔV p值为正则为健康相。 If the ΔV p value is negative, it is a fault phase, and if the ΔV p value is positive, it is a healthy phase.
前述的步骤6)中，如果开关分合操作零序电流的极性与故障相电压的瞬时电压相同，则为故障馈线；如果开关分合操作零序电流的极性与故障相电压的瞬时电压相反，则为正常线路；In the foregoing step 6), if the polarity of the zero-sequence current of the switching operation is the same as the instantaneous voltage of the fault phase voltage, it is a fault feeder; if the polarity of the switching operation of the zero-sequence current is the same as the instantaneous voltage of the fault phase voltage On the contrary, it is a normal line;
开关分合操作零序电流通过零序电流偏差计算如下：The zero sequence current of the switch opening and closing operation is calculated as follows through the zero sequence current deviation:
Figure PCTCN2019120481-appb-000009
Figure PCTCN2019120481-appb-000009
Figure PCTCN2019120481-appb-000010
Figure PCTCN2019120481-appb-000010
Figure PCTCN2019120481-appb-000011
Figure PCTCN2019120481-appb-000011
其中，Δi 0为零序电流偏差，
Figure PCTCN2019120481-appb-000012
和
Figure PCTCN2019120481-appb-000013
分别是故障后和故障前的零序电流的瞬时值，
Figure PCTCN2019120481-appb-000014
和
Figure PCTCN2019120481-appb-000015
通过保护电流互感器获取，
Figure PCTCN2019120481-appb-000016
和
Figure PCTCN2019120481-appb-000017
为故障发生前和发生后时刻，t f为故障发生时间。 Among them, Δi 0 is the zero sequence current deviation,
Figure PCTCN2019120481-appb-000012
with
Figure PCTCN2019120481-appb-000013
Are the instantaneous values of the zero sequence current after the fault and before the fault,
Figure PCTCN2019120481-appb-000014
with
Figure PCTCN2019120481-appb-000015
Obtained by protecting current transformer,
Figure PCTCN2019120481-appb-000016
with
Figure PCTCN2019120481-appb-000017
Is the time before and after the fault occurs, and t f is the time when the fault occurs.
本发明所达到的有益效果为：The beneficial effects achieved by the present invention are:
本发明使用来自相应电压互感器和电流互感器的电压和电流信号，因此，在同一条或不同的馈线中，保护装置之间不需要通信来识别故障的馈线。本发明还能够甄别故障的性质，区分故障是否为永久性故障。The present invention uses voltage and current signals from corresponding voltage transformers and current transformers. Therefore, in the same or different feeders, there is no need for communication between protection devices to identify faulty feeders. The invention can also identify the nature of the fault and distinguish whether the fault is a permanent fault.
附图说明Description of the drawings
图1为单相接地故障谐振接地配电系统的等效电路图；Figure 1 is an equivalent circuit diagram of a single-phase ground fault resonant grounded power distribution system;
图2为故障相等效电路；Figure 2 shows the equivalent circuit of the fault phase;
图3为本发明故障检测流程图。Figure 3 is a flow chart of fault detection of the present invention.
具体实施方式detailed description
下面对本发明作进一步描述。以下实施例仅用于更加清楚地说明本发明的技术方案，而不能以此来限制本发明的保护范围。The present invention will be further described below. The following embodiments are only used to explain the technical solutions of the present invention more clearly, and cannot be used to limit the protection scope of the present invention.
本发明提供一种具有谐振接地的配电系统分散式故障检测方法，包括以下几个部分：The present invention provides a distributed fault detection method for a power distribution system with resonance grounding, which includes the following parts:
一，进行故障检测1. Perform fault detection
在RG系统发生SPG故障时，相电压之间会产生不平衡，从而增加中性点对地电压。为了解释这种情况，图1显示了一个带有两条馈电线的配电系统，其中一条SPG故障应用于馈电线1的A相。图1中，出线1故障，出线2正常，Z l1为出线1的等效电感，i c1c为出线1中C相的充电电流，i c1b为出线1中B相的充电电流，i d1a为出线1中A相的放电电流，Z l2为出线2的等效电感，i c2c为出线2中C相 的充电电流，i c2b为出线2中B相的充电电流，i d2a为出线2中A相的放电电流。在这种情况下，虽然合成的故障电流由于共振而接近于零，但电压将遵循基尔霍夫电压定律(KVL)。故障相位的简化电路如图2所示，故障期间的中性点对地电压(VN)可表示为： When an SPG fault occurs in the RG system, there will be an imbalance between the phase voltages, thereby increasing the neutral-to-ground voltage. To explain this situation, Figure 1 shows a power distribution system with two feeders, one of which is an SPG fault applied to phase A of feeder 1. In Figure 1, outlet 1 is faulty, outlet 2 is normal, Z l1 is the equivalent inductance of outlet 1, i c1c is the charging current of phase C in outlet 1, i c1b is the charging current of phase B in outlet 1, and i d1a is the outlet The discharge current of phase A in 1, Z l2 is the equivalent inductance of outlet 2, i c2c is the charging current of phase C in outlet 2, i c2b is the charging current of phase B in outlet 2, and i d2a is phase A in outlet 2. The discharge current. In this case, although the synthesized fault current is close to zero due to resonance, the voltage will follow Kirchhoff's voltage law (KVL). The simplified circuit of the fault phase is shown in Figure 2. The neutral-to-ground voltage (VN) during the fault period can be expressed as:
Figure PCTCN2019120481-appb-000018
Figure PCTCN2019120481-appb-000018
其中，Z ASC是通过消弧线圈(ASC)的阻抗，Z l和Z c分别是配电线路的电感和电容阻抗，Z f是系统故障阻抗(FI)，V pn是相间电压。 Among them, Z ASC is the impedance through the arc suppression coil (ASC), Z l and Z c are the inductance and capacitance impedance of the distribution line, respectively, Z f is the system fault impedance (FI), and V pn is the phase-to-phase voltage.
对于健康状况，V n是： For health conditions, V n is:
Figure PCTCN2019120481-appb-000019
Figure PCTCN2019120481-appb-000019
从这些方程可以看出，系统的中性点对地电压在发生故障时会随着Z c||Z f<Z c而升高。因此，中性点对地电压可用于检测由中性点对地电压超过设定阈值指示故障的接地故障。这里，每个系统的中性点对地电压阈值是不同的，取决于系统参数，如系统不平衡。 It can be seen from these equations that the neutral-to-ground voltage of the system will increase as Z c ||Z f <Z c when a fault occurs. Therefore, the neutral-to-ground voltage can be used to detect a ground fault in which the neutral-to-ground voltage exceeds a set threshold indicating a fault. Here, the neutral point-to-ground voltage threshold of each system is different, depending on system parameters, such as system imbalance.
二、故障发生时刻估算2. Estimate the time of failure
当中性点对地电压在一个时间延迟后超过阈值时，需要时间来检测故障。这个时间延迟取决于系统的动态以及故障阻抗(FI)。因为中性点对地电压的斜率在故障发生时很陡，中性点对地电压的斜率可用于估计故障发生时间。本发明提出，如果中性点对地电压的斜率大于设定值并持续到中性点对地电压超过其阈值，则斜率变陡的起始点时间可被视为故障发生时间。When the neutral point to ground voltage exceeds the threshold after a time delay, it takes time to detect the fault. This time delay depends on the dynamics of the system and the fault impedance (FI). Because the slope of the neutral-to-ground voltage is steep when the fault occurs, the slope of the neutral-to-ground voltage can be used to estimate the time of the fault. The present invention proposes that if the slope of the neutral-to-ground voltage is greater than the set value and continues until the neutral-to-ground voltage exceeds its threshold, the time at which the slope becomes steeper can be regarded as the fault occurrence time.
三、故障特征识别Three, fault feature recognition
在故障期间，中性点对地电压很高。此外，从公式(1)和(2)可知，故障清除后，电压将恢复正 常值。因此，如果中性点对地电压的大小超过设定的阈值V th，并在高于该阈值的指定时间内持续存在，则该故障可定义为永久性故障。 During a fault, the neutral point has a high voltage to ground. In addition, from formulas (1) and (2), it can be known that after the fault is cleared, the voltage will return to its normal value. Therefore, if the magnitude of the neutral point-to-ground voltage exceeds the set threshold V th and persists for a specified period of time higher than the threshold, the fault can be defined as a permanent fault.
在RG系统的SPG故障过程中，故障相的电荷通过同一相的相对地电容放电。从图2可以看出，故障相(A相)的电压通过FI放电，所有馈电线的相同相(即A相)的相对地电容放电。另一方面，充电电流从健康相(即B相和C相)流过健康相和FI的相对地电容，进入故障相。因此，相地电压变化并稳定到不同的值，其中故障相的电压降低到较低的值，健康相的电压增加到较高的值。因此，通过计算相地电压(ΔV p)的均方根(RMS)值偏差，可以很容易地识别出故障相和健康相，如下所示： During the SPG fault of the RG system, the charge of the faulty phase is discharged through the phase-to-ground capacitance of the same phase. It can be seen from Figure 2 that the voltage of the faulty phase (phase A) is discharged through FI, and the relative ground capacitances of the same phase (namely phase A) of all feeders are discharged. On the other hand, the charging current flows from the healthy phase (ie, phase B and phase C) through the relative ground capacitance of the healthy phase and FI, and enters the fault phase. Therefore, the phase-to-ground voltage changes and stabilizes to different values, where the voltage of the faulty phase decreases to a lower value, and the voltage of the healthy phase increases to a higher value. Therefore, by calculating the root mean square (RMS) deviation of the phase-to-ground voltage (ΔV p ), the fault phase and the healthy phase can be easily identified, as shown below:
Figure PCTCN2019120481-appb-000020
Figure PCTCN2019120481-appb-000020
其中，
Figure PCTCN2019120481-appb-000021
和
Figure PCTCN2019120481-appb-000022
是故障前和故障后的RMS值，
Figure PCTCN2019120481-appb-000023
和
Figure PCTCN2019120481-appb-000024
通过保护PT(电压互感器)获取，t f为故障发生时间。故障相的ΔV p值为负值，而健康相的ΔV p值为正值。因此，使用ΔV p识别故障相位。 among them,
Figure PCTCN2019120481-appb-000021
with
Figure PCTCN2019120481-appb-000022
Is the RMS value before and after the failure,
Figure PCTCN2019120481-appb-000023
with
Figure PCTCN2019120481-appb-000024
Obtained through the protection of PT (voltage transformer), t f is the time when the fault occurs. The ΔV p value of the fault phase is negative, and the ΔV p value of the healthy phase is positive. Therefore, ΔV p is used to identify the faulty phase.
四、故障馈线识别Four, fault feeder identification
为了识别故障馈线，在SPG故障期间，首先需要识别故障和正常馈线的特征。本发明中，故障电流I f在故障的第一次发生时流过故障的馈电线，可以表示为： In order to identify the faulty feeder, during the SPG fault, it is first necessary to identify the characteristics of the faulty and normal feeder. In the present invention, the fault current I f flows through the faulty feeder when the fault occurs for the first time, which can be expressed as:
Figure PCTCN2019120481-appb-000025
Figure PCTCN2019120481-appb-000025
Figure PCTCN2019120481-appb-000026
Figure PCTCN2019120481-appb-000026
其中，i f是故障电流瞬时值，ω为角频率，V f＝V f∠δ v为故障阻抗处的电压，I f＝I f∠δ i为故障电流，Z f＝Z f∠δ z为故障阻抗。δ v，δ i，δ z的分别为V f，I f，Z f三个相量的角度值。 Among them, i f is the instantaneous value of the fault current, ω is the angular frequency, V f ＝V f ∠δ v is the voltage at the fault impedance, I f ＝I f ∠δ i is the fault current, Z f ＝Z f ∠δ z Is the fault impedance. δ v , δ i , and δ z are the angle values of the three phasors V f , I f , and Z f respectively.
因为故障阻抗FI通常是电阻的，δ z≈0。因此，式(5)可以写为： Because the fault impedance FI is usually resistive, δ z ≈0. Therefore, formula (5) can be written as:
δ i≈δ v δ i ≈δ v
(t-t f)＞≈0          (6) (tt f )＞≈0 (6)
从(4)–(6)得出结论，故障馈线瞬时故障相电压的极性和故障电流在故障点(FL)处相同。此外，该故障电流的一个重要部分通过零序路径，因为这是接地故障。因此，当故障发生时，馈电线的零序电流会相应地改变。可以得出这样的结论：故障发生时，故障馈线零序电流的变化与故障相的瞬时电压具有相同的极性。It is concluded from (4)–(6) that the polarity of the instantaneous fault phase voltage of the faulted feeder and the fault current are the same at the fault point (FL). In addition, an important part of the fault current passes through the zero sequence path because this is a ground fault. Therefore, when a fault occurs, the zero sequence current of the feeder will change accordingly. It can be concluded that when a fault occurs, the zero-sequence current of the faulted feeder has the same polarity as the instantaneous voltage of the faulty phase.
综上，本发明提出故障线路零序电流偏差的极性与故障相电压的瞬时电压相同，而正常线路零序电流偏差的极性则相反。这也适用于间歇性电弧故障，因为电弧和非电弧故障的初始瞬态相同。在这种情况下，零序电流(Δi 0)的偏差可以表示为： In summary, the present invention proposes that the polarity of the zero sequence current deviation of the fault line is the same as the instantaneous voltage of the fault phase voltage, while the polarity of the zero sequence current deviation of the normal line is opposite. This also applies to intermittent arc faults because the initial transients of arc and non-arc faults are the same. In this case, the deviation of the zero sequence current (Δi 0 ) can be expressed as:
Figure PCTCN2019120481-appb-000027
Figure PCTCN2019120481-appb-000027
Figure PCTCN2019120481-appb-000028
Figure PCTCN2019120481-appb-000028
Figure PCTCN2019120481-appb-000029
Figure PCTCN2019120481-appb-000029
其中，
Figure PCTCN2019120481-appb-000030
和
Figure PCTCN2019120481-appb-000031
分别是故障后和故障前零序电流的瞬时值，
Figure PCTCN2019120481-appb-000032
和
Figure PCTCN2019120481-appb-000033
通过保护CT(电流互感器)获取。 among them,
Figure PCTCN2019120481-appb-000030
with
Figure PCTCN2019120481-appb-000031
Are the instantaneous values of the zero sequence current after the fault and before the fault,
Figure PCTCN2019120481-appb-000032
with
Figure PCTCN2019120481-appb-000033
Obtained by protecting CT (current transformer).
综上所述，本发明利用电网中性点对地电压位移检测电网故障，利用中性点对地电压的斜率估计故障发生时间，对故障线路进行识别。在检测到故障后，通过比较故障前和故障后的相电压来识别故障相。本发明根据故障发生后零序电流的初始瞬态与故障相电压之间的关系来识别故障馈线。同时故障的性质(暂时性或永久性)也可以通过中性点对地电压位移来识别。In summary, the present invention uses the neutral point-to-ground voltage displacement of the power grid to detect power grid faults, uses the slope of the neutral point to ground voltage to estimate the time of occurrence of the fault, and identifies the faulty line. After the fault is detected, the faulty phase is identified by comparing the phase voltages before and after the fault. The present invention identifies the faulty feeder based on the relationship between the initial transient state of the zero sequence current and the fault phase voltage after the fault occurs. At the same time, the nature of the fault (temporary or permanent) can also be identified by the neutral point to ground voltage displacement.
参见图3，本发明的具有谐振接地的配电系统分散式故障检测方法，包括以下步骤：Referring to Fig. 3, the distributed fault detection method for power distribution system with resonance grounding of the present invention includes the following steps:
11)测量故障馈线上的电压和零序电流I 0。 11) Measure the voltage and zero sequence current I 0 on the faulty feeder.
12)将中性点对地电压V n与设定的电压阈值V th进行比较，以检测故障。如果V n大于电压阈值，则系统被识别为故障系统，进入步骤16)。否则，转入下一步。 12) Compare the neutral point-to-ground voltage V n with the set voltage threshold V th to detect faults. If V n is greater than the voltage threshold, the system is identified as a faulty system, and step 16) is entered. Otherwise, go to the next step.
13)计算中性点对地电压的斜率dV n，并检查其是否超过设定的斜率阈值dV th。在这里，估计故障发生时间的准确性将取决于dV th，其中较小的dV th将提供更好的准确性。然而，很小的dV th值可以与系统通常的瞬态混合。如果dV n<dV th，则表示系统正常。否则，进入下一步。 13) Calculate the slope dV n of the neutral point to ground voltage and check whether it exceeds the set slope threshold dV th . Here, the accuracy of the estimated failure time will depend on dV th , where a smaller dV th will provide better accuracy. However, small dV th values can be mixed with the usual transients of the system. If dV n <dV th , the system is normal. Otherwise, go to the next step.
14)将当前时间记录为t l，并在Δt 0(通常为几毫秒)的持续时间内再次检查dV n，以确认它是故障还是其他干扰。如果在Δt 0期间中性点对地电压的斜率dV n的平均值大于dV th，则进入下一步；否则识别为系统正常。 14) Record the current time as t l , and check dV n again within the duration of Δt 0 (usually a few milliseconds) to confirm whether it is a fault or other interference. If the average value of the slope dV n of the neutral point to ground voltage during Δt 0 is greater than dV th , proceed to the next step; otherwise, it is recognized that the system is normal.
15)再次检查V n，如果在Δt 0期间中性点对地电压V n的平均值大于V th，则识别为故障系统，然后进入下一步。否则，识别为系统正常。 15) Check V n again, if the average value of the neutral point-to-ground voltage V n is greater than V th during Δt 0 , it is identified as a faulty system, and then go to the next step. Otherwise, the system is recognized as normal.
16)估计故障发生时间，并记录故障发生时间为t f＝min[t，t l]，t l即中性点对地电压的斜率大于设定的斜率阈值的起始点。 16) Estimate the time of occurrence of the fault, and record the time of occurrence of the fault as t f =min[t, t l ], where t l is the starting point where the slope of the neutral point to ground voltage is greater than the set slope threshold.
17)在Δt c延时后比较V n和V th，检查故障是永久性的还是暂时性的。如果V n>V th，则故障将被识别为永久性故障，然后转入步骤18)。但是，由于在故障期间，电弧故障的中性电压可能会低于临界值，因此可能无法检测到某些永久性间歇性电弧故障。因此，如果V n≤V th，需再次将另一个时间段Δt h(从t f+Δt c到t f+Δt c+Δt h)期间内中性点对地电压V n的平均值与阈值进行比较。如果V n超过阈值，则将其识别为永久性故障，转入步骤18)。否则将其识别为暂时故障。 17) Compare V n and V th after Δt c delay, and check whether the fault is permanent or temporary. If V n > V th , the fault will be recognized as a permanent fault, and then go to step 18). However, since the neutral voltage of the arc fault may be lower than the critical value during the fault, some permanent intermittent arc faults may not be detected. Therefore, if V n ≤V th , the average value of the neutral point-to-ground voltage V n and the threshold value during another time period Δt h (from t f +Δt c to t f +Δt c +Δt h ) Compare. If V n exceeds the threshold, it is identified as a permanent fault and go to step 18). Otherwise, it is recognized as a temporary fault.
18)一旦检测到永久性故障，就需要进行故障相位识别和故障定位。为了识别故障相位，故障发生时各相电压的偏差将使用公式(3)计算。如果三相的均方根值偏差均大于0，则三相正常，即系统正常。如果三相的均方根值偏差均小于0，则判断为故障相，进入下一步。18) Once a permanent fault is detected, fault phase identification and fault location are required. In order to identify the fault phase, the deviation of the voltage of each phase when the fault occurs will be calculated using formula (3). If the root mean square deviation of the three phases is greater than 0, then the three phases are normal, that is, the system is normal. If the root mean square deviations of the three phases are all less than 0, it is judged as a faulty phase and the next step is to proceed.
19)计算F CODO(t f)，如果F CODO(t f)＞0则判断为出线故障，否则出线正常。 19) Calculate F CODO (t f ), if F CODO (t f )>0, it is judged as outgoing fault, otherwise the outgoing is normal.
closing opening difference operation(CODO)，F CODO(t f)即在t f时刻的开关分合操作零序电流，用于判别出现故障，这个电流可以直接通过互感器采集。 closing opening difference operation (CODO), F CODO (t f ) is the zero-sequence current of the switch opening and closing operation at t f , which is used to determine the occurrence of a fault. This current can be collected directly through the transformer.
以上所述仅是本发明的优选实施方式，应当指出，对于本技术领域的普通技术人员来说，在不脱离本发明技术原理的前提下，还可以做出若干改进和变形，这些改进和变形也应视为本发明的保护范围。The above are only the preferred embodiments of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the technical principles of the present invention, several improvements and modifications can be made. These improvements and modifications It should also be regarded as the protection scope of the present invention.

Claims (7)

  1. 一种具有谐振接地的配电系统分散式故障检测方法，其特征在于，包括以下步骤：A distributed fault detection method for a power distribution system with resonance grounding is characterized in that it comprises the following steps:
    1)测量故障馈线上的电压和零序电流，计算中性点对地电压及中性点对地电压斜率；1) Measure the voltage and zero sequence current on the faulted feeder, and calculate the neutral point-to-ground voltage and the neutral point-to-ground voltage slope;
    2)将中性点对地电压与设定的电压阈值进行比较，检测故障；2) Compare the neutral point to ground voltage with the set voltage threshold to detect faults;
    3)估计故障发生时间；3) Estimate the time of failure;
    4)将延时一段时间后的中性点对地电压与设定的电压阈值进行比较，识别故障类型；4) Compare the neutral-to-ground voltage after a delay of a period of time with the set voltage threshold to identify the fault type;
    5)基于相地电压的均方根值偏差识别故障相位；5) Identify the fault phase based on the root mean square deviation of the phase-to-ground voltage;
    6)基于故障发生时刻的开关分合操作零序电流识别故障馈线。6) The faulty feeder is identified based on the zero sequence current of the switch opening and closing operation at the time the fault occurs.
  2. 根据权利要求1所述的一种具有谐振接地的配电系统分散式故障检测方法，其特征在于，所述步骤2)中，检测故障分为初步检测和二次检测；A distributed fault detection method for a power distribution system with resonance grounding according to claim 1, characterized in that, in said step 2), the detection fault is divided into preliminary detection and secondary detection;
    所述初步检测是指，将中性点对地电压V n与设定的电压阈值V th进行比较，如果中性点对地电压V n大于电压阈值V th，则系统被识别为故障系统； The preliminary detection refers to comparing the neutral point-to-ground voltage V n with a set voltage threshold V th . If the neutral point-to-ground voltage V n is greater than the voltage threshold V th , the system is identified as a faulty system;
    所述二次检测是指，对于中性点对地电压V n小于等于电压阈值V th的情况，将中性点对地电压的斜率dV n与设定的斜率阈值dV th进行比较，如果dV n<dV th，则表示系统正常，否则，将当前时间记录为t l，在Δt 0的持续时间内持续检查dV n和V n，如果在Δt 0期间中性点对地电压的斜率dV n的平均值大于dV th，且在Δt 0期间中性点对地电压V n的平均值大于V th，则识别为故障系统。 The second detection refers to comparing the slope dV n of the neutral point-to-ground voltage with the set slope threshold dV th in the case that the neutral point-to-ground voltage V n is less than or equal to the voltage threshold V th , if dV n <dV th, then the system is normal, otherwise, the current time is recorded as t l, and continuously checks dV V n in the n-duration Δt 0, if the slope of the ground voltage dV at the neutral point period Δt 0 n The average value of is greater than dV th , and the average value of the neutral point-to-ground voltage V n is greater than V th during Δt 0 , it is identified as a faulty system.
  3. 根据权利要求2所述的一种具有谐振接地的配电系统分散式故障检测方法，其特征在于，所述中性点对地电压V n计算如下： The distributed fault detection method for a power distribution system with resonance grounding according to claim 2, wherein the neutral point-to-ground voltage V n is calculated as follows:
    Figure PCTCN2019120481-appb-100001
    Figure PCTCN2019120481-appb-100001
    其中，Z ASC是通过消弧线圈的阻抗，Z l和Z c分别是配电线路的电感和电容阻抗，Z f是系统故障 阻抗，V pn是相间电压。 Among them, Z ASC is the impedance through the arc suppression coil, Z l and Z c are the inductance and capacitance impedance of the distribution line, respectively, Z f is the system fault impedance, and V pn is the phase-to-phase voltage.
  4. 根据权利要求2所述的一种具有谐振接地的配电系统分散式故障检测方法，其特征在于，所述步骤3)中，故障发生时间为：t f＝min[t，t l]，其中，t f为故障发生时间，t l为中性点对地电压的斜率大于斜率阈值的起始点，t为当前时间。 The distributed fault detection method for a power distribution system with resonance grounding according to claim 2, characterized in that, in the step 3), the fault occurrence time is: t f =min[t, t l ], where , T f is the fault occurrence time, t l is the starting point where the slope of the neutral-to-ground voltage is greater than the slope threshold, and t is the current time.
  5. 根据权利要求4所述的一种具有谐振接地的配电系统分散式故障检测方法，其特征在于，所述步骤4)中，识别故障类型分为初步识别和二次识别，The distributed fault detection method for power distribution system with resonance grounding according to claim 4, characterized in that, in said step 4), identifying the fault type is divided into preliminary identification and secondary identification,
    所述初步识别为，设定延时Δt c，在Δt c延时后，比较中性点对地电压V n与设定的电压阈值V th，如果中性点对地电压V n大于电压阈值V th，则系统被识别为永久性故障； The preliminary identification is, set the delay Δt c, after a delay Δt c, compare the neutral point voltage to the threshold voltage V th and V n is set, if the neutral-to-ground voltage is greater than the voltage threshold V n V th , the system is identified as a permanent fault;
    所述二次识别为，对于中性点对地电压V n小于等于电压阈值V th的情况，设定二次延时Δt h，比较t f+Δt c到t f+Δt c+Δt h期间内中性点对地电压V n的平均值与设定的电压阈值，如果V n的平均值超过电压阈值，则识别为永久性故障，否则识别为暂时故障。 The secondary identification is, for the case where the neutral point-to-ground voltage V n is less than or equal to the voltage threshold V th , set the secondary delay Δt h , and compare the period from t f +Δt c to t f +Δt c +Δt h The average value of the internal neutral point-to-ground voltage V n and the set voltage threshold. If the average value of V n exceeds the voltage threshold, it is recognized as a permanent fault, otherwise it is recognized as a temporary fault.
  6. 根据权利要求1所述的一种具有谐振接地的配电系统分散式故障检测方法，其特征在于，所述步骤5)中，相地电压的均方根值偏差计算如下：The distributed fault detection method for power distribution system with resonance grounding according to claim 1, characterized in that, in the step 5), the root mean square value deviation of the phase-to-ground voltage is calculated as follows:
    Figure PCTCN2019120481-appb-100002
    Figure PCTCN2019120481-appb-100002
    其中，ΔV p为相地电压故障前后的均方根值偏差，
    Figure PCTCN2019120481-appb-100003
    和
    Figure PCTCN2019120481-appb-100004
    分别为相地电压故障前和故障后的均方根值，
    Figure PCTCN2019120481-appb-100005
    和
    Figure PCTCN2019120481-appb-100006
    通过保护电压互感器获取，
    Figure PCTCN2019120481-appb-100007
    和
    Figure PCTCN2019120481-appb-100008
    为故障发生前和发生后时刻；     Among them, ΔV p is the deviation of the root mean square value before and after the phase-to-ground voltage fault,
    Figure PCTCN2019120481-appb-100003
    with
    Figure PCTCN2019120481-appb-100004
    Are the root-mean-square values of the phase-to-ground voltage before and after the fault,
    Figure PCTCN2019120481-appb-100005
    with
    Figure PCTCN2019120481-appb-100006
    Obtained by protecting voltage transformer,
    Figure PCTCN2019120481-appb-100007
    with
    Figure PCTCN2019120481-appb-100008
    Is the time before and after the failure;
    如果ΔV p值为负则为故障相，如果ΔV p值为正则为健康相。 If the ΔV p value is negative, it is a fault phase, and if the ΔV p value is positive, it is a healthy phase.
  7. 根据权利要求1所述的一种具有谐振接地的配电系统分散式故障检测方法，其特征在于，所述步骤6)中，如果开关分合操作零序电流的极性与故障相电压的瞬时电压相同，则为故障馈线；如果开关 分合操作零序电流的极性与故障相电压的瞬时电压相反，则为正常线路；The distributed fault detection method for a power distribution system with resonance grounding according to claim 1, characterized in that, in step 6), if the polarity of the zero-sequence current of the switch switching operation and the instantaneous phase voltage of the fault If the voltage is the same, it is a faulty feeder; if the polarity of the zero sequence current of the switching operation is opposite to the instantaneous voltage of the fault phase voltage, it is a normal line;
    开关分合操作零序电流通过零序电流偏差计算如下：The zero sequence current of the switch opening and closing operation is calculated as follows through the zero sequence current deviation:
    Figure PCTCN2019120481-appb-100009
    Figure PCTCN2019120481-appb-100009
    Figure PCTCN2019120481-appb-100010
    Figure PCTCN2019120481-appb-100010
    Figure PCTCN2019120481-appb-100011
    Figure PCTCN2019120481-appb-100011
    其中，Δi 0为零序电流偏差，
    Figure PCTCN2019120481-appb-100012
    和
    Figure PCTCN2019120481-appb-100013
    分别是故障后和故障前的零序电流的瞬时值，
    Figure PCTCN2019120481-appb-100014
    和
    Figure PCTCN2019120481-appb-100015
    通过保护电流互感器获取，
    Figure PCTCN2019120481-appb-100016
    和
    Figure PCTCN2019120481-appb-100017
    为故障发生前和发生后时刻，t f为故障发生时间。     Among them, Δi 0 is the zero sequence current deviation,
    Figure PCTCN2019120481-appb-100012
    with
    Figure PCTCN2019120481-appb-100013
    Are the instantaneous values of the zero sequence current after the fault and before the fault,
    Figure PCTCN2019120481-appb-100014
    with
    Figure PCTCN2019120481-appb-100015
    Obtained by protecting current transformer,
    Figure PCTCN2019120481-appb-100016
    with
    Figure PCTCN2019120481-appb-100017
    Is the time before and after the fault occurs, and t f is the time when the fault occurs.
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CN110031716B (en) * 2019-03-26 2020-12-08 国电南瑞科技股份有限公司 Distributed fault detection method for power distribution system with resonant grounding
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