CN102279349B

CN102279349B - Low current grounding wire selection method based on residual current variable

Info

Publication number: CN102279349B
Application number: CN2011101953167A
Authority: CN
Inventors: 吴维宁; 朱金大; 王长宝; 阙连元; 于海波; 范志刚; 杨锐; 姜铁卫
Original assignee: Nari Technology Co Ltd; State Grid Electric Power Research Institute
Current assignee: Nari Technology Co Ltd; State Grid Electric Power Research Institute
Priority date: 2011-07-13
Filing date: 2011-07-13
Publication date: 2013-10-02
Anticipated expiration: 2031-07-13
Also published as: CN102279349A; WO2013007051A1

Abstract

The invention discloses a low current grounding wire selection method based on residual current variable, and the method comprises the following steps of: (1) correctly identifying whether an electric distribution network has a single-phase ground fault by adopting the neutral point displacement voltage of the electric distribution network as characteristic quantity; (2) after the ground fault happens, compensating the grounding current of a fault point by virtue of an arc-suppression coil to achieve the effects of reducing the grounding current and extinguishing grounding arc light; (3) adjusting the tap position of a first tap arc-suppression coil on the premise of ensuring that the grounding residual current meets the standard request; (4) because the neutral point displacement voltagebefore and after the tap position adjustment of the arc-suppression coil changes, converting the zero-sequence current of each outgoing line subjected to the tap position adjustment to be below the voltage level before the top position adjustment by utilizing a voltage translation method so as to prevent the wire selection characteristic quantity from being influenced by the neutral point displacement voltage; and (5) selecting the line with the single-phase ground fault according to the change values of the zero-sequence current of each outgoing line after voltage translation before and after the tap position adjustment. The low current grounding wire selection method based on residual current variable can be used for improving the accuracy of wire selection.

Description

Small current grounding line selection method based on residual current variable

技术领域 technical field

本发明属电力系统自动化领域，本发明主要适用于配电网中性点经消弧线圈接地系统，更准确地说是一种选出发生单相接地故障线路的方法。The invention belongs to the field of electric power system automation. The invention is mainly applicable to the grounding system of the neutral point of the distribution network through the arc suppressing coil, and more precisely, it is a method for selecting a single-phase grounding fault line.

背景技术 Background technique

我国配电网运行过程中单相短路接地故障多发，同时随着城市配电网改造，电缆出线日渐增多，系统对地电容电流急剧增加，接地弧光不易自动熄灭，容易产生间隙弧光过电压，如果不采取有效措施，极易造成相间短路，使事故扩大，影响供电质量，因此经消弧线圈的接地方式逐渐获得认可，在中低压配电网中逐步被广泛采用。During the operation of my country's distribution network, single-phase short-circuit grounding faults frequently occur. At the same time, with the transformation of urban distribution network, the number of cable outlets is increasing day by day, and the capacitive current of the system to ground increases sharply. If effective measures are not taken, it is very easy to cause phase-to-phase short circuit, expand the accident, and affect the quality of power supply. Therefore, the grounding method through the arc suppression coil is gradually recognized and widely used in medium and low voltage distribution networks.

但是，配电网接入消弧线圈后给接地选线技术带来了难题，由于消弧线圈对接地点的故障电流进行了补偿，使得故障线路的零序电流特征量变得很不明显，从而影响了单相接地故障选线的准确性，降低了配电网运行控制的自动化水平，增加了运行现场的维护工作量。如果在实现系统消弧线圈自动跟踪补偿功能的基础上，能够为接地选线提供显著的选线特征量，以解决消弧线圈对传统单相接地选线技术造成影响的难题，这对于提高配电网运行的安全性、可靠性、经济性和自动化水平均具有十分重要的意义。However, after the distribution network is connected to the arc-suppression coil, it brings difficulties to the grounding line selection technology. Since the arc-suppression coil compensates the fault current at the ground point, the characteristic value of the zero-sequence current of the fault line becomes very inconspicuous, thus affecting The accuracy of single-phase ground fault line selection is reduced, the automation level of distribution network operation control is reduced, and the maintenance workload on the operation site is increased. If on the basis of realizing the automatic tracking and compensation function of the arc suppression coil of the system, it can provide a significant line selection feature quantity for the grounding line selection, so as to solve the problem that the arc suppression coil affects the traditional single-phase grounding line selection technology. The safety, reliability, economy and automation level of power grid operation are of great significance.

文献一《小电流接地系统中一种新型故障选线方法》(中国专利申请号200910230433.5)披露了一种在消弧线圈接地系统中利用各条线路零序电流的五次谐波进行选线的方法，该方法先选出三个幅值最大的零序五次谐波电流，然后对选出的三个零序五次谐波电流进行相位比较，从而判别出故障线路或母线故障。该专利所描述的方法以五次谐波为选线特征量，不过由于消弧线圈的补偿效果，各条线路的零序电流值很小，其五次谐波值更为微弱，加之使用现场的电磁干扰严重，很难准确测量五次谐波值，使得该方法的实用效果不理想，选线准确性不高。Document 1 "A New Type of Fault Line Selection Method in Small Current Grounding System" (Chinese Patent Application No. 200910230433.5) discloses a method for line selection using the fifth harmonic of the zero-sequence current of each line in the arc suppression coil grounding system In this method, three zero-sequence fifth harmonic currents with the largest amplitudes are selected first, and then phase comparisons are performed on the three selected zero-sequence fifth harmonic currents, so as to identify faulty line or bus faults. The method described in this patent uses the fifth harmonic as the line selection feature quantity, but due to the compensation effect of the arc suppression coil, the zero-sequence current value of each line is very small, and the fifth harmonic value is even weaker. The electromagnetic interference is serious, and it is difficult to accurately measure the fifth harmonic value, which makes the practical effect of this method unsatisfactory, and the accuracy of line selection is not high.

文献二《配电网小电流接地系统故障选线方法》(中国专利申请号200910304934.3)，披露了一种利用并联电阻进行选线的方法，该方法将并联电阻接在变压器中性点与地之间，与消弧线圈并联连接，当配电网系统发生接地故障后投切并联电阻，通过比较并联电阻投切前后各条出线的零序电流实现故障选线。该方法具备一定的实用性，不过从选线特征量的显著性考虑还具备提升的空间，此外，并联电阻直接接在中性点与地之间，实际运行时对电阻的要求很高，因此该方法的准确性和可靠性还需要进一步提高。Document 2, "Method for Fault Line Selection of Small Current Grounding System of Distribution Network" (Chinese Patent Application No. 200910304934.3), discloses a method for line selection using parallel resistors. In this method, the parallel resistors are connected between the neutral point of the transformer and the ground. When a ground fault occurs in the distribution network system, the parallel resistors are switched, and the fault line selection is realized by comparing the zero-sequence current of each outgoing line before and after the parallel resistors are switched. This method has certain practicability, but there is still room for improvement in terms of the significance of the line selection feature quantity. In addition, the parallel resistor is directly connected between the neutral point and the ground, and the requirements for the resistance are very high during actual operation. Therefore, The accuracy and reliability of this method need to be further improved.

发明内容 Contents of the invention

本发明的发明目的是：为配电网中性点经消弧线圈接地系统提供一种准确性高且运行可靠的接地选线方法，该方法能够提供明显的选线特征量，同时该方法实用性好，准确性高，且不会降低现场运行的可靠性和安全性。The purpose of the present invention is to provide a high-accuracy and reliable grounding line selection method for the neutral point of the distribution network through the arc suppression coil grounding system. The method can provide obvious line selection characteristics, and the method is practical Good performance, high accuracy, and will not reduce the reliability and safety of field operation.

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 object, the present invention is achieved by taking the following technical solutions:

基于残流变量的小电流接地选线方法，包括下列步骤：The small current grounding line selection method based on the residual current variable includes the following steps:

(1)采用配电网中性点位移电压作为特征量，正确识别配电网是否发生了单相接地故障；(1) Use the neutral point displacement voltage of the distribution network as the characteristic quantity to correctly identify whether a single-phase ground fault has occurred in the distribution network;

(2)发生接地故障后，消弧线圈对故障点的接地电流进行补偿，以达到减小接地电流、熄灭接地弧光的效果；(2) After a ground fault occurs, the arc suppression coil compensates the ground current at the fault point to achieve the effect of reducing the ground current and extinguishing the ground arc;

(3)在保证接地残流满足标准要求的同时，根据实际情况向上或下调节一档消弧线圈的档位；(3) While ensuring that the grounding residual current meets the standard requirements, adjust the gear position of the first gear arc suppression coil up or down according to the actual situation;

(4)由于消弧线圈档位调节前后中性点位移电压会有变化，故采用电压折算方法，把调档后的各出线的零序电流折算到调档前的电压等级下，以避免中性点位移电压对选线特征量的影响；(4) Since the neutral point displacement voltage will change before and after the gear adjustment of the arc suppressing coil, the voltage conversion method is adopted to convert the zero-sequence current of each outgoing line after the gear adjustment to the voltage level before the gear adjustment, so as to avoid neutral The influence of the neutral point displacement voltage on the characteristic quantity of line selection;

(5)根据电压折算后各出线零序电流在调档前后的变化量，能够准确、可靠地选出发生单相接地故障的线路。(5) According to the change amount of the zero-sequence current of each outgoing line before and after shifting after voltage conversion, the line with single-phase ground fault can be accurately and reliably selected.

前述的小电流接地选线方法，其特征在于：在所述步骤(1)中，识别是否发生单相接地故障的方法为：The aforesaid low-current grounding line selection method is characterized in that: in the step (1), the method for identifying whether a single-phase ground fault occurs is:

中性点位移电压U₀的计算公式为：The calculation formula of the neutral point displacement voltage U ₀ is:

${\overset{\cdot &Center Dot;}{U u}}_{00} = = {\overset{\cdot &Center Dot;}{I I}}_{δ δ} * * \frac{11}{j j ((33 ωC ω C + + \frac{11}{ωL ωL}))} = = \frac{- - {\overset{\cdot &Center Dot;}{U u}}_{ψ ψ}}{(({R R}_{d d} + + \frac{11}{j j ((33 ωC ω C + + \frac{11}{ωL ωL}))}))} * * \frac{11}{j j ((33 ωC ω C + + \frac{11}{ωL ωL}))}$

$= = \frac{- - {\overset{\cdot &Center Dot;}{U u}}_{ψ ψ}}{11 + + j j {R R}_{d d} ((33 ωC ω C + + \frac{11}{ωL ω L}))} - - - - - - ((11)),,$

式中U₀为中性点位移电压；U_ψ为系统相电压；R_d为接地电阻；L为消弧线圈的电感；C为系统单相对地电容；I_δ为消弧线圈补偿后的残流，In the formula, U ₀ is the neutral point displacement voltage; U _ψ is the phase voltage of the system; R _d is the grounding resistance; L is the inductance of the arc suppression coil; _C is the single-phase ground capacitance of the system; flow,

当中性点位移电压U₀的值小于15％U_ψ时为正常运行，当U₀大于预先设定的阈值U_0zd(通常U_0zd可取30％U_ψ)，则判定为发生单相接地故障。When the value of the neutral point displacement voltage U ₀ is less than 15% U _ψ , it is normal operation. When U ₀ is greater than the preset threshold U _0zd (usually U _0zd can be 30% U _ψ ), it is determined that a single-phase ground fault has occurred.

前述的小电流接地选线方法，其特征在于：在所述步骤(5)中，如果调档前后零序电流的变化量为零，则为非故障线路；如果故障线路的零序电流变化量等于消弧线圈输出电流变化量，则为故障线路。The aforementioned small current grounding line selection method is characterized in that: in the step (5), if the variation of the zero-sequence current before and after shifting is zero, it is a non-faulty line; if the zero-sequence current variation of the faulty line If it is equal to the output current variation of the arc suppression coil, it is a faulty line.

本发明所达到的有益效果：本发明的基于残流变量的小电流接地选线方法，在配电网发生单相接地故障后，使调匝式消弧线圈的档位调节一档，以提高接地选线的特征量。通过比较调匝式消弧线圈调档前后各条出线零序电流的变化情况，选出发生单相接地故障的线路。通过对调匝式消弧线圈调档前后各零序电流的特征量进行电压折算，减小中性点电压变化对选线结果的影响，提高该选线方法的准确性。本发明实现简便，成本可控，实用性好，并且不影响现场运行的可靠性和安全性，对消弧线圈的补偿效果影响不大。The beneficial effects achieved by the present invention: the small current grounding line selection method based on the residual current variable of the present invention, after a single-phase grounding fault occurs in the distribution network, the gear of the turn-adjusting arc suppression coil is adjusted to a gear to improve The characteristic quantity of grounding line selection. By comparing the change of the zero-sequence current of each outgoing line before and after the turn-adjusting arc suppression coil is shifted, the line where the single-phase ground fault occurs is selected. Through the voltage conversion of the characteristic quantities of each zero-sequence current before and after the turn-adjusting arc suppression coil is shifted, the influence of the neutral point voltage change on the line selection result is reduced, and the accuracy of the line selection method is improved. The invention has the advantages of simple realization, controllable cost and good practicability, does not affect the reliability and safety of on-site operation, and has little influence on the compensation effect of the arc suppression coil.

附图说明 Description of drawings

图1是采用本发明的配电网中性点经消弧线圈接地系统的结构图；Fig. 1 is the structural diagram of the neutral point of the distribution network adopting the present invention through the arc-suppression coil grounding system;

图2是配电网经中性点消弧线圈接地系统的等效电路图；Fig. 2 is the equivalent circuit diagram of the grounding system of the distribution network through the neutral point arc suppressing coil;

图3是配电网中性点消弧线圈接地系统调档后的等效电路图；Fig. 3 is the equivalent circuit diagram of the neutral point arc suppressing coil grounding system of the distribution network after shifting;

图4是实施例的系统结构图；Fig. 4 is the system structural diagram of embodiment;

图5是实施例的仿真波形图。Fig. 5 is a simulation waveform diagram of the embodiment.

具体实施方式 Detailed ways

在本发明中，披露了通过改变消弧线圈的运行状态进行接地选线的方法。图1是配电网中性点经消弧线圈接地的系统模型，当配电网发生单相接地故障时，待确认故障状态后，将消弧线圈调节一档，这样会产生明显的零序电流特征量，有利于准确选出故障线路。In the present invention, a method for selecting the grounding line by changing the operating state of the arc suppression coil is disclosed. Figure 1 is a system model in which the neutral point of the distribution network is grounded through the arc-suppression coil. When a single-phase ground fault occurs in the distribution network, after the fault state is confirmed, the arc-suppression coil is adjusted to a gear, which will produce an obvious zero-sequence The current characteristic quantity is beneficial to accurately select the fault line.

图2为发生单相接地故障时，接入消弧线圈的配电网等效电路。图中U₀为中性点位移电压；U_ψ为系统相电压；R_d为接地电阻；L为消弧线圈的电感；C为系统单相对地电容；I_δ为消弧线圈补偿后的残流。Figure 2 is the equivalent circuit of the distribution network connected to the arc suppression coil when a single-phase ground fault occurs. In the figure, U ₀ is the neutral point displacement voltage; U _ψ is the phase voltage of the system; R _d is the grounding resistance; L is the inductance of the arc suppression coil; _C is the single-phase ground capacitance of the system; flow.

${\overset{\cdot &Center Dot;}{U u}}_{00} = = {\overset{\cdot &Center Dot;}{I I}}_{δ δ} * * \frac{11}{j j ((33 ωC ω C - - \frac{11}{ωL ωL}))} = = \frac{- - {\overset{\cdot \cdot}{U u}}_{ψ ψ}}{(({R R}_{d d} + + \frac{11}{j j ((33 ωC ω C - - \frac{11}{ωL ωL}))}))} * * \frac{11}{j j ((33 ωC ω C - - \frac{11}{ωL ωL}))}$

$= = \frac{- - {\overset{\cdot \cdot}{U u}}_{ψ ψ}}{11 + + j j {R R}_{d d} ((33 ωC ω C - - \frac{11}{ωL ωL}))} - - - - - - ((11))$

式中，ω为系统角频率，j为虚数单位In the formula, ω is the angular frequency of the system, and j is the imaginary unit

线路i(i≠n)为非故障线路，其零序电流为：Line i (i≠n) is a non-faulty line, and its zero-sequence current is:

${\overset{\cdot \cdot}{I I}}_{00 i i} = = {\overset{\cdot &Center Dot;}{I I}}_{Ai Ai} + + {\overset{\cdot \cdot}{I I}}_{Bi Bi} + + {\overset{\cdot \cdot}{I I}}_{Ci Ci}$

$= = jω jω {C C}_{00 i i} {\overset{\cdot \cdot}{U u}}_{A A}^{,,} + + jω jω {C C}_{00 i i} {\overset{\cdot &Center Dot;}{U u}}_{B B}^{,,} + + jω jω {C C}_{00 i i} {\overset{\cdot \cdot}{U u}}_{C C}^{,,}$

$= = jω jω {C C}_{00 i i} (({\overset{\cdot &Center Dot;}{U u}}_{00} + + {\overset{\cdot &Center Dot;}{U u}}_{A A})) + + jω jω {C C}_{00 i i} (({\overset{\cdot &Center Dot;}{U u}}_{00} + + {\overset{\cdot &Center Dot;}{U u}}_{B B})) + + jω jω {C C}_{00 i i} (({\overset{\cdot &Center Dot;}{U u}}_{00} + + {\overset{\cdot &Center Dot;}{U u}}_{C C}))$

$= = j j 33 {\overset{\cdot &Center Dot;}{U u}}_{00} ω ω {C C}_{00 i i} - - - - - - ((22))$

其中，C_0i为线路i的单相对地电容，I_Ai、I_Bi、I_Ci为线路i三相对地电容电流，U_A、U_B、U_C为系统相电压。Among them, C _0i is the single-phase-to-ground capacitance of line i, I _Ai , I _Bi , and I _Ci are the three-phase-to-ground capacitance currents of line i, and U _A , _UB , and U _C are system phase voltages.

设线路n为发生单相接地故障的线路，其故障相C相的电流为：Assuming that line n is a line with a single-phase ground fault, the current of the faulty phase C is:

${\overset{\cdot &Center Dot;}{I I}}_{Cn Cn} = = - - (({Σ Σ}_{i i = = 11}^{n no - - 11} {\overset{\cdot &Center Dot;}{I I}}_{00 i i} + + {\overset{\cdot &Center Dot;}{I I}}_{An An} + + {\overset{\cdot &Center Dot;}{I I}}_{Bn Bn})) + + {\overset{\cdot &Center Dot;}{I I}}_{L L} - - - - - - ((33))$

式中，I_An、I_Bn、I_Cn为故障线路n三相对地电容电流，I_L为消弧线圈输出电感电流。In the formula, I _An , I _Bn , and I _Cn are the three phase-to-ground capacitance currents of the fault line n, and I _L is the output inductance current of the arc suppression coil.

则线路n的零序电流为：Then the zero-sequence current of line n is:

${\overset{\cdot &Center Dot;}{I I}}_{00 n no} = = {\overset{\cdot &Center Dot;}{I I}}_{An An} + + {\overset{\cdot &Center Dot;}{I I}}_{Bn Bn} + + {\overset{\cdot &Center Dot;}{I I}}_{Cn Cn} = = - - {Σ Σ}_{i i = = 11}^{n no - - 11} {\overset{\cdot &Center Dot;}{I I}}_{00 i i} + + {\overset{\cdot &Center Dot;}{I I}}_{L L} - - - - - - ((44))$

即故障线路零序电流大小为非故障线路零序电容电流与消弧线圈零序电感电流之和，方向与消弧线圈的补偿度有关。That is, the zero-sequence current of the fault line is the sum of the zero-sequence capacitive current of the non-fault line and the zero-sequence inductance current of the arc suppression coil, and the direction is related to the compensation degree of the arc suppression coil.

图3为发生单相接地故障时，改变消弧线圈档位后的配电网等效电路，其中U₀′为调档后中性点位移电压，L′为调档后消弧线圈电感值。此时，中性点位移电压的变化量为：Figure 3 is the equivalent circuit of the distribution network after changing the gear position of the arc suppression coil when a single-phase ground fault occurs, where U ₀ ′ is the neutral point displacement voltage after gear adjustment, and L’ is the inductance value of the arc suppression coil after gear adjustment . At this time, the variation of the neutral point displacement voltage is:

$Δ Δ {\overset{\cdot &Center Dot;}{U u}}_{00} = = {\overset{\cdot \cdot}{U u}}_{00^{' '}} - - {\overset{\cdot &Center Dot;}{U u}}_{00} = = \frac{{\overset{\cdot \cdot}{U u}}_{Ψ Ψ}}{11 + + j j {R R}_{d d} ((33 ωC ω C - - \frac{11}{ωL ωL}))} - - \frac{{\overset{\cdot \cdot}{U u}}_{ψ ψ}}{11 + + j j {R R}_{d d} ((33 ωC ω C - - \frac{11}{{ωL ωL}^{' '}}))} - - - - - - ((55))$

电压折算后非故障线路i的零序电流变化量为：The zero-sequence current variation of non-fault line i after voltage conversion is:

${ΔI ΔI}_{00 i i} = = \frac{{U u}_{00}}{{U u}_{00}^{' '}} {I I}_{00 i i}^{' '} - - {I I}_{00 i i} = = \frac{{U u}_{00}}{{U u}_{00}^{' '}} ((\frac{{U u}_{00}^{' '}}{{U u}_{00}} {I I}_{00 i i})) - - {I I}_{00 i i} = = {I I}_{00 i i} - - {I I}_{00 i i} = = 00 - - - - - - ((66))$

电压折算后故障线路的零序电流变化量为：After voltage conversion, the zero-sequence current variation of the fault line is:

${ΔI ΔI}_{00 n no} = = \frac{{U u}_{00}}{{U u}_{00}^{' '}} Δ Δ {I I}_{L L} - - Σ Σ {ΔI ΔI}_{00 i i} = = \frac{{U u}_{00}}{{U u}_{00}^{' '}} {ΔI ΔI}_{L L} - - - - - - ((77))$

ΔI_L为调档前后消弧线圈输出电流变化量。ΔI _L is the change in output current of the arc suppression coil before and after shifting gears.

根据以上分析可知，对于非故障线路，采用电压折算原理，调档前后零序电流的变化量为零；对于故障线路来说，零序电流的变化量为消弧线圈输出感性电流的变化量和非故障线路零序电流变化量之差，而后者为零，因此故障线路的零序电流变化量等于消弧线圈输出电流变化量。According to the above analysis, it can be seen that for non-fault lines, the change of zero-sequence current before and after shifting is zero by adopting the voltage conversion principle; for fault lines, the change of zero-sequence current is the change of The difference between the zero-sequence current variation of the non-fault line, and the latter is zero, so the zero-sequence current variation of the fault line is equal to the output current variation of the arc suppression coil.

通过比较(6)式和(7)式可以看出，采用本发明的方法，故障线路与非故障线路的零序电流特征量有着很明显的区别，利用该特点可以准确可靠地选出故障线路。By comparing formula (6) and formula (7), it can be seen that adopting the method of the present invention, the zero-sequence current characteristic quantity of the faulty line and the non-faulty line has a very obvious difference, and the faulty line can be selected accurately and reliably by using this feature .

下面是本发明的一个优选实施例，该实施例针对某一具体的配电网，采用本发明的方法实现单相接地故障选线功能。本发明的其它的特征、目的和优点也可以从实施例的说明和附图中看出。The following is a preferred embodiment of the present invention. This embodiment is aimed at a specific distribution network and adopts the method of the present invention to realize the single-phase grounding fault line selection function. Other characteristics, objects and advantages of the present invention can also be seen from the description of the embodiments and the drawings.

图4中的10kV配电网有5条线路，其中在线路5首端模拟单相金属性接地故障。故障后调节消弧线圈一个档位，分析各条线路的零序电流变化情况，选出故障线路。The 10kV distribution network in Figure 4 has 5 lines, and the single-phase metallic ground fault is simulated at the head end of line 5. After the fault, adjust the arc suppressing coil to a gear, analyze the zero-sequence current change of each line, and select the faulty line.

通过数据分析可得，故障线路的零序电流变化量为2A，非故障线路的零序电流变化量最大为0.001A，各特征量的变化波形如图5所示。通过特征量的变化情况可以准确地选出故障线路，指导现场运行人员准确切除障线路，达到保障配电网安全稳定运行的目的。Through data analysis, the zero-sequence current variation of the faulty line is 2A, and the maximum zero-sequence current variation of the non-faulty line is 0.001A. The variation waveforms of each characteristic quantity are shown in Figure 5. The faulty line can be accurately selected through the change of the characteristic quantity, and the on-site operators can be guided to remove the faulty line accurately, so as to achieve the purpose of ensuring the safe and stable operation of the distribution network.

本发明按照优选实施例进行了说明，应当理解，但上述实施例不以任何形式限定本发明，凡采用等同替换或等效变换的形式所获得的技术方案，均落在本发明的保护范围之内。The present invention has been described according to the preferred embodiments, it should be understood that the above embodiments do not limit the present invention in any form, and all technical solutions obtained in the form of equivalent replacement or equivalent transformation all fall within the protection scope of the present invention Inside.

Claims

1. the small current earthing wire-selecting method based on the residual flow variable is characterized in that, comprises the following steps:

(1) adopts the power network neutral point displacement voltage as characteristic quantity, correctly identify power distribution network whether singlephase earth fault takes place;

(2) after the generation earth fault, arc suppression coil compensates the ground current of trouble spot, to reach the effect that reduces ground current, extinguishes the ground connection arc light;

(3) when guaranteeing that the ground connection residual flow satisfies standard-required, regulate the gear of one grade of arc suppression coil up or down;

(4) owing to neutral point displacement voltage before and after the adjusting of arc suppression coil gear can change, so adopt the voltage translation method, the zero-sequence current of each outlet after transferring the files is converted under the preceding electric pressure of transferring the files, to avoid neutral point displacement voltage to the influence of route selection characteristic quantity;

(5) select the circuit that singlephase earth fault takes place according to each outlet zero-sequence current of voltage conversion back at the variable quantity before and after transferring the files,

In described step (5), if the variable quantity of zero-sequence current is zero before and after transferring the files, then be non-fault line; If the zero-sequence current variable quantity of faulty line equals arc suppression coil output current variable quantity, it then is faulty line.

2. small current earthing wire-selecting method according to claim 1 is characterized in that: in described step (1), the method whether identification singlephase earth fault takes place is:

Neutral point displacement voltage U ₀Computing formula be:

{\overset{\cdot}{U}}_{0} = {\overset{\cdot}{I}}_{δ} * \frac{1}{(3 ωC + \frac{1}{ωL})} = \frac{- {\overset{\cdot}{U}}_{ψ}}{(R_{d} + \frac{1}{j (3 ωC + \frac{1}{ωL})})} * \frac{1}{j (3 ωC + \frac{1}{ωL})}

= \frac{- {\overset{\cdot}{U}}_{ψ}}{1 + j R_{d} (3 ωC + \frac{1}{ωL})} - - - (1),

U in the formula ₀Be neutral point displacement voltage; U _ψBe system's phase voltage; R _dBe stake resistance; L is the inductance of arc suppression coil; C is the single-phase ground capacitance of system; I _δBe the residual flow behind the arc suppression coil compensation, ω is the system angle frequency,

As neutral point displacement voltage U ₀Value less than 15%U _ψThe time be normal operation, work as U ₀More than or equal to pre-set threshold, then be judged to be the generation singlephase earth fault.