CN104237703A

CN104237703A - Method for recognizing properties of three-phase adaptive re-closing faults of lines with parallel reactors

Info

Publication number: CN104237703A
Application number: CN201410520566.7A
Authority: CN
Inventors: 王慧芳; 王庆庆; 林达; 何奔腾
Original assignee: Zhejiang University ZJU
Current assignee: Zhejiang University ZJU
Priority date: 2014-09-30
Filing date: 2014-09-30
Publication date: 2014-12-24
Anticipated expiration: 2034-09-30
Also published as: CN104237703B

Abstract

The invention relates to a method for recognizing properties of three-phase adaptive re-closing faults of lines with parallel reactors. By the aid of the method, problems of different application ranges of existing fault property criteria and high quantities of influence factors on the existing fault property criteria can be solved. The method includes firstly, sampling the magnitude of currents of the single-ended parallel reactors after three-phase tripping occurs, and acquiring corresponding differential-mode components by means of phase-mode transformation; secondly, computing frequencies (periods) of the differential-mode components according to parameters of the lines; thirdly, analyzing waveforms of instantaneous values of differential-mode currents in a period of the differential-mode components. Besides, only attenuation direct-current components are available in the differential-mode currents when permanent faults occur, only attenuation periodic components are available in the differential-mode currents after instantaneous faults occur and then arcs of the faults are blown out, accordingly, novel criteria applicable to recognizing the properties of the phase-to-phase faults during three-phase adaptive re-closing can be provided by the aid of waveform characteristics of the differential-mode currents under different fault property conditions, and arc blowout moments can be identified. The method has the advantages of few influence factors on fault property discrimination and high sensitivity.

Description

Fault nature identification method for three-phase adaptive reclosing of lines with shunt reactors

技术领域technical field

本发明属于电力系统技术领域，具体是涉及一种带并联电抗器线路三相自适应重合闸故障性质识别方法。The invention belongs to the technical field of power systems, and in particular relates to a method for identifying the nature of a three-phase adaptive reclosing fault of a line with a shunt reactor.

背景技术Background technique

目前国内外输电线路中基本都采用的是自动重合闸技术，对保证电力系统稳定运行起着至关重要的作用。然而，自动重合闸在带来巨大经济效益的同时，也给电力系统带来了负面的影响。因为输电线路的故障性质分为瞬时性故障和永久性故障，如果重合于永久性故障上，相当于电力设备再次受到故障电流的冲击，会缩短电力设备的寿命。为了减少电力系统的损失，在重合闸之前判断出故障性质显得至关重要。At present, the automatic reclosing technology is basically adopted in the transmission lines at home and abroad, which plays a vital role in ensuring the stable operation of the power system. However, while automatic reclosing has brought huge economic benefits, it has also brought negative effects to the power system. Because the fault nature of the transmission line is divided into transient fault and permanent fault, if it overlaps with the permanent fault, it is equivalent to the power equipment being impacted by the fault current again, which will shorten the life of the power equipment. In order to reduce the loss of the power system, it is very important to judge the nature of the fault before reclosing.

目前，相关研究主要集中在单相自适应重合闸方面。虽然相间故障在短路故障中所占比例较小，但是重合于多相永久性故障对系统安全稳定运行和电气设备所带来的危害比重合于单相永久性故障更为严重，因此三相自适应重合闸有很大的研究价值。由于三相跳闸之后线路中可提取的信息很少，三相自适应重合闸的研究难度较大，但仍然取得了一定的成果，主要有：①基于线路恢复电压的方法，该方法的判别精度在很大程度上依赖于线路侧电压互感器的测量精度，且很多线路在线路侧未装电压互感器或只装设有一相电压互感器；②基于高频保护通道的方法，需要依赖于高频保护的通道，且对不包括加工相的相间故障存在误判的可能；③基于模糊神经网络的方法，该方法需要大量的训练样本，其可靠性有待检验；④基于并联电抗器电流的方法，包括：基于电感电容参数的辨识方法，但计算过程涉及到微分积分运算，作近似处理时会带来较大误差；基于模型识别和电流差动的方法，当过渡电阻较大时，对判别结果影响很大；基于自由振荡分量频率幅值分离的方法，需要很高的采样率，且区分度较低；上述基于并联电抗器电流的方法在双端带并联电抗器时均需用到双端并联电抗器电流量。At present, related research mainly focuses on single-phase adaptive reclosing. Although phase-to-phase faults account for a small proportion of short-circuit faults, the harm to the safe and stable operation of the system and electrical equipment caused by coincidence with multi-phase permanent faults is more serious than that of single-phase permanent faults. Adaptive reclosing has great research value. Since there is very little information that can be extracted from the line after a three-phase trip, the research on three-phase adaptive reclosing is difficult, but some achievements have been made, mainly as follows: ① Based on the method of line recovery voltage, the discrimination accuracy of this method To a large extent, it depends on the measurement accuracy of the voltage transformer on the line side, and many lines have no voltage transformer or only one phase voltage transformer on the line side; ②The method based on the high frequency protection channel needs to rely on high frequency protection channel, and there is a possibility of misjudgment for phase-to-phase faults that do not include the processing phase; ③ The method based on fuzzy neural network requires a large number of training samples, and its reliability needs to be tested; ④ The method based on shunt reactor current , including: the identification method based on the inductance and capacitance parameters, but the calculation process involves differential and integral operations, which will bring large errors when performing approximate processing; the method based on model identification and current differential, when the transition resistance is large, the discrimination The results have a great influence; the method based on the separation of the frequency and amplitude of the free oscillation component requires a high sampling rate, and the discrimination is low; the above method based on the shunt reactor current needs to use two Terminal shunt reactor current.

发明内容Contents of the invention

本发明的目的在于针对现有技术的不足，提供一种基于并联电抗器差模电流波形特征的三相自适应重合闸永久性故障识别方法。The purpose of the present invention is to provide a three-phase self-adaptive reclosing permanent fault identification method based on the differential mode current waveform characteristics of shunt reactors in view of the deficiencies in the prior art.

本发明首先采样得到三相跳闸后并联电抗器电流量，经过相模变换得到对应的差模分量，然后根据线路参数计算出差模分量频率(周期)，最后对一个差模分量周期内的差模电流瞬时值进行波形分析。如果差模电流中只存在衰减周期分量，即可判定为瞬时性故障，此时即判定为熄弧时刻，经过一定的延时后进行重合闸操作，如果只存在衰减直流分量，则判定为永久性故障，从而闭锁重合闸装置。In the present invention, the current of the shunt reactor after the three-phase trip is obtained by sampling first, and the corresponding differential mode component is obtained through phase-mode conversion, and then the frequency (period) of the differential mode component is calculated according to the line parameters, and finally the differential mode current within a differential mode component period is calculated Instantaneous values for waveform analysis. If there is only a decaying periodic component in the differential mode current, it can be judged as an instantaneous fault. At this time, it is judged as the arc-extinguishing moment. After a certain delay, the reclosing operation is performed. If there is only a decaying DC component, it is judged as a permanent fault. fault, thereby blocking the recloser.

更进一步，利用本发明判断出的故障性质以及瞬时性故障熄弧时间，可以实施自适应重合闸方案。具体是：如果判别出故障为瞬时性故障及熄弧时刻，则投入重合闸；如果判别为永久性故障，则不重合。Furthermore, the self-adaptive reclosing scheme can be implemented by utilizing the nature of the fault judged by the present invention and the arc-off time of the instantaneous fault. Specifically: if it is judged that the fault is an instantaneous fault and the moment of arc extinguishing, it will be put into reclosure; if it is judged as a permanent fault, it will not be reclosed.

本发明方法包括以下步骤：The inventive method comprises the following steps:

步骤(1)：采样获得m端并联电抗器电流量i_mxa、i_mxb、i_mxc,通过相模变换得到对应的差模电流分量：Step (1): Obtain the current quantities i _mxa , i _mxb , and i _mxc of the m-terminal shunt reactor by sampling, and obtain the corresponding differential mode current components through phase-mode transformation:

$\{\begin{matrix} {i i}_{mxα mxα} = = {i i}_{mxa mxa} - - {i i}_{mxb mxb} \\ {i i}_{mxβ mxβ} = = {i i}_{mxa mxa} - - {i i}_{mxc mxc} \\ {i i}_{mxγ mxγ} = = {i i}_{mxb mxb} - - {i i}_{mxc mxc} \end{matrix}$

步骤(2)：根据线路参数计算出差模分量频率(周期)，假设发生瞬时性故障，以单端带并联电抗器模型为例，对线路T型等效模型采用复频域分析，忽略线路阻抗，可以得到复频域下的节点导纳矩阵为：Step (2): Calculate the frequency (period) of the differential mode component according to the line parameters. Assuming that an instantaneous fault occurs, take the single-ended shunt reactor model as an example, and use the complex frequency domain analysis for the T-type equivalent model of the line, ignoring the line impedance , the node admittance matrix in the complex frequency domain can be obtained as:

$Y Y ((s the s)) = = [\begin{matrix} {Y Y}_{s the s} & {- - Y Y}_{m m} & {- - Y Y}_{m m} \\ {- - Y Y}_{m m} & {Y Y}_{s the s} & {- - Y Y}_{m m} \\ {- - Y Y}_{m m} & {- - Y Y}_{m m} & {Y Y}_{s the s} \end{matrix}]$

$\{\begin{matrix} {Y Y}_{s the s} = = s the s (({C C}_{00} + + {22 C C}_{m m})) + + 11 / / {sL s L}_{00} + + 22 / / {sL sL}_{m m} \\ {Y Y}_{m m} = = s the s {C C}_{m m} + + 11 / / {sL s L}_{m m} \end{matrix}$

其中，Ys为自导纳，Ym为相间互导纳，C0为线路对地电容，Cm为相间电容，Lm和L0分别为并联电抗器电感L1及中性点小电抗电感Ln等效后的相间电感和对地电感。Among them, Ys is the self-admittance, Ym is the phase-to-phase mutual admittance, C0 is the line-to-ground capacitance, Cm is the phase-to-phase capacitance, Lm and L0 are the parallel reactor inductance L1 and the neutral point small reactance inductance Ln equivalent phase-to-phase inductance and ground inductance.

通过相模变换可以得到复频域下的差模节点导纳矩阵：The differential-mode node admittance matrix in the complex frequency domain can be obtained by phase-mode transformation:

${Y Y}_{αβγ αβγ} ((s the s)) = = ((\frac{11}{{L L}_{00} s the s} + + \frac{33}{{L L}_{m m} s the s} + + {33 C C}_{m m} s the s + + {C C}_{00} s the s)) \cdot &Center Dot; {E E.}_{33 \times \times 33}$

通过求解特征方程det(Y_αβγ(s))＝0可以得到差模分量频率：The frequency of the differential mode component can be obtained by solving the characteristic equation det(Y _αβγ (s))=0:

${f f}_{D D.} = = \frac{11}{22 π π} \sqrt{\frac{{L L}_{m m} + + {33 L L}_{00}}{{L L}_{m m} {L L}_{00} (({C C}_{00} + + {33 C C}_{m m}))}} = = \frac{11}{22 π π} \sqrt{\frac{11}{{C C}_{11} {L L}_{11}}}$

其中，C1即为正序电容，L1即为并联电抗器电感。Among them, C1 is the positive sequence capacitor, and L1 is the inductance of the shunt reactor.

同理，对于双端带并联电抗器模型，节点导纳矩阵为：Similarly, for the double-terminal shunt reactor model, the node admittance matrix is:

$\{\begin{matrix} {Y Y}_{s the s} = = s the s (({C C}_{00} + + {22 C C}_{m m})) + + 22 / / {sL sL}_{00} + + 44 / / {sL sL}_{m m} \\ {Y Y}_{m m} = = s the s {C C}_{m m} + + 22 / / {sL sL}_{m m} \end{matrix}$

通过相模变换后得到差模节点导纳矩阵：After the phase-mode transformation, the differential-mode node admittance matrix is obtained:

${Y Y}_{αβγ αβγ} ((s the s)) = = ((\frac{22}{{L L}_{00} s the s} + + \frac{66}{{L L}_{m m} s the s} + + {33 C C}_{m m} s the s + + {C C}_{00} s the s)) \cdot \cdot {E E.}_{33 \times \times 33}$

求解特征方程det(Y_αβγ(s))＝0得到差模分量频率：Solve the characteristic equation det(Y _αβγ (s))=0 to get the frequency of the differential mode component:

${f f}_{D D.} = = \frac{11}{22 π π} \sqrt{\frac{22 (({L L}_{m m} + + {33 L L}_{00}))}{{L L}_{m m} {L L}_{00} (({C C}_{00} + + {33 C C}_{m m}))}} = = \frac{11}{22 π π} \sqrt{\frac{22}{{C C}_{11} {L L}_{11}}}$

综上所述，可以得到差模分量周期 In summary, the differential mode component period can be obtained

步骤(3)：对一个差模分量周期内的差模电流瞬时值进行波形分析，判据为:Step (3): Carry out waveform analysis to the instantaneous value of the differential mode current in a differential mode component period, and the criterion is:

$λ λ = = \frac{| | {Σ Σ}_{i i = = 11}^{n no} {x x}_{i i} | |}{{Σ Σ}_{i i = = 11}^{n no} | | {x x}_{i i} | |} > > 0.5 0.5$

其中，n为各数据窗内的采样点数，取为T_D(T_D为差模分量周期)内的采样点数，x_i为数据窗内第i个采样点的差模电流采样值。Among them, n is the number of sampling points in each data window, which is taken as the number of sampling points in T _D (T _D is the period of the differential mode component), and _xi is the differential mode current sampling value of the i-th sampling point in the data window.

鉴于发生永久性故障时，差模电流中只存在衰减直流分量，此时判据始终成立，而发生瞬时性故障时，在故障熄弧以后，差模电流中只存在衰减周期分量，上述判据不成立，利用差模电流在不同故障性质条件下的波形特征可以提出一种适用于三相自适应重合闸中相间故障性质识别的新判据，并鉴别熄弧时刻。当判定为瞬时性故障时，经过一定的延时后进行重合闸操作，当判定为永久性故障时，则闭锁重合闸装置。In view of the fact that when a permanent fault occurs, there is only a decaying DC component in the differential-mode current, the criterion is always valid at this time, while in the case of a transient fault, after the fault is extinguished, there is only a decaying periodic component in the differential-mode current, the above criterion If it is not established, a new criterion suitable for phase-to-phase fault identification in three-phase adaptive reclosing can be proposed by using the waveform characteristics of differential mode current under different fault properties, and the arc-extinguishing time can be identified. When it is judged as an instantaneous fault, the reclosing operation is performed after a certain delay, and when it is judged as a permanent fault, the reclosing device is blocked.

本发明充分利用不同故障性质下的故障特征，鉴于发生永久性故障时，差模电流中只存在衰减直流分量，而发生瞬时性故障时，在故障熄弧以后，差模电流中只存在衰减周期分量，据此可以简便地识别故障性质。本发明具有应用范围广，判断灵敏度高，不受故障位置、过渡电阻、采样频率、负荷电流、故障时刻、跳闸时刻、故障点熄弧时刻影响等优点，且同时适用于单端和双端带并联电抗器的输电线路。The present invention makes full use of the fault characteristics under different fault properties. In view of the fact that when a permanent fault occurs, there is only an attenuating DC component in the differential mode current, and when an instantaneous fault occurs, after the fault arc is extinguished, there is only an attenuation period in the differential mode current Components, according to which the nature of the fault can be easily identified. The invention has the advantages of wide application range, high judgment sensitivity, and is not affected by fault location, transition resistance, sampling frequency, load current, fault time, tripping time, and arc extinguishing time of fault point, etc., and is applicable to both single-ended and double-ended belt Transmission lines with shunt reactors.

具体实施方式Detailed ways

浙江大学继电保护实验室在分析两相或三相故障时发现，不同性质的故障具有不同的故障特征。可以先采样得到三相跳闸后单端并联电抗器电流量，经过相模变换得到对应的差模分量，然后根据线路参数计算出差模分量频率(周期)，最后对一个差模分量周期内的差模电流瞬时值进行波形分析。由于发生永久性故障时，差模电流中只存在衰减直流分量，而发生瞬时性故障时，在故障熄弧以后，差模电流中只存在衰减周期分量，利用差模电流在不同故障性质条件下的波形特征可以提出一种适用于三相自适应重合闸中相间故障性质识别的新判据，并鉴别熄弧时刻，该方法的具体步骤如下：The Relay Protection Laboratory of Zhejiang University found that different types of faults have different fault characteristics when analyzing two-phase or three-phase faults. The current of the single-ended shunt reactor after the three-phase trip can be sampled first, and the corresponding differential mode component can be obtained through phase-to-mode conversion, and then the frequency (period) of the differential mode component can be calculated according to the line parameters, and finally the differential mode component within a differential mode component cycle can be calculated The instantaneous value of the current is used for waveform analysis. When a permanent fault occurs, there is only a decaying DC component in the differential mode current, and when a transient fault occurs, after the fault is extinguished, there is only a decaying periodic component in the differential mode current. Using the differential mode current under different fault conditions The waveform characteristics of the three-phase adaptive reclosing can propose a new criterion suitable for identifying the nature of phase-to-phase faults in three-phase adaptive reclosing, and identify the moment of arc extinguishing. The specific steps of this method are as follows:

步骤(1)：采样获得m端并联电抗器电流量i_mxa、i_mxb、i_mxc,通过相模变换得到对应的差模电流分量Step (1): Obtain the current quantities i _mxa , i _mxb , and i _mxc of the m-terminal shunt reactor by sampling, and obtain the corresponding differential mode current components through phase-mode transformation

步骤(2)：根据线路参数计算出差模分量频率(周期)，单端带并联电抗器时为：Step (2): Calculate the frequency (period) of the differential mode component according to the line parameters. When the single-end is equipped with a shunt reactor, it is:

其中C₁为正序电容，L₁为并联电抗器电感。Among them, C ₁ is the positive sequence capacitance, and L ₁ is the inductance of the shunt reactor.

双端带并联电抗器时为：When both ends have shunt reactors:

从而可以得到差模分量周期 Thus the differential mode component period can be obtained

步骤(3)：对一个差模分量周期内的差模电流瞬时值进行波形分析，判据为：Step (3): Carry out waveform analysis on the instantaneous value of the differential mode current within a period of the differential mode component, and the criterion is:

其中，n为各数据窗内的采样点数，取为T_D(T_D为差模分量周期)内的采样点数，x_i为数据窗内第i个采样点的差模电流采样值)。鉴于发生永久性故障时，差模电流中只存在衰减直流分量，此时判据始终成立，而发生瞬时性故障时，在故障熄弧以后，差模电流中只存在衰减周期分量，上述判据不成立，利用差模电流在不同故障性质条件下的波形特征可以提出一种适用于三相自适应重合闸中相间故障性质识别的新判据，并鉴别熄弧时刻。当判定为瞬时性故障时，经过一定的延时后进行重合闸操作，当判定为永久性故障时，则闭锁重合闸装置。Among them, n is the number of sampling points in each data window, which is taken as the number of sampling points in T _D (T _D is the period of the differential mode component), x _i is the differential mode current sampling value of the i-th sampling point in the data window). In view of the fact that when a permanent fault occurs, there is only a decaying DC component in the differential-mode current, the criterion is always valid at this time, while in the case of a transient fault, after the fault is extinguished, there is only a decaying periodic component in the differential-mode current, the above criterion If it is not established, a new criterion suitable for phase-to-phase fault identification in three-phase adaptive reclosing can be proposed by using the waveform characteristics of differential mode current under different fault properties, and the arc-extinguishing time can be identified. When it is judged as an instantaneous fault, the reclosing operation is performed after a certain delay, and when it is judged as a permanent fault, the reclosing device is blocked.

本发明只需利用单端并联电抗器电流即可实现，故障性质判别受影响因素少、灵敏度高。The invention can be realized only by using the current of the single-end shunt reactor, and the fault property judgment has few affected factors and high sensitivity.

Claims

1. A method for identifying the nature of a three-phase adaptive reclosing fault on a line with a shunt reactor, characterized in that: after a phase-to-phase fault occurs in the transmission line and the circuit breakers on both sides of the line are tripped in three phases, the following steps are performed:

Step (1): Obtain the current quantities i _mxa , i _mxb , and i _mxc of the m-terminal shunt reactor by sampling, and obtain the corresponding differential mode current components through phase-mode transformation:

\{\begin{matrix} {i i}_{mxα mxα} = = {i i}_{mxa mxa} - - {i i}_{mxb mxb} \\ {i i}_{mxβ mxβ} = = {i i}_{mxa mxa} - - {i i}_{mxc mxc} \\ {i i}_{mxγ mxγ} = = {i i}_{mxb mxb} - - {i i}_{mxc mxc} \end{matrix}

Step (2): Calculate the frequency (period) of the differential mode component according to the line parameters. Assuming that an instantaneous fault occurs, take the single-ended shunt reactor model as an example, and use the complex frequency domain analysis for the T-type equivalent model of the line, ignoring the line impedance , the node admittance matrix in the complex frequency domain is obtained as:

Y Y ((s the s)) = = [\begin{matrix} {Y Y}_{s the s} & - - {Y Y}_{m m} & - - {Y Y}_{m m} \\ - - {Y Y}_{m m} & {Y Y}_{s the s} & - - {Y Y}_{m m} \\ {- - Y Y}_{m m} & - - {Y Y}_{m m} & {Y Y}_{s the s} \end{matrix}]

\{\begin{matrix} {Y Y}_{s the s} = = s the s (({C C}_{00} + + {22 C C}_{m m})) + + 11 / / s the s {L L}_{00} + + 22 / / s the s {L L}_{m m} \\ {Y Y}_{m m} = = s the s {C C}_{m m} + + 11 / / s the s {L L}_{m m} \end{matrix}

Among them, Y _s is the self-admittance, Y _m is the phase-to-phase mutual admittance, C ₀ is the line-to-ground capacitance, C _m is the phase-to-phase capacitance, L _m and L ₀ are the shunt reactor inductance L ₁ and the neutral point small reactance Phase-to-phase inductance and ground-to-ground inductance after inductance L _n is equivalent;

The differential-mode nodal admittance matrix in the complex frequency domain is obtained by phase-mode transformation:

{Y Y}_{αβγ αβγ} ((s the s)) = = ((\frac{11}{{L L}_{00} s the s} + + \frac{33}{{L L}_{m m} s the s} + + {33 C C}_{m m} s the s + + {C C}_{00} s the s)) \cdot &Center Dot; {E E.}_{33 \times \times 33};;

The frequency of the differential mode component is obtained by solving the characteristic equation det(Y _αβγ (s))=0:

{f f}_{D D.} = = \frac{11}{22 π π} \sqrt{\frac{{L L}_{m m} + + {33 L L}_{00}}{{L L}_{m m} {L L}_{00} (({C C}_{00} + + {33 C C}_{m m}))}} = = \frac{11}{33 π π} \sqrt{\frac{11}{{C C}_{11} {L L}_{11}}};;

Among them, C ₁ is the positive sequence capacitance, L ₁ is the shunt reactor inductance;

Similarly, for the double-terminal shunt reactor model, the node admittance matrix is:

Y Y ((s the s)) = = [\begin{matrix} {Y Y}_{s the s} & - - {Y Y}_{m m} & - - {Y Y}_{m m} \\ - - {Y Y}_{m m} & {Y Y}_{s the s} & - - {Y Y}_{m m} \\ {- - Y Y}_{m m} & - - {Y Y}_{m m} & {Y Y}_{s the s} \end{matrix}]

\{\begin{matrix} {Y Y}_{s the s} = = s the s (({C C}_{00} + + {22 C C}_{m m})) + + 22 / / s the s {L L}_{00} + + 44 / / s the s {L L}_{m m} \\ {Y Y}_{m m} = = s the s {C C}_{m m} + + 22 / / s the s {L L}_{m m} \end{matrix}

After the phase-mode transformation, the differential-mode node admittance matrix is obtained:

{Y Y}_{αβγ αβγ} ((s the s)) = = ((\frac{11}{{L L}_{00} s the s} + + \frac{33}{{L L}_{m m} s the s} + + {33 C C}_{m m} s the s + + {C C}_{00} s the s)) \cdot &Center Dot; {E E.}_{33 \times \times 33};;

Solve the characteristic equation det(Y _αβγ (s))=0 to get the frequency of the differential mode component:

{f f}_{D D.} = = \frac{11}{22 π π} \sqrt{\frac{22 (({L L}_{m m} + + {33 L L}_{00}))}{{L L}_{m m} {L L}_{00} (({C C}_{00} + + {33 C C}_{m m}))}} = = \frac{11}{22 π π} \sqrt{\frac{22}{{C C}_{11} {L L}_{11}}};;

In summary, the differential mode component cycle is obtained

Step (3): Carry out waveform analysis on the instantaneous value of the differential mode current within a period of the differential mode component, and the criterion is:

λ λ = = \frac{| | {Σ Σ}_{i i = = 11}^{n no} {x x}_{i i} | |}{{Σ Σ}_{i i = = 11}^{n no} | | {x x}_{i i} | |} > > 0.5 0.5

Wherein, n is the number of sampling points in each data window, which is taken as the number of sampling points in the differential mode component cycle T _D , and x _i is the differential mode current sampling value of the ith sampling point in the data window;

In view of the fact that when a permanent fault occurs, there is only a decaying DC component in the differential mode current, the criterion is always valid at this time, and when a transient fault occurs, after the fault is extinguished, there is only a decaying periodic component in the differential mode current. The above criterion If it is not established, a new criterion suitable for identifying the nature of phase-to-phase faults in three-phase adaptive reclosing is proposed by using the waveform characteristics of differential mode currents under different fault conditions, and the arc-extinguishing time is identified. When it is judged as an instantaneous fault, After a certain delay, the reclosing operation is performed, and when it is judged to be a permanent fault, the reclosing device is blocked.

2. The method for identifying the nature of a three-phase adaptive reclosing fault in a line with a shunt reactor according to claim 1, wherein the method is used to form a three-phase adaptive reclosing scheme, and whether to carry out reclosing is determined according to the judgment result of the fault nature If it is judged to be a transient fault, it will be switched on for reclosing; if it is judged to be a permanent fault, the two ends of the line will not reclose after being tripped.