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CN111581903A - Method and device for determining impedance spectrum of distribution cable based on improved micro-element equivalent model - Google Patents

Method and device for determining impedance spectrum of distribution cable based on improved micro-element equivalent model Download PDF

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CN111581903A
CN111581903A CN202010256438.1A CN202010256438A CN111581903A CN 111581903 A CN111581903 A CN 111581903A CN 202010256438 A CN202010256438 A CN 202010256438A CN 111581903 A CN111581903 A CN 111581903A
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distribution cable
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CN111581903B (en
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王昱力
欧阳本红
夏荣
李文杰
王格
刘松华
张振鹏
邓显波
赵鹏
刘宗喜
陈铮铮
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State Grid Corp of China SGCC
China Electric Power Research Institute Co Ltd CEPRI
State Grid Shandong Electric Power Co Ltd
Jinan Power Supply Co of State Grid Shandong Electric Power Co Ltd
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State Grid Corp of China SGCC
China Electric Power Research Institute Co Ltd CEPRI
State Grid Shandong Electric Power Co Ltd
Jinan Power Supply Co of State Grid Shandong Electric Power Co Ltd
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    • G06FELECTRIC DIGITAL DATA PROCESSING
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    • G06F30/30Circuit design
    • G06F30/36Circuit design at the analogue level
    • G06F30/367Design verification, e.g. using simulation, simulation program with integrated circuit emphasis [SPICE], direct methods or relaxation methods
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    • G01RMEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R27/00Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
    • G01R27/02Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
    • GPHYSICS
    • G06COMPUTING; CALCULATING OR COUNTING
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Abstract

本发明公开基于改进微元等效模型的配电电缆阻抗谱确定方法及装置该方法包括:将目标配电电缆等效为多个改进微元等效模型,并分别确定各电缆微元等效模型的电气参数;将所述多个电缆微元等效模型级联,形成与所述目标配电电缆对应的等效电路模型,并确定所述等效电路模型的频率上限;获取预先确定的局部缺陷的信息,并根据所述局部缺陷的信息调整对应的改进微元等效模型的电气参数;利用预先确定的首端阻抗计算方法,在所述频率上限的约束下,分别确定与所述目标配电电缆对应的幅频数据和相频数据,并绘制阻抗谱。该方法利用分布式模型快速计算配电电缆的阻抗谱,准确度高,速度快,对计算资源的需求低,可应用在投运现场快速计算10‑35kV配电电缆不同老化阶段的阻抗谱,服务于电力电缆在线性能检验测试。

Figure 202010256438

The invention discloses a method and device for determining the impedance spectrum of a distribution cable based on an improved micro-element equivalent model. The method includes: equivalently converting a target distribution cable into a plurality of improved micro-element equivalent models, and determining the equivalent micro-elements of each cable separately. electrical parameters of the model; cascade the multiple equivalent models of cable micro-elements to form an equivalent circuit model corresponding to the target distribution cable, and determine the upper frequency limit of the equivalent circuit model; obtain a predetermined information of local defects, and adjust the electrical parameters of the corresponding improved micro-element equivalent model according to the information of the local defects; using the predetermined head-end impedance calculation method, under the constraint of the upper frequency limit, The amplitude-frequency data and phase-frequency data corresponding to the target distribution cable are drawn, and the impedance spectrum is drawn. The method uses the distributed model to quickly calculate the impedance spectrum of the distribution cable, with high accuracy, high speed, and low demand for computing resources. Serve the online performance inspection and testing of power cables.

Figure 202010256438

Description

基于改进微元等效模型的配电电缆阻抗谱确定方法及装置Method and device for determining impedance spectrum of distribution cable based on improved micro-element equivalent model

技术领域technical field

本发明属于电力电缆技术领域,具体涉及基于改进微元等效模型的配电电缆阻抗谱确定方法及装置。The invention belongs to the technical field of power cables, in particular to a method and a device for determining the impedance spectrum of a distribution cable based on an improved micro-element equivalent model.

背景技术Background technique

目前,电缆线路局部缺陷定位手段主要依赖离线试验。而离线试验以振荡波局放与超低频介损检测为主。At present, the local defect location method of cable lines mainly relies on off-line tests. The offline test is mainly based on oscillating wave partial discharge and ultra-low frequency dielectric loss detection.

电缆振荡波局放检测方法的主要缺陷在于噪声对局部放电信号的干扰,噪声甚至会导致误判。另一方面,检测到的局部放电信号中包含的放电源可能为电缆线路、电缆终端开关柜、电缆线路所连接的发电机或者变压器等,局部放电信号中各放电源的确定是这一方法的难点之一;其次,信号在电缆中转播会发生衰减和形变,使得局放监测技术的实际应用效果远不及理论研究成果。The main defect of the cable oscillating wave partial discharge detection method is the interference of noise on the partial discharge signal, and the noise may even lead to misjudgment. On the other hand, the discharge sources contained in the detected partial discharge signal may be cable lines, cable terminal switch cabinets, generators or transformers connected to the cable lines, etc. The determination of each discharge source in the partial discharge signal is based on this method. One of the difficulties; secondly, the signal will be attenuated and deformed during the retransmission of the cable, which makes the practical application effect of the PD monitoring technology far less than the theoretical research results.

而超低频介损检测时,在超低频条件下,超低频电压会对绝缘有一定累计损伤风险;且该方法只能反映电缆绝缘的整体老化水平,对局部的绝缘缺陷不敏感,无法对电缆故障进行定位。In the case of ultra-low frequency dielectric loss testing, under ultra-low frequency conditions, the ultra-low frequency voltage will have a certain risk of cumulative damage to the insulation; and this method can only reflect the overall aging level of the cable insulation, and is not sensitive to local insulation defects. Locating the fault.

尽管目前阻抗谱检测技术为实现电缆线路的局部缺陷定位提供了可行的解决方案,但由于在线路敷设完成后无法获取配电电缆初期的阻抗谱及其特征(如,畸变度初始值),导致在现场检测过程中因为缺少作为参考基准的初始值而造成电缆状态误判的情形。Although the current impedance spectrum detection technology provides a feasible solution for localized defect location of cable lines, the impedance spectrum and its characteristics (such as the initial value of distortion) cannot be obtained at the initial stage of the distribution cable after the line is laid. In the process of on-site inspection, due to the lack of the initial value as a reference, the misjudgment of the cable state is caused.

发明内容SUMMARY OF THE INVENTION

本发明提供基于改进微元等效模型的配电电缆阻抗谱确定方法及装置,以解决现有技术中缺少配电电缆线路在投运初期的阻抗谱数据的问题。The present invention provides a method and device for determining the impedance spectrum of a distribution cable based on an improved micro-element equivalent model, so as to solve the problem of lack of impedance spectrum data of the distribution cable line in the early stage of commissioning in the prior art.

第一方面,本发明提供的基于改进微元等效模型的配电电缆阻抗谱确定方法,包括:In a first aspect, the method for determining the impedance spectrum of a distribution cable based on the improved micro-element equivalent model provided by the present invention includes:

步骤S100、将目标配电电缆等效为多个改进微元等效模型,并分别确定各电缆微元等效模型的电气参数;Step S100: Equivalent the target power distribution cable into a plurality of improved micro-element equivalent models, and determine the electrical parameters of each cable micro-element equivalent model respectively;

步骤S200、将所述多个电缆微元等效模型级联,形成与所述目标配电电缆对应的等效电路模型,并确定所述等效电路模型的频率上限;Step S200, cascading the plurality of cable micro-element equivalent models to form an equivalent circuit model corresponding to the target power distribution cable, and determining an upper limit of the frequency of the equivalent circuit model;

步骤S300、获取预先确定的局部缺陷的信息,并根据所述局部缺陷的信息调整对应的改进微元等效模型的电气参数;Step S300, obtaining predetermined information of local defects, and adjusting the electrical parameters of the corresponding improved micro-element equivalent model according to the information of the local defects;

步骤S400、利用预先确定的首端阻抗计算方法,在所述频率上限的约束下,分别确定与所述目标配电电缆对应的幅频数据和相频数据,并绘制阻抗谱。Step S400 , using a predetermined head-end impedance calculation method, and under the constraint of the upper frequency limit, respectively determine the amplitude-frequency data and phase-frequency data corresponding to the target power distribution cable, and draw an impedance spectrum.

第二方面,本发明提供的基于改进微元等效模型的配电电缆阻抗谱确定装置,包括:In a second aspect, the device for determining the impedance spectrum of a distribution cable based on the improved micro-element equivalent model provided by the present invention includes:

改进微元等效模型确定单元,用于将目标配电电缆等效为多个改进微元等效模型,并分别确定各电缆微元等效模型的电气参数;The improved micro-element equivalent model determination unit is used to equivalently convert the target distribution cable into multiple improved micro-element equivalent models, and determine the electrical parameters of each cable micro-element equivalent model respectively;

等效电路模型确定单元,用于将所述多个电缆微元等效模型级联,形成与所述目标配电电缆对应的等效电路模型,并确定所述等效电路模型的频率上限;an equivalent circuit model determining unit, configured to cascade the multiple equivalent models of cable micro-elements to form an equivalent circuit model corresponding to the target power distribution cable, and determine the upper limit of the frequency of the equivalent circuit model;

电气参数调整单元,用于获取预先确定的局部缺陷的信息,并根据所述局部缺陷的信息调整对应的改进微元等效模型的电气参数;an electrical parameter adjustment unit, configured to acquire predetermined local defect information, and adjust the electrical parameters of the corresponding improved micro-element equivalent model according to the local defect information;

阻抗计算单元,用于利用预先确定的首端阻抗计算方法,在所述频率上限的约束下,分别确定与所述目标配电电缆对应的幅频数据和相频数据,并绘制阻抗谱。The impedance calculation unit is used to determine the amplitude-frequency data and phase-frequency data corresponding to the target power distribution cable respectively, and draw an impedance spectrum under the constraint of the upper frequency limit by using a predetermined head-end impedance calculation method.

本发明提供的基于改进微元等效模型的配电电缆阻抗谱确定方法及装置,利用分布式模型快速计算配电电缆的阻抗谱,准确度高,速度快,对计算资源的需求低;可应用在投运现场快速计算10-35kV配电电缆不同老化阶段的阻抗谱,服务于电力电缆在线性能检验测试。The method and device for determining the impedance spectrum of a distribution cable based on the improved micro-element equivalent model provided by the present invention utilize the distributed model to quickly calculate the impedance spectrum of the distribution cable, with high accuracy, high speed, and low demand for computing resources; It is used to quickly calculate the impedance spectrum of different aging stages of 10-35kV distribution cables at the commissioning site, and serve the online performance inspection and testing of power cables.

附图说明Description of drawings

通过参考下面的附图,可以更为完整地理解本发明的示例性实施方式:Exemplary embodiments of the present invention may be more fully understood by reference to the following drawings:

图1为本发明实施例的基于改进微元等效模型的配电电缆阻抗谱确定方法的流程示意图;1 is a schematic flowchart of a method for determining an impedance spectrum of a distribution cable based on an improved micro-element equivalent model according to an embodiment of the present invention;

图2为本发明实施例的基于改进微元等效模型的配电电缆阻抗谱确定装置的组成示意图;2 is a schematic diagram of the composition of a device for determining the impedance spectrum of a distribution cable based on an improved micro-element equivalent model according to an embodiment of the present invention;

图3为单芯同轴电缆的横截面示意图;3 is a schematic cross-sectional view of a single-core coaxial cable;

图4为三芯同轴电缆的横截面示意图;4 is a schematic cross-sectional view of a triaxial cable;

图5为现有技术中通用传输线微元等效模型;5 is an equivalent model of a general transmission line micro-element in the prior art;

图6为本发明实施例的改进微元等效模型;6 is an improved micro-element equivalent model according to an embodiment of the present invention;

图7为本发明实施例的由多个改进微元等效模型级联后形成的等效电路模型;7 is an equivalent circuit model formed by cascading a plurality of improved micro-element equivalent models according to an embodiment of the present invention;

图8为本发明实施例中,采用微元等效模型获得的首端输入阻抗仿真结果(即阻抗谱图),其中:FIG. 8 is a simulation result (ie, an impedance spectrum) of the input impedance of the head end obtained by using the micro-element equivalent model in the embodiment of the present invention, wherein:

(a)为根据通用传输线微元等效模型计算得到的阻抗幅频图;(a) is the impedance amplitude-frequency diagram calculated according to the general transmission line micro-element equivalent model;

(b)为根据通用传输线微元等效模型计算得到的阻抗相位图;(b) is the impedance phase diagram calculated according to the general transmission line micro-element equivalent model;

(c)为根据改进微元等效模型计算得到的阻抗幅频图;(c) is the impedance amplitude-frequency diagram calculated according to the improved micro-element equivalent model;

(c’)为(c)的局部放大图;(c') is a partial enlarged view of (c);

(d)为根据改进微元等效模型计算得到的阻抗相位图。(d) is the impedance phase diagram calculated according to the improved micro-element equivalent model.

具体实施方式Detailed ways

现在参考附图介绍本发明的示例性实施方式,然而,本发明可以用许多不同的形式来实施,并且不局限于此处描述的实施例,提供这些实施例是为了详尽地且完全地公开本发明,并且向所属技术领域的技术人员充分传达本发明的范围。对于表示在附图中的示例性实施方式中的术语并不是对本发明的限定。在附图中,相同的单元/元件使用相同的附图标记。Exemplary embodiments of the present invention will now be described with reference to the accompanying drawings, however, the present invention may be embodied in many different forms and is not limited to the embodiments described herein, which are provided for the purpose of this thorough and complete disclosure invention, and fully convey the scope of the invention to those skilled in the art. The terms used in the exemplary embodiments shown in the drawings are not intended to limit the invention. In the drawings, the same elements/elements are given the same reference numerals.

除非另有说明,此处使用的术语(包括科技术语)对所属技术领域的技术人员具有通常的理解含义。另外,可以理解的是,以通常使用的词典限定的术语,应当被理解为与其相关领域的语境具有一致的含义,而不应该被理解为理想化的或过于正式的意义。Unless otherwise defined, terms (including scientific and technical terms) used herein have the commonly understood meanings to those skilled in the art. In addition, it is to be understood that terms defined in commonly used dictionaries should be construed as having meanings consistent with the context in the related art, and should not be construed as idealized or overly formal meanings.

为解决现有技术中缺少配电电缆线路在投运初期的阻抗谱数据的问题,本发明实施例提供了一种配电电缆阻抗谱快速计算方法,用于根据电缆分布式等效模型计算得到电缆的阻抗谱数据。In order to solve the problem of the lack of impedance spectrum data of the distribution cable line in the early stage of operation in the prior art, the embodiment of the present invention provides a fast calculation method for the impedance spectrum of the distribution cable, which is used to calculate and obtain the distribution cable according to the distributed equivalent model of the cable. Impedance spectrum data for cables.

本发明实施例的基于改进微元等效模型的配电电缆阻抗谱确定方法,通过固定电缆的相关电气参数及计算模型,在配电电缆现场有限的计算资源条件下,可以实现利用电缆沿线级联的改进微元等效模型快速计算正常状态/不同局部老化程度下的阻抗谱。The method for determining the impedance spectrum of a distribution cable based on the improved micro-element equivalent model in the embodiment of the present invention, by fixing the relevant electrical parameters of the cable and the calculation model, under the condition of limited computing resources on the distribution cable site, can realize the use of the level of the cable along the line. The combined improved micro-element equivalent model can quickly calculate the impedance spectrum under normal state/different local aging degrees.

如图1所示,本发明实施例的基于改进微元等效模型的配电电缆阻抗谱确定方法,包括:As shown in FIG. 1 , the method for determining the impedance spectrum of a distribution cable based on an improved micro-element equivalent model according to an embodiment of the present invention includes:

步骤S100、将目标配电电缆等效为多个改进微元等效模型,并分别确定各电缆微元等效模型的电气参数;Step S100: Equivalent the target power distribution cable into a plurality of improved micro-element equivalent models, and determine the electrical parameters of each cable micro-element equivalent model respectively;

步骤S200、将所述多个电缆微元等效模型级联,形成与所述目标配电电缆对应的等效电路模型,并确定所述等效电路模型的频率上限;Step S200, cascading the plurality of cable micro-element equivalent models to form an equivalent circuit model corresponding to the target power distribution cable, and determining an upper limit of the frequency of the equivalent circuit model;

步骤S300、获取预先确定的局部缺陷的信息,并根据所述局部缺陷的信息调整对应的改进微元等效模型的电气参数;Step S300, obtaining predetermined information of local defects, and adjusting the electrical parameters of the corresponding improved micro-element equivalent model according to the information of the local defects;

步骤S400、利用预先确定的首端阻抗计算方法,在所述频率上限的约束下,分别确定与所述目标配电电缆对应的幅频数据和相频数据,并绘制阻抗谱。Step S400 , using a predetermined head-end impedance calculation method, and under the constraint of the upper frequency limit, respectively determine the amplitude-frequency data and phase-frequency data corresponding to the target power distribution cable, and draw an impedance spectrum.

进一步地,所述的基于改进微元等效模型的配电电缆阻抗谱确定方法,所述步骤S100中,任一改进微元等效模型的电气参数包括:Further, in the method for determining the impedance spectrum of a distribution cable based on the improved micro-element equivalent model, in the step S100, the electrical parameters of any improved micro-element equivalent model include:

电缆芯线电阻Rc、电缆芯线电感Lc、电缆金属屏蔽层电阻Rs、电缆金属屏蔽层电感Ls、电缆绝缘电容CICable core wire resistance R c , cable core wire inductance L c , cable metal shielding layer resistance R s , cable metal shielding layer inductance L s , cable insulation capacitance CI ;

其中,电缆芯线电阻Rc和电缆芯线电感Lc串联后作为一个整体,分别在其两端与电缆绝缘电容CI并联;电缆金属屏蔽层电阻Rs和电缆金属屏蔽层电感Ls串联后作为一个整体,分别在其两端与电缆绝缘电容CI并联。Among them, the cable core wire resistance R c and the cable core wire inductance L c are connected in series as a whole, and are connected in parallel with the cable insulation capacitor CI at both ends respectively; the cable metal shielding layer resistance R s and the cable metal shielding layer inductance L s are connected in series Then as a whole, it is connected in parallel with the cable insulation capacitor C I at both ends respectively.

进一步地,所述的基于改进微元等效模型的配电电缆阻抗谱确定方法,Further, the method for determining the impedance spectrum of the distribution cable based on the improved micro-element equivalent model,

所述步骤S100中,所述目标配电电缆被均匀地划分为M段电缆微元,每一所述电缆微元与一个改进微元等效模型相对应;所述M段电缆微元的长度之和与所述目标配电电缆的长度相同;In the step S100, the target power distribution cable is evenly divided into M segments of cable micro-elements, each of the cable micro-elements corresponds to an improved micro-element equivalent model; the length of the M-segment cable micro-elements the sum is the same length as said target distribution cable;

相应地,所述步骤S200中,按照各改进微元等效模型分别对应的电缆微元在电缆中的位置,依次将所述改进微元等效模型级联,形成与所述目标配电电缆对应的等效电路模型。Correspondingly, in the step S200, according to the positions of the cable micro-elements in the cable corresponding to the improved micro-element equivalent models, the improved micro-element equivalent models are cascaded in turn to form a distribution cable with the target power distribution cable. The corresponding equivalent circuit model.

进一步地,所述的基于改进微元等效模型的配电电缆阻抗谱确定方法,Further, the method for determining the impedance spectrum of the distribution cable based on the improved micro-element equivalent model,

所述步骤S200中,根据下式确定所述等效电路模型的频率上限fmaxIn the step S200, the frequency upper limit f max of the equivalent circuit model is determined according to the following formula:

Figure BDA0002437503540000061
Figure BDA0002437503540000061

其中,n为改进微元等效模型的个数;Among them, n is the number of improved micro-element equivalent models;

l为电缆微元的长度;l is the length of the cable element;

Figure BDA0002437503540000066
为信号在电缆中的传播速度函数;
Figure BDA0002437503540000066
is a function of the propagation velocity of the signal in the cable;

Figure BDA0002437503540000064
Figure BDA0002437503540000065
分别为频率fmax时电缆芯线电感和电缆绝缘电容;
Figure BDA0002437503540000064
and
Figure BDA0002437503540000065
are the cable core inductance and the cable insulation capacitance at the frequency f max , respectively;

其中,

Figure BDA0002437503540000062
in,
Figure BDA0002437503540000062

进一步地,所述的基于改进微元等效模型的配电电缆阻抗谱确定方法,Further, the method for determining the impedance spectrum of the distribution cable based on the improved micro-element equivalent model,

所述步骤S300中,所述预先确定的局部缺陷的信息,包括:In the step S300, the predetermined local defect information includes:

局部缺陷在电缆中的位置、局部缺陷的严重程度、与局部缺陷的严重程度对应的电气参数影响函数。The location of the local defect in the cable, the severity of the local defect, and the influence function of electrical parameters corresponding to the severity of the local defect.

进一步地,所述的基于改进微元等效模型的配电电缆阻抗谱确定方法,Further, the method for determining the impedance spectrum of the distribution cable based on the improved micro-element equivalent model,

所述与局部缺陷的严重程度对应的电气参数影响函数,包括:The electrical parameter influence function corresponding to the severity of the local defect includes:

用于确定电缆绝缘电容CI的下式:The following formula is used to determine the cable insulation capacitance C I :

Figure BDA0002437503540000063
Figure BDA0002437503540000063

其中,rc为电缆芯线的外半径;Among them, rc is the outer radius of the cable core;

rs为电缆绝缘金属屏蔽层的内半径;r s is the inner radius of the cable insulating metal shielding layer;

ε为相对介电常数。ε is the relative permittivity.

进一步地,所述的基于改进微元等效模型的配电电缆阻抗谱确定方法,Further, the method for determining the impedance spectrum of the distribution cable based on the improved micro-element equivalent model,

所述步骤S400中,所述预先确定的首端阻抗计算方法,包括:In the step S400, the predetermined head-end impedance calculation method includes:

根据下式确定首端输入阻抗Z:Determine the head-end input impedance Z according to the following formula:

Figure BDA0002437503540000071
Figure BDA0002437503540000071

其中,XC为电缆绝缘的容抗;Among them, X C is the capacitive reactance of the cable insulation;

RAC为电缆芯线的交流电阻;R AC is the AC resistance of the cable core;

XL为电缆芯线的感抗。 XL is the inductive reactance of the cable core.

进一步地,所述的基于改进微元等效模型的配电电缆阻抗谱确定方法,还包括:Further, the method for determining the impedance spectrum of a distribution cable based on the improved micro-element equivalent model further includes:

根据下式,利用电缆芯线的直流电阻RDC,修正电缆芯线的交流电阻RACUse the DC resistance R DC of the cable core to correct the AC resistance R AC of the cable core according to the following formula:

RAC=RDC(1+ys+yp);R AC =R DC (1+y s +y p );

其中,ys为趋肤效应因数;Among them, y s is the skin effect factor;

yp为邻近效应因数。y p is the proximity effect factor.

进一步地,所述的基于改进微元等效模型的配电电缆阻抗谱确定方法,Further, the method for determining the impedance spectrum of the distribution cable based on the improved micro-element equivalent model,

所述目标配电电缆适用于10-35kV线路;The target distribution cable is suitable for 10-35kV lines;

所述目标配电电缆为同轴电缆,自内向外依次为导体层、内半导电层、绝缘层、外半导电层和金属屏蔽层。The target distribution cable is a coaxial cable, which is a conductor layer, an inner semi-conductive layer, an insulating layer, an outer semi-conductive layer and a metal shielding layer in sequence from the inside to the outside.

该基于改进微元等效模型的配电电缆阻抗谱确定方法,考虑电缆在横截面内的多层结构,提出了改进的电缆分布式模型,即改进微元等效模型;通过改变各改进微元等效模型中不同频率下的复介电常数来计算有关的电缆电气参数;根据局部缺陷的严重程度,调整复介电常数的计算公式,以计算不同严重程度的局部缺陷下的电缆电气参数;通过设置各改进微元等效模型的长度,可以计算不同长度范围内多种局部缺陷下的电缆阻抗。This method for determining the impedance spectrum of a distribution cable based on the improved micro-element equivalent model, considering the multi-layer structure of the cable in the cross-section, proposes an improved cable distributed model, that is, the improved micro-element equivalent model; Calculate the relevant electrical parameters of the cable according to the complex permittivity at different frequencies in the element equivalent model; according to the severity of the local defect, adjust the calculation formula of the complex permittivity to calculate the electrical parameters of the cable under the local defects of different severity ; By setting the length of each improved micro-element equivalent model, the cable impedance under various local defects in different length ranges can be calculated.

如图3及图4所示,用于配电网的中压电缆为多层同轴结构,自内向外,依次为导体层(如,芯线)、内半导电层、绝缘层、外半导电层和金属屏蔽层。这种结构关系决定了等效模型中电气参数之间的串并联关系。阻抗谱描述了电缆首端输入阻抗和频率的对应关系。具体实施时,不同频率下的输入阻抗值构成了电缆的阻抗谱。As shown in Figure 3 and Figure 4, the medium voltage cable used in the distribution network is a multi-layer coaxial structure. Conductive layer and metal shield. This structural relationship determines the series-parallel relationship between electrical parameters in the equivalent model. Impedance spectrum describes the relationship between input impedance and frequency at the head end of the cable. During specific implementation, the input impedance values at different frequencies constitute the impedance spectrum of the cable.

在现场进行阻抗谱测试时,电缆是离线的。阻抗谱测试时,向电缆一端输入激励电压,并测量该端输出电流的大小,并通过时频变换,利用频域数据获取该段电缆的阻抗数据。When performing impedance spectroscopy tests in the field, the cables are off-line. In the impedance spectrum test, the excitation voltage is input to one end of the cable, and the output current of the end is measured, and the impedance data of the cable is obtained by using the frequency domain data through time-frequency transformation.

目前,根据作业规范,无需在配电电缆投运前进行所在线路的参数试验,因此,通常不会记载有配电电缆在投运前或投运初期的阻抗谱数据,而这些阻抗谱数据可以作为后续利用阻抗谱进行局部缺陷定位时的基准。At present, according to the operating specifications, it is not necessary to carry out the parameter test of the line where the distribution cable is put into operation. Therefore, the impedance spectrum data of the distribution cable before or at the initial stage of operation is usually not recorded, and these impedance spectrum data can be As a reference for subsequent local defect localization using impedance spectroscopy.

随着投运时间逐渐加长,电缆中逐渐发生的局部缺陷(结构性损坏)或局部老化改变了电缆中绝缘介质或导体或半导体的形状、接触关系、绝缘介质的介电常数等。通常,局部缺陷在电缆横截面方向形成的凹陷或划痕越深,则缺陷越严重;这时,缺陷段电缆的阻抗特性与非缺陷段电缆的阻抗特性存在的差异更为明显。As the commissioning time gradually increases, the local defects (structural damage) or local aging that gradually occur in the cable change the shape, contact relationship, dielectric constant of the insulating medium, etc. of the insulating medium or conductor or semiconductor in the cable. Generally, the deeper the depression or scratch formed by the local defect in the cable cross-section direction, the more serious the defect; at this time, the difference between the impedance characteristics of the cable in the defective section and the impedance characteristic of the cable in the non-defective section is more obvious.

架空线路中配电电缆的绝缘材料是逐渐老化的,并表现为相对介电常数逐渐变化,并且,因为绝缘材料在不同频率下极化的机理不同,绝缘材料老化过程中介电常数的变化并不是线性的,而是与频率相关。介电常数等与电缆电气特性有关的参数的变化,可以反映在阻抗谱的变化趋势或极点所对应的频率上。The insulating material of power distribution cables in overhead lines is gradually aging, and shows a gradual change in relative permittivity, and because the mechanism of polarization of insulating materials at different frequencies is different, the change in permittivity during aging of insulating materials is not. Linear, but frequency dependent. The change of the parameters related to the electrical characteristics of the cable, such as the dielectric constant, can be reflected in the change trend of the impedance spectrum or the frequency corresponding to the pole.

绝缘老化表现为介电常数变化,介电常数是用于表征电介质在电场中贮存静电能的相对能力。在低频段(<1kHz),相对介电常数保持为一个常数;在高频段(>1kHz),由于极化机理的改变,通常使用复介电常数来描述。复介电常数中的虚数部分用于表征电介质极化中的损耗。Insulation aging is manifested as a change in dielectric constant, which is used to characterize the relative ability of a dielectric to store electrostatic energy in an electric field. At low frequency (<1kHz), the relative permittivity remains a constant; at high frequency (>1kHz), the complex permittivity is usually described due to changes in the polarization mechanism. The imaginary part of the complex permittivity is used to characterize losses in dielectric polarization.

电缆等效电路模型可以分为集总式模型和分布式模型这两类。这里的同轴电缆传输线等效模型和同轴电缆改进电缆微元等效模型均为分布式模型。需要说明的是,鉴于内半导电层和外半导电层较薄,在建立分布式模型时,通常忽略内半导电层和外半导电层对阻抗谱的影响。Cable equivalent circuit models can be divided into lumped models and distributed models. The equivalent model of the coaxial cable transmission line and the equivalent model of the micro-element of the improved coaxial cable are distributed models. It should be noted that, in view of the thinness of the inner semiconducting layer and the outer semiconducting layer, the influence of the inner semiconducting layer and the outer semiconducting layer on the impedance spectrum is usually ignored when establishing the distributed model.

如图5所示的同轴电缆传输线微元等效模型中,传输线的电阻(R)和传输线的电感(L)串联后作为一个整体,分别在其两端与传输线的绝缘电容(C)并联。In the micro-element equivalent model of the coaxial cable transmission line shown in Figure 5, the resistance (R) of the transmission line and the inductance (L) of the transmission line are connected in series as a whole, and are connected in parallel with the insulation capacitance (C) of the transmission line at both ends respectively. .

如图6所示的同轴电缆改进电缆微元等效模型中,电气参数包括:电缆芯线电阻Rc、电缆芯线电感Lc、电缆金属屏蔽层电阻Rs、电缆金属屏蔽层电感Ls、电缆绝缘电容CI。其中,电缆芯线电阻(Rc)和电缆芯线电感(Lc)串联后作为一个整体,分别在其两端与电缆绝缘电容(CI)并联;电缆金属屏蔽层电阻(Rs)和金属屏蔽层电感(Ls)串联后作为一个整体,分别在其两端与电缆绝缘电容(CI)并联。In the micro-element equivalent model of the improved coaxial cable shown in Figure 6, the electrical parameters include: cable core resistance R c , cable core inductance L c , cable metal shielding layer resistance R s , cable metal shielding layer inductance L s , cable insulation capacitance C I . Among them, the cable core resistance (R c ) and the cable core inductance (L c ) are connected in series as a whole, and are connected in parallel with the cable insulation capacitance (C I ) at both ends respectively; the cable metal shielding layer resistance (R s ) and The metal shielding layer inductance (L s ) is connected in series as a whole, and is connected in parallel with the cable insulation capacitance (C I ) at both ends.

需要说明的是,以下的计算步骤以单芯电缆为示例。三芯电缆可以视为三个独立的单芯电缆,并分别求解电缆阻抗,这里不再赘述。It should be noted that the following calculation steps take a single-core cable as an example. The three-core cable can be regarded as three independent single-core cables, and the cable impedances are solved separately, which will not be repeated here.

以图6的改进微元等效模型为例,给出首端输入阻抗的计算方法。该改进微元等效模型(这里指单芯电缆)的首端输入阻抗(为复数)Z记为:Taking the improved micro-element equivalent model in Figure 6 as an example, the calculation method of the input impedance of the head end is given. The head-end input impedance (a complex number) Z of the improved micro-element equivalent model (here refers to a single-core cable) is recorded as:

Figure BDA0002437503540000091
Figure BDA0002437503540000091

式(1)中,XC为电缆绝缘的容抗;In formula (1), X C is the capacitive reactance of the cable insulation;

Figure BDA0002437503540000092
Figure BDA0002437503540000092

其中,CI为电缆绝缘电容:Among them, C I is the cable insulation capacitance:

XL=2πfL; XL = 2πfL;

其中,L为电缆芯线电感和金属屏蔽层电感;Among them, L is the inductance of the cable core wire and the inductance of the metal shielding layer;

L=Lc+LsL= Lc + Ls .

根据《IEC60287-1-1-2014电缆额定电流的计算第1部分:额定电流方程式(负荷率100%)和损失》,电缆芯线的交流电阻RAC和直流电阻RDC具有如下关系:According to "IEC60287-1-1-2014 Calculation of Cable Rated Current Part 1: Rated Current Equation (100% Load Rate) and Loss", the AC resistance R AC and DC resistance R DC of the cable core have the following relationship:

RAC=RDC(1+ys+yp); (2)R AC =R DC (1+y s +y p ); (2)

式(2)中,ys为趋肤效应因数。In formula (2), y s is the skin effect factor.

式(2)中,RDC可以根据电缆芯线的尺寸和电缆芯线材料的电阻率,计算得到(如,通过MATLAB内置的模块计算得到)。In formula (2), R DC can be calculated according to the size of the cable core wire and the resistivity of the cable core wire material (for example, calculated by the built-in module of MATLAB).

根据下式计算趋肤效应因数ysCalculate the skin effect factor y s according to the following formula:

Figure BDA0002437503540000101
Figure BDA0002437503540000101

其中,0<xs≤2.8;Among them, 0<x s ≤2.8;

ys=-0.136-0.0177xs+0.0563xs 2y s =-0.136-0.0177x s +0.0563x s 2 ,

其中,2.8<xs≤3.8;Among them, 2.8<x s ≤3.8;

ys=0.354xs+0.733;y s = 0.354 x s +0.733;

其中,3.8<xswhere 3.8<x s .

根据下式计算变量xsCalculate the variable x s according to:

Figure BDA0002437503540000102
Figure BDA0002437503540000102

上式中,ks为用于计算趋肤效应的无量纲数,其数值通过工程经验和/或实验获得。In the above formula, k s is a dimensionless number used to calculate the skin effect, and its value is obtained through engineering experience and/or experiments.

式(2)中,yp为邻近效应因数;In formula (2), y p is the proximity effect factor;

单芯电缆则不存在邻近效应因数yp,即yp为0。For single-core cables, there is no proximity effect factor y p , that is, y p is zero.

对于三芯电缆,其邻近效应因数yp通过式(3)确定:For a three-core cable, its proximity effect factor y p is determined by equation (3):

Figure BDA0002437503540000111
Figure BDA0002437503540000111

式(3)中,xp通过下式确定:In formula (3), x p is determined by the following formula:

Figure BDA0002437503540000112
Figure BDA0002437503540000112

式(4)中,kp为用于计算临近效应因数的无量纲数,其数值通过工程经验和实验获得。In formula (4), k p is a dimensionless number used to calculate the proximity effect factor, and its value is obtained through engineering experience and experiments.

一般来说,绝大多数情况下,xp不会超过2.8。Generally speaking, in the vast majority of cases, xp will not exceed 2.8.

式(3)中,如图4所示,dc为电缆芯线的外直径;In formula ( 3 ), as shown in Figure 4, dc is the outer diameter of the cable core;

s为两相邻芯线之间的距离。s is the distance between two adjacent core wires.

具体实施时,对于以交联聚乙烯(XLPE)为绝缘材料的电缆,ks可以取1,kp可以取0.8。During specific implementation, for a cable using cross-linked polyethylene (XLPE) as an insulating material, k s may be 1, and k p may be 0.8.

在不同老化阶段,电缆绝缘的复介电常数不同。复介电常数与老化程度的对应关系如表1所列,其中,ε0为真空介电常数;ω=2πf,其中,f为频率(Hz)。In different aging stages, the complex permittivity of cable insulation is different. The corresponding relationship between the complex permittivity and the degree of aging is listed in Table 1, where ε 0 is the vacuum permittivity; ω=2πf, where f is the frequency (Hz).

表1复介电常数与老化程度的对应关系Table 1 Corresponding relationship between complex permittivity and aging degree

Figure BDA0002437503540000113
Figure BDA0002437503540000113

进一步地,由相对介电常数/复介电常数ε,根据式(5)确定绝缘电容CIFurther, according to the relative permittivity/complex permittivity ε, the insulation capacitance C I is determined according to formula (5):

Figure BDA0002437503540000121
Figure BDA0002437503540000121

式(5)中,rc为电缆芯线的外半径,rs为电缆绝缘金属屏蔽层的内半径In formula (5), rc is the outer radius of the cable core wire, and rs is the inner radius of the cable insulating metal shielding layer

具体实施时,从图7所示等效电路模型的首端(如图7中左侧)开始,计算输入阻抗,如,根据下式计算改进微元等效模型的首端输入阻抗:In specific implementation, starting from the head end of the equivalent circuit model shown in Figure 7 (the left side in Figure 7), the input impedance is calculated, for example, the head end input impedance of the improved micro-element equivalent model is calculated according to the following formula:

Figure BDA0002437503540000122
Figure BDA0002437503540000122

当XL=-2XC时,阻抗谱出现极值点;When XL = -2X C , the impedance spectrum has an extreme point;

随着级联的电缆微元等效模型数量的增加,Z可以写成关于XL和XC的高次函数;而极值点的个数也相应地增加,也即,极值点的个数与级联电路中包括的改进微元等效模型的个数相同。With the increase in the number of equivalent models of cascaded cable micro-elements, Z can be written as a high - order function about XL and XC; and the number of extreme points also increases accordingly, that is, the number of extreme points It is the same as the number of improved micro-element equivalent models included in the cascade circuit.

如图7所示的n个微元等效模型级联后等效电路的传输参数矩阵Tcable为每个微元等效模型的传输参数矩阵T依次相乘,即:As shown in Figure 7, the transmission parameter matrix T cable of the equivalent circuit after the cascaded n micro-element equivalent models is multiplied by the transmission parameter matrix T of each micro-element equivalent model in turn, namely:

Figure BDA0002437503540000123
Figure BDA0002437503540000123

式(8)中,每个传输参数矩阵的第一列的两个参数分别为电路的开路参数,第二列的两个参数分别为电路的短路参数。In formula (8), the two parameters in the first column of each transmission parameter matrix are respectively the open circuit parameters of the circuit, and the two parameters in the second column are respectively the short circuit parameters of the circuit.

而由n个微元等效模型的级联电路的输入阻抗Zcable可以由传输参数矩阵直接计算得到:The input impedance Z cable of the cascaded circuit of the equivalent model of n micro-elements can be directly calculated from the transmission parameter matrix:

Zcable=Tcable11/Tcable21 (9)Z cable =T cable11 /T cable21 (9)

具体实施时,对于改进的电缆微元等效模型和级联后的电路等效模型,其首端输入阻抗可由MATLAB内置的阻抗计算模块计算。During specific implementation, for the improved cable micro-element equivalent model and the cascaded circuit equivalent model, the input impedance of the head end can be calculated by the built-in impedance calculation module of MATLAB.

具体实施时,根据电缆长度选取级联模型个数(通常,为提高局部缺陷的定位效果,级联模型个数不少于10个),并根据级联后等效电路的参数,确定频率上限。During specific implementation, the number of cascaded models is selected according to the cable length (usually, in order to improve the localization effect of local defects, the number of cascaded models is not less than 10), and the upper limit of frequency is determined according to the parameters of the equivalent circuit after the cascade .

具体实施时,由式(10)确定频率上限fmaxIn specific implementation, the upper limit of frequency f max is determined by formula (10):

Figure BDA0002437503540000131
Figure BDA0002437503540000131

其中,n为改进微元等效模型的个数,如,10;Among them, n is the number of improved micro-element equivalent models, such as 10;

l为电缆微元的长度,如1m;l is the length of the cable element, such as 1m;

v为信号在电缆中的传播速度函数;v is a function of the propagation velocity of the signal in the cable;

Figure BDA0002437503540000135
Figure BDA0002437503540000136
分别为频率fmax时的电缆芯线电感和电缆绝缘电容;
Figure BDA0002437503540000135
and
Figure BDA0002437503540000136
are the cable core inductance and cable insulation capacitance at the frequency f max , respectively;

其中,

Figure BDA0002437503540000132
in,
Figure BDA0002437503540000132

其中,

Figure BDA0002437503540000137
是关于频率fmax的函数;in,
Figure BDA0002437503540000137
is a function of frequency f max ;

其中,

Figure BDA0002437503540000134
是与fmax无关的函数,可以根据电缆尺寸参数,利用MATLAB中的mutualinductance元件计算;in,
Figure BDA0002437503540000134
is a function independent of f max , which can be calculated by using the mutualinductance element in MATLAB according to the cable size parameters;

Figure BDA0002437503540000133
得fmax
Figure BDA0002437503540000133
get f max .

设置仿真频率范围,其中,取仿真频率范围的下限为1kHz,也即,取频率的最低值为1kHz;利用仿真软件MATLAB Simulink,利用循环指令,逐一改变频率f(i);根据预先确定的电缆老化程度,根据表1计算得到频率f(i)下电缆中绝缘层对应的相对介电常数ε(i)/复介电常数根及相应的电气参数的数值;如,各电缆微元等效模型的电气参数的数值通过MATLAB Simulink内置的界面程序power_cableparam可以得到。Set the simulation frequency range, wherein, the lower limit of the simulation frequency range is 1kHz, that is, the lowest value of the frequency is 1kHz; the simulation software MATLAB Simulink is used, and the loop instruction is used to change the frequency f (i) one by one; According to the predetermined cable Aging degree, according to Table 1, the relative permittivity ε (i)/ complex permittivity root corresponding to the insulating layer in the cable under the frequency f (i) and the corresponding electrical parameters are calculated; for example, the equivalent of each cable element is equivalent The numerical values of the electrical parameters of the model can be obtained through the built-in interface program power_cableparam of MATLAB Simulink.

另外,根据趋肤效应因数ys和邻近效应因数yp,根据仿真软件计算出来的直流电阻RDC对交流电阻RAC进行修正:In addition, according to the skin effect factor y s and the proximity effect factor y p , the AC resistance R AC is corrected according to the DC resistance R DC calculated by the simulation software:

RAC=RDC(1+ys+yp),R AC =R DC (1+y s +y p ),

随后,在仿真软件MATLAB Simulink中,在级联后的电缆微元等效模型的首端连接阻抗计算模块,计算出在设定的频率范围下的电缆首端输入阻抗值Zdata(i)(或在频率范围内,分别计算频率为f(i)时的电缆输入阻抗值Zdata(i))。Then, in the simulation software MATLAB Simulink, connect the impedance calculation module to the head end of the cascaded cable micro-element equivalent model, and calculate the input impedance value Z data(i) ( Or in the frequency range, calculate the cable input impedance value Z data(i) ) when the frequency is f(i) , respectively.

最后,在频率范围内,根据f(i)和Zdata(i),绘制出级联后等效电路模型对应的首端输入阻抗作为待分析配电电缆的阻抗谱。Finally, in the frequency range, according to f (i) and Z data(i) , draw the input impedance of the head end corresponding to the equivalent circuit model after the cascade as the impedance spectrum of the distribution cable to be analyzed.

具体地,将MATLAB Simulink中的阻抗计算模块(Impedance Measurement Block)连在级联后等效电路的的首端,通过计算不同频率输入电压和输出电流之比,获取阻抗谱。Specifically, the impedance calculation module (Impedance Measurement Block) in MATLAB Simulink is connected to the head end of the cascaded equivalent circuit, and the impedance spectrum is obtained by calculating the ratio of input voltage and output current at different frequencies.

在本发明实施例的一个实施例中,计算10m长的XLPE配电电缆的分布式阻抗谱时,分别采用了如图5和如图6所示的两类分布式模型,以对比两类模型的计算准确度。In an embodiment of the embodiment of the present invention, when calculating the distributed impedance spectrum of a 10m-long XLPE distribution cable, two types of distributed models as shown in Figure 5 and Figure 6 are respectively used to compare the two types of models calculation accuracy.

具体实施时,以1m作为电缆微元的长度,将10m长的XLPE配电电缆等效为依次级联的10个电缆微元等效模型(其等效电路示意图如图7所示),也即,采用十个级联的电缆微元等效模型(其电路示意图如图5或图6所示)来等效10m长的XLPE配电电缆。In the specific implementation, taking 1m as the length of the cable micro-element, the 10m-long XLPE distribution cable is equivalent to the equivalent model of 10 cable micro-elements cascaded in sequence (the schematic diagram of the equivalent circuit is shown in Figure 7). That is, ten cascaded cable micro-element equivalent models (the schematic diagram of which is shown in Fig. 5 or Fig. 6 ) is used to be equivalent to a 10m-long XLPE distribution cable.

图8分别给出了根据图5和图6的微元等效模型仿真得到的10m长的状态良好的XLPE单芯配电电缆的阻抗谱。Figure 8 shows the impedance spectrum of the 10m long XLPE single-core power distribution cable in good condition obtained by the simulation of the micro-element equivalent model in Figure 5 and Figure 6, respectively.

如图8所示,利用改进前后的微元等效模型得到的阻抗谱上都可以观察到十个极值点(也即,极值点的个数与电缆微元等效模型的个数相同),其中,各极值点出现的位置均在阻抗相位的过零点,符合阻抗谱理论,因此,利用改进前后的微元等效模型均可以计算得到较为准确的阻抗谱。As shown in Figure 8, ten extreme points (that is, the number of extreme points is the same as the number of the equivalent model of the cable micro element) can be observed on the impedance spectrum obtained by using the equivalent model of the micro element before and after the improvement ), where each extreme point appears at the zero-crossing point of the impedance phase, which conforms to the impedance spectrum theory. Therefore, a relatively accurate impedance spectrum can be calculated by using the micro-element equivalent model before and after the improvement.

如图8(a)所示,在低频段(<1MHz),电缆阻抗谱的幅值随频率的增大而下降,阻抗谱的相位为90度;考虑到电缆在横向的多层结构后,阻抗相频谱(如图8(d))所示,相频曲线变得圆滑,在1MHz到fmax的频率范围内可以观察到相频曲线有规律的衰减。As shown in Figure 8(a), at low frequency (<1MHz), the amplitude of the cable impedance spectrum decreases with the increase of frequency, and the phase of the impedance spectrum is 90 degrees; after considering the multi-layer structure of the cable in the transverse direction, As shown in the impedance phase spectrum (Fig. 8(d)), the phase-frequency curve becomes smooth, and a regular attenuation of the phase-frequency curve can be observed in the frequency range from 1MHz to fmax .

在阻抗幅频图上,改进前(如图8(a)所示)极值点的幅值变化没有规律且数值很大;改进后(如图8(c)所示)极值点的幅值随着频率的增加逐渐降低。On the impedance amplitude-frequency diagram, before the improvement (as shown in Figure 8(a)) the amplitude of the extreme point changes irregularly and the value is large; after the improvement (as shown in Figure 8(c)) the amplitude of the extreme point The value gradually decreases with increasing frequency.

需要说明的是,微元等效模型的个数和微元等效模型对应的电缆长度决定了级联电路模型中的频率上限fmax。如,该实施例中10m长的XLPE配电电缆对应的级联电路模型的fmax为21MHz,超出该频率,阻抗谱的计算结果将不能够再精确逼近实际情况。因此,尽管图8中给出的频率范围为1k~45MHz,但是,在21MHz之前的数据已经可以精确反映阻抗谱的变化情况,前述分析也主要引用的是频率上限之前的计算结果。图8中给出所有的计算结果主要是为了和改进后的模型的计算结果进行对比,并不用于说明频率上限。It should be noted that the number of micro-element equivalent models and the cable length corresponding to the micro-element equivalent models determine the frequency upper limit f max in the cascaded circuit model. For example, the f max of the cascaded circuit model corresponding to the 10m-long XLPE power distribution cable in this embodiment is 21MHz, beyond this frequency, the calculation result of the impedance spectrum will no longer be able to accurately approximate the actual situation. Therefore, although the frequency range given in Figure 8 is from 1k to 45MHz, the data before 21MHz can already accurately reflect the change of the impedance spectrum, and the above analysis mainly refers to the calculation results before the upper frequency limit. All the calculation results given in Fig. 8 are mainly for comparison with the calculation results of the improved model, and are not used to illustrate the upper limit of frequency.

综上,在仿真软件MATLAB Simulink中实现本实施例的方法时,包括以下步骤:To sum up, when the method of this embodiment is implemented in the simulation software MATLAB Simulink, the following steps are included:

1)、根据微元等效模型个数n,计算频率上限fmax,并据此设置仿真频率范围f(i)1) Calculate the upper limit of frequency f max according to the number n of equivalent models of micro-elements, and set the simulation frequency range f (i) accordingly;

2)、确定具有局部缺陷的电缆微元对应于第k个电缆微元等效模型;2), determine that the cable micro-element with local defects corresponds to the equivalent model of the k-th cable micro-element;

3)、利用循环指令,逐一改变频率并计算该频率下的复介电常数,并得到频率f(i)下具有局部缺陷的绝缘介质对应的相对介电常数ε(i)(可调整局部缺陷的严重程度);3) Using the loop command, change the frequency one by one and calculate the complex permittivity at the frequency, and obtain the relative permittivity ε (i) corresponding to the insulating medium with local defects at the frequency f (i ) (local defects can be adjusted. severity);

4)、计算与f(i)和ε(i)对应的电缆分布参数;4) Calculate the cable distribution parameters corresponding to f (i) and ε (i) ;

5)、根据趋肤效应因数和邻近效应因数修正电阻参数,计算对应频率下的电缆阻抗,即频率为f(i)时的电缆阻抗值Zdata(i)5), modify the resistance parameters according to the skin effect factor and the proximity effect factor, and calculate the cable impedance at the corresponding frequency, that is, the cable impedance value Z data(i ) when the frequency is f( i);

6)、根据f(i)和Zdata(i),绘制出电缆阻抗谱。6), according to f (i) and Z data (i) , draw the cable impedance spectrum.

综上,本发明实施例的基于改进微元等效模型的配电电缆阻抗谱确定方法,解决了在阻抗谱测试过程中由于电缆线路初始状态缺失导致的评估准确度较低的现实问题,通过固化相关参数及计算模型,在有限的计算资源条件下,实现电缆线路沿线正常状态/不同老化程度下的分布式阻抗谱快速计算。To sum up, the method for determining the impedance spectrum of a distribution cable based on the improved micro-element equivalent model according to the embodiment of the present invention solves the practical problem of low evaluation accuracy caused by the lack of the initial state of the cable line during the impedance spectrum test process. Relevant parameters and calculation models are solidified, and under the condition of limited computing resources, the distributed impedance spectrum rapid calculation of normal state/different aging degrees along the cable line can be realized.

通过采用上述方法计算所得的理论数值曲线与阻抗谱测试设备在现场实际测试曲线的比对,可以实现基于分布式阻抗谱的电缆线路绝缘状态快速诊断以及基于畸变点的缺陷定位,提升现场检测效率,优化状态检测与缺陷定位精度。By comparing the theoretical numerical curve calculated by the above method with the actual test curve of the impedance spectrum test equipment in the field, the rapid diagnosis of the insulation state of the cable line based on the distributed impedance spectrum and the defect location based on the distortion point can be realized, and the field detection efficiency can be improved. , optimize the state detection and defect location accuracy.

该方法在现场可获得的参数有限的条件下,实现级联电缆微元等效模型沿线电缆正常状态/不同老化程度下的阻抗谱快速计算。该方法解决了在阻抗谱测试过程中由于电缆线路初始状态缺失导致的评估准确度较低的现实问题。进一步地,通过比较分析阻抗测试仪器的测试数据与理论数据,即可评估配电电缆的局部缺陷及老化状态。Under the condition of limited parameters available in the field, this method realizes the fast calculation of the impedance spectrum of the cable in the normal state/different aging degree along the micro-element equivalent model of the cascaded cable. This method solves the practical problem of low evaluation accuracy caused by the absence of the initial state of the cable line during the impedance spectrum test. Further, by comparing and analyzing the test data and theoretical data of the impedance test instrument, the local defects and aging state of the distribution cable can be evaluated.

如图2所示,本发明实施例的基于改进微元等效模型的配电电缆阻抗谱确定装置,包括:As shown in FIG. 2 , the apparatus for determining the impedance spectrum of a distribution cable based on the improved micro-element equivalent model according to the embodiment of the present invention includes:

改进微元等效模型确定单元10,用于将目标配电电缆等效为多个改进微元等效模型,并分别确定各电缆微元等效模型的电气参数;The improved micro-element equivalent model determination unit 10 is used for equivalently converting the target distribution cable into a plurality of improved micro-element equivalent models, and respectively determining the electrical parameters of each cable micro-element equivalent model;

等效电路模型确定单元20,用于将所述多个电缆微元等效模型级联,形成与所述目标配电电缆对应的等效电路模型,并确定所述等效电路模型的频率上限;The equivalent circuit model determination unit 20 is used for cascading the equivalent models of the plurality of cable micro-elements to form an equivalent circuit model corresponding to the target distribution cable, and to determine the upper frequency limit of the equivalent circuit model ;

电气参数调整单元30,用于获取预先确定的局部缺陷的信息,并根据所述局部缺陷的信息调整对应的改进微元等效模型的电气参数;The electrical parameter adjustment unit 30 is configured to acquire the information of the predetermined local defects, and adjust the electrical parameters of the corresponding improved micro-element equivalent model according to the information of the local defects;

阻抗计算单元40,用于利用预先确定的首端阻抗计算方法,在所述频率上限的约束下,分别确定与所述目标配电电缆对应的幅频数据和相频数据,并绘制阻抗谱。The impedance calculation unit 40 is configured to use a predetermined head-end impedance calculation method, under the constraint of the upper frequency limit, to respectively determine amplitude-frequency data and phase-frequency data corresponding to the target distribution cable, and draw an impedance spectrum.

该基于改进微元等效模型的配电电缆阻抗谱确定装置与前述的基于改进微元等效模型的配电电缆阻抗谱确定方法具有相同的构思、技术方案和技术效果,这里不再赘述。The device for determining the impedance spectrum of a distribution cable based on the improved micro-element equivalent model has the same concept, technical solution and technical effect as the aforementioned method for determining the impedance spectrum of a distribution cable based on the improved micro-element equivalent model, which will not be repeated here.

本领域内的技术人员应明白,本申请的实施例可提供为方法、系统、或计算机程序产品。因此,本申请可采用完全硬件实施例、完全软件实施例、或结合软件和硬件方面的实施例的形式。而且,本申请可采用在一个或多个其中包含有计算机可用程序代码的计算机可用存储介质(包括但不限于磁盘存储器、CD-ROM、光学存储器等)上实施的计算机程序产品的形式。As will be appreciated by those skilled in the art, the embodiments of the present application may be provided as a method, a system, or a computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) having computer-usable program code embodied therein.

本申请是参照根据本申请实施例的方法、设备(系统)、和计算机程序产品的流程图和/或方框图来描述的。应理解可由计算机程序指令实现流程图和/或方框图中的每一流程和/或方框、以及流程图和/或方框图中的流程和/或方框的结合。可提供这些计算机程序指令到通用计算机、专用计算机、嵌入式处理机或其他可编程数据处理设备的处理器以产生一个机器,使得通过计算机或其他可编程数据处理设备的处理器执行的指令产生用于实现在流程图一个流程或多个流程和/或方框图一个方框或多个方框中指定的功能的装置。The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the present application. It will be understood that each flow and/or block in the flowchart illustrations and/or block diagrams, and combinations of flows and/or blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to the processor of a general purpose computer, special purpose computer, embedded processor or other programmable data processing device to produce a machine such that the instructions executed by the processor of the computer or other programmable data processing device produce Means for implementing the functions specified in a flow or flow of a flowchart and/or a block or blocks of a block diagram.

这些计算机程序指令也可存储在能引导计算机或其他可编程数据处理设备以特定方式工作的计算机可读存储器中,使得存储在该计算机可读存储器中的指令产生包括指令装置的制造品,该指令装置实现在流程图一个流程或多个流程和/或方框图一个方框或多个方框中指定的功能。These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory result in an article of manufacture comprising instruction means, the instructions The apparatus implements the functions specified in the flow or flow of the flowcharts and/or the block or blocks of the block diagrams.

这些计算机程序指令也可装载到计算机或其他可编程数据处理设备上,使得在计算机或其他可编程设备上执行一系列操作步骤以产生计算机实现的处理,从而在计算机或其他可编程设备上执行的指令提供用于实现在流程图一个流程或多个流程和/或方框图一个方框或多个方框中指定的功能的步骤。These computer program instructions can also be loaded on a computer or other programmable data processing device to cause a series of operational steps to be performed on the computer or other programmable device to produce a computer-implemented process such that The instructions provide steps for implementing the functions specified in the flow or blocks of the flowcharts and/or the block or blocks of the block diagrams.

以上已经通过参考少量实施方式描述了本发明。然而,本领域技术人员所公知的,正如附带的专利权利要求所限定的,除了本发明以上公开的其他的实施例等同地落在本发明的范围内。The present invention has been described above with reference to a few embodiments. However, as is known to those skilled in the art, other embodiments than the above disclosed invention are equally within the scope of the invention, as defined by the appended patent claims.

通常地,在权利要求中使用的所有术语都根据他们在技术领域的通常含义被解释,除非在其中被另外明确地定义。所有的参考“一个//该[装置、组件等]”都被开放地解释为装置、组件等中的至少一个实例,除非另外明确地说明。这里公开的任何方法的步骤都没必要以公开的准确的顺序运行,除非明确地说明。Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a//the [means, component, etc.]" are open to interpretation as at least one instance of a means, component, etc., unless expressly stated otherwise. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless explicitly stated.

Claims (10)

1. A distribution cable impedance spectrum determination method based on an improved infinitesimal equivalent model is characterized by comprising the following steps:
s100, enabling a target distribution cable to be equivalent to a plurality of improved infinitesimal equivalent models, and respectively determining electrical parameters of each cable infinitesimal equivalent model;
step S200, cascading the plurality of cable infinitesimal equivalent models to form an equivalent circuit model corresponding to the target distribution cable, and determining the upper frequency limit of the equivalent circuit model;
step S300, obtaining information of a predetermined local defect, and adjusting an electrical parameter of a corresponding improved infinitesimal equivalent model according to the information of the local defect;
and S400, respectively determining amplitude-frequency data and phase-frequency data corresponding to the target distribution cable under the constraint of the upper frequency limit by using a predetermined head end impedance calculation method, and drawing an impedance spectrum.
2. The method of claim 1 wherein the distribution cable impedance spectrum determination based on the improved infinitesimal equivalent model,
in step S100, the electrical parameters of any improved infinitesimal equivalent model include:
resistance R of cable corecInductance L of cable corecElectricity, electricityCable metal shielding layer resistance RsCable metal shielding layer inductance LsCable insulation capacitor CI
Wherein, the cable core wire resistance RcAnd a cable core inductance LcAfter being connected in series, the two ends of the capacitor are respectively connected with the cable insulation capacitor CIParallel connection; resistance R of cable metal shielding layersAnd cable metal shielding layer inductance LsAfter being connected in series, the two ends of the capacitor are respectively connected with the cable insulation capacitor CIAnd (4) connecting in parallel.
3. The method of claim 1 wherein the distribution cable impedance spectrum determination based on the improved infinitesimal equivalent model,
in step S100, the target distribution cable is uniformly divided into M sections of cable microelements, and each cable microelement corresponds to an improved microelement equivalent model; the sum of the lengths of the M sections of cable elements is the same as the length of the target distribution cable;
correspondingly, in step S200, the improved infinitesimal equivalent models are sequentially cascaded according to the positions of the cable infinitesimal in the cable corresponding to each improved infinitesimal equivalent model, so as to form an equivalent circuit model corresponding to the target distribution cable.
4. The method of claim 3 wherein the distribution cable impedance spectrum is determined based on an improved infinitesimal equivalent model,
in the step S200, the upper frequency limit f of the equivalent circuit model is determined according to the following formulamax
Figure FDA0002437503530000021
Wherein n is the number of the infinitesimal equivalent models;
l is the length of a single cable element;
v(fmax) As a function of the propagation speed of the signal in the cable;
L(fmax)and C(fmax)Are respectively the frequency fmaxThe core wire inductance and the insulation capacitance of the cable;
wherein,
Figure FDA0002437503530000022
5. the method of claim 1 wherein the distribution cable impedance spectrum determination based on the improved infinitesimal equivalent model,
in step S300, the information about the predetermined local defect includes:
the location of the local defect in the cable, the severity of the local defect, and an electrical parameter impact function corresponding to the severity of the local defect.
6. The method of claim 5 wherein the distribution cable impedance spectrum is determined based on an improved infinitesimal equivalent model,
the electrical parameter impact function corresponding to the severity of the local defect comprises:
for determining the insulation capacitance C of a cableIThe following formula:
Figure FDA0002437503530000031
wherein r iscIs the outer radius of the cable core;
rsthe inner radius of the cable insulation metal shielding layer;
is the relative dielectric constant.
7. The method of claim 1 wherein the distribution cable impedance spectrum determination based on the improved infinitesimal equivalent model,
in the step S400, the predetermined head end impedance calculation method includes:
determining a head-end input impedance Z according to:
Figure FDA0002437503530000032
wherein, XCCapacitive reactance for cable insulation;
RACan alternating current resistance of a cable core;
XLis the inductive reactance of the cable core.
8. The method of claim 7 for determining the impedance spectrum of a distribution cable based on the improved infinitesimal equivalent model, further comprising:
using the DC resistance R of the cable core according toDCCorrection of the AC resistance R of the core wire of a cableAC
RAC=RDC(1+ys+yp);
Wherein, ysIs the skin effect factor;
ypis the proximity effect factor.
9. Method for improved infinitesimal equivalent model based distribution cable impedance spectrum determination according to any one of claims 1 to 8,
the target distribution cable is suitable for 10-35kV lines;
the target distribution cable is a coaxial cable and sequentially comprises a conductor layer, an inner semi-conducting layer, an insulating layer, an outer semi-conducting layer and a metal shielding layer from inside to outside.
10. An apparatus for determining an impedance spectrum of a distribution cable based on an improved infinitesimal equivalent model, comprising:
the improved infinitesimal equivalent model determining unit is used for enabling the target distribution cable to be equivalent to a plurality of improved infinitesimal equivalent models and respectively determining the electrical parameters of the cable infinitesimal equivalent models;
the equivalent circuit model determining unit is used for cascading the plurality of cable infinitesimal equivalent models to form an equivalent circuit model corresponding to the target distribution cable and determining the upper frequency limit of the equivalent circuit model;
the electrical parameter adjusting unit is used for acquiring the information of the predetermined local defect and adjusting the electrical parameters of the corresponding improved infinitesimal equivalent model according to the information of the local defect;
and the impedance calculation unit is used for respectively determining amplitude-frequency data and phase-frequency data corresponding to the target distribution cable under the constraint of the upper frequency limit by using a predetermined head end impedance calculation method, and drawing an impedance spectrum.
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