Distribution network hybrid line fault traveling wave energy distribution uniformity index prediction method

Abstract

The application provides a distribution network hybrid line fault traveling wave energy distribution uniformity index prediction method, and relates to the technical field of distribution network hybrid power supply line fault prediction.The application measures the line parameter values such as the hybrid line fault traveling wave voltage, and calculates the distribution network hybrid line fault traveling wave energy distribution uniformity index according to the related parameters such as the line power frequency voltage and the hybrid line power frequency current, predicts the distribution network hybrid line fault in real time according to the calculation result, and calculates the prediction value of the distribution network hybrid line fault traveling wave energy distribution uniformity index; thereby the distribution network hybrid line fault traveling wave energy distribution uniformity index prediction method is realized, and the fault traveling wave uniformity distribution is understood.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power distribution network hybrid power supply line fault prediction, and particularly relates to a power distribution network hybrid line fault traveling wave energy distribution uniformity index prediction method. BACKGROUND

[0002] With the change of urban development demand and the development of cable line power supply technology, and due to the advantages of cable line, such as convenient laying, less occupation of land resources, and no influence on urban appearance, more and more cable lines are used for power supply in the power distribution network, which makes a large number of cable and overhead line hybrid power supply lines appear in the power distribution network. In addition, the large-scale popularization of cable branch boxes leads to a geometric increase in the branches of the hybrid line of the power distribution network, greatly increasing the complexity of the power distribution network. Because the structures of the sections of the hybrid line are different, the line parameters are greatly different, and the corresponding wave impedance is also different, once the cable hybrid line fails, the difference in wave impedance will cause the transmission speed of the fault traveling wave in the hybrid line to be different, and then cause great difficulty in fault prediction for the current power distribution network with complex structure and numerous branches. Therefore, monitoring the energy distribution of the fault traveling wave in the hybrid line becomes the key to accurately predicting the fault point of the power distribution network. SUMMARY

[0003] In view of the deficiencies of the prior art, the present application provides a power distribution network hybrid line fault traveling wave energy distribution uniformity index prediction method, so as to understand the uniformity distribution of the fault traveling wave.

[0004] A power distribution network hybrid line fault traveling wave energy distribution uniformity index prediction method, specifically comprising the following steps:

[0005] Step 1: Establishing a power distribution network hybrid line fault traveling wave energy distribution uniformity index prediction data time sequence;

[0006] Defining a power distribution network hybrid line fault traveling wave energy distribution uniformity index prediction function f:

[0007]

[0008] In the formula, n is a natural number, n = 1, 2, …, t1, t2, …, t n is the time of n fixed time intervals, F N is the rated voltage of the hybrid line, is the nth measurement value of the fault traveling wave voltage of the hybrid line, t Fmax is the time corresponding to the maximum value of the n measurement values of the fault traveling wave voltage of the hybrid line, t Fmin is the time corresponding to the minimum value of the n measurement values of the fault traveling wave voltage of the hybrid line.

[0009] At the time points t1, t2, t3, …, t mon ,…,t n , where mon∈{1, 2, …, n}, the measurement time series of the mixed line power frequency current I lo , the mixed line power frequency voltage U tr , the mixed line active power P ac , the mixed line reactive power P re , and the mixed line power frequency voltage frequency f mix of the mixed line at the head end are:

[0010]

[0011] In the formula, represents the measurement value of the mixed line power frequency current at t1, t2, t3, …, t n corresponding time points; represents the measurement value of the mixed line power frequency voltage at t1, t2, t3, …, t n corresponding time points; represents the measurement value of the mixed line active power at t1, t2, t3, …, t n corresponding time points; represents the measurement value of the mixed line reactive power at t1, t2, t3, …, t n corresponding time points; represents the measurement value of the mixed line power frequency voltage frequency at t1, t2, t3, …, t n corresponding time points;

[0012] Step 2: The measurement time series data of the mixed line power frequency current I lo , the mixed line power frequency voltage U tr , the mixed line active power P ac , the mixed line reactive power P re , and the mixed line power frequency voltage frequency f mix are normalized as follows:

[0013]

[0014] In the formula, is the normalized value of the mixed line power frequency current, is the normalized value of the mixed line power frequency voltage, is the normalized value of the mixed line active power, is the normalized value of the mixed line reactive power, is the normalized value of the mixed line power frequency voltage frequency.I lo,max , I lo,minrespectively, are the maximum and minimum values of the mixed line power frequency voltage measured at the time of n fixed time intervals, P tr,max 、U tr,min respectively, are the maximum and minimum values of the mixed line power frequency voltage measured at the time of n fixed time intervals, P ac,max 、P ac,min respectively, are the maximum and minimum values of the mixed line power frequency voltage measured at the time of n fixed time intervals, P re,max 、P re,min respectively, are the maximum and minimum values of the mixed line power frequency voltage measured at the time of n fixed time intervals, f mix,max 、f mix,min respectively, are the maximum and minimum values of the mixed line power frequency voltage measured at the time of n fixed time intervals.

[0015] Step 3: Calculate the influence factor of the ratio of overhead line length to total length of mixed line and the relative dielectric constant of air on the uniformity index of fault traveling wave energy distribution of distribution network mixed line

[0016] Design an influence factor f of the ratio of overhead line length to total length of mixed line and the relative dielectric constant of air on the uniformity index of fault traveling wave energy distribution of distribution network mixed line ca The calculation method is as follows:

[0017]

[0018] In the formula, ε ca is the relative dielectric constant of air of overhead line, β ca is the ratio of overhead line length to total length of mixed line;

[0019] Step 4: Calculate the influence factor of the ratio of cable length to total length of mixed line and the relative dielectric constant of insulation layer on the uniformity index of fault traveling wave energy distribution of distribution network mixed line

[0020] Design an influence factor f of the ratio of cable length to total length of mixed line and the relative dielectric constant of insulation layer on the uniformity index of fault traveling wave energy distribution of distribution network mixed line ov The calculation method is as follows:

[0021]

[0022] In the formula, ε ov is the relative dielectric constant of insulation layer of cable, β ov is the ratio of cable length to total length of mixed line.

[0023] Step 5: Calculate the predicted value of the uniformity index of fault traveling wave energy distribution of distribution network mixed line:

[0024] Based on the influence factor f in step 3 ca With the influence factor f in step 4 ov , the predicted value of the distribution uniformity index of the fault traveling wave energy of the distribution network mixed line at the future t n+1 moment is calculated:

[0025]

[0026] In the formula, W1 is the weight coefficient of the influence factor f ca , W2 is the weight coefficient of the influence factor f ov , wherein W1+W2=1, and W1, W2 are not 0.

[0027] If the predicted value of the distribution uniformity index of the fault traveling wave energy of the distribution network mixed line is calculated according to formula (6);

[0028] When the mixed line fails, and the predicted value is greater than 0.6, the fault positioning judgment result L GZCJ given by the existing fault ranging device is corrected according to the index predicted value, L GZCJ ∈[0,1], and the correction value is △L GZCJ1 =0.12f pre , then the corrected ranging result is L' GZCJ =L GZCJ +△L GZCJ1 .

[0029] When the mixed line fails, and the predicted value is less than 0.6, the fault positioning judgment result L GZCJ given by the existing fault ranging device is corrected according to the index predicted value, L GZCJ ∈[0,1], and the correction value is △L GZCJ2 =-0.1098f pre , then the corrected ranging result is L' GZCJ =L GZCJ +△L GZCJ2 .

[0030] The beneficial effects produced by the above technical scheme are as follows:

[0031] The present application provides a kind of distribution network mixed line fault traveling wave energy distribution uniformity index prediction method, and the line parameter value measurement such as mixed line fault traveling wave voltage is carried out, and the distribution network mixed line fault traveling wave energy distribution uniformity index is calculated according to relevant parameters such as line power frequency voltage, mixed line power frequency current, and the calculation result is in real time to the prediction of distribution network mixed line fault, can be according to the index predicted value, the positioning result of the existing fault traveling wave fault ranging device or fault positioning device is corrected, effectively improve the fault positioning precision based on fault traveling wave fault. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 This is a flowchart of the method for predicting the uniformity index of traveling wave energy distribution in a hybrid distribution network fault, as described in this embodiment of the invention. Detailed Implementation

[0033] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0034] A method for predicting the uniformity index of traveling wave energy distribution in a hybrid distribution network fault, such as... Figure 1 As shown, the specific steps include:

[0035] Step 1: Establish time series data for predicting the uniformity of traveling wave energy distribution indices in mixed distribution network faults;

[0036] Define the exponential prediction function f for the uniformity of energy distribution of traveling waves during faults in hybrid distribution networks:

[0037]

[0038] In the formula, n is a natural number, n = 1, 2, ..., t1, t2, ..., tt3. n F represents n fixed time intervals. N For the mixed line rated voltage, t represents the nth measurement of the traveling wave voltage during a mixed line fault. Fmax The time t corresponds to the maximum value among n measurements of the traveling wave voltage of a hybrid line fault. Fmin The time corresponding to the minimum value among n measurements of the traveling wave voltage of a hybrid line fault.

[0039] At n fixed time intervals t1, t2, t3, ..., t mon ,…,t n Where mon∈{1,2,…,n}, the hybrid line power frequency current I is measured at the beginning of the hybrid line. lo Hybrid line power frequency voltage U tr Active power P of hybrid lines ac Reactive power P of mixed lines re Hybrid line power frequency voltage frequency f mix The time series of the measured values ​​is as follows:

[0040]

[0041] In the formula, This indicates the power frequency current of the hybrid line at t1, t2, t3, ..., t n The measurement value at the corresponding time; the measured value of the power frequency voltage of the hybrid line at t1, t2, t3, …, t n the measured value of the corresponding moment; the measured value of the power frequency voltage of the hybrid line at t1, t2, t3, …, t n the measured value of the corresponding moment; the measured value of the power frequency voltage of the hybrid line at t1, t2, t3, …, t n the measured value of the corresponding moment; the measured value of the power frequency voltage of the hybrid line at t1, t2, t3, …, t n the measured value of the corresponding moment;

[0042] In this embodiment, the actual operation status of a certain hydropower plant hybrid line is selected as a case. When the first section of the line detects a fault traveling wave voltage, the measurement is started, and n fixed time interval moments t1, t2, t3, …, t n are set, and the values of the fault traveling wave voltage are measured n times. At the same time, the relative dielectric constant of air in the overhead line ε ca = 1.00015, the relative dielectric constant of the insulation layer in the cable line ε ov = 2.59, the ratio of the length of the overhead line to the total length of the hybrid line β ca = 0.4, and the ratio of the length of the cable line to the total length of the hybrid line β ov = 0.6. The measurement time series data of the power frequency current I lo , the power frequency voltage U tr , the active power P ac , the reactive power P re , and the power frequency voltage frequency f mix of the hybrid line are measured, and the measurement number is 8, that is, n = 8, and the following 5 groups of results are obtained:

[0043]

[0044] Step 2: The measurement time series data of the power frequency current I lo , the power frequency voltage U tr , the active power P ac , the reactive power P re , and the power frequency voltage frequency f mix of the hybrid line are normalized as follows:

[0045]

[0046] In the formula, is the normalized value of the power frequency current of the hybrid line, is the normalized value of the power frequency voltage of the hybrid line, is the normalized value of the active power of the hybrid line, is the normalized value of the reactive power of the hybrid line, is the normalized value of the frequency of the power frequency voltage of the hybrid line. lo,max , I lo,min are respectively the maximum and minimum values of the measured values of the power frequency current of the hybrid line at the time of n fixed time intervals, tr,max , U tr,min are respectively the maximum and minimum values of the measured values of the power frequency voltage of the hybrid line at the time of n fixed time intervals, ac,max , P ac,min are respectively the maximum and minimum values of the measured values of the active power of the hybrid line at the time of n fixed time intervals, re,max , P re,min are respectively the maximum and minimum values of the measured values of the reactive power of the hybrid line at the time of n fixed time intervals, mix,max , f mix,min are respectively the maximum and minimum values of the measured values of the frequency of the power frequency voltage of the hybrid line at the time of n fixed time intervals.

[0047] In this embodiment, the maximum and minimum values in the 5 groups of data are calculated according to the measured data in the above formula. At the same time, the above data is normalized according to formula (3), and the result is as follows:

[0048]

[0049] Step 3: Calculate the influence factor of the ratio of the length of the overhead line to the total length of the hybrid line and the relative dielectric constant of air on the uniformity index of the fault traveling wave energy distribution of the distribution network hybrid line

[0050] A kind of influence factor f of the ratio of the length of the overhead line to the total length of the hybrid line and the relative dielectric constant of air on the uniformity index of the fault traveling wave energy distribution of the distribution network hybrid line is designed ca The calculation method is shown in the following formula:

[0051]

[0052] In the formula, ε ca is the relative dielectric constant of air of overhead line, β ca is the ratio of the length of the overhead line to the total length of the hybrid line;

[0053] In this embodiment, it is shown in the following formula:

[0054]

[0055] Step 4: Calculate the influence factor of the ratio of the length of the cable line to the total length of the hybrid line and the relative dielectric constant of insulation layer on the uniformity index of the fault traveling wave energy distribution of the distribution network hybrid line;

[0056] An influence factor f of a ratio of a cable length to a total length of a mixed line, and a relative dielectric constant of an insulation layer on a fault traveling wave energy distribution uniformity index of a mixed line of a distribution network is designed ov The calculation method is shown in the following formula:

[0057]

[0058] In the formula, ε ov is the relative dielectric constant of the insulation layer of the cable, β ov is the ratio of the cable length to the total length of the mixed line.

[0059] In the embodiment, the formula is as follows:

[0060]

[0061] Step 5: Calculate the predicted value of the fault traveling wave energy distribution uniformity index of the mixed line of the distribution network:

[0062] Based on the influence factor f ca in step 3 and the influence factor f ov in step 4, the predicted value of the fault traveling wave energy distribution uniformity index of the mixed line of the distribution network at a future time t n+1 is calculated:

[0063]

[0064] In the formula, W1 is the weight coefficient of the influence factor f ca , W2 is the weight coefficient of the influence factor f ov , wherein W1+W2=1, and W1 and W2 are not 0.

[0065] If the predicted value of the fault traveling wave energy distribution uniformity index of the mixed line of the distribution network is calculated according to formula (6);

[0066] When the mixed line fails, and the predicted value is greater than 0.6, the fault positioning judgment result L GZCJ given by the existing fault ranging device is corrected according to the index predicted value, L GZCJ ∈[0,1], and the correction value is ΔL GZCJ1 =0.12f pre , and the corrected ranging result is L' GZCJ =L GZCJ +ΔL GZCJ1 .

[0067] When the mixed line fails, and the predicted value is less than 0.6, the fault positioning judgment result L GZCJ given by the existing fault ranging device is corrected according to the index predicted value, LGZCJ ∈[0,1], the correction value is △L GZCJ2 =-0.1098f pre The corrected distance measurement result is L′ GZCJ =L GZCJ +△L GZCJ2 .

[0068] In this embodiment, the weighting coefficients of the influencing factors are set to W1 = 0.4 and W2 = 0.6 based on the actual application status of the hydropower plant's lines. This allows for the calculation of the predicted value f of the uniformity index of the traveling wave energy distribution of the mixed distribution network fault at future measurement times t9 (n+1 = 9). pre :

[0069]

[0070] The predicted value of the uniformity index of the traveling wave energy distribution of the mixed line fault in the distribution network is obtained by calculating the above formula.

[0071] When a fault occurs on a hybrid line and the predicted value is greater than 0.6, the fault location judgment result L given by the existing fault location device is based on the exponential predicted value. GZCJ Make corrections, L GZCJ ∈[0,1], the correction value is △L GZCJ1 =0.12f pre The corrected distance measurement result is L′ GZCJ =L GZCJ +△L GZCJ1

[0072] When a fault occurs in the hybrid line, and the predicted value is less than 0.6, the fault location judgment result L given by the existing fault location device is based on the exponential predicted value. GZCJ Make corrections, L GZCJ ∈[0,1], the correction value is △L GZCJ2 =-0.1098f pre The corrected distance measurement result is L′ GZCJ =L GZCJ +△L GZCJ2 .

[0073] The above description is merely a preferred embodiment of this disclosure and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of the invention involved in the embodiments of this disclosure is not limited to technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the above-described inventive concept. For example, technical solutions formed by substituting the above-described features with (but not limited to) technical features with similar functions disclosed in the embodiments of this disclosure.

Claims

1.A method for predicting a distribution uniformity index of fault traveling wave energy of a distribution network hybrid line, characterized in that: The method comprises the following steps: Step 1: establishing a distribution uniformity index prediction data time series of a fault traveling wave of a distribution network hybrid line; The step 1 is specifically defined as a distribution uniformity index prediction function f of the fault traveling wave of the distribution network hybrid line: In the formula, n is a natural number, n = 1, 2, …, t1, t2, …, t n is the time of n fixed time intervals, F N is the rated voltage of the hybrid line, is the n th measurement value of the fault traveling wave voltage of the hybrid line, t Fmax is the time corresponding to the maximum value in the n measurement values of the fault traveling wave voltage of the hybrid line, t Fmin is the time corresponding to the minimum value in the n measurement values of the fault traveling wave voltage of the hybrid line; At n fixed time intervals t1, t2, t3, ..., t mon ,...,t n Where mon∈{1,2,…,n}, the hybrid line power frequency current I is measured at the beginning of the hybrid line. lo Hybrid line power frequency voltage U tr Active power P of hybrid lines ac Reactive power P of mixed lines re Hybrid line power frequency voltage frequency f mix The time series of the measured values ​​is as follows: wherein represents the power frequency current of the hybrid line at t1, t2, t3,..., t n the measured value at the corresponding time instant; represents the power frequency voltage of the hybrid line at t1, t2, t3,..., t n the measured value at the corresponding time instant; represents the active power of the hybrid line at t1, t2, t3,..., t n the measured value at the corresponding time instant; represents the reactive power of the hybrid line at t1, t2, t3,..., t n the measured value at the corresponding time instant; represents the power frequency voltage frequency of the hybrid line at t1, t2, t3,..., t n the measured value at the corresponding time instant; Step 2: Normalization of the measurement time series data of the mixed line power frequency current I lo , the mixed line power frequency voltage U tr , the mixed line active power P ac , the mixed line reactive power P re , the mixed line power frequency voltage frequency f mix ; The normalization processing in the step 2; wherein is the normalized value of the power frequency current of the hybrid line, is the normalized value of the power frequency voltage of the hybrid line, is the normalized value of the active power of the hybrid line, is the normalized value of the reactive power of the hybrid line, is the normalized value of the power frequency voltage frequency of the hybrid line, I lo,max , I lo,min are, respectively, the maximum and minimum values of the measured values of the power frequency current of the hybrid line at the instants of the n fixed time intervals, U tr,max , U tr,min are, respectively, the maximum and minimum values of the measured values of the power frequency voltage of the hybrid line at the instants of the n fixed time intervals, P ac,max , P ac,min are, respectively, the maximum and minimum values of the measured values of the active power of the hybrid line at the instants of the n fixed time intervals, P re,max , P re,min are, respectively, the maximum and minimum values of the measured values of the reactive power of the hybrid line at the instants of the n fixed time intervals, f mix,max , f mix,min are, respectively, the maximum and minimum values of the measured values of the power frequency voltage frequency of the hybrid line at the instants of the n fixed time intervals. Step 3: calculating an influence factor of a ratio of an overhead line length to a total length of the hybrid line and a relative dielectric constant of air on the distribution uniformity index of the fault traveling wave of the distribution network hybrid line; The step 3 is specifically designed as an influence factor f of a ratio of the length of the overhead line to the total length of the mixed line, and a relative dielectric constant of air on the evenness index of the fault traveling wave energy distribution of the mixed line of the distribution network ca The calculation method is shown in the following formula: where ε ca is the relative dielectric constant of air, β ca is the ratio of the length of the overhead line to the total length of the hybrid line Step 4: calculating an influence factor of a ratio of a cable line length to the total length of the hybrid line and a relative dielectric constant of an insulation layer on the distribution uniformity index of the fault traveling wave of the distribution network hybrid line; The step 4 is specifically designing an influence factor f of the ratio of the cable length to the total length of the mixed line, and the relative dielectric constant of the insulation layer on the uniformity index of the fault traveling wave energy distribution of the distribution network mixed line ov The calculation method is shown in the following formula: where ε ov is the relative dielectric constant of the cable insulation, β ov is the ratio of the cable length to the total length of the hybrid line; Step 5: calculating a prediction value of the distribution uniformity index of the fault traveling wave of the distribution network hybrid line, and realizing the distribution uniformity index prediction of the fault traveling wave of the distribution network hybrid line; The step 5 is specifically, based on the influence factor f in step 3 ca With the influence factor f in step 4 ov , the prediction value f of the distribution uniformity index of the fault traveling wave energy of the distribution network hybrid line at the future time t n+1 : pre : wherein W1 is a weight coefficient of the influence factor f ca and W2 is a weight coefficient of the influence factor f ov , wherein W1+W2=1 and W1, W2 are not 0. If the prediction value of the distribution uniformity index of the fault traveling wave of the distribution network hybrid line is calculated according to the formula (6); When the hybrid line is faulty and the prediction value is greater than 0.6, the fault positioning judgment result L given by the existing fault ranging device is corrected according to the exponential prediction value GZCJ The correction is L GZCJ ∈[0, 1], and the correction value is ΔL GZCJ1 = 0.12f pre Then the corrected ranging result is L' GZCJ = L GZCJ + ΔL GZCJ1 ; When the hybrid line is in failure and the predicted value is less than 0.6, the fault positioning judgment result L given by the existing fault ranging device according to the exponential predicted value GZCJ The correction is made, L GZCJ ∈[0, 1], the correction value is ΔL GZCJ2 =-0.1098f pre Then the corrected ranging result is L' GZCJ =L GZCJ +ΔL GZCJ2 .

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