CN101363880A - Method for live line measurement of zero sequence admittance of transmission line by industrial frequency interference source - Google Patents

Abstract

The invention provides a method for electrified measurement of the zero-sequence admittance of a transmission line by utilizing a power-frequency interference source. When the admittance of a new line not in service or a certain dead line in a mutual inductance line assembly is measured, no extra zero-sequence power supply for measuring is added to the new line or the dead line, and the power-frequency interference source due to the zero-sequence mutual inductance between the mutual inductance lines is directly utilized as the zero-sequence power supply for measuring. The zero-sequence interference voltage on the new line or the dead line is measured, and then the zero-sequence interference current thereon is measured; or the zero-sequence interference current is measured, and then the zero-sequence interference voltage is measured. After the zero-sequence interference voltage and the zero-sequence interference current on the new line or the dead line are acquired, the zero-sequence admittance of the new line or the dead line is calculated by utilizing the algebraic equation method, the differential equation method and the integral equation method.

Description

A kind of method of utilizing the admittance of power frequency interference source live line measurement transmission line of electricity zero sequence

Technical field

The invention belongs to the power system transmission line parameter field of measuring technique, particularly relate to the method for the zero sequence admittance live line measurement of newly-built circuit and dead line in the mutual inductance circuit group;

Background technology

Along with the development of electric system scale, generating plant (transformer station) outlet increases, and mutual inductance circuit is more and more.

Because the zero sequence admittance of mutual inductance circuit is subjected to the influence of several factors, the flow through stake resistance rate etc. in zone of line alignment, zero-sequence current; Calculated value can't satisfy the accuracy requirement that the relay protection setting value is calculated, and as adopting calculated value as the foundation of adjusting and calculating, can make protection produce tripping or malfunction when the system failure, and this directly threatens the safety and stablization operation of system; Therefore; in People's Republic of China's power industry standard; point out about the regulation of relay protection setting in " 220kV-500kV electric grid relay protection operating standard (DL/T559-94,1995-05-01 implement) ": the zero sequence impedance of overhead transmission line and cable, other should use measured value to the bigger parameter of relay protection influence.

The method of traditional definite transmission line of electricity Zero sequence parameter has computing method of formula and power failure mensuration; Owing to relate to imprecise parameters such as ground resistivity in the computing formula, so formula result of calculation is inaccurate.

Before a newly-built transmission line of electricity puts into operation, need to measure the parameters such as zero sequence admittance of newly-built circuit, this circuit and other have been built and have been had mutual inductance between the circuit; The method of measuring the admittance of mutual inductance circuit zero sequence with traditional power failure mensuration requires test line all to have a power failure, otherwise when mutual inductance was very big, its measuring error was very big; To measure often be impossible and will have a power failure fully to mutual inductance circuit; Therefore, seeking a kind of new mutual inductance circuit zero sequence admittance live line measurement method, is that Operation of Electric Systems department is badly in need of, and not only has important theory and is worth, and have very big economic benefit and social benefit.

Summary of the invention:

Needs are with the shortcoming of all mutual inductance circuits power failures when the objective of the invention is to overcome traditional power failure mensuration and measuring newly-built mutual inductance circuit zero sequence admittance in the mutual inductance circuit group, the newly-built circuit in a kind of new mutual inductance circuit group and the zero sequence admittance live line measurement method of certain bar dead line have been proposed, when having realized the N-1 bar circuit charging operation in the N bar mutual inductance circuit group or when having a circuit charging operation at least, to the accurate measurement of newly-built circuit or the admittance of dead line zero sequence.

For realizing purpose of the present invention, technical scheme provided by the invention is: a kind of power frequency interference source live line measurement mutual inductance circuit zero sequence admittance measurement method of utilizing may further comprise the steps:

(1) utilize zero-sequence mutual inductance between the mutual inductance circuit, this mutual inductance is called interference source, as measuring zero sequence power supply, turns harm into good, and obtains zero sequence interference current and zero sequence interference voltage data on the transmission line of electricity

When measuring the admittance of transmission line of electricity zero sequence: for the newly-built circuit that does not put into operation in the mutual inductance circuit group or a certain dead line, behind zero sequence interference voltage on the circuit and the external voltage transformer (VT) summation current transformer of zero sequence interference current process, be linked in the voltage channel and current channel of measurement mechanism.

When measuring the zero sequence admittance of transmission line of electricity, undertaken by following measuring sequence and step:

1. measure the zero sequence interference voltage of transmission line of electricity earlier, again the zero sequence interference current of measuring circuit

At first that the terminal three-phase short circuit of transmission line of electricity is earth-free, head end three-phase short circuit is earth-free, measure the zero sequence interference voltage and the zero sequence interference current of transmission line of electricity head end simultaneously, Measuring Time is 1 second, in fact the useful signal that measure this moment has only the zero sequence interference voltage, adopt these data during calculating, the zero sequence interference current of measurement is invalid, does not adopt these data during calculating; The band auxiliary switching-in that the head end on the transmission line of electricity of closing again is external and the air switch of switching winding, with transmission line of electricity head end three-phase short circuit ground connection, continue to measure simultaneously the zero sequence interference voltage and the zero sequence interference current of transmission line of electricity head end, Measuring Time also is 1 second, in fact the useful signal that measure this moment has only the zero sequence interference current, adopt these data during calculating, the zero sequence interference voltage of measurement is invalid, does not adopt these data during calculating; After the measuring process in 2 seconds is finished, the zero sequence interference voltage data in 2 seconds of collecting and the zero sequence interference current data in the 2 seconds mode with file is deposited in the storer.

Zero sequence interference current on the continuous coverage transmission line of electricity and zero sequence interference voltage, whole measuring process data acquisition time is 2 seconds, in the data in zero sequence interference voltage and 2 seconds of zero sequence interference current, real separately active data all has only 1 second data.

2. or measure earlier the zero sequence interference current of transmission line of electricity, measure the zero sequence interference voltage of transmission line of electricity again

At first that the terminal three-phase short circuit of transmission line of electricity is earth-free, head end three-phase short circuit ground connection, measure the zero sequence interference voltage and the zero sequence interference current of dead line head end simultaneously, Measuring Time is 1 second, in fact the useful signal that measure this moment has only the zero sequence interference current, adopt these data during calculating, it is invalid that the zero sequence of measurement is disturbed piezoelectricity, does not adopt these data during calculating; Disconnect the external band auxiliary switching-in of head end on the transmission line of electricity and the air switch of switching winding again, transmission line of electricity head end three-phase short circuit is earth-free, continue to measure simultaneously the zero sequence interference voltage and the zero sequence interference current of transmission line of electricity head end, Measuring Time also is 1 second, in fact the useful signal that measure this moment has only the zero sequence interference voltage, adopt these data during calculating, the zero sequence interference current of measurement is invalid, does not adopt these data during calculating; After the measuring process in 2 seconds is finished, the zero sequence interference voltage data in 2 seconds of collecting and the zero sequence interference current data in the 2 seconds mode with file is deposited in the storer.

Zero sequence interference current on the continuous coverage transmission line of electricity and zero sequence interference voltage, whole measuring process data acquisition time is 2 seconds, in the data in zero sequence interference voltage and 2 seconds of zero sequence interference current, real separately active data all has only 1 second data.

(2) behind the zero sequence interference current and zero sequence interference voltage sampled data that obtain on the transmission line of electricity, adopt following algebraic equation method, differential equation method or integral equation method to calculate the zero sequence admittance of test line:

(1), algebraic equation method

Zero sequence admittance computing formula:

$Y=\left|\frac{\stackrel{.}{I}}{\stackrel{.}{U}}\right|\×[\cos ({\mathrm{\θ}}_I-{\mathrm{\θ}}_U+180)+j\sin ({\mathrm{\θ}}_I-{\mathrm{\θ}}_U+180)]---\left(1\right)$

In the following formula, Y is the zero sequence admittance of transmission line of electricity, and unit is a Siemens;

Be the zero sequence first-harmonic interference current phasor of transmission line of electricity, unit is an ampere,

Be the zero sequence first-harmonic interference voltage phasor on the transmission line of electricity, unit is a volt;

Be the mould value of zero sequence admittance, θ _IBe zero sequence first-harmonic interference current phase angle, unit is degree, θ _UBe zero sequence first-harmonic interference voltage phase angle, unit is degree; " 180 " in the phasing degree are because the measurement of zero sequence interference voltage and zero sequence interference current is not carried out simultaneously, the zero sequence admittance phasing degree of zero sequence admittance phasing degree that calculates and circuit reality differs 180 degree, so add 180 degree on the basis, phasing degree that calculates;

To the zero sequence interference current and the zero sequence interference voltage data of gathering, adopt the Fourier filtering algorithm, obtain zero sequence first-harmonic interference current phasor With zero sequence first-harmonic interference voltage phasor

For eliminating the influence of transient state process, to the interference current phasor to measurement result

With the interference voltage phasor Calculate used data, get in the steady-state process after zero sequence interference current signal and the zero sequence interference voltage signal transient state process pairing sampled data and calculate; Be to improve computational accuracy, calculate earlier each the result of the number of winning the confidence cycle correspondence, get the final calculation result of the mean value of these cycle result of calculations again as the zero sequence admittance.

(2) differential equation method

Ignore the zero sequence electricity of circuit and lead, it is as follows to be listed as the differential equation that writes out transmission line of electricity zero sequence electric capacity:

$i=C\frac{\mathrm{du}}{\mathrm{dt}}---\left(2\right)$

(2) in the formula, C is the zero sequence electric capacity of transmission line of electricity, and u is the zero sequence interference voltage sampled value on the transmission line of electricity; I is the zero sequence interference current sampled value on the transmission line of electricity; Zero sequence interference current and zero sequence interference voltage are calculated used data, get in the 1 second real useful separately sampled data, pairing sampled data is calculated in the steady-state process after zero sequence current signal and the residual voltage signal transient state process.

With [u (k+1)-u (k-1)]/(2T _s) replace the derivative term in the differential equation group The sampled value of zero sequence interference voltage when u (k+1) and u (k-1) are respectively sampling instant k+1 and k-1, the sampled value of zero sequence interference current when i (k) is sampling instant k, k is sampling instant, T _SBe the sampling period.

Write the differential equation (2) as discrete form:

Appoint the zero sequence interference voltage sampled value and the zero sequence interference current sampled value of getting 3 adjacent sampling instant k-1, k, k+1 correspondence, obtain an independent equation.

1. measure the zero sequence interference voltage earlier, measure the zero sequence interference current again, following discrete form is then arranged:

$i(k+\frac{N}{4})=C\frac{u(k+1)-u(k-1)}{{2T}_s}---\left(3\right)$

Here N is the sampling rate of zero sequence interference current and zero sequence interference voltage.Be to improve measuring accuracy, generally requiring sampling rate is 80 points/more than the cycle; The sampling instant k here is the pairing sampling instant of sampled data in zero sequence current signal and the residual voltage signal steady-state process, and is as follows.

(3) occur in the formula Being equivalent to 90 ° phase differential, is because the measurement of zero sequence interference voltage and zero sequence interference current is not carried out simultaneously, for the measurement data with both is mapped, so sampling instant adds to the zero sequence interference voltage

Zero sequence interference current and zero sequence interference voltage are all only got the stable state sampled data that each has usefulness.

Separating of equation (3) is as follows:

$C=\frac{{2T}_s\×i(k+\frac{N}{4})}{u(k+1)-u(k-1)}---\left(4\right)$

Calculate if get the stable state sampled data of the individual cycle of M (1≤M＜50), and sampling rate is N point/cycle that then sampled data points is total M * N, in these sampled datas, the span of sampling instant k is $2\&le;k<M\&times;N-\frac{N}{4};$ In the span of k, get one group of sampled data of any sampling instant k correspondence, after substitution (4) formula, calculate the zero sequence capacitor C _k, get the zero sequence capacitor C again _kMean value $\stackrel{\&OverBar;}{C}=\frac{1}{M\&times;N-\frac{N}{4}-1}\&times;\underset{k=2}{\overset{M\&times;N-\frac{N}{4}}{\mathrm{\&Sigma;}}}{C}_k;$ Then the zero sequence susceptance of test line is: B=2 π fC, f=50Hz.

The zero sequence electricity is led very little, can ignore, so the zero sequence susceptance numerically is approximately equal to the zero sequence admittance.Be that the zero sequence admittance value is 2 π fC.

2. or earlier measure the zero sequence interference current, measure the zero sequence interference voltage again, following discrete form is then arranged:

$\mathrm{ik}=C\frac{u(k+1+\frac{N}{4})-u(k-1+\frac{N}{4})}{{2T}_s}---\left(5\right)$

Here N is the sampling rate of zero sequence interference current and zero sequence interference voltage.Be to improve measuring accuracy, generally requiring sampling rate is 80 points/more than week;

(5) occur in the formula

Being equivalent to 90 ° phase differential, is because the measurement of zero sequence interference voltage and zero sequence interference current is not carried out simultaneously, for the measurement data with both is mapped, so sampling instant adds to the zero sequence interference voltage Zero sequence interference current and zero sequence interference voltage are all only got the stable state sampled data that each has usefulness;

Separating of equation (5) is as follows:

$C=\frac{{2T}_s\&times;i\left(k\right)}{u(k+1+\frac{N}{4})-u(k-1+\frac{N}{4})}---\left(6\right)$

In the zero sequence interference voltage data and the zero sequence interference current data in 1 second in the 1 useful second of being gathered, get in the steady-state process after zero sequence interference current signal and the zero sequence interference voltage signal transient state process pairing sampled data and calculate;

Calculate if get the stable state sampled data of the individual cycle of M (1≤M＜50), and sampling rate is N point/cycle that then sampled data points is total M * N, in these sampled datas, the span of sampling instant k is $1\&le;k<M\&times;N-\frac{N}{4}-1;$ In the span of k, get one group of sampled data of any sampling instant k correspondence, after substitution (6) formula, calculate the zero sequence capacitor C _k, get the zero sequence capacitor C again _kMean value $\stackrel{\&OverBar;}{C}=\frac{1}{M\&times;N-\frac{N}{4}-1}\&times;\underset{k=1}{\overset{M\&times;N-\frac{N}{4}-1}{\mathrm{\&Sigma;}}}{C}_k;$ Then the zero sequence susceptance of test line is: B=2 π fC, f=50Hz.

The zero sequence electricity is led very little, can ignore, so the zero sequence susceptance numerically is approximately equal to the zero sequence admittance.Be that the zero sequence admittance value is 2 π fC.

(3) integral equation method

The differential equation (2) the right and left integration is got integral equation (7):

${\&Integral;}_2^{t_2}\mathrm{idt}=C[u\left(t_2\right)-u\left(t_1\right)]---\left(7\right)$

With [i (k)+i (k-1)] T _s/ 2 replace respectively in the integral equations integral and

I (k-1) and i (k) are the sampled value of interior adjacent two the sampling instant zero sequence interference currents of steady-state process of current signal, and u (k-1) and u (k) are the sampled value of interior adjacent two the sampling instant zero sequence interference voltages of steady-state process of voltage signal, and k is sampling instant, T _SBe the sampling period, and T _S=t ₂-t ₁Zero sequence interference current and zero sequence interference voltage are calculated used data, get in the 1 second real useful separately sampled data, pairing sampled data is calculated in the steady-state process after zero sequence current signal and the residual voltage signal transient state process;

Write integral equation (7) as discrete form:

Appoint the zero sequence interference voltage sampled value and the zero sequence interference current sampled value of getting 3 adjacent sampling instant k-1, k, k+1 correspondence, obtain an independent equation;

1. measure the zero sequence interference voltage earlier, measure the zero sequence interference current again, following discrete form is then arranged:

$[i(k+\frac{N}{4})+i(k-1+\frac{N}{4})]T_s/2=C[u\left(k\right)-u(k-1)]---\left(8\right)$

Here N is the sampling rate of zero sequence interference current and zero sequence interference voltage.Be to improve measuring accuracy, generally requiring sampling rate is 80 points/more than the cycle;

(8) occur in the formula Being equivalent to 90 ° phase differential, is because the measurement of zero sequence interference voltage and zero sequence interference current is not carried out simultaneously, for the measurement data with both is mapped, so sampling instant adds to the zero sequence interference current

Zero sequence interference current and zero sequence interference voltage are all only got the stable state sampled data constantly that each has usefulness;

Separating of equation (8) is as follows:

$C=\frac{\frac{T_s}{2}\left[i(k+\frac{N}{4})+i(k-1+\frac{N}{4})\right]}{u\left(k\right)-u(k-1)}---\left(9\right)$

Calculate if get the stable state sampled data of the individual cycle of M (1≤M＜50), and sampling rate is N point/cycle that then sampled data points is total M * N, in these sampled datas, the span of sampling instant k is $2\&le;k<M\&times;N-\frac{N}{4};$ In the span of k, get one group of sampled data of any sampling instant k correspondence, after substitution (9) formula, calculate the zero sequence capacitor C _k, get the zero sequence capacitor C again _kMean value $\stackrel{\&OverBar;}{C}=\frac{1}{M\&times;N-\frac{N}{4}-1}\&times;\underset{k=2}{\overset{M\&times;N-\frac{N}{4}}{\mathrm{\&Sigma;}}}{C}_k,$ Then be: B=2 π fC, f=50Hz by the zero sequence susceptance of transmission line of electricity;

The zero sequence electricity is led very little, can ignore, so the zero sequence susceptance numerically is approximately equal to the zero sequence admittance.

2. or earlier measure the zero sequence interference current, measure the zero sequence interference voltage again, following discrete form is then arranged:

$[i\left(k\right)+i(k-1)]T_s/2=C[u(k+\frac{N}{4})-u(k-1+\frac{N}{4})]---\left(10\right)$

Here N is the sampling rate of zero sequence interference current and zero sequence interference voltage.Be to improve measuring accuracy, generally requiring sampling rate is 80 points/more than week;

(10) occur in the formula

Being equivalent to 90 ° phase differential, is because the measurement of zero sequence interference voltage and zero sequence interference current is not carried out simultaneously, for the measurement data with both is mapped, so sampling instant adds to the zero sequence interference voltage

Zero sequence interference current and zero sequence interference voltage are all only got the stable state sampled data constantly that each has usefulness;

Separating of equation (10) is as follows:

$C=\frac{\frac{T_s}{2}\left[i\left(k\right)+i(k-1)\right]}{u(k+\frac{N}{4})-u(k-1+\frac{N}{4})}---\left(11\right)$

In the zero sequence interference voltage data and the zero sequence interference current data in 1 second in the 1 useful second of being gathered, get in the steady-state process after zero sequence current signal and the residual voltage signal transient state process pairing sampled data and calculate;

Calculate if get the stable state sampled data of the individual cycle of M (1≤M＜50), and sampling rate is N point/cycle that then sampled data points is total M * N, in these sampled datas, the span of sampling instant k is $2\&le;k<M\&times;N-\frac{N}{4};$ In the span of k, get one group of sampled data of any sampling instant k correspondence, after substitution (11) formula, calculate the zero sequence capacitor C _k, get the zero sequence capacitor C again _kMean value $\stackrel{\&OverBar;}{C}=\frac{1}{M\&times;N-\frac{N}{4}-1}\&times;\underset{k=2}{\overset{M\&times;N-\frac{N}{4}}{\mathrm{\&Sigma;}}}{C}_k;$ Then the zero sequence susceptance of transmission line of electricity is: B=2 π fC, f=50Hz;

The zero sequence electricity is led very little, can ignore, so the zero sequence susceptance numerically is approximately equal to the zero sequence admittance.

The characteristics of the inventive method are:

Need not transmission line of electricity is added the zero sequence power supply again, but directly utilize the power frequency that the zero-sequence mutual inductance between the mutual inductance circuit causes to disturb, turn harm into good as measuring zero sequence power supply.

The present invention has the following advantages and good effect:

1. traditional measuring method, just can measure when can only all circuits in the mutual inductance circuit group having a power failure fully, and the inventive method can or have at least a circuit to be under the situation of charging operation state at the N-1 bar circuit charging operation in the N bar mutual inductance circuit group, measure the newly-built circuit in the mutual inductance circuit group or the zero sequence admittance of dead line, and do not need all line outages in the mutual inductance circuit group, thereby reduced loss of outage, improved economic benefit and social benefit;

2. but the zero sequence admittance of newly-built circuit and dead line in the inventive method live line measurement mutual inductance circuit group;

Description of drawings

When Fig. 1 measures the zero sequence admittance, the data layout synoptic diagram when measurement zero sequence interference voltage is measured the zero sequence interference current more earlier;

When Fig. 2 measures the zero sequence admittance, the data layout synoptic diagram when measurement zero sequence interference current is measured the zero sequence interference voltage more earlier.

Concrete embodiment:

(1) the zero sequence interference voltage of transmission line of electricity is measured by elder generation, measures the situation of the zero sequence interference current of transmission line of electricity again

At first with the terminal three-phase short circuit of transmission line of electricity but earth-free, head end three-phase short circuit is earth-free, since 0 second constantly, measures the zero sequence interference voltage of dead line head end, Measuring Time is 1 second; The band auxiliary switching-in that the head end on the transmission line of electricity of closing again is external and the air switch of sub-gate circuit with transmission line of electricity head end three-phase short circuit ground connection, are measured the zero sequence interference current of transmission line of electricity head end, and Measuring Time also is 1 second; After measuring process is finished, the zero sequence interference voltage data that collect and the zero sequence interference current data mode with file is deposited in the storer; Data are preserved form as shown in Figure 1, as can be seen from Figure 1, though the data acquisition time of zero sequence interference voltage and zero sequence interference current all has 2 seconds, but real separately useful data all have only 1 second, when calculating the zero sequence admittance, only get separately in 1 second useful data, pairing sampled data is calculated in the steady-state process after zero sequence current signal and the residual voltage signal transient state process.

When adopting the differential method or integral method to calculate, to calculating in the zero sequence interference current sampled value of the individual cycle of M (1≤M＜50) gathered in the steady-state process and zero sequence interference voltage sampled value substitution formula (4) or (9), and average as the final measurement of zero sequence admittance.

When adopting algebraic approach to calculate, zero sequence interference current sampled value and zero sequence interference voltage sampled value to the individual cycle of M (1≤M＜50) gathered in the steady-state process adopt the Fourier filtering algorithm to obtain the zero sequence first-harmonic interference voltage amplitude of each cycle

And phase angle theta _U, and zero sequence first-harmonic interference current amplitude And phase angle theta _I, in the substitution formula (1), calculating the zero sequence admittance of the steady state measurement data correspondence of this cycle again, the mean value of getting this M cycle again is as circuit zero sequence admittance The ultimate results.

(2) the zero sequence interference current of transmission line of electricity is measured by elder generation, measures the situation of the zero sequence interference voltage of transmission line of electricity again

At first that the terminal three-phase short circuit of transmission line of electricity is earth-free, head end three-phase short circuit ground connection since 0 second constantly, is measured the zero sequence interference current of dead line head end, and Measuring Time is 1 second; Disconnect the external band auxiliary switching-in of head end on the transmission line of electricity and the air switch of sub-gate circuit again, transmission line of electricity head end three-phase short circuit is earth-free, measure the zero sequence interference voltage of transmission line of electricity head end, Measuring Time also is 1 second; After measuring process is finished, the zero sequence interference current data that collect and the zero sequence interference voltage data mode with file is deposited in the storer; Data are preserved form as shown in Figure 2, as can be seen from Figure 2, though the data acquisition time of zero sequence interference voltage and zero sequence interference current all has 2 seconds, but real separately useful data all have only 1 second, when calculating the zero sequence admittance, only get separately in 1 second useful data, pairing sampled data is calculated in the steady-state process after zero sequence current signal and the residual voltage signal transient state process.

When adopting the differential method or integral method to calculate, to calculating in the zero sequence interference current sampled value of the individual cycle of M (1≤M＜50) gathered in the steady-state process and zero sequence interference voltage sampled value substitution formula (6) or (11), and average as the final measurement of zero sequence admittance.

When adopting algebraic approach to calculate, zero sequence interference current sampled value and zero sequence interference voltage sampled value to the individual cycle of M (1≤M＜50) gathered in the steady-state process adopt the Fourier filtering algorithm to obtain the zero sequence first-harmonic interference voltage amplitude of each cycle

And phase angle theta _U, and zero sequence first-harmonic interference current amplitude i and phase angle theta _I, in the substitution formula (1), calculating the zero sequence admittance of the steady state measurement data correspondence of this cycle again, the mean value of getting this M cycle again is as zero sequence admittance The ultimate results.

Claims (1)

1. method of utilizing the admittance of power frequency interference source live line measurement transmission line of electricity zero sequence may further comprise the steps:

(1) utilizes zero-sequence mutual inductance between the mutual inductance circuit,, obtain zero sequence interference current data and zero sequence interference voltage data on the transmission line of electricity by following (1) or (2) as measuring zero sequence power supply

(1) the zero sequence interference voltage of transmission line of electricity is measured by elder generation, measures the zero sequence interference current of transmission line of electricity again

At first with the terminal three-phase short circuit of transmission line of electricity but earth-free, head end three-phase short circuit is earth-free, measures the zero sequence interference voltage of transmission line of electricity head end, Measuring Time is 1 second; The band auxiliary switching-in that the head end on the transmission line of electricity of closing again is external and the air switch of switching winding with transmission line of electricity head end three-phase short circuit ground connection, are measured the zero sequence interference current of transmission line of electricity head end, and Measuring Time also is 1 second; After measuring process is finished, the zero sequence interference voltage data that collect and the zero sequence interference current data mode with file is deposited in the storer;

(2) the zero sequence interference current of transmission line of electricity is measured by elder generation, measures the zero sequence interference voltage of transmission line of electricity again

At first that the terminal three-phase short circuit of transmission line of electricity is earth-free, head end three-phase short circuit ground connection, the zero sequence interference current of measurement transmission line of electricity head end, Measuring Time is 1 second; Disconnect the external band auxiliary switching-in of head end on the transmission line of electricity and the air switch of switching winding again, transmission line of electricity head end three-phase short circuit is earth-free, measure the zero sequence interference voltage of transmission line of electricity head end, Measuring Time also is 1 second; After measuring process is finished, the zero sequence interference current data that collect and the zero sequence interference voltage data mode with file is deposited in the storer;

(2) after the zero sequence interference current data and zero sequence interference voltage data that obtain on the transmission line of electricity, adopt following algebraic equation method, differential equation method or integral equation method to calculate the zero sequence admittance of test line:

(1), algebraic equation method

Zero sequence admittance computing formula:

$Y=\left|\frac{\stackrel{.}{I}}{\stackrel{.}{U}}\right|\&times;[\cos ({\mathrm{\&theta;}}_I-{\mathrm{\&theta;}}_U+180)+j\sin ({\mathrm{\&theta;}}_I-{\mathrm{\&theta;}}_U+180)]---\left(A1\right)$

In the following formula, Y is the zero sequence admittance of transmission line of electricity;

Be the zero sequence first-harmonic interference current phasor on the transmission line of electricity,

Be the zero sequence first-harmonic interference voltage phasor on the transmission line of electricity;

Be the mould value of zero sequence admittance, θ _IBe zero sequence first-harmonic interference current phase angle, θ _UBe zero sequence first-harmonic interference voltage phase angle;

(2) differential equation method

A. for measuring the zero sequence interference voltage earlier, measure the situation of zero sequence interference current again:

Zero sequence CALCULATION OF CAPACITANCE formula is:

$C=\frac{2T_s\&times;i(k+\frac{N}{4})}{u(k+1)-u(k-1)}---\left(B1\right)$

(B1) in, N is the sampling rate of zero sequence interference current and zero sequence interference voltage; K is sampling instant, T _SBe the sampling period;

In the zero sequence interference voltage data and the zero sequence interference current data in 1 second in 1 second of being gathered, get in the steady-state process after zero sequence current signal and the residual voltage signal transient state process pairing sampled data and calculate;

Calculate if get the stable state sampled data of the individual cycle of M (1≤M＜50), and sampling rate is N point/cycle that then sampled data points is total M * N, in these sampled datas, the span of sampling instant k is $2\&le;k<M\&times;N-\frac{N}{4};$ In the span of k, get one group of sampled data of any sampling instant k correspondence, after substitution (B1) formula, calculate the zero sequence capacitor C _k, get the zero sequence capacitor C again _kMean value $\stackrel{\&OverBar;}{C}=\frac{1}{M\&times;N-\frac{N}{4}-1}\&times;\underset{k=2}{\overset{M\&times;N-\frac{N}{4}}{\mathrm{\&Sigma;}}}{C}_k;$ Then the zero sequence admittance of transmission line of electricity is 2 π fC, f=50Hz;

B. for measuring the zero sequence interference current earlier, measure the situation of zero sequence interference voltage again:

Zero sequence CALCULATION OF CAPACITANCE formula is:

$C=\frac{2T_s\&times;i\left(k\right)}{u(k+1+\frac{N}{4})-u(k-1+\frac{N}{4})}---\left(B2\right)$

(B2) in, N is the sampling rate of zero sequence interference current and zero sequence interference voltage; K is sampling instant, T _SBe the sampling period;

In the zero sequence interference voltage data and the zero sequence interference current data in 1 second in 1 second of being gathered, get in the steady-state process after zero sequence current signal and the residual voltage signal transient state process pairing sampled data and calculate;

Calculate if get the stable state sampled data of the individual cycle of M (1≤M＜50), and sampling rate is N point/cycle that then sampled data points is total M * N,

In these sampled datas, the span of sampling instant k is $1\&le;k<M\&times;N-\frac{N}{4}-1;$ In the span of k, get one group of sampled data of any sampling instant k correspondence, after substitution (B2) formula, calculate the zero sequence capacitor C _k, get the zero sequence capacitor C again _kMean value $\stackrel{\&OverBar;}{C}=\frac{1}{M\&times;N-\frac{N}{4}-1}\&times;\underset{k=1}{\overset{M\&times;N-\frac{N}{4}-1}{\mathrm{\&Sigma;}}}{C}_k;$ Then the zero sequence admittance of transmission line of electricity is 2 π fC, f=50Hz.

(3) integral equation method

A. for measuring the zero sequence interference voltage earlier, measure the situation of zero sequence interference current again:

Zero sequence CALCULATION OF CAPACITANCE formula is:

$C=\frac{\frac{T_s}{2}[i(k+\frac{N}{4})+i(k-1+\frac{N}{4})]}{u\left(k\right)-u(k-1)}---\left(C1\right)$

(C1) in, N is the sampling rate of zero sequence interference current and zero sequence interference voltage; K is sampling instant, T _SBe the sampling period;

In the zero sequence interference voltage data and the zero sequence interference current data in 1 second in 1 second of being gathered, get in the steady-state process after zero sequence current signal and the residual voltage signal transient state process pairing sampled data and calculate;

Calculate if get the stable state sampled data of the individual cycle of M (1≤M＜50), and sampling rate is N point/cycle that then sampled data points is total M * N, in these sampled datas, the span of sampling instant k is $2\&le;k<M\&times;N-\frac{N}{4};$ In the span of k, get one group of sampled data of any sampling instant k correspondence, after substitution (C1) formula, calculate the zero sequence capacitor C _k, get the zero sequence capacitor C again _kMean value $\stackrel{\&OverBar;}{C}=\frac{1}{M\&times;N-\frac{N}{4}-1}\&times;\underset{k=2}{\overset{M\&times;N-\frac{N}{4}}{\mathrm{\&Sigma;}}}{C}_k;$ Then the zero sequence admittance of transmission line of electricity is 2 π fC, f=50Hz;

B. for measuring the zero sequence interference current earlier, measure the situation of zero sequence interference voltage again:

Zero sequence CALCULATION OF CAPACITANCE formula is:

$C=\frac{\frac{T_s}{2}[i\left(k\right)+i(k-1)]}{u(k+\frac{N}{4})-u(k-1+\frac{N}{4})}---\left(C2\right)$

(C2) in, N is the sampling rate of zero sequence interference current and zero sequence interference voltage; K is sampling instant, T _SBe the sampling period;

In the zero sequence interference voltage data and the zero sequence interference current data in 1 second in 1 second of being gathered, get in the steady-state process after zero sequence current signal and the residual voltage signal transient state process pairing sampled data and calculate;

Calculate if get the stable state sampled data of the individual cycle of M (1≤M＜50), and sampling rate is N point/cycle that then sampled data points is total M * N, in these sampled datas, the span of sampling instant k is $2\&le;k<M\&times;N-\frac{N}{4};$ In the span of k, get one group of sampled data of any sampling instant k correspondence, after substitution (C2) formula, calculate the zero sequence capacitor C _k, get the zero sequence capacitor C again _kMean value $\stackrel{\&OverBar;}{C}=\frac{1}{M\&times;N-\frac{N}{4}-1}\&times;\underset{k=2}{\overset{M\&times;N-\frac{N}{4}}{\mathrm{\&Sigma;}}}{C}_k;$ Then the zero sequence admittance of transmission line of electricity is 2 π fC, f=50Hz.

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