CN109245057B - Time domain full-waveform protection device for power transmission line and interphase mutation direction judgment method - Google Patents
Time domain full-waveform protection device for power transmission line and interphase mutation direction judgment method Download PDFInfo
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/26—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured
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- G01R31/08—Locating faults in cables, transmission lines, or networks
- G01R31/081—Locating faults in cables, transmission lines, or networks according to type of conductors
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Abstract
The invention relates to a time domain full-waveform protection device of a power transmission line and a method for judging the direction of an interphase fault, which are used for calculating the interphase current and the interphase voltage of a sudden change by collecting a first group of interphase current instantaneous values, a second group of interphase current instantaneous values, a first group of interphase voltage instantaneous values and a second group of interphase voltage instantaneous values after a fault and before a set period, then establishing an equation set according to the constraint relation between the interphase current and the interphase voltage of the sudden change, solving the sizes of a positive sequence reactance and a positive sequence resistance, further accurately judging whether the fault is a forward fault, and solving the problems that the direction of the interphase fault cannot be accurately and reliably judged by the existing direction element and the existing direction element is unreliable in an electric power electronic power system.
Description
Technical Field
The invention belongs to the technical field of power system fault judgment, and particularly relates to a time domain full-waveform protection device of a power transmission line and an interphase mutation direction judgment method.
Background
With the development of intelligent substations, the optical current transformer technology has been widely applied, the operation is more and more stable, the optical current transformer solves the problems that many conventional electromagnetic transformers such as magnetic saturation, insulation, secondary circuit and the like cannot solve, primary current full-waveform information can be accurately and rapidly transferred in principle, and the research and development of a full-waveform protection new principle and a new technology are promoted.
The new energy power generation and the direct current transmission are applied to the power system more and more, so that the power electronization of the power system is intensified, the essential difference between the short-circuit fault characteristic and the direct current transmission alternating current side short-circuit fault characteristic in the modern power system and the fault characteristic of the traditional alternating current synchronous motor power supply system is caused, and the great challenge is brought to the normal and stable work of the traditional relay protection device. When an alternating current circuit containing new energy or a direct current drop point has a short-circuit fault, the fault characteristics of the alternating current circuit are influenced by power electronic equipment and a control system of the new energy or the direct current converter valve, so that the fault characteristics are complex and various, and the traditional direction element cannot reliably judge the fault direction and is difficult to adapt to the change of a power system.
Chinese patent No. CN102508098B discloses a fast zero-sequence direction element discrimination method for an ac/dc series-parallel power grid, which calculates sampling values of zero-sequence voltage and current according to sampling values of three-phase voltage and current at a protection installation site; establishing a time domain differential equation based on the instantaneous sampling values of zero sequence voltage and phase current; calculating zero-sequence resistance and zero-sequence inductance components by using a time domain differential equation and a least square method; converting the zero sequence resistance and zero sequence inductance components of the system into a frequency domain, and calculating power frequency zero sequence impedance; judging whether a positive or negative earth fault occurs according to the fact that the zero sequence impedance falls in a positive or negative direction action area in the area where the impedance plane is located; the method is not affected by low-frequency components and fractional harmonics and unequal positive sequence and negative sequence impedances after the fault of the alternating-current and direct-current hybrid power grid, the reliability of a calculation result is ensured, the action performance is far superior to that of the method based on a semi-cycle Fourier algorithm and various power frequency direction elements thereof, and the direction element based on zero sequence can judge that the positive direction ground fault occurs but can not locate a fault phase; when a non-ground fault of the same pole line and the other return line occurs, the fault direction element of the method is judged to be invalid, and the judgment of the method based on the zero sequence can only aim at the ground fault and is not applicable to phase-to-phase and non-ground faults.
Disclosure of Invention
The invention aims to provide a time domain full-waveform protection device of a power transmission line and a method for judging the direction of an interphase sudden change, which are used for solving the problem that the direction of an interphase fault cannot be accurately and reliably judged by the conventional zero-sequence directional element.
In order to solve the technical problems, realize a direction judgment method of a non-grounded fault and accurately position a fault phase, the invention provides a method for judging the direction of an interphase mutation of a time domain full-waveform protection device of a power transmission line, which comprises the following steps:
1) according to the sampling value information of three-phase voltage and current at the protection installation site, calculating a first group of interphase current instantaneous values of n +1 sampling points after the fault occurs and a second group of interphase current instantaneous values of each corresponding sampling point before the set period, and calculating a first group of interphase voltage instantaneous values of n sampling points after the fault occurs and a second group of interphase voltage instantaneous values of each corresponding sampling point before the set period;
2) obtaining the variable quantity phase-to-phase current of each sampling point according to the first group of phase-to-phase current instantaneous values and the second group of phase-to-phase current instantaneous values; obtaining the variable interphase voltage of each sampling point according to the first group of interphase voltage instantaneous values and the second group of interphase voltage instantaneous values;
3) establishing an n-dimensional equation set according to the constraint relation among the mutation quantity interphase current, the mutation quantity interphase voltage, the positive sequence reactance and the positive sequence resistance;
4) solving the n-dimensional equation set to obtain a positive sequence reactance and a positive sequence resistance;
5) and judging whether the positive sequence reactance and the positive sequence resistance are both smaller than zero, if so, generating forward faults at corresponding phases.
In consideration of the fact that the existing rapid direction element which is not suitable for the full-waveform distance protection technology is adopted, the method calculates the inter-phase current and the inter-phase voltage of the mutation quantity by collecting the first group of inter-phase current instantaneous values, the second group of inter-phase current instantaneous values, the first group of inter-phase voltage instantaneous values and the second group of inter-phase voltage instantaneous values after the fault and before the set period, then establishes an equation set according to the constraint relation of the calculated inter-phase current and the inter-phase voltage of the mutation quantity, solves the size of the positive sequence reactance and the positive sequence resistance, further accurately judges whether the fault is a forward fault, and solves the problems that the existing direction element cannot accurately and reliably judge the inter-phase fault direction and the existing direction element is unreliable in an electric power electronic power system.
Further, the formula of n abrupt change interphase voltages of any interphase of the n sampling points is
k is the sampling time of the first sampling point after the fault occurs, N is the period, m is the number of periods,
for a first set of phase-to-phase voltage transients,
a second set of phase-to-phase voltage transients; the formula of the n +1 mutation quantity phase current corresponding to the phases is
For a first set of phase-to-phase current transients,
a second set of phase-to-phase current transients;
the formula of the constraint relationship is as follows:
in the formula, L1、R1Respectively an equivalent positive sequence reactance and a positive sequence resistance of the positive sequence network; wherein
tsIs the sampling interval.
Further, the formula of the n-dimensional equation set is:
further, the n-dimensional equation set is solved by using a least square method in the step 4).
In order to solve the above technical problem, the present invention further provides a time-domain full-waveform protection device for a power transmission line, including a memory, a processor, and a computer program stored in the memory and operable on the processor, where the processor implements the following steps when executing the program:
1) according to the sampling value information of three-phase voltage and current at the protection installation site, calculating a first group of interphase current instantaneous values of n +1 sampling points after the fault occurs and a second group of interphase current instantaneous values of each corresponding sampling point before the set period, and calculating a first group of interphase voltage instantaneous values of n sampling points after the fault occurs and a second group of interphase voltage instantaneous values of each corresponding sampling point before the set period;
2) obtaining the variable quantity phase-to-phase current of each sampling point according to the first group of phase-to-phase current instantaneous values and the second group of phase-to-phase current instantaneous values; obtaining the variable interphase voltage of each sampling point according to the first group of interphase voltage instantaneous values and the second group of interphase voltage instantaneous values;
3) establishing an n-dimensional equation set according to the constraint relation among the mutation quantity interphase current, the mutation quantity interphase voltage, the positive sequence reactance and the positive sequence resistance;
4) solving the n-dimensional equation set to obtain a positive sequence reactance and a positive sequence resistance;
5) and judging whether the positive sequence reactance and the positive sequence resistance are both smaller than zero, if so, generating forward faults at corresponding phases.
Further, n mutation quantity phases among any one phase of the n sampling pointsThe formula of the voltage is
k is the sampling time of the first sampling point after the fault occurs, N is the period, m is the number of periods,
for a first set of phase-to-phase voltage transients,
a second set of phase-to-phase voltage transients; the formula of the n +1 mutation quantity phase current corresponding to the phases is
For a first set of phase-to-phase current transients,
a second set of phase-to-phase current transients;
the formula of the constraint relationship is as follows:
in the formula, L1、R1Respectively an equivalent positive sequence reactance and a positive sequence resistance of the positive sequence network; wherein
tsIs the sampling interval.
Further, the formula of the n-dimensional equation set is:
further, the n-dimensional equation set is solved by using a least square method in the step 4).
Drawings
Fig. 1 is a flow chart of a method for judging the direction of an interphase mutation of a power transmission line time domain full waveform protection device.
Detailed Description
The following further describes embodiments of the present invention with reference to the drawings.
The invention provides a method for judging the direction of interphase mutation of a time domain full-waveform protection device of a power transmission line, which comprises the following steps as shown in figure 1:
1) according to the sampling value information of three-phase voltage and current at the protection installation site, a first group of interphase current instantaneous values of n +1 sampling points after the fault occurs and a second group of interphase current instantaneous values of each corresponding sampling point before the set period are calculated, and a first group of interphase voltage instantaneous values of n sampling points after the fault occurs and a second group of interphase voltage instantaneous values of each corresponding sampling point before the set period are calculated. Specifically, the method comprises the following steps:
calculating to obtain the interphase voltage of the corresponding sampling point through the three-phase voltage of n sampling points after the fault occurs
Namely, a first group of interphase voltage instantaneous values, wherein the interphase voltage calculation formula takes ab phase as an example:
uab(j1)＝ua(j1)-ub(j1)
in the formula, j1K-n +1, k being the sampling instant of the first sampling point after the occurrence of the fault.
Calculating to obtain corresponding interphase voltage according to the three-phase voltages of n sampling points before m periods
Namely, a second group of interphase voltage instantaneous values, N is the period, m is the number of periods, wherein the interphase voltage calculation formula takes ab phase as an example:
uab(j1)＝ua(j1)-ub(j1)
in the formula, j1＝k、k-1...k-n+1。
Calculating to obtain the interphase current of the corresponding sampling point through the three-phase current of n +1 sampling points after the fault occurs
Namely, a first set of phase-to-phase current transients, where the phase-to-phase current calculation formula, for example ab:
iab(j2)＝ia(j2)-ib(j2)
in the formula, j2＝k、k-1...k-n。
Calculating to obtain corresponding interphase current according to the three-phase current of n +1 sampling points before m periods
I.e. a second set of phase-to-phase current transients, wherein the phase-to-phase current calculation formula, for example ab phase:
iab(j2)＝ia(j2)-ib(j2)
in the formula, j2＝k、k-1...k-n。
2) Obtaining the variable quantity phase-to-phase current of each sampling point according to the first group of phase-to-phase current instantaneous values and the second group of phase-to-phase current instantaneous values; and obtaining the variable interphase voltage of each sampling point according to the first group of interphase voltage instantaneous values and the second group of interphase voltage instantaneous values. Specifically, the method comprises the following steps:
the formula of n abrupt change interphase voltages of any interphase of the n sampling points is
k is the sampling time of the first sampling point after the fault occurs, N is the period, m is the number of periods,
for a first set of phase-to-phase voltage transients,
a second set of phase-to-phase voltage transients; corresponding n +1 protrusionsThe formula of the variable interphase current is
For a first set of phase-to-phase current transients,
a second set of phase-to-phase current transients.
3) Establishing an n-dimensional equation set according to the constraint relation among the mutation quantity interphase current, the mutation quantity interphase voltage, the positive sequence reactance and the positive sequence resistance; specifically, the constraint relationship is as follows:
L1、R1the impedance is the equivalent positive sequence reactance and the positive sequence resistance of the positive sequence network; wherein
The method can be obtained by a two-point differential algorithm formula:
if the frequency is 50Hz, the sampling rate is 1200, then tsThe sampling interval is 0.833333 ms.
The n-dimensional equation set is a binary one-time n-dimensional equation set and comprises the following steps:
by dividing L in the above formula1、R1In addition, other parameters are known.
4) And solving the n-dimensional equation set by using a least square method to obtain a positive sequence reactance and a positive sequence resistance.
5) And judging whether the positive sequence reactance and the positive sequence resistance are both smaller than zero, if so, generating interphase forward fault.
Acquiring voltage and current sampling value information of a relay protection installation position by using an optical current transformer, acquiring voltage and current sampling value information after a fault occurs at the relay protection installation position when a short-circuit fault occurs in a line, processing the voltage and current sampling value information to acquire interphase current instantaneous value information, interphase voltage instantaneous value information, an interphase current instantaneous value and an interphase voltage instantaneous value, and calculating an abrupt change interphase voltage instantaneous value and an abrupt change interphase current instantaneous value; listing differential equations according to an R-L line model by utilizing full waveform information; obtaining n differential equations by using n sampling points; solving the differential equation to obtain R1、L1Is finally based on R1And L1The fault direction is judged according to the sign of the fault signal, and the judgment of the fault direction is realized.
The method can be applied to a time-domain full-waveform protection device of the power transmission line, the device comprises a memory, a processor and a computer program which is stored in the memory and can run on the processor, and the processor realizes the judgment method when executing the program.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the claims of the present invention.
Claims (8)
1. A method for judging the direction of an interphase mutation of a time domain full-waveform protection device of a power transmission line is characterized by comprising the following steps of:
1) according to the sampling value information of three-phase voltage and current at a protection installation place, calculating a first group of interphase current instantaneous values of n +1 sampling points after a fault occurs and a second group of interphase current instantaneous values of each corresponding sampling point before a set period, calculating a first group of interphase voltage instantaneous values of n sampling points after the fault occurs and a second group of interphase voltage instantaneous values of each corresponding sampling point before the set period;
2) obtaining the variable quantity phase-to-phase current of each sampling point according to the first group of phase-to-phase current instantaneous values and the second group of phase-to-phase current instantaneous values; obtaining the variable interphase voltage of each sampling point according to the first group of interphase voltage instantaneous values and the second group of interphase voltage instantaneous values;
3) establishing an n-dimensional equation set according to the constraint relation among the mutation quantity phase current, the mutation quantity phase voltage, the positive sequence inductance and the positive sequence resistance;
4) solving the n-dimensional equation set to obtain a positive sequence inductance and a positive sequence resistance;
5) and judging whether the positive sequence inductance and the positive sequence resistance are both smaller than zero, if so, generating a positive fault between corresponding phases.
2. The method for judging the interphase mutation direction of the electric transmission line time domain full waveform protection device according to claim 1, wherein the formula of the n mutation interphase voltage of any interphase of the n sampling points is
j1k-N +1, where k is the sampling time of the first sampling point after the fault occurs, N is the period, m is the number of periods,
for a first set of phase-to-phase voltage transients,
a second set of phase-to-phase voltage transients; the formula of the n +1 mutation quantity phase current corresponding to the phases is
j2＝k、k-1...k-n，
For a first set of phase-to-phase current transients,
a second set of phase-to-phase current transients;
the formula of the constraint relationship is as follows:
in the formula, L1、R1Respectively an equivalent positive sequence inductance and a positive sequence resistance of the positive sequence network; wherein
tsIs the sampling interval.
3. The method for judging the interphase mutation direction of the power transmission line time domain full waveform protection device according to claim 2, wherein the formula of the n-dimensional equation set is as follows:
4. the method for judging the direction of the interphase mutation of the time-domain full-waveform protection device of the power transmission line according to claim 3, characterized in that the n-dimensional equation set is solved by using a least square method in the step 4).
5. A time domain full waveform protection device for a power transmission line comprises a memory, a processor and a computer program which is stored in the memory and can run on the processor, and is characterized in that the processor executes the program to realize the following steps:
1) according to the sampling value information of three-phase voltage and current at the protection installation site, calculating a first group of interphase current instantaneous values of n +1 sampling points after the fault occurs and a second group of interphase current instantaneous values of each corresponding sampling point before the set period, and calculating a first group of interphase voltage instantaneous values of n sampling points after the fault occurs and a second group of interphase voltage instantaneous values of each corresponding sampling point before the set period;
2) obtaining the variable quantity phase-to-phase current of each sampling point according to the first group of phase-to-phase current instantaneous values and the second group of phase-to-phase current instantaneous values; obtaining the variable interphase voltage of each sampling point according to the first group of interphase voltage instantaneous values and the second group of interphase voltage instantaneous values;
3) establishing an n-dimensional equation set according to the constraint relation among the mutation quantity phase current, the mutation quantity phase voltage, the positive sequence inductance and the positive sequence resistance;
4) solving the n-dimensional equation set to obtain a positive sequence inductance and a positive sequence resistance;
5) and judging whether the positive sequence inductance and the positive sequence resistance are both smaller than zero, if so, generating a positive fault between corresponding phases.
6. The time-domain full waveform protection device of the power transmission line of claim 5, wherein the formula of the n abrupt phase voltages between any two of the n sampling points is
j1k-N +1, where k is the sampling time of the first sampling point after the fault occurs, N is the period, m is the number of periods,
for a first set of phase-to-phase voltage transients,
a second set of phase-to-phase voltage transients; the formula of the n +1 mutation quantity phase current corresponding to the phases is
j2＝k、k-1...k-n，
For a first set of phase-to-phase current transients,
is a second group of phasesAn instantaneous value of current;
the formula of the constraint relationship is as follows:
in the formula, L1、R1Respectively an equivalent positive sequence inductance and a positive sequence resistance of the positive sequence network; wherein
tsIs the sampling interval.
7. The apparatus of claim 6, wherein the equation of the n-dimensional system of equations is:
8. the time-domain full waveform protection device for the power transmission line according to claim 7, wherein the n-dimensional equation set is solved by using a least square method in the step 4).
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