CN115015686A - LCC-VSC hybrid high-voltage direct-current transmission line fault distance measurement method and system - Google Patents
LCC-VSC hybrid high-voltage direct-current transmission line fault distance measurement method and system Download PDFInfo
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Abstract
The invention relates to a fault distance measurement method and system for an LCC-VSC hybrid high-voltage direct-current transmission line, and belongs to the technical field of relay protection of power systems. Acquiring an initial fault voltage signal and a current signal at a measuring end; calculating the voltage and the current of any point along the line according to the fault voltage signal and the current signal of the measuring end; calculating a voltage forward traveling wave and a voltage reverse traveling wave of any point according to the voltage and the current; respectively calculating the 5 th power of the forward traveling wave burst variable of the voltage and the 5 th power of the reverse traveling wave burst variable of the voltage; respectively calculating the superposed values of the 5 th power of the voltage forward traveling wave variable quantity and the 5 th power of the voltage reverse traveling wave variable quantity by using sliding integrals with the window length of 3, and performing product operation on the two groups of values; integrating the products in an observation time window respectively; and fault location is carried out according to the polarities of the abrupt change points of the integral values in the two observation time windows. The method does not need to calibrate the fault traveling wave head, and solves the problem that the traditional single-ended distance measurement method cannot accurately measure the distance by utilizing wave head information.
Description
Technical Field
The invention relates to a fault location method and a fault location system for an LCC-VSC hybrid high-voltage direct-current transmission line, and belongs to the technical field of relay protection of power systems.
Background
After the high-voltage direct-current transmission line breaks down, if the fault can be quickly and accurately eliminated, the operation reliability of a power system can be improved, and huge loss caused by power failure can be reduced. Therefore, after the line breaks down, if different fault characteristics can be analyzed and mastered, the fault distance can be rapidly and accurately predicted, the potential insulation hazard can be found in time, inconvenience brought by line faults can be eliminated by a user, not only can the fault line be repaired in the first time, safe and stable operation of a power grid system can be ensured, economic loss caused by the line faults can be reduced, but also physical labor of line patrol personnel can be reduced, the cost is reduced, and huge economic benefits are generated. In a high-voltage direct-current transmission system, the transmission distance is long, a communication channel is needed by adopting a double-end quantity method, data at two ends are required to be synchronous, and the action speed is slow; therefore, the fault location can be carried out by adopting a single-end method, and double-end data does not need to be synchronized. In the conventional ranging method for calculating the fault distance, basically, the traveling wave head is observed, calibrated and identified on a time axis, and if the wave head is not calibrated accurately, ranging fails.
Disclosure of Invention
The invention aims to provide a fault location method and a fault location system for an LCC-VSC hybrid high-voltage direct-current transmission line, which are used for solving the technical problems.
The technical scheme of the invention is as follows: a fault location method for an LCC-VSC hybrid high-voltage direct-current transmission line is based on a single-ended traveling wave location principle, and when a point (such as a hard fault point, a positive traveling wave superposition point and a reverse traveling wave superposition point) with discontinuous wave impedance is not met, sudden changes of voltage traveling waves obtained based on a Berilong line transmission equation are continuously changed. When a line is in fault, the traveling wave encounters a point with discontinuous wave impedance to generate refraction and reflection, the voltage traveling wave distributed in the full-line-length range is discontinuously changed, when a hard fault point is encountered, the forward voltage traveling wave and the reverse voltage traveling wave are superposed in opposite polarities, and the amplitude of the voltage traveling wave at the fault point is smaller than the amplitudes of the voltage traveling waves at other positions before and after the fault position, namely, the amplitude of the voltage traveling wave at the fault point generates negative polarity mutation; for a dual fault point, the forward voltage traveling wave and the reverse voltage traveling wave are superposed in the same polarity, so that the amplitude of the voltage traveling wave of the dual fault point is greater than the amplitudes of the voltage traveling waves at the positions before and after the dual fault point, namely, the positive polarity mutation occurs in the amplitude of the voltage traveling wave of the fault point; and the sum of the distances corresponding to the hard fault point and the dual fault point is equal to the total line length, so that the fault current traveling wave data acquired at a single end is utilized, a Bergeron line transmission line equation is applied to calculate the voltage traveling wave and the current traveling wave at any time and any position in the whole line length range, the directional traveling wave is decomposed, an integral function is constructed by utilizing the directional traveling wave, and the position of the fault point is determined according to the integral function mutation point.
The method comprises the following specific steps:
step 1: the protection method based on single-ended traveling wave ranging needs to construct a protection boundary, and when the system frequency is high, the boundary presents a larger impedance characteristic, which is equivalent to an open circuit, so that the current traveling wave cannot be detected. A traveling wave coupling box and a current transformer can be installed at the measuring point. After the fault, the voltage traveling wave generates a current signal after passing through the traveling wave coupling box, and the current transformer is utilized to measure the current signal so as to indirectly measure the voltage signal. And acquiring an initial fault voltage signal and a current signal at a measuring end.
Step 2: the Bergeron circuit model is a very accurate power transmission line model, fully considers the influence of distributed capacitance of high-voltage direct-current long-distance power transmission, and therefore the Bergeron circuit model is adopted to analyze transient characteristics. And calculating the voltage and the current at any point along the line according to the fault voltage signal and the current signal of the measuring end. The calculation formula is as follows:
wherein, Z c,s Is the line mode wave impedance, x is the length from the sending end, v s Is the linear mode wave velocity, r s Line mode resistance per unit length, Z 1 ＝r s x/4，Z 2 ＝Z c,s +Z 1 ，Z 3 ＝Z c,s -Z 1 ，Z 4 ＝Z c,s -4Z 1 ，u M,s Representing the voltage measured at a certain time at the transmitting end, i M,s Representing the current measured at the transmitting end at a certain moment.
Step 3: for the beginning, the traveling wave from the end of the transmission line to the beginning of the transmission line is defined as a forward traveling wave, and the traveling wave from the beginning of the transmission line to the end of the transmission line is defined as a backward traveling wave. And calculating the forward voltage traveling wave and the reverse voltage traveling wave at any point according to the voltage and the current, wherein the calculation formula is as follows.
Step 4: and respectively calculating the 5 th power of the forward traveling wave burst quantity of the voltage and the 5 th power of the reverse traveling wave burst quantity of the voltage.
Step 5: and respectively calculating the superposition value of the 5 th power of the voltage forward traveling wave burst quantity and the 5 th power of the voltage reverse traveling wave burst quantity by using the sliding integral with the window length of 3.
Step5.1: in order to restrain the influence of Gaussian noise on fault signals, the variation quantity of the forward traveling wave of the voltage is changed by a power h of 5 + Starting with the kth sample value of (1), every N h + The sampled value is used for obtaining a primary superposition value as the sudden change energy E of the forward voltage traveling wave + The k-th value of the voltage forward traveling wave variable quantity can be obtained, the superposed value of the 5 th power of the voltage forward traveling wave variable quantity at any time and any position in the full line length range can be obtained, and the calculation formula is as follows.
Where k is the kth sampling point and N is h each time + The number of the superposed sampling values can be selected according to the requirement.
Step5.2: variation of reverse voltage traveling wave by power of 5 h - Starting with the kth sample value of (1), every n h - The sampled value is used for obtaining a primary superposition value as the voltage reverse traveling wave sudden change energy E - The k-th value of (2) can obtain the superposition value of the voltage reverse traveling wave variation quantity of 5 th power at any time and any position in the full line length range, and the calculation formula is as follows.
Where k is the kth sampling point and N is h each time - The number of the superposed sampling values can be selected according to the requirement.
Step 6: and multiplying the two groups of values in Step5. After the products are made, respectively in the observation time window t 1 ，t 1 +l/(2v)]And [ t 1 +l/(2v)，l/v]And (4) internal integration.
The calculation formula is as follows.
In the formula, t 1 ，t 1 +l/2v。t 1 +l/2v，t 1 And + l/v are the upper limit and the lower limit of the two groups of traveling wave observation time windows respectively.
Step 7: equations (8) and (9) show that when no discontinuous points (such as hard fault points and positive and reverse traveling wave superposition points) are encountered, voltage traveling wave abrupt changes calculated based on the Bailon line transmission equation are continuously changed, and when hard fault points or dual fault points are encountered, the distribution of superposition values presenting traveling wave variation of 5 th power at any time in the full line length range is discontinuous, and negative polarity abrupt changes occur. Will [ t 1 ，t 1 +l/(2v)]And [ t 1 +l/(2v)，l/v]Integration at any time between two intervalsAs a function, when a failure occurs at a certain point at a certain time, first, the distance corresponding to the first abrupt change point of the integral function is measured. Secondly, judging the polarity of the first catastrophe point of the integral function, and if the polarity is negative, judging the fault distance x f Line length x corresponding to the point m1 . If positive, the fault distance x f Subtracting the corresponding length x from the total length l of the transmission line m1 。
The utility model provides a LCC-VSC mixes HVDC transmission line fault location system which characterized in that includes:
and the electric signal acquisition module is used for acquiring and storing data information, and a traveling wave coupling box and a current transformer are arranged at the measuring end to acquire an initial fault voltage signal and an initial fault current signal.
And the numerical value calculation module is used for calculating the superposition value of the h-th power of the forward traveling wave burst variable and the superposition value of the h-th power of the reverse traveling wave burst variable at any time and any position in the full line length range.
And the fault distance measurement module is used for constructing an integral function, integrating the two superposed values calculated by the numerical value calculation module after the product processing is carried out on the two superposed values, and carrying out fault distance measurement by using a catastrophe point of the integral function to obtain a fault distance measurement result at the exit.
The electrical signal acquisition module comprises:
and the data acquisition unit is used for acquiring analog signals output by the secondary side of the mutual inductor installed at the measuring end.
And the analog-to-digital conversion unit is used for converting the analog signals acquired by the data acquisition unit into digital signals.
And the protection starting unit is used for judging whether the digital signal is greater than a set starting threshold value or not, and if so, reading starting time and storing data.
The numerical calculation module comprises:
and the line-mode conversion unit is used for calculating the line-mode component of the voltage traveling wave at the measuring end.
And the numerical value calculating unit is used for carrying out fault distance measurement according to the polarities of the mutation points of the integral values in the two observation time windows.
The fault location module includes:
and the integral function constructing unit is used for solving the product of the superposed value of the 5 th power of the voltage forward traveling wave variable quantity and the superposed value of the 5 th power of the voltage reverse traveling wave variable quantity at any time and any position in the whole line length range, and integrating the product in a certain time window to obtain an integral function.
And the distance measuring unit is used for measuring the distance of the first catastrophe point of the integral function relative to the head end of the line.
And the polarity judging unit is used for judging whether the polarity of the first mutation point of the integral function is positive or negative.
The invention has the beneficial effects that:
1. compared with a distance measurement method based on the fault analysis method principle, the distance measurement method based on the traveling wave method has the advantage that the distance measurement precision is higher by utilizing the traveling wave method distance measurement principle.
2. The invention carries out fault location on the high-voltage direct-current transmission line, adopts single-ended traveling wave location, and has no data synchronization problem.
3. The invention has smaller distance measurement error, can greatly reduce the cost of manual line patrol and has better economic benefit.
4. The method does not need to calibrate the fault traveling wave head, and overcomes the problem that the traditional single-ended distance measurement method is inaccurate in distance measurement by utilizing wave head information.
Drawings
FIG. 1 is a simulation model topology of the present invention;
FIG. 2 is a schematic diagram of an equivalent model of a Bergeron line according to the present invention;
FIG. 3 is a system block diagram of embodiment 1 of the present invention;
FIG. 4 is a graph showing the results of the first half time window integration function in example 1 of the present invention;
FIG. 5 is a graph showing the integration function result of the second half time window in example 1 of the present invention;
FIG. 6 is a graph showing the result of the first half time window integration function in example 2 of the present invention
FIG. 7 is a graph of the integration function result of the second half time window in example 2 of the present invention.
Detailed Description
The invention is further described with reference to the following drawings and detailed description.
Example 1: the LCC-VSC simulation model system is shown in figure 1, the whole line length of the line is 1500km, and the voltage level is +/-800 kV. The fault is set to occur at 600km of the line, the fault type is set to be a positive electrode grounding permanent fault, the transition resistance is set to be 0.01 omega, and the sampling rate is 1 MHz.
The method comprises the following specific steps:
step 1: acquiring an initial fault voltage signal and a current signal at a measuring end;
step 2: the distributed parameter characteristics in the high-voltage direct-current remote power transmission system are obvious, the charging current generated by the distributed capacitors in the line cannot be ignored, and the Berilon line model is a very accurate power transmission line model and fully considers the influence of the distributed capacitors, so that the Berilon line model is adopted to analyze the transient characteristics. The power transmission line is equivalent to a Bailon line model, and an equivalent diagram is shown in the attached figure 2.
The distance measurement process based on the high-voltage direct-current transmission line fault distance measurement method provided by the invention comprises the following specific steps: and calculating the voltage and the current at any position at any time in the whole line length range, wherein the calculation formula is as follows:
wherein Z is c,s Is the line mode wave impedance, x is the length from the sending end, v s Is the linear mode wave velocity, r s Line mode resistance per unit length, Z 1 ＝r s x/4，Z 2 ＝Z c,s +Z 1 ，Z 3 ＝Z c,s -Z 1 ，Z 4 ＝Z c,s -4Z 1 ，u M,s Representing the voltage measured at a certain moment at the transmitting end, i M,s Representing the current measured at the transmitting end at a certain moment.
Step 3: for the beginning, the traveling wave from the end of the transmission line to the beginning of the transmission line is defined as a forward traveling wave, and the traveling wave from the beginning of the transmission line to the end of the transmission line is defined as a backward traveling wave. Calculating the forward traveling wave and the reverse traveling wave of the voltage at any point according to the voltage and the current, wherein the calculation formula is as follows;
step 4: in order to amplify the fault characteristics of the voltage forward traveling wave and the voltage backward traveling wave and highlight the mutation quantity of a fault point, a first-order linear differential equation is utilized to respectively calculate the voltage forward traveling wave variation quantity and the voltage backward traveling wave variation quantity, in order to further highlight the variation quantity of a fault signal, restrain the point with smaller variation quantity and eliminate the influence of a small mutation point, the 5 th power of the voltage forward traveling wave variation quantity and the 5 th power of the voltage backward traveling wave variation quantity are calculated, and the odd power is taken to ensure that the original polarities of the calculated voltage forward traveling wave and the voltage backward traveling wave mutation point are kept.
Step 5: in order to inhibit the influence of Gaussian noise on fault signals, the variation quantity of forward traveling waves of the voltage is changed by a power of 5 h + Starting with the kth sample value of (1), every N h + The sampled value is used for obtaining a primary superposition value as the sudden change energy E of the forward voltage traveling wave + The k value of the voltage forward traveling wave can be obtained, the superposed value of the 5 th power of the voltage forward traveling wave variation at any time and any position in the full line length range can be obtained, and the calculation formula is as follows;
where k is the kth sampling point and N is h each time + The number of the superposed sampling values can be selected according to the requirement.
Variation of reverse voltage traveling wave by power of 5 h - Starting with the kth sample value of (1), every n h - The sampled value is used for obtaining a primary superposition value as the voltage reverse traveling wave sudden change energy E - The k-th value of the voltage reverse traveling wave variable quantity can obtain a superposed value of the 5 th power of the voltage reverse traveling wave variable quantity at any time and any position in the full line length range, and the calculation formula is as follows;
where k is the kth sampling point and N is h each time - The number of the superposed sampling values can be selected according to the requirement.
Step 6: the product of the superposition value of the 5 th power of the voltage forward traveling wave variable quantity and the superposition value of the 5 th power of the voltage reverse traveling wave variable quantity at any time and any position in the whole line length range is obtained, and the product is integrated in a certain time window, wherein the calculation formula is as follows;
in the formula, t 1 ，t 1 +l/2v；t 1 +l/2v，t 1 And + l/v are the upper limit and the lower limit of the two groups of traveling wave observation time windows respectively. In the present embodiment, t 1 The moment when the initial traveling wave of the fault reaches the measurement end, t 1 And + l/v is the time corresponding to the l/v time window length after the fault initial traveling wave reaches the measurement end.
Step 7: because the voltage traveling wave mutation calculated by the Bailon line transmission equation is continuously changed, when a hard fault point or a dual fault point is met, the distribution of the superposition value of the traveling wave variation h power at any time in the full line length range is discontinuous, namely, a mutation point occurs. Will [ t 1 ，t 1 +l/(2v)]And [ t 1 +l/(2v)，l/v]The integral at any time in the two integration intervals is taken as a function, and the distribution results of the integral function are shown in fig. 4 and fig. 5. Firstly, measuring the distance corresponding to a first mutation point of an integral function to be 600 km; secondly, judging whether the polarity of the first catastrophe point of the integral function is negative or not, and if so, judging the fault distance x f Line length x corresponding to the point m1 (ii) a If not, the fault distance x f Subtracting the corresponding length x from the total length l of the transmission line m1 . In this embodiment, the polarity of the first discontinuity is negative, and the fault distance x f The corresponding line length is 600 km.
Fig. 3 is a functional block diagram of a fault location system of an LCC-VSC hybrid high-voltage direct-current transmission line provided by the present invention, which includes:
the electric signal acquisition module is used for acquiring and storing data information, and a traveling wave coupling box and a current transformer are arranged at a measuring end to acquire an initial fault voltage signal and a current signal;
the numerical value calculation module is used for calculating the superposition value of the h-th power of the forward traveling wave burst variable and the superposition value of the h-th power of the reverse traveling wave burst variable at any time and any position in the full line length range;
and the fault distance measurement module is used for constructing an integral function, integrating the two superposed values calculated by the numerical value calculation module after the product processing is carried out on the two superposed values, and carrying out fault distance measurement by using a catastrophe point of the integral function to obtain a fault distance measurement result at the exit.
The electrical signal acquisition module specifically includes:
the data acquisition unit is used for acquiring analog signals output by the secondary side of a mutual inductor installed at the measuring end;
the analog-to-digital conversion unit is used for converting the analog signals acquired by the data acquisition unit into digital signals;
and the protection starting unit is used for judging whether the digital signal is greater than a set starting threshold value or not, and if so, reading starting time and storing data.
The numerical calculation module specifically comprises:
the line-mode conversion unit is used for calculating the line-mode component of the voltage traveling wave at the measuring end;
the numerical value calculating unit is used for firstly acquiring an initial fault voltage signal and a current signal at a measuring end and calculating the voltage and the current of any point along the line according to the fault voltage signal and the current signal of the measuring end; secondly, calculating a voltage forward traveling wave and a voltage reverse traveling wave of any point according to the voltage and the current; thirdly, respectively calculating the 5 th power of the forward traveling wave burst variable of the voltage and the 5 th power of the reverse traveling wave burst variable of the voltage; finally, respectively calculating the 5 th power of the voltage forward traveling wave variable quantity and the 5 th power of the voltage backward traveling wave variable quantity by utilizing sliding integrals with the window length of 3, and multiplying the two groups of values; the above products are respectively observed in the observation time window t 1 ，t 1 +l/(2v)]And [ t 1 +l/(2v)，l/v]Internal integration; and fault location is carried out according to the polarities of the abrupt change points of the integral values in the two observation time windows.
The fault location module specifically comprises:
the integral function constructing unit is used for solving the product of the superposed value of the 5 th power of the voltage forward traveling wave variable quantity and the superposed value of the 5 th power of the voltage reverse traveling wave variable quantity at any time and any position in the whole line length range, and integrating the product in a certain time window to obtain an integral function;
and the distance measuring unit is used for measuring the distance of the first catastrophe point of the integral function relative to the head end of the line. The distance was found to be 600 km.
And the polarity judging unit is used for judging the polarity of the first catastrophe point of the integral function to obtain that the polarity is negative.
Thus, the fault distance x is obtained f The reference value is 600 km.
Example 2: the LCC-VSC simulation model system is shown in figure 1, the whole line length of the line is 1500km, and the voltage level is +/-800 kV. The fault is set to occur at 100km of the line, the fault type is set to be a positive electrode grounding permanent fault, the transition resistance is set to be 0.01 omega, and the sampling rate is 1 MHz. The method comprises the following specific steps:
step 1: in a transmitting end and a receiving end in a high-voltage direct-current transmission system, a boundary formed by a smoothing reactor and a direct-current filter is generally arranged, and when the system frequency is high, the boundary can present a relatively large impedance characteristic, namely, an open circuit, and a current traveling wave can not be detected. For high-frequency signals, the transmission and transformation capacity of a voltage transformer is poor, and the voltage transformer is not generally used for measuring voltage signals, so that a traveling wave coupling box is arranged at a measuring point, a fault voltage traveling wave can generate a current traveling wave after passing through the traveling wave coupling box, and then the current transformer is used for measuring the current signals, so that the voltage signals are indirectly measured. And acquiring an initial fault voltage signal and a current signal at a measuring end.
Step 2: the high-voltage direct-current transmission system is long in transmission line, electromagnetic coupling exists between the positive pole and the negative pole of the transmission line, therefore, fault voltage traveling waves need to be decoupled, positive and negative voltages are decoupled into independent line mode components and zero mode components, zero mode electric quantity is seriously attenuated in the transmission process, the zero mode electric quantity only exists in the condition of ground faults, the line mode electric quantity not only exists in the ground faults but also exists in interpolar faults, and therefore the high-voltage direct-current transmission system is more suitable for analysis of different fault types by utilizing line modulus. And decoupling the fault voltage traveling wave to obtain the line mode voltage traveling waves of the transmitting end and the receiving end.
The distributed parameter characteristics in the high-voltage direct-current long-distance power transmission system are obvious, the charging current generated by distributed capacitors in a circuit cannot be ignored, and the Berilon circuit model is a very accurate power transmission line model and fully considers the influence of the distributed capacitors, so that the Berilon circuit model is adopted to analyze the transient characteristics. The electrical transmission line is equivalent by using a Bailon line model, and an equivalent diagram is shown in the attached figure 2. And calculating the voltage and the current at any position at any time within the full line length range, wherein the calculation formula is as follows:
wherein Z is c,s Is the line mode wave impedance, x is the length from the sending end, v s Is the linear mode wave velocity, r s Line mode resistance per unit length, Z 1 ＝r s x/4，Z 2 ＝Z c,s +Z 1 ，Z 3 ＝Z c,s -Z 1 ，Z 4 ＝Z c,s -4Z 1 ，u M,s Representing the voltage measured at a certain moment at the transmitting end, i M,s Representing the current measured at the transmitting end at a certain time.
Step 3: for the beginning, the traveling wave from the end of the transmission line to the beginning of the transmission line is defined as a forward traveling wave, and the traveling wave from the beginning of the transmission line to the end of the transmission line is defined as a backward traveling wave. Calculating the forward traveling wave and the reverse traveling wave of the voltage at any point according to the voltage and the current, wherein the calculation formula is as follows;
step 4: in order to amplify the fault characteristics of the voltage forward traveling wave and the voltage backward traveling wave and highlight the mutation quantity of a fault point, a first-order linear differential equation is utilized to respectively calculate the voltage forward traveling wave variation quantity and the voltage backward traveling wave variation quantity, in order to further highlight the variation quantity of a fault signal, restrain the point with smaller variation quantity and eliminate the influence of a small mutation point, the 5 th power of the voltage forward traveling wave variation quantity and the 5 th power of the voltage backward traveling wave variation quantity are calculated, and the odd power is taken to ensure that the original polarities of the calculated voltage forward traveling wave and the voltage backward traveling wave mutation point are kept.
Step 5: in order to restrain the influence of Gaussian noise on fault signals, the variation quantity of the forward traveling wave of the voltage is changed by a power h of 5 + Every N h samples, starting with the kth sample value + The sampled value is used for obtaining a primary superposition value as the sudden change energy E of the forward voltage traveling wave + The k value of the voltage forward traveling wave can be obtained, the superposed value of the 5 th power of the voltage forward traveling wave variation at any time and any position in the full line length range can be obtained, and the calculation formula is as follows;
wherein k is the kth sampling point, and N is h each time + The number of the superposed sampling values can be selected according to the requirement.
Variation of reverse voltage traveling wave by power of 5 h - Starting with the kth sample value of (1), every n h - The sampled value is added to obtain a primary superposition value as the voltage reverse traveling wave sudden change energy E - The k value of the voltage reversal traveling wave can obtain the superposed value of the 5 th power of the voltage reversal traveling wave variation at any time and any position in the full line length range, and the calculation formula is as follows;
where k is the kth sampling point and N is h each time - The number of the superposed sampling values can be selected according to the requirement.
Step 6: the product of the superposition value of the 5 th power of the voltage forward traveling wave variable quantity and the superposition value of the 5 th power of the voltage reverse traveling wave variable quantity at any time and any position in the whole line length range is obtained, and the product is integrated in a certain time window, wherein the calculation formula is as follows;
in the formula, t 1 ，t 1 +l/2v；t 1 +l/2v，t 1 And + l/v are the upper limit and the lower limit of the two groups of traveling wave observation time windows respectively. In the present embodiment, t 1 The moment when the initial traveling wave of the fault reaches the measuring end, t 1 And + l/v is the time corresponding to the l/v time window length after the fault initial traveling wave reaches the measurement end.
Step 7: because the voltage traveling wave mutation calculated by the Bailon line transmission equation is continuously changed, when a hard fault point or a dual fault point is met, the distribution of the superposition value presenting the traveling wave variation of 5 th power at any time in the full line length range is discontinuous, namely, the mutation point occurs. Taking the integral of any position at any time in the whole line length range as a function, wherein the distribution result of the integral function is shown in fig. 6 and 7, firstly, measuring the distance corresponding to the first break point of the integral function as 100 km; secondly, judging whether the polarity of the first catastrophe point of the integral function is negative or not, and if so, judging the fault distance x f Line length x corresponding to the point m1 (ii) a If not, the fault distance x f Subtracting the corresponding length x from the total length l of the transmission line m1 . In this embodiment, if the polarity of the first abrupt change point is negative, the fault distance x f For the corresponding line length of this point, i.e. 100km, the fault distance is 100 km.
The LCC-VSC hybrid HVDC transmission line fault location system of this embodiment includes:
the electric signal acquisition module is used for acquiring and storing data information, and a traveling wave coupling box and a current transformer are arranged at the measuring end to acquire an initial fault voltage signal and a current signal;
the numerical value calculation module is used for calculating the superposition value of the h-th power of the forward traveling wave mutation quantity and the superposition value of the h-th power of the reverse traveling wave mutation quantity at any time and any position in the full line length range;
and the fault distance measurement module is used for constructing an integral function, integrating the two superposed values calculated by the numerical value calculation module after the product processing is carried out on the two superposed values, and carrying out fault distance measurement by using a catastrophe point of the integral function to obtain a fault distance measurement result at the exit.
The electrical signal acquisition module specifically includes:
the data acquisition unit is used for acquiring analog signals output by the secondary side of a mutual inductor installed at the measuring end;
the analog-to-digital conversion unit is used for converting the analog signals acquired by the data acquisition unit into digital signals;
and the protection starting unit is used for judging whether the digital signal is greater than a set starting threshold value or not, and if so, reading starting time and storing data.
The numerical calculation module specifically comprises:
the line-mode conversion unit is used for calculating a line-mode component of the voltage traveling wave at the measurement end;
and the numerical value calculating unit is used for carrying out fault distance measurement according to the polarities of the mutation points of the integral values in the two observation time windows.
The fault location module specifically comprises:
the integral function constructing unit is used for solving the product of the superposition value of the 5 th power of the voltage forward traveling wave variable quantity and the superposition value of the 5 th power of the voltage reverse traveling wave variable quantity at any time and any position in the whole line length range, and integrating the product in a certain time window to obtain an integral function;
and the distance measuring unit is used for measuring the distance between the first catastrophe point of the integral function and the head end of the line to obtain the distance of 100 km.
And the polarity judging unit is used for judging the polarity of the first mutation point of the integral function to obtain that the polarity is negative.
Thus, the fault distance x is obtained f For the corresponding line length of this point, i.e. 100km, the fault distance is 100 km.
While the present invention has been described in detail with reference to the embodiments shown in the drawings, the present invention is not limited to the embodiments, and various changes can be made without departing from the spirit and scope of the present invention.
Claims (10)
1. A fault location method for an LCC-VSC hybrid high-voltage direct-current transmission line is characterized by comprising the following steps:
step 1: acquiring an initial fault voltage signal and a current signal at a measuring end;
step 2: calculating the voltage and the current of any point along the line according to the fault voltage signal and the current signal of the measuring end;
step 3: calculating a voltage forward traveling wave and a voltage reverse traveling wave of any point according to the voltage and the current;
step 4: respectively calculating the 5 th power of the forward traveling wave burst variable of the voltage and the 5 th power of the reverse traveling wave burst variable of the voltage;
step 5: respectively calculating the superposition value of the 5 th power of the voltage forward traveling wave burst variable and the 5 th power of the voltage reverse traveling wave burst variable by using the sliding integral with the window length of 3;
step 6: the two groups of values in Step5 are multiplied and then are respectively observed in the time window t 1 ，t 1 +l/(2v)]And [ t 1 +l/(2v)，l/v]Internal integration;
step 7: and fault location is carried out according to the polarities of the abrupt change points of the integral value in the two observation time windows.
2. The LCC-VSC hybrid HVDC transmission line fault location method of claim 1, wherein the voltage forward traveling wave and the voltage reverse traveling wave in Step3 are:
in the formula, Z c,s Is the line mode wave impedance, u x,s To measure the voltage at the transmitting end at a certain moment, i x,s u x,s Is the current measured at a certain time at the transmitting end.
3. The LCC-VSC hybrid HVDC transmission line fault location method of claim 1, wherein the 5 th power of the voltage forward traveling wave burst quantity and the 5 th power of the voltage reverse traveling wave burst quantity in Step4 are:
4. the LCC-VSC hybrid high-voltage direct current transmission line fault location method according to claim 1, characterized in that Step5 specifically is:
step5.1: from voltage forward traveling wave variation by power of 5 h + Starting with the kth sample value of (1), every N h + The sampling value of the voltage converter is used for obtaining a primary superposition value as a voltage forward traveling waveMutation energy E + The sum of the 5 th power of the voltage forward traveling wave variation at any time and any position in the full line length range can be obtained as follows:
where k is the kth sampling point and N is h each time + The number of the superposed sampling values;
step5.2: variation of reverse voltage traveling wave by power of 5 h - Starting with the kth sample value of (1), every n h - The sampled value is used for obtaining a primary superposition value as the voltage reverse traveling wave sudden change energy E - The k-th value of (2) can obtain the superposition value of the voltage reverse traveling wave variation quantity of 5 th power at any time and any position in the full line length range, and the superposition value is as follows:
wherein k is the kth sampling point, and N is h each time - The number of samples superimposed.
5. The LCC-VSC hybrid high-voltage direct current transmission line fault location method according to claim 1, characterized in that Step6 specifically is:
in the formula, t 1 ，t 1 +l/2v；t 1 +l/2v，t 1 And + l/v are the upper limit and the lower limit of the two groups of traveling wave observation time windows respectively.
6. The LCC-VSC hybrid high-voltage direct current transmission line fault location method according to claim 1, characterized in that Step7 specifically is: will [ t 1 ，t 1 +l/(2v)]And [ t 1 +l/(2v)，l/v]The integral of any time between two intervals is used as a function, when a certain point has a fault at a certain time, firstly, the distance corresponding to the first mutation point of the integral function is measured; secondly, judging the polarity of a first catastrophe point of the integral function;
if negative, the fault distance x f Line length x corresponding to the point m1 ；
If positive, the fault distance x f The total length l of the transmission line is subtracted by the corresponding length x m1 。
7. The utility model provides a LCC-VSC mixes HVDC transmission line fault location system which characterized in that includes:
the electric signal acquisition module is used for acquiring and storing data information, and a traveling wave coupling box and a current transformer are arranged at a measuring end to acquire an initial fault voltage signal and a current signal;
the numerical value calculation module is used for calculating the superposition value of the h-th power of the forward traveling wave burst variable and the superposition value of the h-th power of the reverse traveling wave burst variable at any time and any position in the full line length range;
and the fault distance measurement module is used for constructing an integral function, integrating the two superposed values calculated by the numerical value calculation module after the product processing is carried out on the two superposed values, and carrying out fault distance measurement by using a catastrophe point of the integral function to obtain a fault distance measurement result at the exit.
8. The LCC-VSC hybrid HVDC transmission line fault location system of claim 7, wherein the electrical signal acquisition module comprises:
the data acquisition unit is used for acquiring analog signals output by the secondary side of a mutual inductor installed at the measuring end;
the analog-to-digital conversion unit is used for converting the analog signals acquired by the data acquisition unit into digital signals;
and the protection starting unit is used for judging whether the digital signal is greater than a set starting threshold value or not, and if so, reading starting time and storing data.
9. The LCC-VSC hybrid HVDC transmission line fault location system of claim 7, wherein the numerical calculation module comprises:
the line-mode conversion unit is used for calculating a line-mode component of the voltage traveling wave at the measurement end;
and the numerical value calculating unit is used for carrying out fault distance measurement according to the polarities of the integral value catastrophe points in the two observation time windows.
10. The LCC-VSC hybrid HVDC line fault location system of claim 7, wherein the fault location module comprises:
the integral function constructing unit is used for solving the product of the superposition value of the 5 th power of the voltage forward traveling wave variable quantity and the superposition value of the 5 th power of the voltage reverse traveling wave variable quantity at any time and any position in the whole line length range, and integrating the product in a certain time window to obtain an integral function;
and the distance measuring unit is used for measuring the distance of the first catastrophe point of the integral function relative to the head end of the line.
And the polarity judging unit is used for judging whether the polarity of the first mutation point of the integral function is positive or negative.
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Cited By (3)
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| CN117192292A (en) * | 2023-11-07 | 2023-12-08 | 昆明理工大学 | Lightning grounding electrode line fault distance measurement method and system |
| CN117434389A (en) * | 2023-12-20 | 2024-01-23 | 昆明理工大学 | Line fault detection method, system, equipment and computer readable storage medium |
| CN117805555A (en) * | 2024-02-28 | 2024-04-02 | 昆明理工大学 | Two-way deduction four-terminal flexible direct current transmission line fault location method and system |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN117192292A (en) * | 2023-11-07 | 2023-12-08 | 昆明理工大学 | Lightning grounding electrode line fault distance measurement method and system |
| CN117192292B (en) * | 2023-11-07 | 2024-02-06 | 昆明理工大学 | Lightning grounding electrode line fault distance measurement method and system |
| CN117434389A (en) * | 2023-12-20 | 2024-01-23 | 昆明理工大学 | Line fault detection method, system, equipment and computer readable storage medium |
| CN117434389B (en) * | 2023-12-20 | 2024-04-09 | 昆明理工大学 | Line fault detection method, system, equipment and computer readable storage medium |
| CN117805555A (en) * | 2024-02-28 | 2024-04-02 | 昆明理工大学 | Two-way deduction four-terminal flexible direct current transmission line fault location method and system |
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