CN115047284A - Fault distance measuring method and system for high-voltage direct-current transmission line - Google Patents

Fault distance measuring method and system for high-voltage direct-current transmission line Download PDF

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CN115047284A
CN115047284A CN202210096565.9A CN202210096565A CN115047284A CN 115047284 A CN115047284 A CN 115047284A CN 202210096565 A CN202210096565 A CN 202210096565A CN 115047284 A CN115047284 A CN 115047284A
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traveling wave
voltage
fault
power
line
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束洪春
代月
董俊
田鑫萃
韩一鸣
安娜
唐玉涛
杨竞及
蒋晓涵
赵红芳
雷顺广
邓亚琪
王广雪
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Kunming University of Science and Technology
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/08—Locating faults in cables, transmission lines, or networks
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • 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
    • G01R31/085—Locating faults in cables, transmission lines, or networks according to type of conductors in power transmission or distribution lines, e.g. overhead
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/08—Locating faults in cables, transmission lines, or networks
    • G01R31/088—Aspects of digital computing
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y04—INFORMATION OR COMMUNICATION TECHNOLOGIES HAVING AN IMPACT ON OTHER TECHNOLOGY AREAS
    • Y04S—SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS
    • Y04S10/00—Systems supporting electrical power generation, transmission or distribution
    • Y04S10/50—Systems or methods supporting the power network operation or management, involving a certain degree of interaction with the load-side end user applications
    • Y04S10/52—Outage or fault management, e.g. fault detection or location

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Abstract

The invention relates to a fault distance measurement method and system for a high-voltage direct-current transmission line, and belongs to the technical field of relay protection of power systems. The method utilizes fault voltage traveling wave data acquired at a single end, applies a Berilong line transmission line equation to calculate voltage traveling waves and current traveling waves at any position at any time in the full line length range, carries out directional traveling wave decomposition, constructs an integral function by utilizing the directional traveling waves, and determines the position of a fault point according to the mutation point of the integral function. The invention aims at fault location of the high-voltage direct-current transmission line, only single-ended data is needed, and the problem of data synchronization does not exist. Compared with a distance measurement method based on a fault analysis method principle, the distance measurement method is higher in distance measurement precision. The fault traveling wave head is not required to be calibrated, and the problem that the traditional single-ended distance measurement method is inaccurate in distance measurement by utilizing wave head information is solved.

Description

Fault distance measuring method and system for high-voltage direct-current transmission line
Technical Field
The invention relates to a fault location method and a fault location system for a high-voltage direct-current transmission line, and belongs to the field of relay protection of power systems.
Background
In order to meet the power transmission requirement of long distance and large capacity, an overhead line is used as a trend of direct current power transmission, but compared with a cable line, the overhead line is easier to fail, the damping of a direct current system is smaller than that of an alternating current system, the probability of failure is higher, and a power transmission line is very important in the whole power transmission system. Therefore, after the transmission line breaks down, the fault point must be accurately and quickly found, and the subsequent line emergency repair work and the power supply of the recovery system are guaranteed, so that the stability and the economy of the operation of the transmission system are improved. The fault location method comprises a single-ended quantity method and a double-ended quantity method according to the required information source, and comprises a fault analysis method and a traveling wave method according to the location principle, wherein in the high-voltage direct-current transmission system, the transmission distance is longer, and if the double-ended method is utilized, double-ended data are difficult to synchronize; if a fault analysis method is used, the attenuation of the fault transient process in the long-distance power transmission line is serious. Therefore, if the distance measurement is carried out based on the single-ended traveling wave, the problems that double-ended data needs to be synchronized and fault information is lost are solved. Most of the previous distance measurement methods are based on traveling wave time domain characteristics, observation, calibration and identification are carried out on traveling wave heads on a time axis so as to realize calculation of fault distance, and if the wave heads are not accurately calibrated, the distance measurement fails, and the reliability of a power transmission system cannot be ensured.
Disclosure of Invention
The invention aims to solve the technical problem of providing a fault location method and a fault location system for a high-voltage direct-current transmission line, and aims to solve the problem of limitation of inaccurate location due to incorrect calibration of a traveling wave head in the traditional location method.
The technical scheme of the invention is as follows: a high-voltage direct-current transmission line fault location method is based on a single-ended traveling wave location principle, when a line has a fault, a traveling wave encounters a point with discontinuous wave impedance to be refracted and reflected, voltage traveling waves distributed in the whole line length range are discontinuously changed, for the fault point, a forward voltage traveling wave and a reverse voltage traveling wave are superposed in opposite polarities, the amplitude of the voltage traveling wave of the fault point is smaller than the amplitudes of the voltage traveling waves at other positions before and after the fault point, namely the amplitude of the voltage traveling wave of the fault point is changed, and the polarity is negative; 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 amplitude of the voltage traveling wave at the fault point is changed and the polarity is positive; and the sum of the distances between the fault point and the dual fault point is equal to the total length of the line, so that the fault voltage 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 position in the whole line length range at any moment, 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: and collecting fault signals of a transmitting end and a receiving end of the high-voltage direct-current transmission line. Because the transmitting end and the receiving end of the high-voltage direct-current transmission system are generally provided with boundaries formed by a smoothing reactor and a direct-current filter, when the frequency is higher, the boundaries have larger impedance characteristics and are equivalent to open circuits, so that the current traveling wave cannot be measured, the capacity of a voltage transformer for transmitting a high-frequency signal is poorer, the voltage transformer is generally not used for measuring the voltage traveling wave, but a traveling wave coupling box is arranged at a measuring point, the fault voltage traveling wave generates a current signal after passing through the traveling wave coupling box, and the current transformer is used for measuring the current signal so as to indirectly measure the voltage signal.
In actual engineering, voltage traveling wave information can be acquired only through the traveling wave coupling box, and the acquired voltage traveling wave information is secondary side information.
Step 2: and acquiring the voltage and the current of any position at any time in the whole line length range based on the fault signal, wherein the any position at any time refers to each position at each time.
The method specifically comprises the following steps:
step2.1: and decoupling the fault voltage traveling wave signal to obtain line mode traveling waves of a transmitting end and a receiving end. Because the transmission line in the high-voltage direct-current transmission system is long, and electromagnetic coupling exists between the positive pole and the negative pole of the transmission line, the traveling wave of the fault voltage needs to be decoupled, so that the positive voltage and the negative voltage need to be decoupled into independent line mode components and zero mode components, and because the zero mode electric quantity is seriously attenuated in the propagation process, and only exists in the case of the ground fault, but also exists in the inter-pole fault, the line mode electric quantity is more suitable for the analysis of different fault types by utilizing the line modulus.
Step2.2: in the high-voltage direct-current transmission system, the transmission line is long, the influence of distributed capacitance current must be considered, and the Bergeron transmission line model is a line model adopting distributed parameters and takes the influence of distributed capacitance into consideration, so that the transient characteristics are analyzed by adopting the Bergeron transmission line model.
In an alternating current system, a capacitor voltage transformer cannot effectively transmit a broadband voltage traveling wave signal, so that a secondary side transient voltage traveling wave transmitted by the capacitor voltage transformer cannot be directly adopted as a voltage traveling wave signal in the alternating current system, but a current traveling wave transmitted by a secondary side of an adjacent healthy line electromagnetic voltage transformer is adopted, and a bus voltage traveling wave on the same side is obtained through calculation by combining the wave impedance value of an overhead line, namely:
u M,s ＝i k,s Z c,s (1)
in the formula i k,s Is the line mode current traveling wave at the k measurement end of the healthy line.
In an alternating current system, the calculation formula of voltage and current in the whole line length range is as follows:
Figure BDA0003491019170000021
Figure BDA0003491019170000022
Figure BDA0003491019170000031
in the formula, 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 i k,s The line mode current traveling wave at the k measuring end of the healthy line at a certain moment. I 1 M,s Representing the current measured at the transmitting end at a certain time.
In a direct current transmission system, only a single transmission line exists, no adjacent sound line exists, that is, equation (1) does not exist, voltage traveling wave is directly detected by a direct current traveling wave coupling device, a physical boundary formed by a smoothing reactor exists in the direct current system, the smoothing reactor has the characteristics of passing low frequency and blocking high frequency, and the boundary corresponds to open circuit for high frequency fault current traveling wave, so that a measuring point can only detect the instantaneous value of the current traveling wave, that is, only i exists M,s (t) without the presence of i M,s (t+x/v s ) And i M,s (t-x/v s ) Therefore, in the dc system, the voltage and current at any position at any time within the whole line range are calculated by the following formula:
Figure BDA0003491019170000032
Figure BDA0003491019170000033
in the formula, 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, 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: and acquiring the voltage forward traveling wave and the voltage reverse traveling wave at any time and any position in the full line length range by using the voltage and the current at any time and any position in the full line length range.
Figure BDA0003491019170000034
Figure BDA0003491019170000035
The voltage forward traveling wave is a traveling wave which is transmitted to the receiving end along the transmitting end, and the voltage reverse traveling wave is a traveling wave which is transmitted to the transmitting end along the receiving end.
Step 4: acquiring the variable quantities of the voltage forward traveling wave and the voltage backward traveling wave, and then acquiring the h-th power of the variable quantity of the voltage forward traveling wave and the h-th power of the variable quantity of the voltage backward traveling wave, wherein h is an odd-numbered power, and specifically:
step4.1: in order to amplify the fault characteristics of the voltage forward traveling wave and the voltage reverse traveling wave, the abrupt change of a fault point is highlighted, and the voltage forward traveling wave variable quantity and the voltage reverse traveling wave variable quantity are respectively obtained:
Figure BDA0003491019170000041
Figure BDA0003491019170000042
step4.2: in order to further highlight the variation of the fault signal, inhibit the point with smaller variation, eliminate the influence of small mutation points and obtain the h-th power of the variation of the forward traveling wave of the voltage and the h-th power of the variation of the backward traveling wave of the voltage, wherein h is an odd-numbered power, and the odd-numbered power of h is used for keeping the original polarity of the mutation points of the forward traveling wave and the backward traveling wave of the voltage after calculation.
Step 5: through the h power of forward traveling wave variable quantity and the h power of reverse traveling wave variable quantity, obtain the superimposed value of the h power of forward traveling wave variable quantity and the superimposed value of the h power of reverse traveling wave variable quantity, specifically do:
step5.1: to suppress the influence of Gaussian noise on fault signals, the variation of forward traveling wave from voltage is raised to the power of h
Figure BDA0003491019170000043
Every N samples, starting with the kth sample value of
Figure BDA0003491019170000044
The sampled value is added to obtain a primary superposition value as the sudden change energy of the forward traveling wave of the voltage
Figure BDA0003491019170000045
The kth value of (2) can obtain the superposed value of the voltage forward traveling wave variation quantity h power at any time and any position in the full line length range:
Figure BDA0003491019170000046
step5.2: from voltage reverse traveling wave variation quantity h power
Figure BDA0003491019170000047
Every N samples, starting with the kth sample value
Figure BDA0003491019170000048
The sampled value is obtained as a primary superposition valueFor sudden energy change of forward travelling wave of voltage
Figure BDA0003491019170000049
The kth value of (2) can obtain the superposed value of the voltage reverse traveling wave variation quantity h power at any time and any position in the full line length range:
Figure BDA00034910191700000410
in the equations (7) and (8), k is the kth sampling point, and N is each time
Figure BDA00034910191700000411
The number of samples superimposed.
Step 6: acquiring the product of the superposition value of the h-th power of the traveling wave variable quantity and the superposition value of the h-th power of the reverse traveling wave variable quantity, and integrating the product in a certain time window:
Figure BDA00034910191700000412
in the formula, t 1 ，t 2 The upper limit and the lower limit of the traveling wave observation time window.
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. Therefore, the integral of any position at any time within the full-line length range is taken as a function, and the catastrophe point in the function can be used for fault location, which specifically comprises the following steps:
step7.1: and taking the integral of any position at any time within the full-line length range as a function, and measuring the distance corresponding to the first mutation point of the integral function.
Step7.2: and judging whether the polarity of the first mutation point of the integral function is negative or not.
If so, the fault distance x f Correspond to the pointLine length x of m1 。
If not, the fault distance x f Subtracting the corresponding length x from the total length l of the transmission line m2 。
A high voltage direct current transmission line fault location system comprising:
and the electric signal acquisition module operates in the high-speed data acquisition device at the transmitting end or/and the receiving end of the power transmission line and is used for acquiring and storing data.
And the numerical value calculation module is used for calculating the superposition value of the h power of the voltage forward traveling wave variable quantity and the superposition value of the h power of the voltage reverse traveling wave variable 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, and performing fault distance measurement by using an abrupt change point of the integral function to obtain a fault distance rear outlet distance measurement result.
The electrical signal acquisition module specifically includes:
and the data acquisition unit is used for acquiring the analog signal output by the secondary side of the mutual inductor.
And the analog-to-digital conversion unit is used for converting the analog signal into a digital signal.
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:
and 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 calculation unit is used for calculating the voltage and the current at any time in the whole line length range and calculating the forward traveling wave and the reverse traveling wave; secondly, calculating the variable quantity of the forward traveling wave and the variable quantity of the reverse traveling wave, and respectively calculating the h power of the variable quantity of the forward traveling wave and the h power of the variable quantity of the reverse traveling wave; thirdly, calculating a superposition value of the forward traveling wave variable quantity raised to the power h and a superposition value of the reverse traveling wave variable quantity raised to the power h; and finally, calculating the product of the superposition value of the forward traveling wave variable quantity k to the power and the superposition value of the reverse traveling wave variable quantity k to the power at any time in the full line length range, and integrating the product in a certain time window.
The fault location module specifically comprises:
and the integral function construction unit is used for obtaining the product of the superposition value of the h-th power of the voltage forward traveling wave variable quantity and the superposition value of the h-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 corresponding to the first abrupt change point of the integral function.
And the polarity judging unit is used for judging the polarity of the first catastrophe point of the integral function.
The invention has the beneficial effects that:
1. the invention aims at fault location of the high-voltage direct-current transmission line, only single-ended data is needed, and the problem of data synchronization does not exist.
2. The invention utilizes the traveling wave method distance measurement principle, and compared with the distance measurement method based on the fault analysis method principle, the distance measurement precision is higher.
3. 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.
4. The invention has smaller distance measurement error and can greatly reduce the cost of manual line patrol.
Drawings
FIG. 1 is a simulation model topology of the present invention;
FIG. 2 is a schematic diagram of an equivalent model of the Bergeron line of the present invention;
FIG. 3 is a system block diagram of embodiment 1 of the present invention;
FIG. 4 is a graph showing the result of the integration function in example 1 of the present invention;
FIG. 5 is a graph showing the results of the integration function 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-HVDC simulation model system is shown in figure 1, the whole line length of the line is 1500km, and the voltage class is +/-800 kV. The fault is set to occur at 675.4km of the line, the fault type is set to be a permanent fault with the anode grounded, the transition resistance is set to be 0.01 omega, and the sampling rate is 1 MHz.
The method comprises the following specific steps:
because the sending end and the receiving end of the high-voltage direct-current transmission system are both provided with boundaries formed by a smoothing reactor and a direct-current filter, when the frequency is higher, the boundaries present larger impedance characteristics, which is equivalent to open circuits, so that the current traveling wave can not be measured, the capacity of a voltage transformer for transmitting high-frequency signals is poorer, the voltage transformer is not used for measuring voltage traveling waves generally, but a traveling wave coupling box is arranged at a measuring point, a current signal is generated after the fault voltage traveling wave passes through the traveling wave coupling box, and the current transformer is used for measuring the current signal so as to indirectly measure the voltage signal at the measuring point. And acquiring fault voltage traveling wave signals of a transmitting end and a receiving end of the transmission line by utilizing the acquisition devices at the head end or/and the tail end of the high-voltage direct-current transmission line.
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.
In a high-voltage direct-current transmission system, a transmission line is long, the influence of distributed capacitance current must be considered, a Bergeron transmission line model is a line model adopting distributed parameters, and the influence of distributed capacitance is considered, so that the transient characteristics are analyzed by adopting the Bergeron transmission line model. 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 within the full line length range, wherein the calculation formula is as follows:
Figure BDA0003491019170000071
Figure BDA0003491019170000072
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, 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.
For the transmitting end, the traveling wave propagating to the receiving end along the transmitting end is defined as a forward traveling wave, and the traveling wave propagating to the transmitting end along the receiving end is defined as a reverse traveling wave. According to the voltage and the current at any position in the whole line length range at any time, calculating the voltage forward traveling wave and the voltage reverse traveling wave at any position in the whole line length range at any time, wherein the calculation formula is as follows:
Figure BDA0003491019170000073
Figure BDA0003491019170000074
in order to amplify the fault characteristics of the voltage forward traveling wave and the voltage reverse traveling wave and highlight the sudden change of a fault point, the voltage forward traveling wave variation and the voltage reverse traveling wave variation are respectively calculated by utilizing a first-order linear differential equation:
Figure BDA0003491019170000075
Figure BDA0003491019170000076
in order to further highlight the variation of the fault signal, inhibit the point with smaller variation and eliminate the influence of small mutation points, the h-th power of the variation of the forward traveling wave of the voltage and the h-th power of the variation of the backward traveling wave of the voltage are calculated, wherein h is an odd power, and the odd power of h is used for keeping the original polarity of the mutation points of the forward traveling wave and the backward traveling wave of the voltage after calculation.
To suppress the influence of Gaussian noise on fault signals, the variation of forward traveling wave from voltage is raised to the power of h
Figure BDA0003491019170000081
Every N samples, starting with the kth sample value
Figure BDA0003491019170000082
The sampled value is used for obtaining a primary superposition value as the sudden change energy of the forward traveling wave of the voltage
Figure BDA0003491019170000083
The k-th value of the voltage forward traveling wave variable quantity can be obtained, the superposed value of the h-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;
Figure BDA0003491019170000084
where k is the kth sample point and N is each time
Figure BDA0003491019170000085
The number of the superposed sampling values can be selected according to the requirement. In this example, N is 5 and h is 5.
From voltage reverse traveling wave variation quantity h power
Figure BDA0003491019170000086
Every N samples, starting with the kth sample value of
Figure BDA0003491019170000087
The sampled value is used for obtaining a primary superposition value as the sudden change energy of the forward traveling wave of the voltage
Figure BDA0003491019170000088
The k-th value of the voltage reverse traveling wave can obtain the superposed value of the variation h power of the voltage reverse traveling wave at any time and any position in the full line length range, and the calculation formula is as follows;
Figure BDA0003491019170000089
where k is the kth sample point and N is each time
Figure BDA00034910191700000810
The number of the superposed sampling values can be selected according to the requirement. In this example, N is 5 and h is 5.
Step 6: the product of the superposition value of the h power of the voltage forward traveling wave variable quantity and the superposition value of the h 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;
Figure BDA00034910191700000811
in the formula, t 1 ，t 2 The upper limit and the lower limit of the traveling wave observation time window. In the present embodiment, t 1 The moment when the initial traveling wave of the fault reaches the measuring end, t 2 And the time corresponding to the l/v time window length after the initial fault traveling wave reaches the measuring end.
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. Taking the integral of any position at any time within the whole line length range as a function, wherein the distribution result of the integral function is shown in figure 4, firstly, measuring the distance corresponding to the first break point of the integral function as 675 km; it is provided withSecondly, 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 m2 . In this embodiment, the polarity of the first discontinuity is negative, and the fault distance x f For line length 675km for that point.
Fig. 3 is a functional block diagram of a fault location system of a high-voltage direct-current transmission line provided by the invention, which includes:
the electric signal acquisition module runs in a high-speed data acquisition device at the transmitting end or/and the receiving end of the power transmission line and is used for acquiring and storing data;
the numerical value calculation module is used for calculating the superposition value of the h power of the forward traveling wave variable quantity and the superposition value of the h power of the reverse traveling wave variable 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, and performing fault distance measurement by using an abrupt change point of the integral function to obtain a fault distance rear outlet distance measurement result.
Wherein, electric signal acquisition module specifically includes:
the data acquisition unit is used for acquiring analog signals output by the secondary side of the mutual inductor;
the analog-to-digital conversion unit is used for converting the analog signal into a digital signal;
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 the starting time and storing data.
Wherein, 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 calculation unit is used for calculating the voltage and the current at any time in the whole line length range and calculating the voltage forward traveling wave and the voltage reverse traveling wave; secondly, calculating the voltage forward traveling wave variable quantity and the voltage backward traveling wave variable quantity, and respectively calculating the h-th power of the voltage forward traveling wave variable quantity and the h-th power of the voltage backward traveling wave variable quantity; thirdly, calculating a superposition value of the voltage forward traveling wave variable quantity raised to the power h and a superposition value of the voltage reverse traveling wave variable quantity raised to the power h; and finally, calculating the product of the superposition value of the voltage forward traveling wave variable quantity k power and the superposition value of the voltage reverse traveling wave variable quantity k power at any time in the whole line length range, and integrating the product in a certain time window.
Wherein, the fault location module specifically includes:
the integral function constructing unit is used for solving the product of the superposition value of the h power of the voltage forward traveling wave variable quantity and the superposition value of the h 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 corresponding to the first catastrophe point of the integral function to obtain the distance of 675 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 675 km.
Example 2: the LCC-HVDC simulation model system is shown in figure 1, the whole line length of the line is 1500km, and the voltage class is +/-800 kV. The fault is set to occur at 1280km of a line, the fault type is set to be a permanent fault of anode grounding, the transition resistance is set to be 0.01 omega, and the sampling rate is 1 MHz. The method comprises the following specific steps:
because the sending end and the receiving end of the high-voltage direct-current transmission system are both provided with boundaries formed by a smoothing reactor and a direct-current filter, when the frequency is higher, the boundaries present larger impedance characteristics, which is equivalent to open circuits, so that the current traveling wave can not be measured, the capacity of a voltage transformer for transmitting high-frequency signals is poorer, the voltage transformer is not used for measuring voltage traveling waves generally, but a traveling wave coupling box is arranged at a measuring point, a current signal is generated after the fault voltage traveling wave passes through the traveling wave coupling box, and the current transformer is used for measuring the current signal so as to indirectly measure the voltage signal at the measuring point. And acquiring fault voltage traveling wave signals of a transmitting end and a receiving end of the transmission line by utilizing an acquisition device at the head end or/and the tail end of the high-voltage direct-current transmission line.
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.
In a high-voltage direct-current transmission system, a transmission line is long, the influence of distributed capacitance current must be considered, a Bergeron transmission line model is a line model adopting distributed parameters, and the influence of distributed capacitance is considered, so that the transient characteristics are analyzed by adopting the Bergeron transmission line model. The power transmission line is equivalent to 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 in the whole line length range, wherein the calculation formula is as follows:
Figure BDA0003491019170000101
Figure BDA0003491019170000102
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, 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.
For the transmitting end, the traveling wave propagating to the receiving end along the transmitting end is defined as a forward traveling wave, and the traveling wave propagating to the transmitting end along the receiving end is defined as a reverse traveling wave. According to the voltage and the current at any position in the whole line length range at any time, calculating the voltage forward traveling wave and the voltage reverse traveling wave at any position in the whole line length range at any time, wherein the calculation formula is as follows:
Figure BDA0003491019170000103
Figure BDA0003491019170000104
in order to amplify the fault characteristics of the voltage forward traveling wave and the voltage reverse traveling wave and highlight the sudden change of a fault point, the voltage forward traveling wave variation and the voltage reverse traveling wave variation are respectively calculated by utilizing a first-order linear differential equation:
Figure BDA0003491019170000111
Figure BDA0003491019170000112
in order to further highlight the variation of the fault signal, inhibit the point with smaller variation and eliminate the influence of small mutation points, the h-th power of the variation of the forward traveling wave of the voltage and the h-th power of the variation of the backward traveling wave of the voltage are calculated, wherein h is an odd power, and the odd power of h is used for keeping the original polarity of the mutation points of the forward traveling wave and the backward traveling wave of the voltage after calculation.
To suppress the influence of Gaussian noise on fault signals, the variation of forward traveling wave from voltage is raised to the power of h
Figure BDA0003491019170000113
Every N samples, starting with the kth sample value of
Figure BDA0003491019170000114
The sampled value is added to obtain a primary superposition value as the sudden change energy of the forward traveling wave of the voltage
Figure BDA0003491019170000115
Kth value of (2)The superposed value of the variation h power of the forward traveling wave of the voltage at any time and any position in the full line length range can be obtained, and the calculation formula is as follows;
Figure BDA0003491019170000116
where k is the kth sample point and N is each time
Figure BDA0003491019170000117
The number of the superposed sampling values can be selected according to the requirement. In this example, N is 5 and h is 5.
From voltage reverse traveling wave variation quantity h power
Figure BDA0003491019170000118
Every N samples, starting with the kth sample value
Figure BDA0003491019170000119
The sampled value is added to obtain a primary superposition value as the sudden change energy of the forward traveling wave of the voltage
Figure BDA00034910191700001110
The k-th value of the voltage reverse traveling wave can obtain the superposed value of the variation h power of the voltage reverse traveling wave at any time and any position in the full line length range, and the calculation formula is as follows;
Figure BDA00034910191700001111
where k is the kth sample point and N is each time
Figure BDA00034910191700001112
The number of the superposed sampling values can be selected according to the requirement. In this example, N is 5 and h is 5.
Step 6: the product of the superposition value of the h power of the voltage forward traveling wave variable quantity and the superposition value of the h 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;
Figure BDA00034910191700001113
in the formula, t 1 ，t 2 The upper limit and the lower limit of the traveling wave observation time window. In the present embodiment, t 1 The moment when the initial traveling wave of the fault reaches the measuring end, t 2 And the time corresponding to the l/v time window length after the initial fault traveling wave reaches the measuring end.
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. 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. 5, firstly, measuring the distance corresponding to the first break point of the integral function as 220 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 m2 . In this embodiment, the polarity of the first discontinuity is positive, and the fault distance x f The length corresponding to the total length l of the transmission line minus the point is 1500-220-1280 km, and the fault distance is 1280 km.
The high voltage direct current transmission line fault location system of this embodiment includes:
the electric signal acquisition module runs in a high-speed data acquisition device at the transmitting end or/and the receiving end of the power transmission line and is used for acquiring and storing data;
the numerical value calculation module is used for calculating the superposition value of the h power of the forward traveling wave variable quantity and the superposition value of the h power of the reverse traveling wave variable 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, and performing fault distance measurement by using an abrupt change point of the integral function to obtain a fault distance rear outlet distance measurement result.
Wherein, electric signal acquisition module specifically includes:
the data acquisition unit is used for acquiring analog signals output by the secondary side of the mutual inductor;
the analog-to-digital conversion unit is used for converting the analog signal into a digital signal;
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.
Wherein, 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 calculation unit is used for calculating the voltage and the current at any time in the whole line length range and calculating the voltage forward traveling wave and the voltage reverse traveling wave; secondly, calculating the voltage forward traveling wave variable quantity and the voltage backward traveling wave variable quantity, and respectively calculating the h-th power of the voltage forward traveling wave variable quantity and the h-th power of the voltage backward traveling wave variable quantity; thirdly, calculating a superposition value of the voltage forward traveling wave variable quantity raised to the power h and a superposition value of the voltage reverse traveling wave variable quantity raised to the power h; and finally, calculating the product of the superposed value of the k-th power of the voltage forward traveling wave variable quantity and the superposed value of the k-th power of the voltage backward traveling wave variable quantity at any time in the whole line length range, and integrating the product in a certain time window.
Wherein, the fault location module specifically includes:
the integral function constructing unit is used for solving the product of the superposition value of the h-th power of the voltage forward traveling wave variable quantity and the superposition value of the h-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 corresponding to the first catastrophe point of the integral function to obtain the distance of 220 km.
And the polarity judging unit is used for judging the polarity of the first mutation point of the integral function to obtain the positive polarity.
Thus, the fault distance x is obtained f The length corresponding to the point is subtracted from the total length l of the transmission line, namely the fault distance is 1280 km.
Verification shows that the high-voltage direct-current transmission line fault distance measurement method and system provided by the invention are high in reliability.
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 (12)

1. A high-voltage direct-current transmission line fault distance measuring method is characterized in that:
step 1: collecting fault signals of a transmitting end and a receiving end of a power transmission line;
step 2: acquiring voltage and current at any position at any time in the full line length range based on the fault signal;
step 3: acquiring forward voltage traveling waves and reverse voltage traveling waves at any time and any position in the full-line length range by using the voltage and the current at any time and any position in the full-line length range;
step 4: acquiring forward voltage traveling wave variable quantities and reverse voltage traveling wave variable quantities of the forward traveling waves and the reverse traveling waves, and then acquiring h-th power of the forward voltage traveling wave variable quantities and h-th power of the reverse voltage traveling wave variable quantities, wherein h is an odd-numbered power;
step 5: acquiring a superposition value of the h-th power of the forward voltage traveling wave variable quantity and a superposition value of the h-th power of the reverse voltage traveling wave variable quantity through the h-th power of the forward voltage traveling wave variable quantity and the h-th power of the reverse voltage traveling wave variable quantity;
step 6: acquiring the product of the superposition value of the h power of the traveling wave variation and the superposition value of the h power of the reverse traveling wave variation, and integrating the product in a certain time window;
step 7: and taking the integral as a function, and utilizing the catastrophe points in the function to carry out fault distance measurement.
2. The method of claim 1 for fault location of an hvdc transmission line, wherein: and in Step1, acquiring fault traveling wave signals of a transmitting end and a receiving end of the transmission line by using an acquisition device at the head end or/and the tail end of the high-voltage direct-current transmission line.
3. The HVDC transmission line fault location method of claim 1, wherein Step2 specifically is:
step2.1: decoupling the fault traveling wave signal to obtain line mode traveling waves of a transmitting end and a receiving end;
step2.2: the method comprises the following steps of (1) enabling a Bailon line model for the transmission line to be equivalent, and calculating the voltage and the current at any position at any time within the full line length range:
Figure FDA0003491019160000011
Figure FDA0003491019160000012
in the formula, 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, 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.
4. The method of claim 1 for fault location of an hvdc transmission line, wherein: in Step3, the forward voltage traveling wave is a traveling wave propagating along the transmitting end to the receiving end, and the reverse voltage traveling wave is a traveling wave propagating along the receiving end to the transmitting end.
5. The HVDC line fault location method of claim 1 or 4, wherein: the voltage forward traveling wave and the voltage reverse traveling wave are specifically as follows:
Figure FDA0003491019160000021
Figure FDA0003491019160000022
6. the HVDC transmission line fault location method of claim 1, wherein Step4 is specifically:
step4.1: respectively acquiring the voltage forward traveling wave variable quantity and the voltage reverse traveling wave variable quantity as follows:
Figure FDA0003491019160000023
Figure FDA0003491019160000024
step4.2: and acquiring the h-th power of the variable quantity of the voltage forward traveling wave and the h-th power of the variable quantity of the voltage backward traveling wave, wherein h is a positive odd power.
7. The HVDC transmission line fault location method of claim 1, wherein Step5 is specifically:
step5.1: acquiring a superposed value of the variation h power of the forward traveling wave of the voltage at any time and any position in the full-line length range;
Figure FDA0003491019160000025
step5.2: acquiring a superposed value of the variation h power of the reverse traveling wave of the voltage at any time and any position in the full-line length range;
Figure FDA0003491019160000026
in the equations (7) and (8), k is the kth sampling point, and N is each time
Figure FDA0003491019160000027
The number of samples superimposed.
8. The HVDC transmission line fault location method of claim 1, wherein Step7 is specifically:
step7.1: taking the integral of any position at any time within the full-line length range as a function, and measuring the distance corresponding to the first mutation point of the integral function;
step7.2: judging whether the polarity of the first catastrophe point of the integral function is negative or not;
if so, the fault distance x f Line length x corresponding to the point m1 ；
If not, the fault distance x f Subtracting the corresponding length x from the total length l of the transmission line m2 。
9. A high voltage direct current transmission line fault location system, characterized by includes:
the electric signal acquisition module is used for acquiring and storing data;
the numerical value calculation module is used for calculating the superposition value of the h power of the forward voltage traveling wave variable quantity and the superposition value of the h power of the reverse voltage traveling wave variable 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 and carrying out fault distance measurement by using an abrupt change point of the integral function to obtain a fault distance rear outlet distance measurement result.
10. The HVDC line fault location system of claim 9, wherein the electrical signal acquisition module comprises:
the data acquisition unit is used for acquiring analog signals output by the secondary side of the mutual inductor;
the analog-to-digital conversion unit is used for converting the analog signal into a digital signal;
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.
11. The HVDC line fault location system of claim 9, wherein the numerical calculation module comprises:
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 calculating the product of the superposition value of the forward voltage traveling wave variable quantity k to the power and the superposition value of the reverse voltage traveling wave variable quantity k to the power at any time in the whole line length range and integrating the product in a certain time window.
12. The HVDC line fault location system of claim 9, wherein the fault location module specifically comprises:
a distance measuring unit for measuring a distance corresponding to a first abrupt change point of the integral function;
and the polarity judging unit is used for judging the polarity of the first catastrophe point of the integral function.
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