CN112462196B - Affine state estimation method for power distribution network - Google Patents
Affine state estimation method for power distribution network Download PDFInfo
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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
- G01R31/081—Locating faults in cables, transmission lines, or networks according to type of conductors
- G01R31/086—Locating faults in cables, transmission lines, or networks according to type of conductors in power transmission or distribution networks, i.e. with interconnected conductors
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R29/00—Arrangements for measuring or indicating electric quantities not covered by groups G01R19/00 - G01R27/00
- G01R29/16—Measuring asymmetry of polyphase networks
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- G—PHYSICS
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
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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
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- 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
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Abstract
The invention discloses a method for estimating affine state of a power distribution network, which comprises the following steps: at the head end of the power distribution network, performing a fault distance acquisition operation on a fault phase and a first normal phase to obtain a first fault distance; at the tail end of the power distribution network, performing a fault distance acquisition operation on the fault phase and the first normal phase to obtain a second fault distance; obtaining a first fault interval according to the first fault distance and the second fault distance; converting the first failure interval into a first affine number; at the head end of the power distribution network, performing a fault distance acquisition operation on the fault phase and the second normal phase to obtain a third fault distance; at the tail end of the power distribution network, performing a fault distance acquisition operation on the fault phase and the second normal phase to obtain a fourth fault distance; obtaining a second fault interval according to the third fault distance and the fourth fault distance; converting the second failure interval into a second affine number; obtaining a third affine number according to the first affine number and the second affine number, and further obtaining a third fault interval; error in fault point location is reduced.
Description
Technical Field
The invention relates to the field of power distribution networks, in particular to an affine state estimation method for a power distribution network.
Background
The electric energy is widely applied to various fields of power, illumination, chemistry, spinning, communication and the like, and the current social development is not separated from the electric energy. The distribution network refers to a type of power network that receives power from a power transmission network or regional power plant, and distributes the power locally or step-by-step according to voltage to various users through a distribution facility. Distribution networks play a vital role in today's power systems.
In the actual power transmission process, the power distribution network may malfunction for various reasons. Most of these distribution network faults are single-phase earth faults. The method for accurately and effectively detecting the single-phase earth fault can reduce power failure loss and restore power at the fastest speed. The existing power distribution network fault detection technology mainly locates one fault point. However, in the running process of the power distribution network, deviation of the positioned fault point may occur due to unbalanced three-phase load, fault of the small-section line caused by the fault point, insufficient calculation method in the detection technology and the like.
Disclosure of Invention
In view of the above-mentioned drawbacks of the prior art, the present invention provides an affine state estimation method for a power distribution network, which aims to locate a fault point of the power distribution network in a section and reduce a fault point locating error, so as to quickly recover power and reduce power outage loss.
Therefore, the invention discloses a method for estimating affine state of a power distribution network, which comprises the following steps:
Step S1, at the head end of the power distribution network, performing a fault distance acquisition operation on a fault phase and a first normal phase to obtain a first fault distance L 1;
S2, at the tail end of the power distribution network, performing a fault distance acquisition operation on the fault phase and the first normal phase to obtain a second fault distance L 2;
Step S3, a first fault interval [ L 1,L2 ] is obtained according to the first fault distance L 1 and the second fault distance L 2;
s4, converting the first fault interval [ L 1,L2 ] into a first affine number Wherein, alpha is a first fault correction coefficient, defaults to 1, and the value range of epsilon 1 is [ -1,1].
S5, at the head end of the power distribution network, performing a fault distance acquisition operation on the fault phase and the second normal phase to obtain a third fault distance L 3;
S6, at the tail end of the power distribution network, performing a fault distance acquisition operation on the fault phase and the second normal phase to obtain a fourth fault distance L 4;
Step S7, a second fault interval [ L 3,L4 ] is obtained according to the third fault distance L 3 and the fourth fault distance L 4;
S8, converting the second fault interval [ L 3,L4 ] into a second affine number Wherein, beta is a second fault correction coefficient, defaulting to 1, epsilon 1 is the value range of [ -1,1], because the three-phase parameter configuration of the distribution network is basically the same, the first fault interval and the second fault interval have strong correlation, so the affine number form of the two has the same noise element epsilon 1;
step S9, according to the first affine number The second affine numberObtaining a third affine number/>And a third failure interval is obtained.
Optionally, the fault distance obtaining operation includes:
At a power distribution network end, high-voltage pulses are injected into a fault phase, a first voltage traveling wave returned by three phases is detected, and the first voltage traveling wave is converted through a phase mode to obtain a first zero-mode voltage traveling wave;
at the power distribution network end, injecting the high-voltage pulse into a non-fault phase, detecting a second voltage traveling wave returned by the three phases, and obtaining a second zero-mode voltage traveling wave through phase-mode transformation of the second voltage traveling wave;
Obtaining a traveling wave difference value according to the first zero-mode voltage traveling wave and the second zero-mode voltage traveling wave;
carrying out differential derivation on the traveling wave difference value to obtain a first non-zero mutation point moment;
Obtaining propagation time according to the first non-zero mutation point moment;
Obtaining a fault distance according to the propagation time, the zero mode wave speed and the linear mode wave speed; the power distribution network comprises a power distribution network head end and a power distribution network tail end, wherein the non-fault phase comprises a first normal phase and a second normal phase, and the first normal phase, the second normal phase and the fault phase form three phases of the power distribution network.
Optionally, the first voltage traveling wave is converted through a phase mode to obtain a first zero-mode voltage traveling wave;
according to the formula Transforming the first voltage traveling wave to obtain a first zero-mode voltage traveling wave U 10 (t); wherein U a1(t),Ub1 (t) and U c1 (t) are respectively the first voltage traveling wave of each phase in the three phases.
Optionally, the second voltage traveling wave is converted through a phase mode to obtain a second zero-mode voltage traveling wave;
according to the formula Transforming the second voltage traveling wave to obtain a second zero-mode voltage traveling wave U 20 (t); wherein U a2(t),Ub2 (t) and U c2 (t) are respectively second voltage traveling waves of each phase of the three phases.
Optionally, obtaining a traveling wave difference according to the first zero-mode voltage traveling wave and the second zero-mode voltage traveling wave includes:
Obtaining the travelling wave difference Δu (t) according to the formula Δu (t) =u 10(t)-U20 (t); wherein U 10 (t) is the first zero-mode voltage traveling wave, and U 20 (t) is the second zero-mode voltage traveling wave.
Optionally, performing differential derivation on the traveling wave difference value to obtain a first non-zero mutation point moment, including:
And carrying out differential derivation on the traveling wave difference value delta U (t), wherein the differential derivation is as follows:
Wherein: Δu' (t) is a differential derivative of Δu (t), Δt is a sampling time interval, and Δu (t) is the traveling wave difference;
Recording a first non-zero mutation point time t 1 in response to the absolute value of Δu' (t) being greater than a determination threshold; the judgment threshold is positive and is related to the sampling time interval and whether the line mode voltage takes a value at the primary side or takes a value at the secondary side.
Optionally, obtaining the propagation time according to the first non-zero mutation point moment includes:
And obtaining the propagation time T according to T=t 1-t0, wherein T 1 is the first non-zero mutation point moment, and T 0 is the time of injecting the first high-voltage pulse into the head end.
Optionally, obtaining the fault distance according to the propagation time, the zero mode wave speed and the line mode wave speed includes:
according to the formula And obtaining the fault distance L, wherein v 0 is the zero mode wave speed, v 1 is the linear mode wave speed, and L is the fault distance.
The invention has the beneficial effects that: 1. according to the invention, the first fault interval and the second fault interval are obtained, the third fault interval is obtained according to the first fault interval and the second fault interval, and the fault point of the power distribution network is positioned in the third fault interval. In the prior art, only one fault point is positioned, and certain error exists in the fault point, but the error range is not known, so that the fault point can be omitted if the error range is small, the error range is large, and the manpower and material resources for investigation are increased. Compared with the prior art, the method and the device for determining the distribution network fault point directly determine the existence interval of the distribution network fault point, reduce uncertainty and improve the accuracy of positioning the distribution network fault point. 2. According to the method, the first fault interval and the second fault interval are converted into the first affine number and the second affine number, the third affine number is obtained according to the strong correlation between the first affine number and the second affine number, and the third fault interval is further obtained, so that the fault interval is reduced, and the accuracy of positioning of the fault points of the power distribution network is improved. In summary, the fault point of the power distribution network is locked in one interval to reduce the fault point positioning error, so that the power is recovered quickly, and the power failure loss is reduced.
Drawings
Fig. 1 is a schematic flow chart of an affine state estimation method for a power distribution network according to an embodiment of the present invention;
FIG. 2 is a waveform signal diagram of a first zero-mode voltage traveling wave according to an embodiment of the present invention;
FIG. 3 is a waveform signal diagram of a second zero-mode voltage traveling wave according to an embodiment of the present invention;
fig. 4 is a graph of a difference derivative of traveling wave differences according to an embodiment of the present invention.
Detailed Description
The invention discloses an affine state estimation method for a power distribution network, and a person skilled in the art can refer to the content of the affine state estimation method and properly improve technical details. It is expressly noted that all such similar substitutions and modifications will be apparent to those skilled in the art, and are deemed to be included in the present invention. While the methods and applications of this invention have been described in terms of preferred embodiments, it will be apparent to those skilled in the relevant art that variations and modifications can be made in the methods and applications described herein, and in the practice and application of the techniques of this invention, without departing from the spirit or scope of the invention.
In the actual power transmission process, the power distribution network may malfunction for various reasons. Most of these distribution network faults are single-phase earth faults. The method for accurately and effectively detecting the single-phase earth fault can reduce power failure loss and restore power at the fastest speed. In the existing power distribution network fault detection technology, a traveling wave method is mainly used for positioning a fault point, but a certain error exists between the fault point and an actual fault point. The reasons are as follows: 1. in the detection process, errors are caused by unbalanced three-phase loads of the power distribution network. 2. Because of the small segment fault caused by the fault point, when the head of the small segment fault is detected, the fault point is mistakenly detected. 3. In the calculation process, some coefficients are determined according to previous experience, and a certain error may be caused.
Example 1:
an affine state estimation method of a power distribution network, as shown in fig. 1, comprises the following steps:
Step S1, at the head end of the power distribution network, performing a fault distance acquisition operation on a fault phase and a first normal phase to obtain a first fault distance L 1.
It should be noted that, the head end of the power distribution network is a power distribution output end, and the first fault distance L 1 is a lower bound of the first fault interval. By the employed failure distance acquisition operation, the obtained failure distance is generally smaller than the distance from the measured end to the actual failure point.
And S2, at the tail end of the power distribution network, performing a fault distance acquisition operation on the fault phase and the first normal phase to obtain a second fault distance L 2.
It should be noted that, the end of the distribution network is a distribution power receiving end, and the second fault distance L 2 is an upper bound of the first fault interval. The second fault distance L 2 is a head-to-fault point distance, and the fault distance measured at the end of the power distribution network can be converted into a head-to-fault point distance through the head-to-end distance. The method comprises the following steps: the head-to-tail distance is S, then the second fault distance is equal to the head-to-tail distance S minus the fault distance measured at the end of the distribution network.
And step S3, obtaining a first fault interval [ L 1,L2 ] according to the first fault distance L 1 and the second fault distance L 2.
S4, converting the first fault interval [ L 1,L2 ] into a first affine number
It should be noted that α is a first failure correction coefficient, default to1, and α may be adjusted according to actual conditions. Epsilon 1 is within the range of [ -1,1].
And S5, at the head end of the power distribution network, performing a fault distance acquisition operation on the fault phase and the second normal phase to obtain a third fault distance L 3.
Note that the third fault distance L 3 is a lower bound of the second fault section.
And S6, at the tail end of the power distribution network, performing a fault distance acquisition operation on the fault phase and the second normal phase to obtain a fourth fault distance L 4.
Note that the fourth fault distance L 4 is an upper bound of the second fault section.
Step S7, obtaining a second fault interval [ L 3,L4 ] according to the third fault distance L 3 and the fourth fault distance L 4;
S8, converting the second fault interval [ L 3,L4 ] into a second affine number
It should be noted that β is the second fault correction coefficient, default to 1, and β may be adjusted according to actual conditions. The value range of epsilon 1 is [ -1,1], and because the three-phase parameter configuration of the power distribution network is basically the same, the first fault interval and the second fault interval have strong correlation, so the affine number form of the first fault interval and the second fault interval has the same noise element epsilon 1.
Optionally, before performing the fault distance acquiring operation, performing an experiment first, setting a second fault phase, and performing the fault distance acquiring operation on the second fault phase and the first normal phase at the head end and the tail end respectively; and performing fault distance acquisition operation on the second fault phase and the second normal phase at the head end and the tail end respectively, so as to obtain the relation between the first fault correction coefficient alpha and the second fault correction coefficient beta.
Step S9, according to the first affine numberSecond affine number/>Obtaining a third affine number/>And a third failure interval is obtained.
Optionally, in a specific embodiment, the fault distance obtaining operation in the method includes:
And B1, injecting high-voltage pulses into a fault phase at the power distribution network end, detecting a first voltage traveling wave returned by the three phases, and obtaining a first zero-mode voltage traveling wave through phase-mode transformation of the first voltage traveling wave.
Optionally, the first voltage traveling wave is converted through a phase mode to obtain a first zero-mode voltage traveling wave;
according to the formula Transforming the first voltage traveling wave to obtain a first zero-mode voltage traveling wave U 10 (t); wherein U a1(t),Ub1 (t) and U c1 (t) are respectively first voltage traveling waves of each phase of the three phases.
Alternatively, in a specific embodiment, the first zero-mode voltage traveling wave may be as shown in fig. 2.
And B2, injecting high-voltage pulse into a non-fault phase at the power distribution network end, detecting a second voltage traveling wave returned by the three phases, and obtaining a second zero-mode voltage traveling wave through phase-mode transformation of the second voltage traveling wave.
Optionally, the second voltage traveling wave is converted through a phase mode to obtain a second zero-mode voltage traveling wave;
according to the formula Transforming the second voltage traveling wave to obtain a second zero-mode voltage traveling wave U 20 (t); wherein U a2(t),Ub2 (t) and U c2 (t) are respectively second voltage traveling waves of each phase of the three phases.
Alternatively, in one embodiment, the second zero-mode voltage traveling wave may be as shown in FIG. 3.
It should be noted that the step B1 and the step B2 are not related to each other.
And step B3, obtaining a traveling wave difference value according to the first zero-mode voltage traveling wave and the second zero-mode voltage traveling wave.
Optionally, obtaining the traveling wave difference according to the first zero-mode voltage traveling wave and the second zero-mode voltage traveling wave includes:
obtaining a traveling wave difference value deltau (t) according to the formula deltau (t) =u 10(t)-U20 (t); wherein U 10 (t) is a first zero-mode voltage traveling wave, and U 20 (t) is a second zero-mode voltage traveling wave.
And step B4, carrying out differential derivation on the traveling wave difference value to obtain a first non-zero mutation point moment.
Optionally, performing differential derivation on the traveling wave difference value to obtain a first non-zero mutation point moment, including:
the difference derivative is carried out on the traveling wave difference value DeltaU (t) as follows:
Wherein: Δu' (t) is the differential derivative of Δu (t), Δt is the sampling time interval, and Δu (t) is the traveling wave difference;
Recording a first non-zero mutation point time t 1 in response to the absolute value of Δu' (t) being greater than a determination threshold; the judgment threshold is positive and is related to whether the sampling time interval and the line mode voltage take a value at the primary side or take a value at the secondary side.
Alternatively, the curve obtained by differentiating the traveling wave difference value may be as shown in fig. 4. When we define the decision threshold to be 4V/s, the time t 1 of the first non-zero mutation is 1.175×10 -4 s.
It should be noted that, the derivative mode is adopted because the derivative shows the change speed of the traveling wave difference function, and only if the change speed is enough, the fault can be considered to occur, rather than the imbalance of the three-phase load. Avoiding the situation of error measurement.
And step B5, obtaining the propagation time according to the moment of the first non-zero mutation point.
Optionally, obtaining the propagation time according to the first non-zero mutation point moment includes:
According to t=t 1-t0, a propagation time T is obtained, where T 1 is the first non-zero point of abrupt change time, and T 0 is the time when the first high voltage pulse is injected from the head end.
Step B6, obtaining a fault distance according to the propagation time, the zero mode wave speed and the linear mode wave speed; the power distribution network end comprises a power distribution network head end and a power distribution network tail end, the non-fault phase comprises a first normal phase and a second normal phase, and the first normal phase, the second normal phase and the fault phase form three phases of the power distribution network.
Optionally, obtaining the fault distance according to the propagation time, the zero mode wave speed and the line mode wave speed includes:
according to the formula And obtaining a fault distance L, wherein v 0 is zero mode wave speed, v 1 is linear mode wave speed, and L is the fault distance.
Example 2:
Assume that the failure point is 15km from the head end.
Through the above-described failure distance obtaining operation, the first failure section [14.990km,15.010km ] and the second failure section [14.995km,15.015km ] are obtained. Through affine number conversion, a first affine number of 15.000+0.010 ε 1 and a second affine number of 15.005+0.010 ε 1 are obtained, wherein the value range of ε 1 is [ -1,1].
And obtaining a third affine number 15.0025+0.010 epsilon 1 according to the first affine number and the second affine number, wherein the value range of epsilon 1 is [ -1,1]. And a third failure zone [14.9925km,15.0125km ] is obtained.
Therefore, the embodiment of the invention further reduces the fault interval by utilizing the characteristic of strong correlation between the first fault interval and the second fault interval in the form of affine number. The accuracy of fault point positioning is improved, and errors are reduced.
The present examples are provided for the purpose of illustration only and are not intended to limit the invention.
According to the embodiment of the invention, the first fault interval and the second fault interval are obtained, the third fault interval is obtained according to the first fault interval and the second fault interval, and the fault point of the power distribution network is positioned in the third fault interval. In the prior art, only one fault point is positioned, and certain error exists in the fault point, but the error range is not known, so that the fault point can be omitted if the error range is small, the error range is large, and the manpower and material resources for investigation are increased. Compared with the prior art, the embodiment of the invention directly determines the existence interval of the fault point of the power distribution network, reduces uncertainty and improves the positioning accuracy of the fault point of the power distribution network. According to the embodiment of the invention, the first fault interval and the second fault interval are converted into the first affine number and the second affine number, and the third affine number is obtained according to the strong correlation between the first affine number and the second affine number, so that the third fault interval is obtained, the fault interval is reduced, and the accuracy of positioning the fault points of the power distribution network is improved. In summary, the embodiment of the invention is used for reducing the fault point positioning error by locking the fault point of the power distribution network in one interval, thereby quickly recovering the power and reducing the power failure loss.
It is noted that relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.
In this specification, each embodiment is described in a related manner, and identical and similar parts of each embodiment are all referred to each other, and each embodiment mainly describes differences from other embodiments. In particular, for system embodiments, since they are substantially similar to method embodiments, the description is relatively simple, as relevant to see a section of the description of method embodiments.
The foregoing description is only of the preferred embodiments of the present invention and is not intended to limit the scope of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention are included in the protection scope of the present invention.
Claims (8)
1. An affine state estimation method for a power distribution network is characterized by comprising the following steps of:
Step S1, at the head end of the power distribution network, performing a fault distance acquisition operation on a fault phase and a first normal phase to obtain a first fault distance L 1;
S2, at the tail end of the power distribution network, performing a fault distance acquisition operation on the fault phase and the first normal phase to obtain a second fault distance L 2;
Step S3, a first fault interval [ L 1,L2 ] is obtained according to the first fault distance L 1 and the second fault distance L 2;
s4, converting the first fault interval [ L 1,L2 ] into a first affine number Wherein, alpha is a first fault correction coefficient, default to 1, and the value range of epsilon 1 is [ -1,1];
S5, at the head end of the power distribution network, performing a fault distance acquisition operation on the fault phase and the second normal phase to obtain a third fault distance L 3;
S6, at the tail end of the power distribution network, performing a fault distance acquisition operation on the fault phase and the second normal phase to obtain a fourth fault distance L 4;
Step S7, a second fault interval [ L 3,L4 ] is obtained according to the third fault distance L 3 and the fourth fault distance L 4;
S8, converting the second fault interval [ L 3,L4 ] into a second affine number Wherein, beta is a second fault correction coefficient, defaulting to 1, epsilon 1 is the value range of [ -1,1], because the three-phase parameter configuration of the distribution network is basically the same, the first fault interval and the second fault interval have strong correlation, so the affine number form of the two has the same noise element epsilon 1;
step S9, according to the first affine number The second affine numberObtaining a third affine number/>And a third failure interval is obtained.
2. The method of claim 1, wherein the distance-to-failure acquisition operation comprises:
At a power distribution network end, high-voltage pulses are injected into a fault phase, a first voltage traveling wave returned by three phases is detected, and the first voltage traveling wave is converted through a phase mode to obtain a first zero-mode voltage traveling wave;
at the power distribution network end, injecting the high-voltage pulse into a non-fault phase, detecting a second voltage traveling wave returned by the three phases, and obtaining a second zero-mode voltage traveling wave through phase-mode transformation of the second voltage traveling wave;
Obtaining a traveling wave difference value according to the first zero-mode voltage traveling wave and the second zero-mode voltage traveling wave;
carrying out differential derivation on the traveling wave difference value to obtain a first non-zero mutation point moment;
Obtaining propagation time according to the first non-zero mutation point moment;
Obtaining a fault distance according to the propagation time, the zero mode wave speed and the linear mode wave speed; the power distribution network comprises a power distribution network head end and a power distribution network tail end, wherein the non-fault phase comprises a first normal phase and a second normal phase, and the first normal phase, the second normal phase and the fault phase form three phases of the power distribution network.
3. The method according to claim 2, characterized in that the first voltage travelling wave is subjected to a phase-mode transformation to obtain a first zero-mode voltage travelling wave;
according to the formula Transforming the first voltage traveling wave to obtain a first zero-mode voltage traveling wave U 10 (t); wherein U a1(t),Ub1 (t) and U c1 (t) are respectively the first voltage traveling wave of each phase in the three phases.
4. The method according to claim 2, characterized in that the second voltage travelling wave is subjected to a phase-mode transformation to obtain a second zero-mode voltage travelling wave;
according to the formula Transforming the second voltage traveling wave to obtain a second zero-mode voltage traveling wave U 20 (t); wherein U a2(t),Ub2 (t) and U c2 (t) are respectively second voltage traveling waves of each phase of the three phases.
5. The method according to claim 3 or 4, wherein obtaining a traveling wave difference from the first zero-mode voltage traveling wave and the second zero-mode voltage traveling wave comprises:
Obtaining the travelling wave difference Δu (t) according to the formula Δu (t) =u 10(t)-U20 (t); wherein U 10 (t) is the first zero-mode voltage traveling wave, and U 20 (t) is the second zero-mode voltage traveling wave.
6. The method of claim 5, wherein differentiating the traveling wave difference to obtain a first non-zero point of mutation time comprises:
And carrying out differential derivation on the traveling wave difference value delta U (t), wherein the differential derivation is as follows:
Wherein: Δu' (t) is a differential derivative of Δu (t), Δt is a sampling time interval, and Δu (t) is the traveling wave difference;
Recording a first non-zero mutation point time t 1 in response to the absolute value of Δu' (t) being greater than a determination threshold; the judgment threshold is positive and is related to the sampling time interval and whether the line mode voltage takes a value at the primary side or takes a value at the secondary side.
7. The method of claim 6, wherein obtaining a propagation time from the first non-zero point of mutation time comprises:
And obtaining the propagation time T according to T=t 1-t0, wherein T 1 is the first non-zero mutation point moment, and T 0 is the time of injecting the first high-voltage pulse into the head end.
8. The method of claim 7, wherein obtaining a fault distance from the travel time, zero mode wave velocity, and line mode wave velocity comprises:
according to the formula And obtaining the fault distance L, wherein v 0 is the zero mode wave speed, v 1 is the linear mode wave speed, and L is the fault distance.
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