A method for locating a fault point of a cable

Abstract

The application discloses a cable fault point positioning method and relates to the technical field of power system fault monitoring, and comprises the following steps: acquiring line fault properties and a fault distance measurement interval; grounding one end of a cable where the fault distance measurement interval is located, inputting a current traveling wave from the other end of the cable, and selecting a measurement point in the fault distance measurement interval; acquiring direction and quantity characteristics of the current traveling wave at the measurement point, and determining a directional relationship between the measurement point and a fault point according to the line fault properties and the direction and quantity characteristics of the current traveling wave at the measurement point; selecting a new measurement point according to a preset rule according to the directional relationship between the measurement point and the fault point; repeating the two steps until the directional relationship between a current measurement point and the fault point changes, and then determining that the fault point is located between the current measurement point and a previous measurement point. The application can quickly narrow the range interval of the fault point on the cable, and facilitates accurate positioning of the fault point.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power system fault monitoring, in particular to a cable fault point positioning method. BACKGROUND

[0002] A cable is usually a rope-like conductor composed of several or several groups of twisted wires, each group of wires is insulated from each other, and is often twisted around a center, and the entire outside is covered with a highly insulated covering layer. Cables are widely used in power systems. Due to the corrosion of rainwater and underground environment, cable faults often occur due to insulation aging, moisture and mechanical damage, etc. Because the cable line is not directly observable like the overhead line, the detection task for cable fault is much more difficult.

[0003] In the prior art, cable fault point positioning is mainly obtained by fault ranging to the approximate distance of the fault point from the cable terminal, and then the detection personnel searches for the fault point in a certain range interval near the distance. However, due to the complex structure of the cable, fault ranging cannot avoid errors, resulting in a usually large range interval searched by the detection personnel, and thus a large human cost and time cost are required to search again to accurately locate the fault point. SUMMARY

[0004] The embodiment of the present application provides a cable fault point positioning method to solve the technical problem in the related art that the existing cable fault point positioning method can only be positioned to a large interval range, and a large human cost and time cost are required to search again to accurately locate the fault point.

[0005] The present application provides a cable fault point positioning method, comprising the following steps:

[0006] Step S10, obtaining a line fault property and a fault ranging interval;

[0007] Step S20, grounding one end of a cable where the fault ranging interval is located, inputting a current traveling wave from the other end of the cable, and selecting a measurement point in the fault ranging interval;

[0008] Step S30, obtaining a direction and quantity characteristic of the current traveling wave at the measurement point, and determining a directional relationship between the measurement point and the fault point according to the line fault property and the direction and quantity characteristic of the current traveling wave at the measurement point;

[0009] Step S40, selecting a new measurement point according to a preset rule according to the directional relationship between the measurement point and the fault point;

[0010] Step S50, repeating step S30-S40 until the direction relationship between the current measurement point and the fault point changes, then determining that the fault point is located between the current measurement point and the last measurement point.

[0011] In some embodiments, the step of obtaining the direction and quantity characteristics of the current traveling wave at the measurement point and determining the direction relationship between the measurement point and the fault point according to the line fault property and the direction and quantity characteristics of the current traveling wave at the measurement point specifically comprises:

[0012] The line fault property includes low resistance fault and high resistance fault.

[0013] If the line fault property is low resistance fault, the current traveling wave at the measurement point has incident wave and reflected wave, and the directions of the incident wave and the reflected wave are the same, then it is determined that the measurement point is located between the input current traveling wave end and the fault point.

[0014] If the line fault property is low resistance fault, the current traveling wave at the measurement point only has refracted wave, then it is determined that the measurement point is located between the fault point and the ground end of the fault distance interval.

[0015] If the line fault property is high resistance fault, the current traveling wave at the measurement point has incident wave and reflected wave, and the directions of the incident wave and the reflected wave are opposite, then it is determined that the measurement point is located between the input current traveling wave end and the fault point.

[0016] If the line fault property is high resistance fault, the current traveling wave at the measurement point only has refracted wave, then it is determined that the measurement point is located between the fault point and the ground end of the fault distance interval.

[0017] In some embodiments, the step of selecting a new measurement point according to the direction relationship between the measurement point and the fault point according to the preset rule specifically comprises:

[0018] If the measurement point is located between the input current traveling wave end and the fault point, then the midpoint between the measurement point and the ground end of the fault distance interval is selected as the new measurement point.

[0019] If the measurement point is located between the fault point and the ground end of the fault distance interval, then the midpoint between the measurement point and the input current traveling wave end is selected as the new measurement point.

[0020] In some embodiments, the step of selecting a new measurement point according to the direction relationship between the measurement point and the fault point according to the preset rule specifically comprises:

[0021] If the measurement point is located between the input current traveling wave end and the fault point, then a preset distance from the input current traveling wave end to the fault point is selected as the new measurement point.

[0022] In some embodiments, the step of selecting the new measuring point according to the directional relationship between the measuring point and the fault point in the preset rule further comprises:

[0023] If the measuring point is located between the fault point and the grounding end of the fault ranging interval, a preset distance is moved from the grounding end of the fault ranging interval to the fault point as the new measuring point.

[0024] In some embodiments, the step of repeating the steps S30-S40 until the directional relationship between the current measuring point and the fault point changes, and then determining that the fault point is located between the current measuring point and the last measuring point comprises:

[0025] If the current measuring point is located between the fault point and the grounding end of the fault ranging interval, and the last measuring point is located between the input current traveling wave end and the fault point, it is determined that the fault point is located between the current measuring point and the last measuring point.

[0026] In some embodiments, the step of repeating the steps S30-S40 until the directional relationship between the current measuring point and the fault point changes, and then determining that the fault point is located between the current measuring point and the last measuring point further comprises:

[0027] If the current measuring point is located between the input current traveling wave end and the fault point, and the last measuring point is located between the fault point and the grounding end of the fault ranging interval, it is determined that the fault point is located between the current measuring point and the last measuring point.

[0028] In some embodiments, the step of obtaining the line fault property and the fault ranging interval comprises:

[0029] If the wave impedance of the fault line is smaller than the wave impedance of the normal line, the line fault property is a low-impedance fault, and the low-voltage pulse reflection method is used to obtain the fault ranging interval.

[0030] In some embodiments, the step of obtaining the line fault property and the fault ranging interval further comprises:

[0031] If the wave impedance of the fault line is greater than the wave impedance of the normal line, the line fault property is a high-impedance fault, and the direct flash method or the surge flash method is used to obtain the fault ranging interval.

[0032] In some embodiments, the step of grounding one end of the cable where the fault ranging interval is located and inputting the current traveling wave from the other end of the cable comprises:

[0033] The two ends of the cable where the fault ranging interval is located are separated, one end of the cable is grounded, and the current traveling wave is input from the other end of the cable.

[0034] The technical scheme provided by the application has the following beneficial effects:

[0035] The cable fault point positioning method provided by the embodiment of the present application firstly acquires the line fault property and the fault ranging interval, secondly grounds one end of the cable where the fault ranging interval is located, inputs the current traveling wave from the other end of the cable, and selects a measurement point in the fault ranging interval, then acquires the direction and quantity characteristics of the current traveling wave at the measurement point, and determines the directional relationship between the measurement point and the fault point according to the line fault property and the direction and quantity characteristics of the current traveling wave at the measurement point, and then selects a new measurement point according to the directional relationship between the measurement point and the fault point and the preset rule, and finally repeats the determination of the directional relationship between the measurement point and the fault point and the selection of the new measurement point until the directional relationship between the current measurement point and the fault point changes, and then it is determined that the fault point is located between the current measurement point and the last measurement point. The positioning method of the present application can quickly narrow the range interval of the fault point on the cable, facilitate the detection personnel to quickly and accurately position the fault point, and reduce the labor cost and time cost. BRIEF DESCRIPTION OF DRAWINGS

[0036] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiment description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort on the basis of these drawings.

[0037] Figure 1 The flow chart of the cable fault point positioning method provided by the embodiment of the present application is shown in the figure.

[0038] Figure 2 The schematic diagram of the fault point positioning of the selected fault ranging interval provided by the embodiment of the present application is shown in the figure.

[0039] Figure 3 The traveling wave waveform schematic diagram of the B point measurement point and the C point measurement point when the fault is low resistance provided by the embodiment of the present application is shown in the figure.

[0040] Figure 4 The traveling wave waveform schematic diagram of the B point measurement point and the C point measurement point when the fault is high resistance provided by the embodiment of the present application is shown in the figure. DETAILED DESCRIPTION

[0041] In order to make the purpose, technical scheme and advantages of the embodiments of the present application more clear, the following will combine the drawings in the embodiments of the present application to clearly and completely describe the technical scheme in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without any creative effort belong to the scope of protection of the present application.

[0042] The embodiment of the present application provides a cable fault point positioning method, which can solve the technical problem that the existing cable fault point positioning method can only be positioned to a larger interval range, and a larger human cost and time cost are required to search again to accurately position the fault point.

[0043] Figure 1 is a flow block diagram of a cable fault point positioning method provided by the embodiment of the present application, comprising the following steps:

[0044] Step S10, acquiring a line fault property and a fault distance measurement interval.

[0045] Specifically, the line fault property comprises a low-resistance fault and a high-resistance fault, the ground impedance of the line fault point can be tested by using an impedance tester, and the ground impedance of the tested fault point is compared with the wave impedance of the normal line; if the ground impedance of the fault point is smaller than the wave impedance of the normal line, the line fault property is a low-resistance fault; if the ground impedance of the fault point is greater than the wave impedance of the normal line, the line fault property is a high-resistance fault, thereby the line fault property is acquired.

[0046] Further, if the line fault property is a low-resistance fault, the low-voltage pulse reflection method is used to acquire the fault distance measurement interval. Specifically, one pulse wave is sent out by a pulse generator, the pulse wave is transmitted to the fault line through a lead, the pulse wave is transmitted to the fault point along the fault line and is reflected back, the time interval between the sending pulse and the reflected pulse is recorded at the test end by using an oscilloscope, the distance between the test end and the fault point is calculated, and the fault distance measurement interval is selected. For example, assuming that the distance between the test end and the fault point is M kilometers, the test end is taken as the starting point, and the point M kilometers away from the starting point is taken as the reference, the line between M-n and M+n is selected as the fault distance measurement interval, wherein n can be selected according to the distance measurement accuracy of the adopted device and the actual line condition.

[0047] Further, if the line fault property is a high-resistance fault, the straight flash method or the flash method is used to acquire the fault distance measurement interval. Specifically, one end of the fault line is grounded, the other end is opened and inputted with a direct-current high voltage or a pulse high voltage to break down the fault point, the time interval of the direct-current high voltage or the pulse high voltage between the test point and the fault point for one round trip is observed, the distance between the test end and the fault point is calculated, and the fault distance measurement interval is selected. The selection method of the fault distance measurement interval is the same as that of the low-resistance fault.

[0048] The determination method of the fault distance measurement interval in the above two fault properties is an offline method, in addition, there is an online fault distance measurement method, that is, the current traveling wave at the fault time is collected by the cable online fault distance measurement device installed in advance on the cable line, the fault position is calculated according to the time difference of the collected current traveling wave reaching two collection devices, thereby the fault distance measurement interval is determined, and this method is applicable to both the high-resistance fault line and the low-resistance fault line.

[0049] Step S20, grounding one end of the cable where the fault location interval is located, inputting current traveling wave from the other end of the cable, and selecting a measurement point in the fault location interval.

[0050] Specifically, the two ends of the cable where the fault location interval is located are disconnected, one end of the cable is grounded, current traveling wave is inputted from the other end, and a measurement point is selected in the fault location interval of the cable.

[0051] Step S30, obtaining the direction and quantity characteristics of the current traveling wave at the measurement point, and determining the directional relationship between the measurement point and the fault point according to the line fault property and the direction and quantity characteristics of the current traveling wave at the measurement point.

[0052] As an optional implementation, in one of the embodiments, the step of obtaining the direction and quantity characteristics of the current traveling wave at the measurement point, and determining the directional relationship between the measurement point and the fault point according to the line fault property and the direction and quantity characteristics of the current traveling wave at the measurement point, specifically comprises:

[0053] If the line fault property is a low-resistance fault, the current traveling wave at the measurement point has an incident wave and a reflected wave, and the directions of the incident wave and the reflected wave are the same, it is determined that the measurement point is located between the input current traveling wave end and the fault point.

[0054] If the line fault property is a low-resistance fault, the current traveling wave at the measurement point only has a refracted wave, it is determined that the measurement point is located between the fault point and the grounding end of the fault location interval.

[0055] If the line fault property is a high-resistance fault, the current traveling wave at the measurement point has an incident wave and a reflected wave, and the directions of the incident wave and the reflected wave are opposite, it is determined that the measurement point is located between the input current traveling wave end and the fault point.

[0056] If the line fault property is a high-resistance fault, the current traveling wave at the measurement point only has a refracted wave, it is determined that the measurement point is located between the fault point and the grounding end of the fault location interval.

[0057] Specifically, referring to FIGS. 1 and 2, Figure 2 and Figure 3 as shown, the left end is the input current traveling wave end of the fault location interval, the right end is the grounding end of the fault location interval, the A point is the fault point, and the B point and the C point are measurement points, if the line fault property is a low-resistance fault, the current traveling wave at the B point measurement point has an incident wave I1f and a reflected wave I2f, and the directions of the incident wave I1f and the reflected wave I2f are the same, it is determined that the B point measurement point is located between the input current traveling wave end and the fault point A point, and the current traveling wave at the C point measurement point only has a refracted wave I1b, it is determined that the C point measurement point is located between the fault point A point and the grounding end of the fault location interval.

[0058] Specifically, referring to Figure 2 and Figure 4 , the left end is the input current traveling wave end of the fault ranging interval, the right end is the ground end of the fault ranging interval, A is the fault point, B and C are the measuring points, if the line fault is a high resistance fault, the current traveling wave at the B measuring point has an incident wave I1f and a reflected wave I2f, and the directions of the incident wave I1f and the reflected wave I2f are opposite, it is determined that the B measuring point is located between the input current traveling wave end and the fault point A, and the current traveling wave at the C measuring point only has a refracted wave I1b, it is determined that the C measuring point is located between the fault point A and the ground end of the fault ranging interval.

[0059] Step S40, according to the directional relationship between the measuring point and the fault point, a new measuring point is selected according to a preset rule.

[0060] As an optional implementation, in one of the embodiments of the application, referring to Figure 2 , the step of selecting a new measuring point according to the directional relationship between the measuring point and the fault point according to a preset rule specifically includes:

[0061] If the measuring point is located between the input current traveling wave end and the fault point A, the midpoint between the measuring point and the ground end of the fault ranging interval is taken as the new measuring point, and if the measuring point is located between the fault point A and the ground end of the fault ranging interval, the midpoint between the measuring point and the input current traveling wave end is taken as the new measuring point. This method of calculating the moving distance is simple in calculation, the calculation result is real and reliable, and the accuracy of the fault point positioning is improved.

[0062] As an optional implementation, in one of the embodiments of the application, referring to Figure 2 , the step of selecting a new measuring point according to the directional relationship between the measuring point and the fault point according to a preset rule specifically includes:

[0063] If the measuring point is located between the input current traveling wave end and the fault point A, a preset distance is moved from the input current traveling wave end to the fault point A as the new measuring point, and if the measuring point is located between the fault point A and the ground end of the fault ranging interval, a preset distance is moved from the ground end of the fault ranging interval to the fault point A as the new measuring point. By moving a preset distance from the corresponding direction end to the fault point as the new measuring point, only the moving direction needs to be determined, the distance of each movement is fixed, and there is no need to calculate the moving distance, so the operation is fast, and the working efficiency of the cable fault point positioning is improved.

[0064] Step S50, steps S30 to S40 are repeated until the directional relationship between the current measuring point and the fault point changes, and it is determined that the fault point is located between the current measuring point and the previous measuring point.

[0065] As an optional implementation, in one of the embodiments of the application, referring to Figure 2 The step of determining the fault point between the current measurement point and the previous measurement point includes the following steps:

[0066] If the current measurement point C is between the fault point A and the ground end of the fault ranging interval, and the previous measurement point B is between the input current traveling wave end and the fault point A, the direction relationship between the measurement points C and B and the fault point A changes, then the fault point A is determined to be between the current measurement point C and the previous measurement point B.

[0067] The embodiment of the application provides a cable fault point positioning method, which first acquires the line fault property and the fault ranging interval, then grounds one end of the cable where the fault ranging interval is located, inputs the current traveling wave from the other end of the cable, selects a measurement point in the fault ranging interval, acquires the direction and quantity characteristics of the current traveling wave at the measurement point, determines the direction relationship between the measurement point and the fault point according to the line fault property and the direction and quantity characteristics of the current traveling wave at the measurement point, selects a new measurement point according to the direction relationship between the measurement point and the fault point, and finally repeats the determination of the direction relationship between the measurement point and the fault point and the selection of the new measurement point until the direction relationship between the current measurement point and the fault point changes, and then determines the fault point to be between the current measurement point and the previous measurement point. The positioning method can quickly narrow the range interval of the fault point on the cable, facilitates the detection personnel to quickly and accurately position the fault point, and reduces the labor cost and time cost.

[0068] In the description of the present application, it should be noted that the terms "upper", "lower", and the like are used for indicating the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. Unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connecting" should be understood broadly, for example, can be fixed connection, can also be detachable connection, or integral connection; can be mechanical connection, can also be electrical connection; can be directly connected, can also be indirectly connected through an intermediate medium, can be internal communication of two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0069] It should be noted that in the present application, relational terms such as "first" and "second" and the like are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. Moreover, the terms "comprise", "include" or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus including a series of elements includes not only those elements, but also other elements not explicitly listed, or other elements inherent in such a process, method, article or apparatus. Without more limitations, the element defined by the statement "comprising a" does not exclude the presence of other identical elements in the process, method, article or apparatus including the element.

[0070] The above is only a specific embodiment of the present application, enabling those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features of the present application.

Claims

1. A method of locating a fault point in a cable, characterized by, The method comprises the following steps: Step S10, obtaining the line fault property and the fault ranging interval; Step S20, grounding one end of the cable where the fault ranging interval is located, inputting the current traveling wave from the other end of the cable, and selecting a measuring point in the fault ranging interval; Step S30, obtaining the direction and quantity characteristics of the current traveling wave at the measuring point, and determining the directional relationship between the measuring point and the fault point according to the line fault property and the direction and quantity characteristics of the current traveling wave at the measuring point; The line fault property comprises low-resistance fault and high-resistance fault; If the line fault property is low-resistance fault, the current traveling wave has incident wave and reflected wave at the measuring point, and the directions of the incident wave and the reflected wave are the same, then it is determined that the measuring point is located between the input current traveling wave end and the fault point; If the line fault property is low-resistance fault, the current traveling wave only has refracted wave at the measuring point, then it is determined that the measuring point is located between the fault point and the grounding end of the fault ranging interval; If the line fault property is high-resistance fault, the current traveling wave has incident wave and reflected wave at the measuring point, and the directions of the incident wave and the reflected wave are opposite, then it is determined that the measuring point is located between the input current traveling wave end and the fault point; If the line fault property is high-resistance fault, the current traveling wave only has refracted wave at the measuring point, then it is determined that the measuring point is located between the fault point and the grounding end of the fault ranging interval; Step S40, selecting a new measuring point according to the preset rule according to the directional relationship between the measuring point and the fault point; Step S50, repeating steps S30-S40 until the directional relationship between the current measuring point and the fault point changes, then determining that the fault point is located between the current measuring point and the last measuring point; If the current measuring point is located between the fault point and the grounding end of the fault ranging interval, and the last measuring point is located between the input current traveling wave end and the fault point, then it is determined that the fault point is located between the current measuring point and the last measuring point; If the current measuring point is located between the input current traveling wave end and the fault point, and the last measuring point is located between the fault point and the grounding end of the fault ranging interval, then it is determined that the fault point is located between the current measuring point and the last measuring point.

2. The method of claim 1, wherein, The step of selecting a new measuring point according to the preset rule according to the directional relationship between the measuring point and the fault point specifically comprises: If the measuring point is located between the input current traveling wave end and the fault point, then the midpoint between the measuring point and the grounding end of the fault ranging interval is taken as the new measuring point; If the measuring point is located between the fault point and the grounding end of the fault ranging interval, then the midpoint between the measuring point and the input current traveling wave end is taken as the new measuring point.

3. The method of claim 1, wherein, The step of selecting a new measuring point according to the preset rule according to the directional relationship between the measuring point and the fault point specifically comprises: If the measuring point is located between the input current traveling wave end and the fault point, then a preset distance is moved from the input current traveling wave end to the fault point direction as the new measuring point.

4. The method of claim 3, wherein, The step of selecting a new measuring point according to the preset rule according to the directional relationship between the measuring point and the fault point specifically further comprises: If the measuring point is located between the fault point and the grounding end of the fault ranging interval, then a preset distance is moved from the grounding end of the fault ranging interval to the fault point direction as the new measuring point.

5. The method of claim 1, wherein, The step of acquiring the line fault property and the fault ranging interval specifically comprises: If the wave impedance of the fault line is less than the wave impedance of the normal line, the line fault property is a low-impedance fault, and the low-voltage pulse reflection method is used to acquire the fault ranging interval.

6. The method of claim 5, wherein, The step of acquiring the line fault property and the fault ranging interval specifically further comprises: If the wave impedance of the fault line is greater than the wave impedance of the normal line, the line fault property is a high-impedance fault, and the direct flash method or the surge flash method is used to acquire the fault ranging interval.

7. The method of claim 1, wherein, The step of grounding one end of the cable where the fault ranging interval is located and inputting the current traveling wave from the other end of the cable specifically comprises: The two ends of the cable where the fault ranging interval is located are untied, one end of the cable is grounded, and the current traveling wave is input from the other end of the cable.

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