Sheath induced current live-line test method, system and device

Abstract

The invention discloses a sheath induced current live-line test method, system and device, and the method comprises the steps: obtaining a three-phase combined induced voltage according to a commutation connection mode of a coaxial cable; wherein the i-th phase joint induced voltage is the difference between the total induced voltage and the coaxial cable induced voltage of the j-th phase joint, the total induced voltage is the sum of the three-phase main cable induced voltage and the coaxial cable induced voltage of the i-th phase joint, and the coaxial cable of the j-th phase joint is in commutation connection with the coaxial cable of the i-th phase joint. The three-phase main cable induced voltage is the induced voltage of the three-phase main cable on the same side of the joint group; and calculating the induced current of the three-phase main cable sheath according to the three-phase combined induced voltage. According to the invention, the measurement result is more practical, the live-line test of the sheath induction current can be realized, the test does not need to dismount the cross interconnection grounding box, and the test is convenient.

Description

Technical Field

[0001] The invention relates to a method, system and device for testing a sheath induced current under live conditions, belonging to the technical field of power transmission and transformation. Background Art

[0002] For the convenience of transportation and installation, high-voltage cables produced in factories need to be mounted on reels and accessories made after being laid on site to achieve cable connection. When the high-voltage cable core runs through a large current, its metal sheath (hereinafter referred to as "sheath") will couple to generate induced current, causing the cable to heat up and even cause accidents.

[0003] In order to suppress the induced current, the long-distance main cable line needs to be connected to the cross-interconnected grounding box through the joint group (the joint group includes three-phase joints) and the coaxial cable to realize the phase-changing connection of the sheath, which has achieved the purpose of partially offsetting the inductive voltage and reducing the induced current. In order to further ensure the safety of cable operation, it is necessary to accurately test the sheath induced current, but it is mainly achieved through two methods. One method is that the current of the coaxial cable drawn from the A-phase joint is tested by the clamp meter, which is the current of the A-phase cable sheath, but there is a huge error with the actual situation, so it is impossible to accurately grasp the state of the sheath induced current; the other method is to open the cross-interconnected grounding box and use the clamp meter to test the current of the cross-interconnected copper busbar of the grounding box to realize the sheath current test. Although this test method can test the metal sheath current, it requires the disassembly of the grounding box, which not only has low test efficiency, but also has safety hazards. Summary of the invention

[0004] The invention provides a method, system and device for testing a sheath induced current live, which solve the problems existing in the background technology.

[0005] According to one aspect of the present disclosure, a method for testing a sheath induced current is provided, comprising: According to the phase-changing connection mode of the coaxial cable, the three-phase joint induced voltage is obtained; wherein, the i-th phase joint induced voltage is the difference between the total induced voltage and the coaxial cable induced voltage of the j-th phase connector, the total induced voltage is the sum of the three-phase main cable induced voltage and the coaxial cable induced voltage of the i-th phase connector, the coaxial cable of the j-th phase connector is connected in phase-changing with the coaxial cable of the i-th phase connector, and the three-phase main cable induced voltage is the induced voltage of the three-phase main cable on the same side of the connector group; i is not equal to j, i=A, B and C, j=A, B and C; According to the three-phase joint induced voltage, the induced current of the three-phase main cable sheath is calculated.

[0006] Furthermore, the induced current of the three-phase main cable sheath is calculated, including: The induced current of the main cable sheath of the i-th phase is the ratio of the i-th phase combined induced voltage to the operation coefficient.

[0007] Further, the phase-changing connection mode of the coaxial cable is predetermined, and the determination process includes: Obtaining the difference between the induced voltage of the main cable on the first side of the i-th phase connector and the induced voltage of the main cable on the second side of the remaining phase connectors; Based on all the differences, determine the phase-changing connection method of the coaxial cable.

[0008] Further, according to all the differences, the phase-changing connection mode of the coaxial cable is determined, including: Calculation parameter F1=|U 1A2B -U 1B2C |+|U 1A2B -U 1C2A |+|U 1B2C -U 1C2A | and parameter F2=|U 1A2C -U 1B2A |+|U 1A2C -U 1C2B |+|U 1B2A -U 1C2B |; Among them, U 1A2B is the difference between the induced voltage of the main cable on the first side of the A phase connector and the induced voltage of the main cable on the second side of the B phase connector, U 1A2C is the difference between the induced voltage of the main cable on the first side of the A phase connector and the induced voltage of the main cable on the second side of the C phase connector, U 1B2A is the difference between the induced voltage of the main cable on the first side of the B phase connector and the induced voltage of the main cable on the second side of the A phase connector, U 1B2C is the difference between the induced voltage of the main cable on the first side of the B phase connector and the induced voltage of the main cable on the second side of the C phase connector, U 1C2A is the difference between the induced voltage of the main cable on the first side of the C phase connector and the induced voltage of the main cable on the second side of the A phase connector, U 1C2B is the difference between the induced voltage of the main cable on the first side of the C phase connector and the induced voltage of the main cable on the second side of the B phase connector; If F1 is less than F2, the main cable sheath on the first side of the A-phase connector is connected to the main cable sheath on the second side of the B-phase connector through the S core of the coaxial cable of the A-phase connector and the T core of the coaxial cable of the B-phase connector in sequence, the main cable sheath on the first side of the B-phase connector is connected to the main cable sheath on the second side of the C-phase connector in sequence through the S core of the coaxial cable of the B-phase connector and the T core of the coaxial cable of the C-phase connector in sequence, and the main cable sheath on the first side of the C-phase connector is connected to the main cable sheath on the second side of the A-phase connector in sequence through the S core of the coaxial cable of the C-phase connector and the T core of the coaxial cable of the A-phase connector;; wherein, S=outer, T=inner or S=inner, T=outer; If F1 is greater than F2, the main cable sheath on the first side of the A phase connector is connected to the main cable sheath on the second side of the C phase connector through the S core of the coaxial cable of the A phase connector and the T core of the coaxial cable of the C phase connector; the main cable sheath on the first side of the C phase connector is connected to the main cable sheath on the second side of the B phase connector through the S core of the coaxial cable of the C phase connector and the T core of the coaxial cable of the B phase connector; the main cable sheath on the first side of the B phase connector is connected to the main cable sheath on the second side of the A phase connector through the S core of the coaxial cable of the B phase connector and the T core of the coaxial cable of the A phase connector.

[0009] According to another aspect of the present disclosure, a sheath induced current live testing system is provided, comprising: The acquisition module acquires the three-phase joint induced voltage according to the phase-changing connection mode of the coaxial cable; wherein the i-th phase joint induced voltage is the difference between the total induced voltage and the coaxial cable induced voltage of the j-th phase connector, the total induced voltage is the sum of the three-phase main cable induced voltage and the coaxial cable induced voltage of the i-th phase connector, the coaxial cable of the j-th phase connector is connected in phase-changing with the coaxial cable of the i-th phase connector, and the three-phase main cable induced voltage is the induced voltage of the three-phase main cable on the same side of the connector group; i is not equal to j, i=A, B and C, j=A, B and C; The calculation module calculates the induced current of the three-phase main cable sheath according to the three-phase joint induced voltage.

[0010] Furthermore, in the calculation module, the induced current of the three-phase main cable sheath is calculated, including: The induced current of the main cable sheath of the i-th phase is the ratio of the i-th phase combined induced voltage to the operation coefficient.

[0011] Furthermore, the system further includes a determination module for predetermining a phase-changing connection mode of the coaxial cable, and the determination module is configured to: Obtaining the difference between the induced voltage of the main cable on the first side of the i-th phase connector and the induced voltage of the main cable on the second side of the remaining phase connectors; Based on all the differences, determine the phase-changing connection method of the coaxial cable.

[0012] Furthermore, in the determination module, the phase switching connection mode of the coaxial cable is determined according to all the differences, including: Calculation parameter F1=|U 1A2B -U 1B2C |+|U 1A2B -U 1C2A |+|U 1B2C -U 1C2A | and parameter F2=|U 1A2C -U 1B2A |+|U 1A2C -U 1C2B |+|U 1B2A -U 1C2B|; Among them, U 1A2B is the difference between the induced voltage of the main cable on the first side of the A phase connector and the induced voltage of the main cable on the second side of the B phase connector, U 1A2C is the difference between the induced voltage of the main cable on the first side of the A phase connector and the induced voltage of the main cable on the second side of the C phase connector, U 1B2A is the difference between the induced voltage of the main cable on the first side of the B phase connector and the induced voltage of the main cable on the second side of the A phase connector, U 1B2C is the difference between the induced voltage of the main cable on the first side of the B phase connector and the induced voltage of the main cable on the second side of the C phase connector, U 1C2A is the difference between the induced voltage of the main cable on the first side of the C phase connector and the induced voltage of the main cable on the second side of the A phase connector, U 1C2B is the difference between the induced voltage of the main cable on the first side of the C phase connector and the induced voltage of the main cable on the second side of the B phase connector; If F1 is less than F2, the main cable sheath on the first side of the A-phase connector is connected to the main cable sheath on the second side of the B-phase connector through the S core of the coaxial cable of the A-phase connector and the T core of the coaxial cable of the B-phase connector in sequence, the main cable sheath on the first side of the B-phase connector is connected to the main cable sheath on the second side of the C-phase connector in sequence through the S core of the coaxial cable of the B-phase connector and the T core of the coaxial cable of the C-phase connector in sequence, and the main cable sheath on the first side of the C-phase connector is connected to the main cable sheath on the second side of the A-phase connector in sequence through the S core of the coaxial cable of the C-phase connector and the T core of the coaxial cable of the A-phase connector;; wherein, S=outer, T=inner or S=inner, T=outer; If F1 is greater than F2, the main cable sheath on the first side of the A phase connector is connected to the main cable sheath on the second side of the C phase connector through the S core of the coaxial cable of the A phase connector and the T core of the coaxial cable of the C phase connector; the main cable sheath on the first side of the C phase connector is connected to the main cable sheath on the second side of the B phase connector through the S core of the coaxial cable of the C phase connector and the T core of the coaxial cable of the B phase connector; the main cable sheath on the first side of the B phase connector is connected to the main cable sheath on the second side of the A phase connector through the S core of the coaxial cable of the B phase connector and the T core of the coaxial cable of the A phase connector.

[0013] According to another aspect of the present disclosure, there is provided a sheath induction current live testing device, comprising a testing host, a first induction device, a second induction device, a third induction device, a fourth induction device and a fifth induction device; The first sensing device, the second sensing device, and the third sensing device respectively sense the induced voltage of the main cable on the same side of the connector group, the fourth sensing device and the fifth sensing device respectively sense the induced voltage of the two coaxial cables connected in phase, and the output ends of all the sensing devices are connected in series and then connected to the test host; The test host adopts the above-mentioned sheath induced current live test method to perform the sheath induced current live test.

[0014] Further, the test host includes a filter, an operational amplifier circuit, an analog-to-digital converter, a controller and a display; The filter, the operational amplifier circuit and the analog-to-digital converter sequentially filter, operationally amplify and perform analog-to-digital conversion on the received voltage; The controller uses a preset calculation method to perform calculations according to the voltage after analog-to-digital conversion; wherein the preset calculation method includes the above-mentioned sheath induced current live test method; The display shows the calculation results of the controller.

[0015] The beneficial effects achieved by the present invention are as follows: the present invention calculates the induced current of the sheath of the three-phase main cable according to the induced voltage of the three-phase main cable on the same side of the connector group and the induced voltage of the two coaxial cables connected in phase change, and the result is more in line with reality. In addition, the live test of the sheath induced current can be realized, and the test does not require the removal of the cross-connected grounding box, so the test is convenient. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the high voltage cable line sheath being connected through the coaxial cable phase change; Figure 2 A flow chart of the sheath induced current live test method; Figure 3 The block diagram of the sheath induced current live test system is shown in FIG. Figure 4 It is a structural schematic diagram of a sheath induced current live testing device; Figure 5 To pass Figure 4 A schematic diagram of a device for determining a phase-changing connection mode of a coaxial cable; Figure 6 To pass Figure 4 Schematic diagram of testing sheath induced current; Figure 7 for Figure 6 Equivalent schematic diagram of . DETAILED DESCRIPTION

[0017] The following will be combined with the drawings in the embodiments of the present disclosure to clearly and completely describe the technical solutions in the embodiments of the present disclosure. It is obvious that the described embodiments are only part of the embodiments of the present disclosure, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present disclosure and its application or use. Based on the embodiments in the present disclosure, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present disclosure.

[0018] Unless specifically stated otherwise, the relative arrangement of components and steps, the numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present disclosure.

[0019] At the same time, it should be understood that for the convenience of description, the sizes of the various parts shown in the drawings are not drawn according to the actual proportional relationship.

[0020] Technologies, methods, and equipment known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, the technologies, methods, and equipment should be considered part of the specification.

[0021] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limiting. Therefore, other examples of the exemplary embodiments may have different values.

[0022] It should be noted that similar symbols and letters refer to similar items in the following figures, and therefore, once an item is defined in one figure, it does not require further discussion in subsequent figures.

[0023] Meanwhile, in the description of the embodiments of the present disclosure, the terms "first", "second", etc. are only used to distinguish the description and cannot be understood as indicating or implying relative importance. Therefore, the features defined as "first" or "second" may explicitly or implicitly include one or more features.

[0024] In order to solve the problem of large errors in traditional sheath induced current testing, the present invention proposes a live testing method, system and device for sheath induced current. Specifically, the live testing of the sheath induced current of the three-phase main cable is achieved by using the induced voltage of the three-phase main cable on the same side of the connector group and the induced voltage of the two coaxial cables connected by phase change.

[0025] See also Figure 1 , Figure 1 This is a schematic diagram of the phase-changing connection of the high-voltage cable line sheath through the coaxial cable. In the figure, from top to bottom are the A, B, and C phase main cables. There are multiple joint groups in the three-phase main cable, and each joint group has a row of three-phase joints, which are A, B, and C phase joints from top to bottom. The joint coaxial cables are connected to the sheath, and the coaxial cables of the joint groups at both ends are directly connected to the grounding box, and the coaxial cables of the remaining joint groups are connected to the cross-interconnected grounding box to realize the phase-changing connection of the sheath.

[0026] See also Figure 2 , Figure 2It is a flow chart of a method for testing the induced current of a sheath provided in an embodiment of the present disclosure. The method can be executed by a test host, which can be a terminal device or a server. Among them, the terminal device can include but is not limited to a mobile phone, a computer, a smart wearable device, etc., which is not limited by the embodiment of the present disclosure; the server can be an independent physical server, or a server cluster or distributed system composed of multiple physical servers, or a cloud server that provides basic cloud computing services such as cloud services, cloud databases, cloud computing, big data and artificial intelligence platforms, etc., which is not limited by the embodiment of the present disclosure. Optionally, the method can also be executed collaboratively by multiple electronic devices with computing power. For the sake of ease of explanation, the subsequent embodiments are described as being executed by the test host.

[0027] Figure 2 The sheath induced current live testing method is used to test the induced current of a section of sheath, that is, the sheath induced current between adjacent joint groups. The method may at least include the following steps S101 to S102: Step S101, obtaining a three-phase joint induced voltage according to a phase-changing connection mode of the coaxial cable; wherein the i-th phase joint induced voltage is the difference between the total induced voltage and the coaxial cable induced voltage of the j-th phase connector, the total induced voltage is the sum of the three-phase main cable induced voltage and the coaxial cable induced voltage of the i-th phase connector, the coaxial cable of the j-th phase connector is connected in phase-changing manner with the coaxial cable of the i-th phase connector, and the three-phase main cable induced voltage is the induced voltage of the main cable on the same side of the connector group; i is not equal to j, i=A, B and C, j=A, B and C.

[0028] It should be noted that for three-phase main cables and coaxial cables, there are two situations in which the phase-changing connection method can be obtained. One is that the phase-changing connection method can be obtained by looking up the design data, and it can be determined that the design data is consistent with the actual situation. The second is that the design data is lost, or the design data is inconsistent with the actual situation, and the specific phase-changing connection method cannot be determined.

[0029] For the second case, in order to ensure that the phase-changing connection mode is accurately known, in some embodiments, the phase-changing connection mode may be determined before implementing the above-mentioned test method.

[0030] It should be noted that the first side is defined as the left side and the second side is the right side. Generally, the cross-connected grounding box is on the first side of the joint group. It is known that one end of the outer core of the coaxial cable in phase A is connected to the sheath of the A phase main cable on the first side, and one end of the inner core is connected to the sheath of the A phase main cable on the second side. Similarly, one end of the outer core of the coaxial cable in phase B is connected to the sheath of the B phase main cable on the first side, and one end of the inner core is connected to the sheath of the B phase main cable on the second side. One end of the outer core of the coaxial cable in phase C is connected to the sheath of the C phase main cable on the first side, and one end of the inner core is connected to the sheath of the C phase main cable on the second side. Therefore, it is necessary to further determine the connection relationship between the outer core and the other end of the inner core.

[0031] The specific process of determining the phase-commutation connection method can be as follows: 1) Obtain the difference between the induced voltage of the main cable on the first side of the i-th phase connector and the induced voltage of the main cable on the second side of the remaining phase connectors.

[0032] By traversing the three-phase joints, six differential voltages can be obtained, namely, the difference U between the induced voltage of the main cable on the first side of the A-phase joint and the induced voltage of the main cable on the second side of the B-phase joint. 1A2B , the difference between the induced voltage of the main cable on the first side of the A phase connector and the induced voltage of the main cable on the second side of the C phase connector U 1A2C , the difference between the induced voltage of the main cable on the first side of the B phase connector and the induced voltage of the main cable on the second side of the A phase connector U 1B2A , the difference between the induced voltage of the main cable on the first side of the B phase connector and the induced voltage of the main cable on the second side of the C phase connector U 1B2C , the difference between the induced voltage of the main cable on the first side of the C phase connector and the induced voltage of the main cable on the second side of the A phase connector U 1C2A , the difference between the induced voltage of the main cable on the first side of the C phase connector and the induced voltage of the main cable on the second side of the B phase connector U 1C2B .

[0033] It should be noted that the above-mentioned induced voltages can all be collected by an induction device, and the voltage subtraction can be directly achieved by a program, a subtractor, etc., or by different installation methods. For example, if the induction device uses a Rogowski coil, then the two Rogowski coils can be installed in reverse and connected in series to achieve the subtraction of the two voltages. The present disclosure adopts the latter method here.

[0034] 2) Based on all the differences, determine the phase-changing connection method of the coaxial cable.

[0035] Based on the obtained difference, the parameter F1=|U 1A2B -U 1B2C |+|U 1A2B -U 1C2A |+|U 1B2C -U 1C2A | and parameter F2=|U 1A2C -U 1B2A |+|U 1A2C -U 1C2B |+|U 1B2A -U 1C2B |.

[0036] If F1 is less than F2, if F1 is less than F2, the main cable sheath on the first side of the A-phase connector is connected to the main cable sheath on the second side of the B-phase connector through the S core of the coaxial cable of the A-phase connector and the T core of the coaxial cable of the B-phase connector in sequence, the main cable sheath on the first side of the B-phase connector is connected to the main cable sheath on the second side of the C-phase connector in sequence through the S core of the coaxial cable of the B-phase connector and the T core of the coaxial cable of the C-phase connector in sequence, and the main cable sheath on the first side of the C-phase connector is connected to the main cable sheath on the second side of the A-phase connector in sequence through the S core of the coaxial cable of the C-phase connector and the T core of the coaxial cable of the A-phase connector; wherein, S=outside, T=inside or S=inside, T=outside.

[0037] Taking S=outer and T=inner as an example, the outer core of the coaxial cable led out of the A-phase connector (connected to the main cable sheath on the first side of the A-phase connector, that is, connected to the main cable sheath of the A-phase on the left) is connected to the inner core of the coaxial cable led out of the B-phase connector (connected to the main cable sheath on the right side of B) through the cross-connected grounding box. The outer core of the coaxial cable led out of the B-phase connector (connected to the main cable sheath of the B-phase on the left) is connected to the inner core of the coaxial cable led out of the C-phase connector (connected to the main cable sheath of the C-phase on the right) through the cross-connected grounding box. The inner core of the coaxial cable led out from the A phase connector is connected (connected to the A phase main cable sheath on the right side); that is, the main cable sheath on the first side of the A phase connector is connected to the main cable sheath on the second side of the B phase connector through the outer core of the coaxial cable of the A phase connector and the inner core of the coaxial cable of the B phase connector in sequence; the main cable sheath on the first side of the B phase connector is connected to the main cable sheath on the second side of the C phase connector through the outer core of the coaxial cable of the B phase connector and the inner core of the coaxial cable of the C phase connector in sequence; the main cable sheath on the first side of the C phase connector is connected to the main cable sheath on the second side of the A phase connector through the outer core of the coaxial cable of the C phase connector and the inner core of the coaxial cable of the A phase connector in sequence.

[0038] On the contrary, if F1 is greater than F2, the main cable sheath on the first side of the A-phase connector is connected to the main cable sheath on the second side of the C-phase connector through the S core of the coaxial cable of the A-phase connector and the T core of the coaxial cable of the C-phase connector; the main cable sheath on the first side of the C-phase connector is connected to the main cable sheath on the second side of the B-phase connector through the S core of the coaxial cable of the C-phase connector and the T core of the coaxial cable of the B-phase connector; the main cable sheath on the first side of the B-phase connector is connected to the main cable sheath on the second side of the A-phase connector through the S core of the coaxial cable of the B-phase connector and the T core of the coaxial cable of the A-phase connector.

[0039] Also taking S=outer and T=inner as an example, the main cable sheath on the first side of the A-phase connector is connected to the main cable sheath on the second side of the C-phase connector through the outer core of the coaxial cable of the A-phase connector and the inner core of the coaxial cable of the C-phase connector; the main cable sheath on the first side of the C-phase connector is connected to the main cable sheath on the second side of the B-phase connector through the outer core of the coaxial cable of the C-phase connector and the inner core of the coaxial cable of the B-phase connector; the main cable sheath on the first side of the B-phase connector is connected to the main cable sheath on the second side of the A-phase connector through the outer core of the coaxial cable of the B-phase connector and the inner core of the coaxial cable of the A-phase connector.

[0040] The phase-changing connection mode is determined by calculating the difference in induced voltages of the main cables at different sides. The method is simple and convenient.

[0041] Taking connector S1 as an example, if it is necessary to measure the induced current of the sheath between connector S1 and the left connector S2, then the induced voltage of the three-phase main cable between connector S1 and connector S2 can be obtained, and the induced voltage of the coaxial cable can be obtained; if the phase change connection mode is that F1 is less than F2, then the difference U(Af-Bz) between the sum of the induced voltage of the three-phase main cable and the induced voltage of the coaxial cable of the A-phase connector and the induced voltage of the coaxial cable of the B-phase connector, the difference U(Bf-Cz) between the sum of the induced voltage of the three-phase main cable and the induced voltage of the coaxial cable of the B-phase connector and the induced voltage of the coaxial cable of the C-phase connector, and the difference U(Cf-Az) between the sum of the induced voltage of the three-phase main cable and the induced voltage of the coaxial cable of the C-phase connector and the induced voltage of the coaxial cable of the A-phase connector can be calculated.

[0042] Similar to determining the commutation connection mode, the difference calculation here can be implemented directly by using a program, a subtractor, etc., or by using different installation methods. The present disclosure adopts the latter method.

[0043] Step S102, calculating the induced current of the three-phase main cable sheath according to the three-phase combined induced voltage.

[0044] It should be noted that, taking the case where F1 is less than F2 as an example, according to Kirchhoff's law and the law of electromagnetic induction: Let (Ia+IA)×k+(Ib+IB)×k+(Ic+IC)×k=(IA+IB+IC)×k=-IN×k; Then, U(Af-Bz)=-IN*k+(IA-IC)* k-(IB-IA)* k=(-IN+IA-IC-IB+IA)* k=3IA*k; U(Af-Bz)=|U(Af-Bz)|=|IA*3k|=IA*3k= IA*K; but: The induced current of the A-phase main cable sheath is I(AL) = U(Af-Bz) / K; Similarly: The induced current of the B-phase main cable sheath is I(BL)=U(Bf-Cz) / K The induced current of the C phase main cable sheath I(CL)=U(Cf-Az) / K Among them, Ia, Ib and Ic are the linear current vectors of phases A, B and C respectively, which are equal normally and have an amplitude difference of 120 degrees. The sum of Ia, Ib and Ic is equal to 0, IA, IB and IC are the sheath current vectors of phases A, B and C respectively, K and k are both operation coefficients, K=3k, unit is Ω, IN is the sum of the sheath current vectors of phases A, B and C, IA+IB+IC+ IN=0, the unit of current is ampere, and the unit of voltage is volt.

[0045] Therefore, the induced current of the i-th phase main cable sheath is the ratio of the i-th phase combined induced voltage to the operation coefficient K.

[0046] The above method calculates the induced current of the sheath of the three-phase main cable according to the induced voltage of the three-phase main cable on the same side of the joint group and the induced voltage of the two coaxial cables connected by phase change. The result is more in line with reality, and the live test of the sheath induced current can also be realized. The test does not need to remove the cross-connection grounding box, and the test is convenient.

[0047] See also Figure 3 , Figure 3 is a block diagram of the sheath induced current live testing system disclosed in the present invention, Figure 3 The embodiment is a virtual system that can be loaded and executed by a computer device, and the computer device may include the above-mentioned test host, Figure 3 The system may include an acquisition module and a calculation module, which, when used to perform the above-mentioned sheath induced current live testing method, can: The acquisition module is configured to acquire the three-phase joint induced voltage according to the phase-changing connection mode of the coaxial cable; wherein the i-th phase joint induced voltage is the difference between the total induced voltage and the coaxial cable induced voltage of the j-th phase connector, the total induced voltage is the sum of the three-phase main cable induced voltage and the coaxial cable induced voltage of the i-th phase connector, the coaxial cable of the j-th phase connector is connected in phase-changing manner with the coaxial cable of the i-th phase connector, and the three-phase main cable induced voltage is the induced voltage of the main cable on the same side of the connector group; i is not equal to j, i=A, B and C, j=A, B and C.

[0048] It should be noted that for three-phase main cables and coaxial cables, there are two situations in which the phase-changing connection method can be obtained. One is that the phase-changing connection method can be obtained by looking up the design data, and it can be determined that the design data is consistent with the actual situation. The second is that the design data is lost, or the design data is inconsistent with the actual situation, and the specific phase-changing connection method cannot be determined.

[0049] For the second case, in order to ensure accurate knowledge of the phase-changing connection mode, in some embodiments, the system further includes a determination module for predetermining the phase-changing connection mode of the coaxial cable, and the determination module is configured as follows: 1) Obtain the difference between the induced voltage of the main cable on the first side of the i-th phase connector and the induced voltage of the main cable on the second side of the remaining phase connectors.

[0050] By traversing the three-phase joints, six differential voltages can be obtained, namely, the difference U between the induced voltage of the main cable on the first side of the A-phase joint and the induced voltage of the main cable on the second side of the B-phase joint. 1A2B , the difference between the induced voltage of the main cable on the first side of the A phase connector and the induced voltage of the main cable on the second side of the C phase connector U 1A2C , the difference between the induced voltage of the main cable on the first side of the B phase connector and the induced voltage of the main cable on the second side of the A phase connector U 1B2A , the difference between the induced voltage of the main cable on the first side of the B phase connector and the induced voltage of the main cable on the second side of the C phase connector U 1B2C , the difference between the induced voltage of the main cable on the first side of the C phase connector and the induced voltage of the main cable on the second side of the A phase connector U 1C2A The difference between the induced voltage of the main cable on the first side of the C phase connector and the induced voltage of the main cable on the second side of the B phase connector is U 1C2B .

[0051] 2) Based on all the differences, determine the phase-changing connection method of the coaxial cable.

[0052] Based on the obtained difference, the parameter F1=|U 1A2B -U 1B2C |+|U 1A2B -U 1C2A |+|U 1B2C -U 1C2A | and parameter F2=|U 1A2C -U 1B2A |+|U 1A2C -U 1C2B |+|U 1B2A -U 1C2B|, if F1 is less than F2, the main cable sheath on the first side of the A-phase connector is connected to the main cable sheath on the second side of the B-phase connector through the S core of the coaxial cable of the A-phase connector and the T core of the coaxial cable of the B-phase connector in sequence, the main cable sheath on the first side of the B-phase connector is connected to the main cable sheath on the second side of the C-phase connector in sequence through the S core of the coaxial cable of the B-phase connector and the T core of the coaxial cable of the C-phase connector in sequence, and the main cable sheath on the first side of the C-phase connector is connected to the main cable sheath on the second side of the A-phase connector in sequence through the S core of the coaxial cable of the C-phase connector and the T core of the coaxial cable of the A-phase connector; if F1 is greater than F2, then The main cable sheath on the first side of the A-phase connector is connected to the main cable sheath on the second side of the C-phase connector via the S core of the coaxial cable of the A-phase connector and the T core of the coaxial cable of the C-phase connector; the main cable sheath on the first side of the C-phase connector is connected to the main cable sheath on the second side of the B-phase connector via the S core of the coaxial cable of the C-phase connector and the T core of the coaxial cable of the B-phase connector; the main cable sheath on the first side of the B-phase connector is connected to the main cable sheath on the second side of the A-phase connector via the S core of the coaxial cable of the B-phase connector and the T core of the coaxial cable of the A-phase connector; wherein, S=outside, T=inside or S=inside, T=outside.

[0053] The calculation module is configured to calculate the induced current of the three-phase main cable sheath according to the three-phase combined induced voltage; wherein the induced current of the i-th phase main cable sheath is the ratio of the i-th phase combined induced voltage to the operation coefficient.

[0054] The above system calculates the induced current of the sheath of the three-phase main cable based on the induced voltage of the three-phase main cable on the same side of the connector group and the induced voltage of the two coaxial cables connected in phase change. The result is more realistic and can also realize the live test of the sheath induced current. The test does not require the removal of the cross-connection grounding box, and the test is convenient.

[0055] To adapt the above method and system, see Figure 4 The present disclosure also discloses a sheath induction current live test device, which at least includes a test host, a first induction device, a second induction device, a third induction device, a fourth induction device and a fifth induction device. The first induction device, the second induction device and the third induction device respectively sense the induction voltage of the main cable on the same side of the connector group, the fourth induction device and the fifth induction device respectively sense the induction voltage of the two coaxial cables connected in phase switching, the output ends of all the induction devices are connected in series to the test host, and the test host adopts the above-mentioned sheath induction current live test method to perform the sheath induction current live test.

[0056] It should be noted that all the induction devices can be Rogowski coils. The first induction device, the second induction device, the third induction device, the fourth induction device and the fifth induction device are represented by letters CT1~CT5 respectively. It is required that the error of the ratio of the secondary output voltage / primary output current of CT1~CT5 is less than 1 / 100, and the angle of the secondary output voltage of CT1~CT5 is less than 1 degree under the same input current state.

[0057] It should be noted that the test host can adopt an existing smart terminal, such as a desktop computer, tablet, etc., and of course a specially designed test host can also be used. The main components of the designed test host include at least a filter, an operational amplifier circuit, an analog-to-digital converter, a controller, a display, and a power supply for supplying power to each electrical component.

[0058] The filter, operational amplifier circuit and analog-to-digital converter perform filtering, operational amplifier and analog-to-digital conversion on the received voltage in sequence.

[0059] The controller uses a preset calculation method to perform calculations based on the voltage after analog-to-digital conversion; wherein the preset calculation method includes the sheath induced current live test method, and may also include a method for determining the phase-changing connection method, that is, calculating F1 and F2, and determining the phase-changing connection method based on F1 and F2.

[0060] The display shows the calculation results of the controller, such as the sheath induction current test results, the phase switching connection parties, the voltage, etc.

[0061] See also Figures 5 to 7 , assuming that the commutation connection method is unknown, the working process of the above device can be as follows: S1) Determine the phase-changing connection method of the coaxial cable.

[0062] See also Figure 5 , select any two sensing devices, such as CT1 and CT2 in the figure, and install them on the main cables on both sides of the three-phase connector in sequence and in opposite directions, and measure: U 1A2B =8.66V, U 1A2C =8.60V, U 1B2A =8.93V, U 1B2C =8.66V, U 1C2A =8.66V, U 1C2B =8.24V.

[0063] Calculate F1=0V, F2=1.38V. Since F1<F2, the main cable sheath on the first side of the A-phase connector is connected to the main cable sheath on the second side of the B-phase connector through the outer core of the coaxial cable of the A-phase connector and the inner core of the coaxial cable of the B-phase connector. The main cable sheath on the first side of the B-phase connector is connected to the main cable sheath on the second side of the C-phase connector through the outer core of the coaxial cable of the B-phase connector and the inner core of the coaxial cable of the C-phase connector. The main cable sheath on the first side of the C-phase connector is connected to the main cable sheath on the second side of the A-phase connector through the outer core of the coaxial cable of the C-phase connector and the inner core of the coaxial cable of the A-phase connector.

[0064] S2) Measure the three-phase combined induced voltage.

[0065] See also Figure 6 and 7 , install the three sensing devices CT1~CT3 on the main cable on the left side of the connector in the same direction, and install the remaining two sensing devices CT4~CT5 in pairs on the coaxial cable of the three-phase connector, as follows: CT4 is installed on the coaxial cable of the A-phase connector, and CT5 is installed on the coaxial cable of the B-phase connector. The direction of CT4 is consistent with that of CT1~CT3, and the direction of CT5 is opposite to that of the other sensing devices. CT4 is installed on the coaxial cable of the B-phase connector, and CT5 is installed on the coaxial cable of the C-phase connector. CT4 is in the same direction as CT1~CT3, and CT5 is in the opposite direction to the other sensing devices. CT4 is installed on the coaxial cable of the C phase connector, and CT5 is installed on the coaxial cable of the A phase connector. CT4 is in the same direction as CT1~CT3, and CT5 is in the opposite direction to the other sensing devices.

[0066] It can be measured that U(Af-Bz)=0.089V, U(Af-Bz)=0.062V, and U(Cf-Az)=0.011V.

[0067] S2) Calculate the induced current in the three-phase main cable sheath.

[0068] I(AL)= U(Af-Bz) / K=89A; I(BL)=U(Bf-Cz) / K=62A; I(CL)=U(Cf-Az) / 3K=11A; In the formula, the operation coefficient K is specifically the ratio of the output secondary voltage of the single induction device (Rogowski coil) to the input primary current, here 0.01Ω.

[0069] The measurement result of the above device is more in line with reality, and the live test of the sheath induced current can be realized. The test does not need to remove the cross-connected grounding box, and the test is convenient.

[0070] It will be appreciated by those skilled in the art that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Furthermore, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0071] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0072] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0073] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0074] The above are merely embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention are included in the scope of the claims of the present invention to be approved.

Claims

1. A method for testing the sheath induced current, characterized in that: include: According to the phase-changing connection mode of the coaxial cable, the three-phase joint induced voltage is obtained; wherein, the i-th phase joint induced voltage is the difference between the total induced voltage and the coaxial cable induced voltage of the j-th phase connector, the total induced voltage is the sum of the three-phase main cable induced voltage and the coaxial cable induced voltage of the i-th phase connector, the coaxial cable of the j-th phase connector is connected in phase-changing with the coaxial cable of the i-th phase connector, and the three-phase main cable induced voltage is the induced voltage of the three-phase main cable on the same side of the connector group; i is not equal to j, i=A, B and C, j=A, B and C; According to the three-phase joint induced voltage, the induced current of the three-phase main cable sheath is calculated.

2. The method according to claim 1, characterized in that: Calculate the induced current in the three-phase main cable sheath, including: The induced current of the main cable sheath of the i-th phase is the ratio of the i-th phase combined induced voltage to the operation coefficient.

3. The method according to claim 1, characterized in that: The phase-changing connection mode of the coaxial cable is predetermined, and the determination process includes: Obtaining the difference between the induced voltage of the main cable on the first side of the i-th phase connector and the induced voltage of the main cable on the second side of the remaining phase connectors; Based on all the differences, determine the phase-changing connection method of the coaxial cable.

4. The method according to claim 3, characterized in that Based on all the differences, determine the phase-changing connection method of the coaxial cable, including: Calculation parameter F1=|U 1A2B -U 1B2C |+|U 1A2B -U 1C2A |+|U 1B2C -U 1C2A | and parameter F2=|U 1A2C -U 1B2A |+|U 1A2C -U 1C2B |+|U 1B2A -U 1C2B |; Among them, U 1A2B is the difference between the induced voltage of the main cable on the first side of the A phase connector and the induced voltage of the main cable on the second side of the B phase connector, U 1A2C is the difference between the induced voltage of the main cable on the first side of the A phase connector and the induced voltage of the main cable on the second side of the C phase connector, U 1B2A is the difference between the induced voltage of the main cable on the first side of the B phase connector and the induced voltage of the main cable on the second side of the A phase connector, U 1B2C is the difference between the induced voltage of the main cable on the first side of the B phase connector and the induced voltage of the main cable on the second side of the C phase connector, U 1C2A is the difference between the induced voltage of the main cable on the first side of the C phase connector and the induced voltage of the main cable on the second side of the A phase connector, U 1C2B is the difference between the induced voltage of the main cable on the first side of the C phase connector and the induced voltage of the main cable on the second side of the B phase connector; If F1 is less than F2, the main cable sheath on the first side of the A-phase connector is connected to the main cable sheath on the second side of the B-phase connector through the S core of the coaxial cable of the A-phase connector and the T core of the coaxial cable of the B-phase connector in sequence, the main cable sheath on the first side of the B-phase connector is connected to the main cable sheath on the second side of the C-phase connector in sequence through the S core of the coaxial cable of the B-phase connector and the T core of the coaxial cable of the C-phase connector in sequence, and the main cable sheath on the first side of the C-phase connector is connected to the main cable sheath on the second side of the A-phase connector in sequence through the S core of the coaxial cable of the C-phase connector and the T core of the coaxial cable of the A-phase connector; wherein, S=outer, T=inner or S=inner, T=outer; If F1 is greater than F2, the main cable sheath on the first side of the A phase connector is connected to the main cable sheath on the second side of the C phase connector through the S core of the coaxial cable of the A phase connector and the T core of the coaxial cable of the C phase connector; the main cable sheath on the first side of the C phase connector is connected to the main cable sheath on the second side of the B phase connector through the S core of the coaxial cable of the C phase connector and the T core of the coaxial cable of the B phase connector; the main cable sheath on the first side of the B phase connector is connected to the main cable sheath on the second side of the A phase connector through the S core of the coaxial cable of the B phase connector and the T core of the coaxial cable of the A phase connector.

5. A sheath induction current live test system, characterized in that: include: The acquisition module acquires the three-phase joint induced voltage according to the phase-changing connection mode of the coaxial cable; wherein the i-th phase joint induced voltage is the difference between the total induced voltage and the coaxial cable induced voltage of the j-th phase connector, the total induced voltage is the sum of the three-phase main cable induced voltage and the coaxial cable induced voltage of the i-th phase connector, the coaxial cable of the j-th phase connector is connected in phase-changing with the coaxial cable of the i-th phase connector, and the three-phase main cable induced voltage is the induced voltage of the three-phase main cable on the same side of the connector group; i is not equal to j, i=A, B and C, j=A, B and C; The calculation module calculates the induced current of the three-phase main cable sheath according to the three-phase joint induced voltage.

6. The system according to claim 5, characterized in that In the calculation module, the induced current of the three-phase main cable sheath is calculated, including: The induced current of the main cable sheath of the i-th phase is the ratio of the i-th phase combined induced voltage to the operation coefficient.

7. The system according to claim 5, characterized in that The system further comprises a determination module for predetermining a phase-changing connection mode of the coaxial cable, wherein the determination module is configured to: Obtaining the difference between the induced voltage of the main cable on the first side of the i-th phase connector and the induced voltage of the main cable on the second side of the remaining phase connectors; Based on all the differences, determine the phase-changing connection method of the coaxial cable.

8. The system according to claim 7, characterized in that In the determination module, the phase switching connection mode of the coaxial cable is determined according to all the differences, including: Calculation parameter F1=|U 1A2B -U 1B2C |+|U 1A2B -U 1C2A |+|U 1B2C -U 1C2A | and parameter F2=|U 1A2C -U 1B2A |+|U 1A2C -U 1C2B |+|U 1B2A -U 1C2B |; Among them, U 1A2B is the difference between the induced voltage of the main cable on the first side of the A phase connector and the induced voltage of the main cable on the second side of the B phase connector, U 1A2C is the difference between the induced voltage of the main cable on the first side of the A phase connector and the induced voltage of the main cable on the second side of the C phase connector, U 1B2A is the difference between the induced voltage of the main cable on the first side of the B phase connector and the induced voltage of the main cable on the second side of the A phase connector, U 1B2C is the difference between the induced voltage of the main cable on the first side of the B phase connector and the induced voltage of the main cable on the second side of the C phase connector, U 1C2A is the difference between the induced voltage of the main cable on the first side of the C phase connector and the induced voltage of the main cable on the second side of the A phase connector, U 1C2B is the difference between the induced voltage of the main cable on the first side of the C phase connector and the induced voltage of the main cable on the second side of the B phase connector; If F1 is less than F2, the main cable sheath on the first side of the A-phase connector is connected to the main cable sheath on the second side of the B-phase connector through the S core of the coaxial cable of the A-phase connector and the T core of the coaxial cable of the B-phase connector in sequence, the main cable sheath on the first side of the B-phase connector is connected to the main cable sheath on the second side of the C-phase connector in sequence through the S core of the coaxial cable of the B-phase connector and the T core of the coaxial cable of the C-phase connector in sequence, and the main cable sheath on the first side of the C-phase connector is connected to the main cable sheath on the second side of the A-phase connector in sequence through the S core of the coaxial cable of the C-phase connector and the T core of the coaxial cable of the A-phase connector; wherein, S=outer, T=inner or S=inner, T=outer; If F1 is greater than F2, the main cable sheath on the first side of the A phase connector is connected to the main cable sheath on the second side of the C phase connector through the S core of the coaxial cable of the A phase connector and the T core of the coaxial cable of the C phase connector; the main cable sheath on the first side of the C phase connector is connected to the main cable sheath on the second side of the B phase connector through the S core of the coaxial cable of the C phase connector and the T core of the coaxial cable of the B phase connector; the main cable sheath on the first side of the B phase connector is connected to the main cable sheath on the second side of the A phase connector through the S core of the coaxial cable of the B phase connector and the T core of the coaxial cable of the A phase connector.

9. A sheath induction current live test device, characterized in that: It includes a test host, a first sensing device, a second sensing device, a third sensing device, a fourth sensing device and a fifth sensing device; The first sensing device, the second sensing device, and the third sensing device respectively sense the induced voltage of the main cable on the same side of the connector group, the fourth sensing device and the fifth sensing device respectively sense the induced voltage of the two coaxial cables connected in phase, and the output ends of all the sensing devices are connected in series and then connected to the test host; The test host adopts the method described in any one of claims 1 to 4 to perform a live test on the sheath induction current.

10. The device according to claim 9, characterized in that The test host includes a filter, an operational amplifier circuit, an analog-to-digital converter, a controller and a display; The filter, the operational amplifier circuit and the analog-to-digital converter sequentially filter, operationally amplify and perform analog-to-digital conversion on the received voltage; The controller performs calculations using a preset calculation method according to the voltage after analog-to-digital conversion; wherein the preset calculation method includes the method described in any one of claims 1 to 4; The display shows the calculation results of the controller.

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