Secondary circuit maintenance method and device

Abstract

A secondary circuit maintenance method and device, comprising a problematic circuit (100), a circuit conductor cross-section S, and a resistivity p; applying a continuously increasing initial voltage U to a secondary circuit within the problematic circuit (100) by means of an alternating voltage signal generator A, and reading a circuit current I within the secondary circuit at such time; if the circuit current I increases with the increase in the initial voltage U and exceeds a protection threshold current I1, the AC voltage signal generator A performs protective de-energization, stores pre-de-energization values of the initial voltage U and circuit current I, calculates a circuit resistance value R, and determines an electrical distance L of a simulated fault point by means of the resistance value R; if the circuit current I floats with the increase in the initial voltage U and is lower than the protection threshold current I1, continue increasing the initial voltage U until a safe voltage U1 terminates. High testing process safety, high accuracy in determining fault point location, and strong universality, greatly improve maintenance efficiency for secondary circuit operating conditions with complex wiring.

Description

Secondary circuit maintenance method and device

[0001] This application claims priority to the Chinese patent application No. 202411276551.0, filed on September 12, 2024, and entitled "Secondary circuit maintenance method", the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0002] The present application relates to the field of secondary circuit, in particular to a secondary circuit maintenance method and device. BACKGROUND

[0003] The voltage transformer plays an extremely important role in power system measurement and protection, which realizes high voltage transformation into low voltage, makes high voltage measurement possible, and through the standard value of its secondary side voltage, it is convenient to manufacture standard electric measuring instruments and measuring devices. The ideal state of the voltage transformer is a low internal resistance voltage source, and the secondary circuit is prohibited from short circuiting, so a fuse is configured at the secondary side of the voltage transformer to protect the voltage transformer.

[0004] In power system applications, a large number of voltage meters, electric energy meters, voltage relays, insulation monitoring devices, and voltage busbars are usually connected in the secondary circuit of the voltage transformer. Due to the short circuit or grounding fault of the secondary circuit, the fuse at the secondary side of the voltage transformer will be blown. If the fault point cannot be eliminated after the fuse is blown, the normal operation of the voltage transformer cannot be restored. In some cases, when the fault point of the secondary circuit of the voltage transformer is located, the voltage transformer is generally taken out of operation, safety isolation measures are taken, and then a large number of segmental inspections are carried out on the line. Because there are many devices connected in the secondary circuit of the voltage transformer, through insulation testing or resistance range testing of the multimeter, the direct current resistance of the circuit is small due to the inductive load, and the measured value is sometimes only a few ohms, which cannot distinguish the grounding short circuit fault, and brings great difficulty to the location of the fault point. If the method of sending electricity to the voltage transformer through directly disassembling the device line on the secondary circuit of the voltage transformer is used to locate the fault point, the voltage transformer will be impacted, and there is the problem of low search efficiency. SUMMARY

[0005] The purpose of this section is to summarize some aspects of the embodiments of the present application and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the abstract and title of the specification to avoid obscuring the purpose of this section, abstract and title, and such simplifications or omissions cannot be used to limit the scope of the present application.

[0006] In view of the difficulty in locating the fault point of the secondary circuit of the voltage transformer, an effective and reasonable testing method is needed, and the present application is proposed.

[0007] Therefore, the technical problem to be solved by the present application is to complete the electrical distance measurement of the fault point of the secondary side in the case of a large number of inductive loads in the circuit.

[0008] In a first aspect, the present application provides a secondary circuit maintenance method, which comprises: a problem circuit (100), a circuit conductor cross section S, and a resistivity p; an alternating voltage signal generator A is used to apply an initial voltage U to the secondary circuit in the problem circuit (100) and read the circuit current I in the secondary circuit at this time; if the circuit current I increases with the increase of the initial voltage U and exceeds the protection judgment current I1, the alternating voltage signal generator A is protected from power failure, the values of the initial voltage U and the circuit current I before power failure are stored, the circuit resistance value R is calculated, and the simulated fault point electrical distance L is confirmed by the resistance value R; if the circuit current I floats with the increase of the initial voltage U and is lower than the protection judgment current I1, the initial voltage U is continuously increased to a safe voltage U1 to terminate.

[0009] In an embodiment, the problem circuit (100) comprises a voltage transformer secondary side (100a); the voltage transformer secondary side (100a) adopts a star connection method and is configured with voltage busbars YM a, YM b, YM c, and YM n; the output ends Ux and Uy of the alternating voltage signal generator A are connected to the problem voltage busbars for fault point confirmation.

[0010] In an embodiment, if the voltage busbars YM a, YM b, YM c, and YM n and the three-phase terminals L1, L2, and L3 are configured with fuses (B), when the circuit current I exceeds the protection judgment current I1, the fuses (B) are disconnected to form the problem circuit (100); the output ends of the voltage signal generator A are connected to the disconnected fuses (B) and the ground terminal, respectively.

[0011] In an embodiment, the voltage transformer secondary side (100a) circuit is configured with a low-voltage relay (C) protection circuit; a voltmeter (V) is configured on the voltage transformer secondary side (100a) circuit; the problem circuit (100) is connected from the voltage transformer primary side (100a) to the three-phase terminals L1, L2, and L3 of the voltage transformer primary side (100a).

[0012] In an embodiment, the initial voltage U is increased in a step-by-step manner; the safe voltage U1 is greater than or equal to 36 V; and the initial voltage U is greater than or equal to 3 V.

[0013] In an embodiment, the simulated fault point electrical distance L / actual fault point electrical distance L1≈110%, or the simulated fault point electrical distance L·90%≈actual fault point electrical distance L1.

[0014] In an embodiment, if the secondary circuit is well insulated, the circuit current I is infinitesimal; at this time, the voltage transformer secondary load resistance, i.e. the circuit resistance value R of the non-faulted circuit > the circuit resistance value of the faulted circuit; the simulated fault point electrical distance L is inversely proportional to the circuit current I; that is, the simulated fault point electrical distance L is an infinite amount, equivalent to the simulated fault point electrical distance L not existing.

[0015] In an embodiment, after the simulated fault point electrical distance is confirmed, the branch of the faulted small bus is tested by a clamp-on ammeter; if the branch current = 0, there is no fault; if the branch current ≠ 0, there is a fault; and then the fault branch is judged, and the fault point positioning is completed.

[0016] In an embodiment, the maximum value of the safety voltage U1 depends on the system normal voltage; and the initial voltage U is increased by 0.1V step by step.

[0017] In a second aspect, the application provides a computer device, comprising: a memory, a processor to store a computer program on the memory and run the computer program on the processor, and the processor executes the computer program to implement the secondary circuit maintenance method described above.

[0018] The application has the following beneficial effects: the test process is safe, the accuracy of judging the fault point position is high, and the universality is strong, and for the secondary circuit working condition with complex wiring, the maintenance efficiency is greatly improved. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments or the related art, the following will briefly introduce the drawings needed in the embodiments. Obviously, the drawings in the following description only some embodiments of the application, and for those skilled in the art, other drawings can also be obtained without creative labor.

[0020] Fig. 1 is a secondary circuit maintenance state structure diagram of the secondary circuit maintenance method according to an embodiment of the application.

[0021] Fig. 2 is a structure diagram of the secondary circuit maintenance method according to an embodiment of the application when the secondary circuit does not form a problem circuit.

[0022] Fig. 3 is a ranging program flow diagram of the secondary circuit maintenance method according to an embodiment of the application.

[0023] Fig. 4 is a structural schematic diagram of a computer device according to an embodiment of the present application. DETAILED DESCRIPTION

[0024] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative effort belong to the scope of protection of the present application.

[0025] In order to make the above objectives, characteristics and advantages of the present application more apparent, the present application will be further described in detail below with reference to the drawings and specific embodiments.

[0026] Secondly, the present application is described in detail in combination with the schematic diagram. In the detailed description of the embodiments of the present application, the cross-sectional view of the device structure is locally enlarged without the general proportion for the convenience of description, and the schematic diagram is only an example, which should not limit the scope of protection of the present application herein. In addition, the three-dimensional spatial dimensions of length, width and depth should be included in the actual manufacture.

[0027] Thirdly, the "one embodiment" or "embodiment" referred to herein means that the specific features, structures or characteristics can be included in at least one implementation of the present application. The "in one embodiment" appearing in different places in the specification does not mean the same embodiment, nor is the embodiment independent or alternative to other embodiments.

[0028] Embodiment 1, with reference to Figs. 1-2, the present embodiment provides a secondary circuit maintenance method, including a problem circuit 100, i.e. the secondary circuit to be maintained, a circuit conductor cross section S, i.e. the cross-sectional area of the secondary circuit conductor, a resistivity p, i.e. the material resistivity of the secondary circuit conductor;

[0029] In an implementation, the secondary circuit in the problem circuit 100 is applied with an initial voltage U continuously rising by an alternating voltage signal generator A. The initial voltage U is usually much smaller than the circuit voltage during the operation of the electrical system, so as not to affect the secondary circuit which has been converted and reduced in voltage. The small voltage can better read the subtle changes of the secondary circuit. The voltage signal generator A itself has the function of reading the circuit current I in the secondary circuit at this time, and then confirming the circuit resistance R.

[0030] In an embodiment, if the circuit current I increases with the increase of the initial voltage U and exceeds the protection judgment current I1, the AC voltage signal generator A is protected from power-off, at this time it can be confirmed that the circuit has a related problem of ground short circuit, and then the initial voltage U and the circuit current I before power-off are stored, the circuit resistance value R is calculated, the analog fault point electrical distance L is confirmed by the resistance value R, and the confirmation direction of the fault point can be better confirmed with the analog fault point electrical distance L;

[0031] In an embodiment, if the circuit current I increases with the increase of the initial voltage U and exceeds the protection judgment current I1, the AC voltage signal generator A is protected from power-off, at this time it can be confirmed that the circuit has a related problem of ground short circuit, and then the initial voltage U and the circuit current I before power-off are stored, the circuit resistance value R is calculated, the analog fault point electrical distance L is confirmed by the resistance value R, and the confirmation direction of the fault point can be better confirmed with the analog fault point electrical distance L;

[0032] Embodiment 2, referring to FIG. 1-2, is the second embodiment of the present application, which is based on the previous embodiment, and the difference between the two is that the problem circuit 100 contains a voltage transformer secondary side 100a, which can be understood as the secondary circuit involved in the technical solution;

[0033] In an embodiment, the voltage transformer secondary side 100a adopts star connection method and is configured with voltage busbars YM a, YM b, YM c and YM n, which correspond to ABC three-phase power supply respectively, and YM n is the neutral line, and the electrical components connected to the phase voltage are connected between one phase and YM n. And YM n forms a complete circuit when the AC voltage signal generator A is connected to the problem circuit, which transmits the information of the circuit back to the generator A and the detection system, and this kind of line design is also a common way of star connection method;

[0034] In an embodiment, it is assumed that n branch fault points on YM c busbar need to be detected, and the output end U x and U y of the AC voltage signal generator A are connected to the problem voltage busbar for fault point confirmation, forming the current signal trend shown in Table 1:

[0035] U x → red dotted line → YM c voltage busbar → fault branch grounding point → red dotted line → U y .

[0036] Among them, the red dotted line is the circuit line, each voltage busbar has multiple branches, and as can be seen from the figure, n branches are taken as the fault branch grounding point and return to the voltage transformer secondary circuit grounding point through the red dotted line, and U y , forming a complete circuit.

[0037] In an embodiment, if fuses B are arranged between voltage small bus YMa, YMb, YMc, YMn and three-phase terminals L1, L2, L3, it indicates that the secondary circuit has not yet occurred any problem and does not need to be detected at any fault point:

[0038] In an embodiment, when the circuit current I exceeds the protection judgment current I1 and the fuse B is disconnected, the problem circuit 100 is formed, at this time, the disconnected fuse B is the circuit that needs to be maintained, and all fuses B need to be removed during detection to ensure the stability and independence of the circuit during maintenance;

[0039] In an embodiment, the output end of the voltage signal generator A, i.e., U x and U y is connected to the disconnected end and the grounding end of the fuse B that needs to be detected, respectively.

[0040] In an embodiment, a low-voltage relay C protection circuit is arranged in the secondary side 100a circuit of the voltage transformer; a voltmeter V is arranged on the secondary side 100a circuit of the voltage transformer, which is also used to monitor the circuit voltage at all times to avoid problems during maintenance;

[0041] In an embodiment, the problem circuit 100 is connected from the primary side 100a of the voltage transformer to the three-phase terminals L1, L2, L3 of the primary side 100a of the voltage transformer, and the primary side 100a of the voltage transformer is the high-voltage line side, which is the 6KV bus terminal with the fuse B.

[0042] Embodiment 3, referring to FIGS. 1-2 and Table 1, is the third embodiment of the present application, which is based on the previous embodiment and different from the previous embodiment in that the initial voltage U is increased in a step-by-step manner, and the voltage is increased by the same amount each time;

[0043] The safety voltage U1 is greater than or equal to 36V, but the normal fault point detection point only needs to be set at 36V, and the circuit that does not have problems at 36V is basically completely stable;

[0044] The initial voltage U is greater than or equal to 3V, and the initial voltage is generally set to 3V. A too small voltage will result in an unobvious circuit current fluctuation, and the precision requirement of the alternating voltage signal generator A will also increase, which will affect the operation and maintenance cost. 3V is a relatively appropriate starting point.

[0045] Table 1: Experimental data table of the secondary circuit maintenance method of the simulated fault point electrical distance

[0046] In an embodiment, a test is performed to confirm the difference between the simulated fault point electrical distance and the actual fault point electrical distance, and the accurate value of the fault point electrical distance is further confirmed according to the ratio, and the process is:

[0047] If the actual fault point electrical distance L1=121m, the loop conductor cross section S=2.5mm, the resistivity p=0.0184Ωmm / m, according to Ohm's law R=pL / S: 2

[0048] When the initial voltage U=3V, the loop current I=3.71A, and the simulated fault point electrical distance L=109.9m;

[0049] When the initial voltage U=5V, the loop current I=6.14A, and the simulated fault point electrical distance L=110.6m;

[0050] When the initial voltage U=10V, the voltage signal generator A is protected from power-off.

[0051] It can be seen that when the initial voltage U reaches 10V, the voltage signal generator A is powered off, which also reflects that when the loop has a problem, the loop current is basically around 10A.

[0052] The initial voltage U stored in the voltage signal generator A before power-off is 10V, the loop current I is 10.23A, and the simulated fault point electrical distance L is calculated to be 132.8m;

[0053] Further confirming the proportion between them, the simulated fault point electrical distance L / actual fault point electrical distance L1≈110%, or the simulated fault point electrical distance L·90%≈actual fault point electrical distance L1.

[0054] Based on the above conclusion, when the simulated fault point electrical distance L is obtained, the actual fault point electrical distance L can be further determined.

[0055] Example 4, referring to FIGS. 1-3, is the fourth embodiment of the present application, which is based on the previous embodiment, and differs from the previous embodiment in that: based on the above test, if the secondary loop insulation is good, the initial voltage U is increased to 36V, and at this time the loop current I≤0.06A, the well-insulated secondary loop has undergone a transformer low voltage treatment, and the current in the loop will be lower;

[0056] In an embodiment, the voltage transformer secondary load resistance, i.e., the loop resistance R=600Ω;

[0057] After calculation, the simulated fault point electrical distance L=81500m;

[0058] That is, when the simulated fault point electrical distance L value is too large, it means that the fault point does not exist, and the loop insulation is normal.

[0059] ​Embodiment 5, referring to FIG. 1-3, is the fifth embodiment of the present application, which is based on the previous embodiment, and is different from the previous embodiment in that: after confirming the electrical distance of the simulated fault point, the branch of the voltage small bus of the fault is tested by a clamp ammeter to confirm which is the fault branch, and the detection range is shortened;

[0060] If the branch current = 0, it means that the grounding is stable, and there is no fault;

[0061] If the branch current ≠ 0, it means that there is a grounding short circuit related problem, and there is a fault;

[0062] Further, the fault branch is judged, and the above series of fault point positioning processes are completed.

[0063] The maximum value of the safety voltage U1 depends on the system normal voltage, and the system normal voltage in the secondary circuit is usually at most 60V, and 36V is sufficient to meet the requirement of the detection range;

[0064] The initial voltage U is increased by 0.1V step by step, and the current change is refined by 0.1V each time, so that the detection result is more accurate.

[0065] Through the test result, the working efficiency and the purpose of fault positioning are improved by combining with the segmented search method, the fault range is quickly narrowed, and finally the fault point can be accurately determined.

[0066] Embodiment 6, the present application also provides a computer device, which can be a server or a terminal, and the internal structure diagram thereof can be as shown in FIG. 4. The computer device includes a processor, a memory, an input / output interface (I / O) and a communication interface. Among them, the processor, the memory and the input / output interface are connected through a system bus, and the communication interface is connected to the system bus through the input / output interface. Among them, the processor of the computer device is used to provide computing and control capability. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system, a computer program and a database. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The database of the computer device is used to store processing data. The input / output interface of the computer device is used to exchange information between the processor and external devices. The communication interface of the computer device is used to communicate with external terminals through network connection. The computer program is executed by the processor to realize the above-mentioned methods.

[0067] Those skilled in the art can understand that the structure shown in FIG. 4 is only a block diagram of part of the structure related to the scheme of the present application, and does not constitute a limitation on the computer device to which the scheme of the present application is applied. The specific computer device can include more or fewer components than those shown in the figure, or combine certain components, or have a different arrangement of components.

[0068] Those skilled in the art can understand that all or part of the processes in the above-mentioned embodiments can be completed by instructing the relevant hardware through a computer program. The computer program can be stored in a non-volatile computer readable storage medium, and when executed, can include the processes of the above-mentioned embodiments. Any reference to memory, database or other medium used in the embodiments provided by the present application can include at least one of non-volatile and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical storage, high-density embedded non-volatile memory, resistive memory (ReRAM), magnetoresistive memory (MRAM), ferroelectric memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. As an illustration but not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM), etc.

[0069] It is important to note that the constructions and arrangements of this application shown in several different exemplary embodiments are merely illustrative. Although only a few embodiments are described in detail in this disclosure, those who consult this disclosure will readily understand that many modifications are possible (e.g., changes in the size, dimensions, structure, shape, and proportions of various elements, as well as parameter values ​​(e.g., temperature, pressure, etc.), installation arrangements, use of materials, color, orientation, etc.) without substantially departing from the novel teachings and advantages of the subject matter described in this application). For example, an element shown as integrally formed may be composed of multiple parts or elements, the position of elements may be inverted or otherwise altered, and the nature or number or position of discrete elements may be changed or altered. Therefore, all such modifications are intended to be included within the scope of this application. The order or sequence of any process or method steps may be changed or rearranged according to alternative embodiments. In the claims, any "apparatus plus function" clause is intended to cover the structure described herein that performs the function, and not only structurally equivalent but also equivalent in structure. Other substitutions, modifications, alterations, and omissions may be made in the design, operation, and arrangement of the exemplary embodiments without departing from the scope of this application. Therefore, this application is not limited to a particular embodiment, but extends to various modifications that still fall within the scope of the appended claims.

[0070] Furthermore, in order to provide a concise description of exemplary embodiments, not all features of actual embodiments (i.e., those features that are not relevant to the best mode of implementing this application as currently considered, or those features that are not relevant to the implementation of this application) may be omitted.

[0071] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0072] This document uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. Furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A secondary circuit servicing method characterized by, The secondary circuit maintenance method comprises: The problem circuit (100), the circuit conductor section S, the resistivity p; The initial voltage U of the secondary circuit in the problem circuit (100) is continuously increased by the alternating voltage signal generator A, and the circuit current I in the secondary circuit at this time is read out; If the circuit current I increases with the growth of the initial voltage U and exceeds the protection judgment current I1, the alternating voltage signal generator A is protected from power-off, the values of the initial voltage U and the circuit current I before power-off are stored, the circuit resistance value R is calculated, and the simulated fault point electrical distance L is confirmed by the resistance value R; If the circuit current I floats with the growth of the initial voltage U and is lower than the protection judgment current I1, the initial voltage U is continuously increased to the safety voltage U1 to terminate.

2. The secondary circuit servicing method of claim 1, wherein, The problem circuit (100) contains the secondary side (100a) of the voltage transformer; The secondary side (100a) of the voltage transformer adopts star connection method and is configured with voltage busbars YM a, YM b, YM c and YM n; The output terminals Ux and Uy of the alternating voltage signal generator A are connected to the problem voltage busbar for fault point confirmation.

3. The secondary circuit servicing method according to claim 2, characterized in that, If the voltage busbars YM a, YM b, YM c and YM n and the three-phase terminals L1, L2 and L3 are all configured with fuses (B): When the circuit current I exceeds the protection judgment current I1, the fuses (B) are disconnected to form the problem circuit (100); The output terminals of the voltage signal generator A are connected to the disconnected fuses (B) and the ground terminal respectively.

4. The secondary circuit servicing method according to claim 3, characterized in that, The secondary side (100a) of the voltage transformer is configured with a low-voltage relay (C) protection circuit; The secondary side (100a) of the voltage transformer is configured with a voltmeter (V); The problem circuit (100) is connected from the primary side (100a) of the voltage transformer to the three-phase terminals L1, L2 and L3 of the primary side (100a) of the voltage transformer.

5. The secondary circuit servicing method according to claim 4, characterized in that, The initial voltage U is increased in steps; The safety voltage U1 is greater than or equal to 36V; The initial voltage U is greater than or equal to 3V.

6. The secondary circuit servicing method according to claim 5, characterized in that, The simulated fault point electrical distance L / actual fault point electrical distance L1 is approximately 110%, or the simulated fault point electrical distance L·90% is approximately the actual fault point electrical distance L1.

7. The secondary circuit servicing method according to claim 6, characterized in that, If the secondary circuit insulation is good, the circuit current I is infinitesimal; At this time, the voltage transformer secondary load resistance, i.e. the circuit resistance value R without fault is greater than the circuit resistance value R with fault; The simulated fault point electrical distance L is inversely proportional to the circuit current I; That is, the simulated fault point electrical distance L is an infinite amount, equivalent to the absence of the simulated fault point electrical distance L.

8. The secondary circuit servicing method according to claim 7, characterized in that, After confirming the simulated fault point electrical distance, the branches of the faulty voltage busbar are tested by a clamp-on ammeter; If the branch current = 0, there is no fault; If the branch current ≠ 0, there is a fault; Then the faulty branch is judged to complete fault point positioning.

9. The secondary circuit servicing method according to claim 5, characterized by, The maximum value of the safety voltage U1 depends on the system normal voltage; The initial voltage U is increased in steps of 0.1V.

10. A computer device comprising: Memory, a processor, and a computer program stored on the memory and executable on the processor, characterized in that the processor executes the computer program to implement the secondary circuit maintenance method of any one of claims 1-9.

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