A method and device for checking phase of power transmission cable line

Abstract

The present invention discloses a power transmission cable line phase check device and method, the device includes a current acquisition device, which is composed of a signal-interactive current acquisition unit and a data processing unit; the current acquisition unit is used to collect current data of the metal sheath grounding wire on one side of the last cable of each phase line in the reference power transmission cable line and the power transmission cable line to be checked; the data processing unit is used to receive the current data of the current acquisition unit, and calculate and obtain the current vector data of the metal sheath grounding wire on one side of the last cable of each phase line in the corresponding line; and also includes a data analysis device, which is used to receive the current vector data of the data processing unit, obtain the vector sum of the current vector data on both sides of the last cable of each phase line in the corresponding line as the capacitive current of the corresponding line, and analyze based on the capacitive current to complete the phase check. When the present invention is applied, it can ensure the safety of equipment and personnel, and the operation is simple, convenient, and efficient, and the phase check result is accurate.

Description

Technical Field

[0001] The invention relates to the technical field of electric power detection, and in particular to a method and a device for checking the phase of a power transmission cable line. Background Art

[0002] In the actual operation, maintenance and inspection of transmission cables, it is often necessary to carry out phase checking operations. For example, before the transmission cable line is officially put into operation, a phase checking test of the transmission cable line is required to ensure that the transmission cable line to be put into operation has the same phase and phase sequence as the power equipment in operation.

[0003] The current phase checking methods are mainly divided into high-voltage primary direct phase checking and voltage transformer secondary indirect phase checking. The high-voltage primary direct phase checking means that the operator uses an insulating rod that meets the voltage level to touch or approach the high-voltage primary side live part of the transmission cable line with a high-voltage measuring instrument, and then uses the high-voltage measuring instrument to collect the operating voltage phase of the transmission cable line. However, this method is heavily dependent on the insulation strength and manufacturing process of the insulating rod, and there is a great risk of high-voltage electric shock; and the voltage transformer secondary indirect phase checking means that the operator collects the operating voltage phase of the transmission cable line through the secondary side of the voltage transformer. In this method, on the one hand, some transmission cable lines are only installed with single-phase voltage transformers, and three-phase voltage transformers are not installed, so this method may not be able to measure the phase of the three-phase transmission cable line; on the other hand, this method sometimes requires adjustment of the original wiring of the power equipment, which may cause grid operation risks and even cause grid accidents.

[0004] The Chinese invention patent with application number 202010843243.7 and name "A phase checking device and method based on the leakage current signal of the arrester" provides a method for measuring the leakage current of the arrester of the transmission cable line for phase checking. The method requires that the current detection host be connected in parallel on both sides of the arrester counter. This operation has the risk of high-voltage electric shock caused by the overvoltage discharge of the arrester; at the same time, the method requires that the arrester is in good operating condition, but the actual operating condition of the arrester is unknown. The Chinese invention patent with application number 202310472642.0 and name "A phase line rapid verification device for GIS equipment hybrid line" provides a method for injecting an abnormal frequency current signal into the aluminum sheath of the cable at the line side, and observing the abnormal frequency current signal of the aluminum sheath of the cable at the phase side to be checked for phase checking. On the one hand, the injected signal in this method may have serious attenuation problems, making the signal detection difficult; on the other hand, this method does not take into account the structure of the three-phase aluminum sheath of the actual cable being connected to the ground in parallel, and the injected signal may penetrate into the aluminum sheath of the remaining phases, causing the failure of the phase checking of the transmission cable line.

[0005] Therefore, the traditional phase checking method for transmission cable lines has many disadvantages, which is not conducive to completing the phase checking work of transmission cable lines safely, accurately and efficiently. Based on this, the present invention aims to provide a safer, more effective and accurate phase checking method and device. Summary of the invention

[0006] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a method and device for checking the phase of a transmission cable line, which can ensure the safety of equipment and personnel when used, is simple, convenient and efficient to operate, and produces accurate phase checking results.

[0007] The purpose of the present invention is mainly achieved through the following technical solutions:

[0008] In a first aspect, the present application proposes a method for checking the phase of a power transmission cable line, which comprises the following steps:

[0009] Collect current data of the metal sheath grounding wires on both sides of the last section cable of each phase of the reference transmission cable line and the transmission cable line of the phase to be checked; the last section cable is the cable between the substation cable terminal at the switch to be closed and the middle joint of the adjacent cable in the reference transmission cable line or the transmission cable line of the phase to be checked;

[0010] Based on the collected current data of the metal sheath grounding wires on both sides of the end cable, the current vector data of the metal sheath grounding wires on both sides of the end cable of each phase line in the corresponding line is obtained;

[0011] Based on the current vector data, obtaining a vector sum of the current vector data of each phase line in the corresponding line, wherein the vector sum is the capacitive current of each phase line in the corresponding line;

[0012] Based on the capacitor current, the phase is cored:

[0013] Assume that the A-phase, B-phase or C-phase line in the reference transmission cable line is represented by m, and the same A-phase, B-phase or C-phase line in the to-be-checked transmission cable line is represented by n;

[0014] Assume that the capacitive current of phase m in the reference transmission cable line is i m , the capacitive current of phase n in the core-phase transmission cable line is i n , then define i m with i n The nuclear phase difference T mn for:

[0015]

[0016] Among them, phase() is the phase of the vector;

[0017] Among them, if T mnLess than or equal to 30°, the m phase in the reference transmission cable line and the n phase in the to-be-checked transmission cable line are in phase; otherwise, the m phase and the n phase are out of phase;

[0018] Based on formula ①, the phase difference T between the reference transmission cable line and the three-phase line in the transmission cable line to be checked is determined in turn. mn , if the core phase difference T in the three-phase line mn If both are less than or equal to 30°, the phase sequence of the power transmission cable line to be checked is determined to be correct; if not, the phase sequence of the power transmission cable line to be checked is determined to be incorrect, and the phase check is completed.

[0019] In this method, the current data of the metal sheath grounding wires on both sides of the last cable of each phase line in the reference transmission cable line and the transmission cable line to be checked are collected, specifically:

[0020] The grounding boxes introduced through grounding wires at both ends of the metal sheath of the final cable of the A-phase, B-phase and C-phase lines of the reference transmission cable line are defined as the first grounding box and the second grounding box, respectively, wherein the first grounding box is located at the substation, and the second grounding box is located in the channel of the reference transmission cable line;

[0021] The grounding boxes introduced through grounding wires at both ends of the metal sheath of the final cable of the A-phase, B-phase and C-phase transmission cable lines to be checked are defined as the third grounding box and the fourth grounding box, respectively. The third grounding box is located at the substation, and the fourth grounding box is located in the channel of the transmission cable line to be checked;

[0022] A set of current collection devices is arranged at the first grounding box, the second grounding box, the third grounding box and the fourth grounding box. The four sets of current collection devices respectively collect the three-phase grounding wire current data at the four grounding boxes at the same time.

[0023] In this method, the current acquisition device is composed of three current transformers and a data processing unit;

[0024] The three current transformers are respectively installed on the metal sheath grounding wires on one side of the terminal cable of the A-phase, B-phase and C-phase lines in the corresponding lines, and the direction of the current transformers is the direction from the metal sheath of the cable to the grounding box, and are used to respectively collect current data of the metal sheath grounding wires on one side of the terminal cable of the A-phase, B-phase and C-phase lines in the corresponding lines;

[0025] The data processing unit is used to receive the metal sheath grounding wire current data collected by the three current transformers, and calculate the amplitude and phase of the power frequency component in the current data based on the metal sheath grounding wire current data, and then obtain the current vector data of the metal sheath grounding wire on one side of the last cable of each phase line in the corresponding line.

[0026] In the method, the four groups of current acquisition devices are all synchronized to ensure that the data acquisition times of the four groups of current acquisition devices are consistent.

[0027] In the method, based on the current vector data, a vector sum of the current vector data of each phase line in the corresponding line is obtained, and the vector sum is the capacitive current of each phase line in the corresponding line, and further includes:

[0028] The current vector data acquired in the second grounding box and the fourth grounding box are corrected for time deviation, and the vector sum is calculated using the corrected current vector data.

[0029] In this method, the current vector data obtained in the second grounding box and the fourth grounding box are corrected for time deviation, and the vector sum is calculated using the corrected current vector data, specifically:

[0030] The current collection devices in the first grounding box, the second grounding box, the third grounding box, and the fourth grounding box are respectively 1# current collection device, 2# current collection device, 3# current collection device, and 4# current collection device;

[0031] The current vector data of the metal sheath grounding wire on the end cable side of phase A, phase B and phase C in the corresponding line collected by the 1# current acquisition device are I a1 ,I b1 ,I c1 ; The current vector data of the metal sheath grounding wire on one side of the end cable of phase A, phase B and phase C in the corresponding line collected by the 2# current collection device are I a2 ,I b2 ,I c2 ; The current vector data of the metal sheath grounding wire on one side of the end cable of phase A, phase B and phase C in the corresponding line collected by the 3# current acquisition device are I a3 ,I b3 ,I c3 ; The current vector data of the metal sheath grounding wire on one side of the end cable of phase A, phase B and phase C in the corresponding line collected by the 4# current collection device are I a4 ,I b4 ,I c4 ;

[0032] Assume that the phase deviation between the current vector data of the 2# current acquisition device and the current vector data of the 1# current acquisition device is Δθ1; the phase deviation between the current vector data of the 4# current acquisition device and the current vector data of the 3# current acquisition device is Δθ2; wherein the ranges of Δθ1 and Δθ2 are both [0,360°);

[0033] In the power system, the phases of the three-phase voltages are 120° apart from each other, and the phases of the three-phase capacitance currents of the transmission cables are also 120° apart from each other. Based on this, the squared residual value of the three-phase capacitance current phase of the last cable in the reference transmission cable line or the transmission cable line to be verified is:

[0034]

[0035] In formula ②: phase() is the phase of the vector; ΔP is the phase deviation independent variable; a, b, c represent phase A, phase B and phase C in the corresponding cable line respectively, and x, y represent the corresponding current acquisition device number;

[0036] Based on formula ②, different ΔP is set in the range of [0,360°). When ΔP = -Δθ1 or -Δθ2, the phase deviation Δθ1 or Δθ2 is eliminated, and R takes the minimum value. Then, the step angle of ΔP is set to 1° in the range of [0,360°), and the corresponding R is calculated in turn. The ΔP corresponding to the minimum value in R is recorded as

[0037] but:

[0038] According to the current vector data collected by the 1# current acquisition device and the 2# current acquisition device, the square value of the phase residual of the three-phase capacitance current of the last cable in the reference transmission cable line is calculated as follows:

[0039]

[0040] At the same time, according to the current vector data collected by the 3# current acquisition device and the 4# current acquisition device, the square value of the phase residual of the three-phase capacitance current of the last cable in the phase transmission cable line to be verified is calculated as follows:

[0041]

[0042] The ΔP1 corresponding to the minimum value in record R1 is The ΔP2 corresponding to the minimum value in R2 is

[0043] Based on the records

[0044] Calculate the current vector data of phase A, phase B, and phase C of the 2# current acquisition device after time deviation correction They are:

[0045]

[0046] Based on the current vector data collected by the 1# current acquisition device and the current vector data corrected by the 2# current device, the vector sum of the three-phase current vector data is calculated, and the capacitance current i of phase A, phase B, and phase C corresponding to the reference transmission cable line is obtained. a 、i b 、i c They are:

[0047]

[0048]

[0049] Record-based

[0050] Calculate the current vector data of phase A, phase B, and phase C of the 4# current acquisition device after time deviation correction They are:

[0051]

[0052] Based on the current vector data collected by the 3# current acquisition device and the current vector data corrected by the 4# current device, the vector sum of the three-phase current vector data is calculated, and the capacitance current i of phase A, phase B, and phase C corresponding to the phase transmission cable line to be checked is obtained. a ′、i b ′、i c ′ are respectively:

[0053]

[0054] In a second aspect, the present application further proposes a power transmission cable line phase checking device, which is used to implement the above-mentioned power transmission cable line phase checking method, and the device specifically comprises:

[0055] The current acquisition device is composed of a current acquisition unit and a data processing unit for signal interaction;

[0056] in,

[0057] The current acquisition unit is used to collect current data of the metal sheath grounding wire on one side of the end cable of each phase of the reference transmission cable line and the transmission cable line of the phase to be checked; the end cable is the cable between the substation cable terminal at the switch to be closed and the middle joint of the adjacent cable in the reference transmission cable line or the transmission cable line of the phase to be checked;

[0058] The data processing unit is used to receive the collected current data of the metal sheath grounding wire on one side of the end cable, and calculate and obtain the current vector data of the metal sheath grounding wire on one side of the end cable of each phase line in the corresponding line;

[0059] Also includes,

[0060] The data analysis device is used to receive the current vector data of the data processing unit, obtain the vector sum of the current vector data of each phase line in the corresponding line, the vector sum is the capacitive current of each phase line in the corresponding line, and perform analysis based on the capacitive current to complete the phase identification.

[0061] In the device, the grounding boxes introduced through grounding wires at both ends of the metal sheath of the end cables of the A-phase, B-phase and C-phase lines in the reference transmission cable line are defined as the first grounding box and the second grounding box, wherein the first grounding box is located at the substation, and the second grounding box is located in the channel of the reference transmission cable line;

[0062] The grounding boxes introduced through grounding wires at both ends of the metal sheath of the final cable of the A-phase, B-phase and C-phase transmission cable lines to be checked are defined as the third grounding box and the fourth grounding box, respectively. The third grounding box is located at the substation, and the fourth grounding box is located in the channel of the transmission cable line to be checked;

[0063] A set of current collection devices is arranged at the first grounding box, the second grounding box, the third grounding box and the fourth grounding box. The four sets of current collection devices respectively collect the three-phase grounding wire current data at the four grounding boxes at the same time.

[0064] In the device, each group of the current collection device comprises three current transformers and a data processing unit;

[0065] The three current transformers are respectively installed on the metal sheath grounding wires on one side of the terminal cable of the A-phase, B-phase and C-phase lines in the corresponding lines, and the direction of the current transformers is the direction from the metal sheath of the cable to the grounding box, and are used to respectively collect current data of the metal sheath grounding wires on one side of the terminal cable of the A-phase, B-phase and C-phase lines in the corresponding lines;

[0066] The data processing unit is used to receive the metal sheath grounding wire current data collected by the three current transformers, and calculate the amplitude and phase of the power frequency component in the current data based on the metal sheath grounding wire current data, and then obtain the current vector data of the metal sheath grounding wire on one side of the last cable of each phase line in the corresponding line.

[0067] In the device, the current collection unit is a current transformer.

[0068] In summary, the method and device of the present invention have the following beneficial effects compared with the prior art:

[0069] 1. The present invention only requires the use of a current acquisition unit (current transformer) to collect the current on the metal sheath grounding wire of the transmission cable line. On the one hand, there is no need to change the original wiring of the power equipment, which can ensure the safe operation of the equipment; on the other hand, only the electrical parameters of the grounding terminal of the power equipment need to be measured, which can ensure the personal safety of the operator.

[0070] 2. The present invention can accurately obtain the capacitive current of the reference transmission cable line and the transmission cable line of the phase to be checked by collecting the metal sheath grounding wire current of the last cable in the reference transmission cable line and the phase to be checked, and use the phase difference between the capacitive current and the cable main core voltage for the line phase check operation by determining the phase difference, so that the detection is more efficient and accurate.

[0071] 3. To address the time deviation problem of the current collection device in the underground channel of the transmission cable line, the present invention uses the square value of the three-phase capacitor current phase residual to solve the optimal phase deviation, thereby eliminating the time deviation of the current collection device in a low-cost manner and ensuring the reliability of the test results.

[0072] 4. The present invention utilizes the capacitive current of the reference transmission cable line and the transmission cable line to be checked to carry out phase checking work. The operation is simple and efficient, is not restricted by the voltage level, has universality, is suitable for large-scale promotion and application, and can effectively improve the accuracy and safety of the line phase checking work. BRIEF DESCRIPTION OF THE DRAWINGS

[0073] The drawings described herein are used to provide a further understanding of the embodiments of the present invention, constitute a part of this application, and do not constitute a limitation of the embodiments of the present invention. In the drawings:

[0074] Figure 1 This is a schematic diagram of the current flow direction in the metal sheath of a certain phase of the last section of the reference transmission cable line.

[0075] Figure 2 It is a schematic diagram of the application of the power transmission cable line phase core device of the present invention; DETAILED DESCRIPTION

[0076] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments and drawings. The exemplary embodiments of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

[0077] The first embodiment of the present invention provides a method for checking the phase of a power transmission cable line, which comprises the following steps:

[0078] S1: Simultaneously collect current data of the metal sheath grounding wires on both sides of the last section cable of each phase of the reference transmission cable line and the transmission cable line of the phase to be checked; the last section cable is the cable between the substation cable terminal at the switch to be closed and the middle joint of the adjacent cable in the reference transmission cable line or the transmission cable line of the phase to be checked.

[0079] As one of the specific implementation methods, the current data of the metal sheath grounding wires on both sides of the last cable of each phase line in the reference transmission cable line and the transmission cable line to be checked are collected, specifically:

[0080] The grounding boxes introduced through grounding wires at both ends of the metal sheaths of the last sections of the A-phase, B-phase and C-phase lines in the reference transmission cable line are defined as the first grounding box and the second grounding box, wherein the first grounding box is located at the substation, and the second grounding box is located in the passage of the reference transmission cable line; the grounding boxes introduced through grounding wires at both ends of the metal sheaths of the last sections of the A-phase, B-phase and C-phase lines in the to-be-checked phase transmission cable line are defined as the third grounding box and the fourth grounding box, wherein the third grounding box is located at the substation, and the fourth grounding box is located in the passage of the to-be-checked phase transmission cable line; a group of current acquisition devices are arranged at the positions of the first grounding box, the second grounding box, the third grounding box and the fourth grounding box, and the four groups of current acquisition devices respectively and simultaneously collect the three-phase grounding wire current data at the four grounding boxes.

[0081] It should be noted that in order to facilitate equipment installation and use, data transmission and subsequent maintenance, the first grounding box in this embodiment is located at the substation position corresponding to the reference transmission cable line, and the second grounding box is located in the channel of the reference transmission cable line. Similarly, the third grounding box is located at the substation position corresponding to the phase transmission cable line to be checked, and the fourth grounding box is located in the channel of the phase transmission cable line to be checked, so that the equipment can be installed nearby, the line layout can be reduced, and the equipment operation and maintenance costs can be reduced.

[0082] As a further implementation scheme, the current acquisition device consists of three current transformers and a data processing unit; the three current transformers are respectively installed on the metal sheath grounding wire on one side of the last cable of the A phase, B phase and C phase lines in the corresponding lines, and the direction of the current transformer is the direction of the cable metal sheath toward the grounding box, and is used to respectively collect current data of the metal sheath grounding wire on one side of the last cable of the A phase, B phase and C phase lines in the corresponding lines; the data processing unit is used to receive the metal sheath grounding wire current data collected by the three current transformers, and calculate the amplitude and phase of the power frequency component in the current data based on the metal sheath grounding wire current data, and then obtain the current vector data of the metal sheath grounding wire on one side of the last cable of each phase line in the corresponding line.

[0083] At the same time, in order to ensure the accuracy of the current data collected by the reference transmission cable line and the transmission cable line to be checked, it is necessary to simultaneously collect current data from the metal sheath grounding wires on both sides of the last section of the cable in the corresponding line. Therefore, the four groups of current collection devices are all synchronized to ensure that the data collection time of the four groups of current collection devices is consistent.

[0084] S2: Based on the collected current data of the metal sheath grounding wires on both sides of the end cable, obtain the current vector data of the metal sheath grounding wires on both sides of the end cable of each phase line in the corresponding line.

[0085] When used, two of the four groups of current acquisition devices are used to collect current data of the metal sheath grounding wires on both sides of the last section of the reference transmission cable line, and the remaining two groups of current acquisition devices are used to collect current data of the metal sheath grounding wires on both sides of the last section of the transmission cable line of the phase to be checked, and the two groups of current acquisition devices in the corresponding lines are each provided with three current transformers and a data processing unit, and the three current transformers respectively collect current data of the metal sheath grounding wires of the A phase, B phase, and C phase lines in the corresponding side lines, so that the current vector data of the metal sheath grounding wires on both sides of the last section of the cable of each phase line in the corresponding line can be obtained through the four groups of current acquisition devices.

[0086] On this basis, based on the current collection devices in the first grounding box and the second grounding box, the current data of the metal sheath grounding wires on both sides of the last section of the cable in the reference transmission cable line can be obtained. Similarly, based on the current collection devices in the third grounding box and the fourth grounding box, the current data of the metal sheath grounding wires on both sides of the last section of the cable in the phase transmission cable line to be checked can be obtained, thereby obtaining the current data of the required lines respectively.

[0087] It should be noted that, due to the poor communication conditions in the transmission cable line channel, the data processing unit can store the corresponding data after obtaining it. When necessary, it can be removed and placed in a convenient location for communication, and the saved current vector data can be sent to the corresponding device (such as the data analysis device described in this article) via Bluetooth, 4G or wired mode for data processing.

[0088] S3: Based on the current vector data, a vector sum of the current vector data of each phase line in the corresponding line is obtained, and the vector sum is the capacitive current of each phase line in the corresponding line.

[0089] In practical applications, such as Figure 1 As shown, taking any single-phase line corresponding to the reference transmission cable line as an example, assume:

[0090] U z is the cable core voltage; C z is the main insulation structure capacitance of the cable; Rz is the main insulation resistance of the cable; i z is the cable main insulation leakage current; Z m1 is the equivalent impedance of the left side of the cable metal sheath; Z m2 is the equivalent impedance on the right side of the cable metal sheath; U m is the induced voltage on the cable metal sheath; i m is the induced current of the cable metal sheath; I1 is the grounding wire current vector data at the first grounding box; I2 is the grounding wire current vector data at the second grounding box.

[0091] Combination Figure 1 It can be seen that I1 and I2 can be expressed as:

[0092]

[0093] Further, we can get:

[0094]

[0095] According to i z The current loop can be obtained:

[0096]

[0097] Where: / / is the parallel calculation of the circuit; ω is the angular frequency of the current; j is the complex unit.

[0098] Typically, consider:

[0099]

[0100] So, z It can be simplified to:

[0101] i z ≈jωC z U z

[0102] Finally, we can get:

[0103] I1+I2=jωC z U z

[0104] According to the above formula, the phase of the vector sum of I1 and I2 is 90° ahead of the cable main core voltage phase, so the capacitive current of the last cable in each phase line can be used for phase checking. Therefore, in this step, by collecting and calculating the vector sum of the current vector data on the grounding wires on both sides of the metal sheath of the last cable in the transmission cable line, the capacitive current of the last cable can be obtained and used for subsequent phase checking operations.

[0105] In the specific implementation, since the first grounding box and the second grounding box are arranged in the substation, the space is relatively open and convenient for communication, the consistency and simultaneity of the data collection time of the corresponding current collection devices in the two grounding boxes can be ensured through mature technologies such as GPS satellite timing technology, wired communication technology, and short-range wireless communication technology.

[0106] However, due to poor communication conditions, the equipment located in the underground passage of the transmission cable line, such as the current collection device in the second grounding box and the fourth grounding box, will have a collection time deviation, resulting in a time deviation in the current collection data, which ultimately affects the subsequent phase verification. Based on this, this step also includes:

[0107] S31, performing time deviation correction on the current vector data obtained in the second grounding box and the fourth grounding box, and calculating the vector sum with the corrected current vector data.

[0108] As a specific time deviation correction method, it is specifically as follows:

[0109] The current collection devices in the first grounding box, the second grounding box, the third grounding box, and the fourth grounding box are respectively 1# current collection device, 2# current collection device, 3# current collection device, and 4# current collection device;

[0110] The current vector data of the metal sheath grounding wire on the end cable side of phase A, phase B and phase C in the corresponding line collected by the 1# current acquisition device are I a1 ,I b1 ,I c1 ; The current vector data of the metal sheath grounding wire on one side of the end cable of phase A, phase B and phase C in the corresponding line collected by the 2# current collection device are I a2 ,I b2 ,I c2 ; The current vector data of the metal sheath grounding wire on one side of the end cable of phase A, phase B and phase C in the corresponding line collected by the 3# current acquisition device are I a3 ,I b3 ,I c3 ; The current vector data of the metal sheath grounding wire on one side of the end cable of phase A, phase B and phase C in the corresponding line collected by the 4# current collection device are I a4 ,I b4 ,I c4 ;

[0111] It should be noted here that the time deviation between the 2# current collection device and the 1# current collection device is defined as Δt1, and the time deviation between the 4# current collection device and the 3# current collection device is defined as Δt2.

[0112] For the same current signal data, if the time domain acquisition result of the 1# current acquisition device is x(t), and its frequency domain transformation result is X(ω), then the time domain acquisition result of the 2# current acquisition device is x(t+Δt1). According to the time shift characteristics of Fourier transform, its frequency domain transformation result is When only the power frequency component of the main component in the current acquisition result is considered, the frequency domain transformation result is obtained as follows:

[0113] Therefore, it can be seen that the current vector data of the 2# current acquisition device and the current vector data of the 1# current acquisition device have a phase deviation of Δθ1. Similarly, the current vector data of the 4# current acquisition device and the current vector data of the 3# current acquisition device have a phase deviation of Δθ2. Since the phase deviation shows a periodicity of [0,360°), the range of Δθ1 and Δθ2 is [0,360°).

[0114] And because the phases of the three-phase voltages in the power system are 120° apart, the phases of the three-phase capacitance currents of the transmission cable are also 120° apart. Based on this, the squared residual value of the three-phase capacitance current phase of the last cable in the reference transmission cable line or the transmission cable line to be verified is:

[0115]

[0116] In formula ②: phase() is the phase of the vector; ΔP is the phase deviation independent variable; a, b, c represent phase A, phase B and phase C in the corresponding cable line respectively, and x, y represent the corresponding current acquisition device number;

[0117] Based on formula ②, different ΔP is set in the range of [0,360°). When ΔP = -Δθ1 or -Δθ2, the phase deviation Δθ1 or Δθ2 is eliminated, and R takes the minimum value. Then, the step angle of ΔP is set to 1° in the range of [0,360°), and the corresponding R is calculated in turn. The ΔP corresponding to the minimum value in R is recorded as

[0118] but:

[0119] According to the current vector data collected by the 1# current acquisition device and the 2# current acquisition device, the square value of the phase residual of the three-phase capacitance current of the last cable in the reference transmission cable line is calculated as follows:

[0120]

[0121] At the same time, according to the current vector data collected by the 3# current acquisition device and the 4# current acquisition device, the square value of the phase residual of the three-phase capacitance current of the last cable in the phase transmission cable line to be verified is calculated as follows:

[0122]

[0123] The ΔP1 corresponding to the minimum value in record R1 is The ΔP2 corresponding to the minimum value in R2 is

[0124] Based on the records

[0125] Calculate the current vector data of phase A, phase B, and phase C of the 2# current acquisition device after time deviation correction They are:

[0126]

[0127] Based on the current vector data collected by the 1# current acquisition device and the current vector data corrected by the 2# current device, the vector sum of the three-phase current vector data is calculated, and the capacitance current i of phase A, phase B, and phase C corresponding to the reference transmission cable line is obtained. a 、i b 、i c They are:

[0128]

[0129] Record-based

[0130] Calculate the current vector data of phase A, phase B, and phase C of the 4# current acquisition device after time deviation correction They are:

[0131]

[0132] Based on the current vector data collected by the 3# current acquisition device and the current vector data corrected by the 4# current device, the vector sum of the three-phase current vector data is calculated, and the capacitance current i of phase A, phase B, and phase C corresponding to the phase transmission cable line to be checked is obtained. a ′、i b ′、i c ′ are respectively:

[0133]

[0134]

[0135] After the above operation, the vector sum is calculated with the corrected current vector data, which can eliminate the data deviation caused by the acquisition time deviation, thereby ensuring the accuracy of the current data collected in the corresponding line, and at the same time ensuring the accuracy of subsequent phase core operations and results.

[0136] S4: performing phase checking based on the capacitor current:

[0137] Assume that the A-phase, B-phase or C-phase line in the reference transmission cable line is represented by m, and the same A-phase, B-phase or C-phase line in the to-be-checked transmission cable line is represented by n;

[0138] Assume that the capacitive current of phase m in the reference transmission cable line is i m , the capacitive current of phase n in the core-phase transmission cable line is i n , where i m with i n are obtained through step S3, then define i m with i n The nuclear phase difference T mn for:

[0139]

[0140] Among them, phase() is the phase of the vector;

[0141] Among them, if T mn If the angle is less than or equal to 30°, the m phase in the reference transmission cable line and the n phase in the transmission cable line to be checked are in phase; otherwise, the m phase and the n phase are out of phase.

[0142] Based on formula ①, the phase difference T between the reference transmission cable line and the three-phase line in the transmission cable line to be checked is determined in turn. mn , that is, determine the phase difference between phase A and phase A′, phase B and phase B′, and phase C and phase C′ in turn. If the phase difference T mn If both are less than or equal to 30°, the phase sequence of the power transmission cable line to be checked is determined to be correct; if not, the phase sequence of the power transmission cable line to be checked is determined to be incorrect, and the phase check is completed.

[0143] The second embodiment of the present invention provides a power transmission cable line phase checking device, which can be used to implement the power transmission cable line phase checking method in the above embodiment, such as Figure 2 As shown, the device specifically includes:

[0144] A current acquisition device, composed of a signal-interactive current acquisition unit and a data processing unit; wherein the current acquisition unit is used to collect current data of the metal sheath grounding wire on one side of the last cable of each phase in a reference transmission cable line and a transmission cable line of a phase to be checked; the last cable is a cable between a substation cable terminal at a switch to be closed and an intermediate joint of an adjacent cable in the reference transmission cable line or the transmission cable line of a phase to be checked; the data processing unit is used to receive the collected current data of the metal sheath grounding wire on one side of the last cable, and calculate and obtain the current vector data of the metal sheath grounding wire on one side of the last cable of each phase in the corresponding line; and also includes a data analysis device, which is used to receive the current vector data of the data processing unit, obtain the vector sum of the current vector data of each phase in the corresponding line, the vector sum being the capacitive current of each phase in the corresponding line, and perform analysis based on the capacitive current to complete the phase check.

[0145] In specific applications, the data processing unit is used to receive current data, and obtain the amplitude and phase of the power frequency component in the current data through Fourier transform, Prony, wavelet analysis and other technologies, and obtain the current vector data of the metal sheath grounding wire on one side of the last cable of each phase line in the corresponding line, and can save it locally. When the communication is normal, the current vector data is sent to the data analysis device through Bluetooth, 4G or wired mode. The data processing unit and data analysis device can be realized by using existing data processing equipment, such as PLC control system.

[0146] In the phase verification device, the grounding boxes introduced through grounding wires at both ends of the metal sheaths of the end cables of the A-phase, B-phase and C-phase lines in the reference transmission cable line are defined as the first grounding box and the second grounding box, wherein the first grounding box is located at the substation, and the second grounding box is located in the passage of the reference transmission cable line; the grounding boxes introduced through grounding wires at both ends of the metal sheaths of the end cables of the A-phase, B-phase and C-phase lines in the to-be-verified phase transmission cable line are defined as the third grounding box and the fourth grounding box, wherein the third grounding box is located at the substation, and the fourth grounding box is located in the passage of the to-be-verified phase transmission cable line; a group of current collection devices are arranged at the positions of the first grounding box, the second grounding box, the third grounding box and the fourth grounding box, and the four groups of current collection devices respectively and simultaneously collect the three-phase grounding wire current data at the four grounding boxes.

[0147] In the phase core device, each group of the current acquisition device includes three current transformers and a data processing unit; the three current transformers are respectively installed on the metal sheath grounding wire on one side of the last cable of the A phase, B phase and C phase lines in the corresponding lines, and the direction of the current transformer is the direction of the cable metal sheath toward the grounding box, which is used to respectively collect the current data of the metal sheath grounding wire on one side of the last cable of the A phase, B phase and C phase lines in the corresponding lines; the data processing unit is used to receive the metal sheath grounding wire current data collected by the three current transformers, and calculate the amplitude and phase of the power frequency component in the current data based on the metal sheath grounding wire current data, and then obtain the current vector data of the metal sheath grounding wire on one side of the last cable of each phase line in the corresponding line.

[0148] In specific applications, if the sheath grounding wire of the corresponding line is a coaxial grounding wire structure, the current transformer can be installed at the horn position of the coaxial grounding wire or the copper busbar position of the grounding box, and it must be the A-phase, B-phase, and C-phase sheath grounding wire on one side of the last cable. The direction of the current transformer is also the direction of the cable metal sheath toward the grounding box.

[0149] In the phase-correlation device, the current acquisition unit is a current transformer. Specifically, the current transformer is a contactless current transformer.

[0150] In summary, the phase checking method and device of the embodiment of the present invention utilizes a contactless current transformer to collect the current on the metal sheath grounding wire of the power transmission cable line. On the one hand, there is no need to change the original wiring of the power equipment, which can ensure the safe operation of the equipment; on the other hand, the electrical parameters of the grounding terminal of the power equipment are measured through a contactless solution, which can ensure the personal safety of the operator; by collecting the metal sheath grounding wire current of the reference transmission cable line and the end cable of the transmission cable line to be checked, the capacitive current of the reference transmission cable line and the end cable of the transmission cable line to be checked can be accurately obtained, and it can be determined that the capacitive current leads the cable main core voltage phase by 9 0°, which can be used for accurate and efficient line phase checking operation; and in view of the time deviation problem of the current acquisition device in the underground channel of the transmission cable line, the square value of the three-phase capacitor current phase residual is used to solve the optimal phase deviation, and the time deviation of the current acquisition device is eliminated in a low-cost manner, ensuring the reliability of the test results; finally, the capacitor current of the reference transmission cable line and the last section of the cable in the transmission cable line to be checked is used to carry out the phase checking work. The operation is simple and efficient, not restricted by the voltage level, and has universality, which effectively improves the accuracy and safety of the line phase checking work, is suitable for large-scale promotion and application, and has broad application prospects.

[0151] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for checking the phase of a power transmission cable line, characterized in that: The following steps are involved: Collect the current data of the metal sheath grounding wires on both sides of the last cable of each phase line in the reference transmission cable line and the transmission cable line to be checked; The terminal cable is a cable between the substation cable terminal at the switch to be closed and the intermediate joint of the adjacent cable in the reference transmission cable line or the transmission cable line of the phase to be checked; Based on the collected current data of the metal sheath grounding wires on both sides of the end cable, the current vector data of the metal sheath grounding wires on both sides of the end cable of each phase line in the corresponding line is obtained; Based on the current vector data, obtaining a vector sum of the current vector data of each phase line in the corresponding line, wherein the vector sum is the capacitive current of each phase line in the corresponding line; Based on the capacitor current, the phase is cored: Assume that the A-phase, B-phase or C-phase line in the reference transmission cable line is represented by m, and the same A-phase, B-phase or C-phase line in the to-be-checked transmission cable line is represented by n; Assume that the capacitive current of phase m in the reference transmission cable line is i m , the capacitive current of phase n in the core-phase transmission cable line is i n , then define i m with i n The nuclear phase difference T mn for: Among them, phase() is the phase of the vector; Among them, if T mn If the angle is less than or equal to 30°, the m phase in the reference transmission cable line and the n phase in the transmission cable line to be verified are in phase; otherwise, the m phase and the n phase are out of phase; Based on formula ①, the phase difference T between the reference transmission cable line and the three-phase line in the transmission cable line to be checked is determined in turn. mn , if the core phase difference T in the three-phase line mn If both are less than or equal to 30°, the phase sequence of the power transmission cable line to be checked is determined to be correct; if not, the phase sequence of the power transmission cable line to be checked is determined to be incorrect, and the phase check is completed; Among them, the current data of the metal sheath grounding wires on both sides of the last cable of each phase line in the reference transmission cable line and the transmission cable line to be checked are collected, specifically: The grounding boxes introduced through grounding wires at both ends of the metal sheath of the final cable of the A-phase, B-phase and C-phase lines of the reference transmission cable line are defined as the first grounding box and the second grounding box, respectively, wherein the first grounding box is located at the substation, and the second grounding box is located in the channel of the reference transmission cable line; The grounding boxes introduced through grounding wires at both ends of the metal sheath of the final cable of the A-phase, B-phase and C-phase transmission cable lines to be checked are defined as the third grounding box and the fourth grounding box, respectively. The third grounding box is located at the substation, and the fourth grounding box is located in the channel of the transmission cable line to be checked; A set of current collection devices is arranged at the first grounding box, the second grounding box, the third grounding box and the fourth grounding box. The four sets of current collection devices respectively collect the three-phase grounding wire current data at the four grounding boxes at the same time.

2. The power transmission cable line phase checking method according to claim 1, characterized in that: The current acquisition device is composed of three current transformers and a data processing unit; The three current transformers are respectively installed on the metal sheath grounding wires on one side of the terminal cable of the A-phase, B-phase and C-phase lines in the corresponding lines, and the direction of the current transformers is the direction from the metal sheath of the cable to the grounding box, and are used to respectively collect current data of the metal sheath grounding wires on one side of the terminal cable of the A-phase, B-phase and C-phase lines in the corresponding lines; The data processing unit is used to receive the metal sheath grounding wire current data collected by the three current transformers, and calculate the amplitude and phase of the power frequency component in the current data based on the metal sheath grounding wire current data, and then obtain the current vector data of the metal sheath grounding wire on one side of the last cable of each phase line in the corresponding line.

3. The power transmission cable line phase checking method according to claim 1, characterized in that: The four groups of current acquisition devices are all synchronized to ensure that the data acquisition time of the four groups of current acquisition devices is consistent.

4. The power transmission cable line phase checking method according to claim 1, characterized in that: Based on the current vector data, a vector sum of the current vector data of each phase line in the corresponding line is obtained, wherein the vector sum is the capacitive current of each phase line in the corresponding line, and further includes: The current vector data acquired in the second grounding box and the fourth grounding box are corrected for time deviation, and the vector sum is calculated using the corrected current vector data.

5. The power transmission cable line phase checking method according to claim 4, characterized in that: The current vector data obtained in the second grounding box and the fourth grounding box are corrected for time deviation, and the vector sum is calculated using the corrected current vector data, specifically: The current collection devices in the first grounding box, the second grounding box, the third grounding box, and the fourth grounding box are respectively 1# current collection device, 2# current collection device, 3# current collection device, and 4# current collection device; The current vector data of the metal sheath grounding wire on the end cable side of phase A, phase B and phase C in the corresponding line collected by the 1# current acquisition device are I a1 ,I b1 ,I c1 ; The current vector data of the metal sheath grounding wire on one side of the end cable of phase A, phase B and phase C in the corresponding line collected by the 2# current collection device are I a2 ,I b2 ,I c2 ; The current vector data of the metal sheath grounding wire on one side of the end cable of phase A, phase B and phase C in the corresponding line collected by the 3# current acquisition device are I a3 ,I b3 ,I c3 ; 4 #The current vector data of the metal sheath grounding wire on the end cable side of phase A, phase B and phase C in the corresponding line collected by the current acquisition device are I a4 ,I b4 ,I c4 ; Assume that the phase deviation between the current vector data of the 2# current acquisition device and the current vector data of the 1# current acquisition device is Δθ1; the phase deviation between the current vector data of the 4# current acquisition device and the current vector data of the 3# current acquisition device is Δθ2; wherein the ranges of Δθ1 and Δθ2 are both [0,360°); In the power system, the phases of the three-phase voltages are 120° apart from each other, and the phases of the three-phase capacitance currents of the transmission cables are also 120° apart from each other. Based on this, the squared residual value of the three-phase capacitance current phase of the last cable in the reference transmission cable line or the transmission cable line to be verified is: In formula ②: phase() is the phase of the vector; ΔP is the phase deviation independent variable; a, b, c represent phase A, phase B and phase C in the corresponding cable line respectively, and x, y represent the corresponding current acquisition device number; Based on formula ②, different ΔP is set in the range of [0,360°). When ΔP = -Δθ1 or -Δθ2, the phase deviation Δθ1 or Δθ2 is eliminated, and R takes the minimum value. Then, the step angle of ΔP is set to 1° in the range of [0,360°), and the corresponding R is calculated in turn. The ΔP corresponding to the minimum value in R is recorded as but: According to the current vector data collected by the 1# current acquisition device and the 2# current acquisition device, the square value of the phase residual of the three-phase capacitance current of the last cable in the reference transmission cable line is calculated as follows: At the same time, according to the current vector data collected by the 3# current acquisition device and the 4# current acquisition device, the square value of the phase residual of the three-phase capacitance current of the last cable in the phase transmission cable line to be verified is calculated as follows: The ΔP1 corresponding to the minimum value in record R1 is The ΔP2 corresponding to the minimum value in R2 is Based on the records Calculate the current vector data of phase A, phase B, and phase C of the 2# current acquisition device after time deviation correction They are: Based on the current vector data collected by the 1# current acquisition device and the current vector data corrected by the 2# current device, the vector sum of the three-phase current vector data is calculated, and the capacitance current i of phase A, phase B, and phase C corresponding to the reference transmission cable line is obtained. a 、i b 、i c They are: Record-based Calculate the current vector data of phase A, phase B, and phase C of the 4# current acquisition device after time deviation correction They are: Based on the current vector data collected by the 3# current acquisition device and the current vector data corrected by the 4# current device, the vector sum of the three-phase current vector data is calculated, and the capacitance current i of phase A, phase B, and phase C corresponding to the phase transmission cable line to be checked is obtained. a′ 、i b′ 、i c′ They are:

6. A power transmission cable line phase checking device, used to implement the power transmission cable line phase checking method according to claim 1, characterized in that: include: The current acquisition device is composed of a current acquisition unit and a data processing unit for signal interaction; in, The current acquisition unit is used to collect current data of the metal sheath grounding wire on one side of the end cable of each phase of the reference transmission cable line and the transmission cable line of the phase to be checked; the end cable is the cable between the substation cable terminal at the switch to be closed and the middle joint of the adjacent cable in the reference transmission cable line or the transmission cable line of the phase to be checked; The data processing unit is used to receive the collected current data of the metal sheath grounding wire on one side of the end cable, and calculate and obtain the current vector data of the metal sheath grounding wire on one side of the end cable of each phase line in the corresponding line; Also includes, The data analysis device is used to receive the current vector data of the data processing unit, obtain the vector sum of the current vector data of each phase line in the corresponding line, the vector sum is the capacitive current of each phase line in the corresponding line, and perform analysis based on the capacitive current to complete the phase identification.

7. The nuclear phase device according to claim 6, characterized in that: The grounding boxes introduced through grounding wires at both ends of the metal sheath of the final cable of the A-phase, B-phase and C-phase lines of the reference transmission cable line are defined as the first grounding box and the second grounding box, respectively, wherein the first grounding box is located at the substation, and the second grounding box is located in the channel of the reference transmission cable line; The grounding boxes introduced through grounding wires at both ends of the metal sheath of the final cable of the A-phase, B-phase and C-phase transmission cable lines to be checked are defined as the third grounding box and the fourth grounding box, respectively. The third grounding box is located at the substation, and the fourth grounding box is located in the channel of the transmission cable line to be checked; A set of current collection devices is arranged at the first grounding box, the second grounding box, the third grounding box and the fourth grounding box. The four sets of current collection devices respectively collect the three-phase grounding wire current data at the four grounding boxes at the same time.

8. The nuclear phase device according to claim 6 or 7, characterized in that: Each group of the current collection devices comprises three current transformers and a data processing unit; The three current transformers are respectively installed on the metal sheath grounding wires on one side of the terminal cable of the A-phase, B-phase and C-phase lines in the corresponding lines, and the direction of the current transformers is the direction from the metal sheath of the cable to the grounding box, and are used to respectively collect current data of the metal sheath grounding wires on one side of the terminal cable of the A-phase, B-phase and C-phase lines in the corresponding lines; The data processing unit is used to receive the metal sheath grounding wire current data collected by the three current transformers, and calculate the amplitude and phase of the power frequency component in the current data based on the metal sheath grounding wire current data, and then obtain the current vector data of the metal sheath grounding wire on one side of the last cable of each phase line in the corresponding line.

9. The nuclear phase device according to claim 8, characterized in that: The current collection unit is a current transformer.

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