A method for identifying power cables

Abstract

The present invention relates to a method for identifying power cables, including steps such as transmitting signals, receiving signals, phase calculation, and line matching determination. The power cable identification method provided by the present invention is based on the double modulation wave technology, utilizes the principle of electromagnetic induction, and realizes the on-line detection of power cables by differentiating different phases of the coupled signals. The transmitting end couples the identification signal to the metal armor of the cable through electromagnetic induction; while the receiving end detects the signal on the metal armor and uses the phase identification technology for differentiation, so as to determine the corresponding relationship between power cables.

Description

Technical Field

[0001] The present invention relates to a method for identifying power cables, belonging to the technical field of cable detection. Background Art

[0002] In cities, power cables are almost all laid in underground pipelines, and then pipeline wellheads are opened on the road surface for equipment maintenance. There are often multiple power cables in the pipeline. There are labels for identification during the initial laying, but after a long time, the labels may corrode and fall off. In addition, most power cable laying is entrusted to external construction units, and there are great differences in technical and management levels. The situation of misalignment up and down during pipe threading often occurs. When passing through fireproof partition walls, connected trenches, and mixed burial sections, entanglement and coiling often occur. After completion, there is also a lack of standardized acceptance procedures and completion data. At this time, it is simply impossible to identify the matching relationship of the cables by visual inspection alone, and it will be very difficult when maintenance is needed again.

[0003] Currently, the commonly used methods for identifying power cables mainly include pulse polarity method, audio signal method, resistance method, GPS synchronization method, etc. The pulse polarity method has the advantage of obvious electromagnetic field change characteristics, but when operating, the grounding wire at the cable end must be disconnected, and the pulse signal source is connected to the grounding system in series. However, in the safety specifications for cable operation and maintenance, it is prohibited to remove the grounding under operating conditions. Therefore, the pulse polarity method can only identify out-of-service cables and cannot perform identification and detection on operating cables. Most of the early cable identification and detection technologies at home and abroad used this method, and it is rarely used at present; the audio induction method can identify and detect operating power cables, but if the grounding of multiple circuits of cables is common grounding (the currently commonly used construction method), due to the difference or absence of the remote grounding resistance, the signal flow of each circuit of cable will change or even there will be no signal flow, resulting in misjudgment or difficulty in discrimination. Moreover, when detecting a double bridge in one path, the signals of the two circuits of cables are equal, and the target cable cannot be discriminated. Currently, most cable identification instruments on the market basically use the audio induction method; the resistance method is simple and practical, but due to the strong electromagnetic field environment around the cable operation environment, there are different interference errors in different detection circuits, and the accuracy is difficult to control. It is difficult to judge the target cable by equivalent value, and it is rarely used at present; the GPS synchronization method is a new method that has emerged in recent years. It can achieve online cable identification with a relatively high identification rate, but it is highly dependent on third-party signals, has a long receiving and processing time, and is not convenient to operate. Coupled with the shielding of high-rise buildings and trees in the city, when the signal is unstable, misjudgment is likely to occur. If the online cable identification technology can remove the dependence on GPS synchronization signals, there will be a greater improvement in terms of practicability and accuracy. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the above-mentioned technical drawbacks and provide a method for on-line cable identification based on the principle of electromagnetic induction and double modulation wave identification technology.

[0005] To solve the above technical problem, the technical solution proposed by the present invention is: A power cable identification method, comprising the following steps:

[0006] Step 1: Input a test signal into a certain line at one end of the cable to be tested. The test signal is modulated by a first sine wave A and a second sine wave B, and the frequency ratio of the first sine wave A and the second sine wave B is 2:3;

[0007] Step 2: Receive the signal from a certain line at the other end of the cable to be tested, compare it with the test signal, and detect the phase of the first sine wave A and the phase of the second sine wave B

[0008] Step 3: When the received signal is in phase with the test signal, determine the value of. If is between 0 and 90°, calculate the phase of the second sine wave B when the phase of the first sine wave A is 90°, that is . If is between 90° and 360°, calculate the phase of the second sine wave B when the phase of the first sine wave A is 90°, that is . Wherein, define as the phase value when the phase of the first sine wave A is 90°;

[0009] When the received signal is out of phase with the test signal, determine the value of. If is between 0 and 180° or between 270° and 360°, calculate the phase of the second sine wave B when the phase of the first sine wave A is 90°, that is . If is between 180° and 270°, calculate the phase of the second sine wave B when the phase of the first sine wave A is 90°, that is .

[0010] Step 4: Calculate according to the formula If or 180°, the line for inputting the test signal and the line for receiving the signal are corresponding; if or 90°, it means that the input line and the received line are not corresponding;

[0011] Step 5: Repeat the above steps until all the lines are corresponding completely.

[0012] A further improvement of the above solution is that: in the step 3 If it is less than 0, add 360° until it is in the range of 0 to 360°. If it is greater than 360°, subtract 360° until it is in the range of 0 to 360°.

[0013] A further improvement of the above solution is that: the frequency of the first sine wave A is 800 Hz, and the frequency of the second sine wave B is 1200 Hz.

[0014] The power cable identification method provided by the present invention is based on the double modulation wave technology, utilizes the electromagnetic induction principle, and realizes the detection of the on-line power cable by identifying different phases of the coupling signal. The transmitting end couples the identification signal to the metal armor of the cable through electromagnetic induction; while the receiving end detects the signal on the metal armor and uses the phase identification technology to identify, so as to judge the corresponding relationship between the power cables. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The present invention will be further described below with reference to the drawings.

[0016] Figure 1 It is a schematic diagram of the system structure of a preferred embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0017] Embodiment

[0018] The power cable identification method of this embodiment includes the following steps:

[0019] Step 1: Input a test signal from a certain line at one end of the cable to be tested. The test signal is modulated by the first sine wave A and the second sine wave B, and the frequency ratio of the first sine wave A and the second sine wave B is 2:3; for the convenience of synthesizing the waveform, the periods of the two waveforms are preferably the least common multiple. Therefore, sine waves with frequencies of 800 Hz and 1.2 kHz can be selected.

[0020] Step 2: Receive the signal from a certain line at the other end of the cable to be tested, compare it with the test signal, and detect the phase of the first sine wave A and the phase of the second sine wave B

[0021] Step 3: When the received signal is in phase with the test signal, it is determined that the value of, if is between 0 and 90°, calculate that when the phase of the first sine wave A is 90°, that is, when, the phase of the second sine wave B If When it is from 90° to 360°, calculate that when the phase of the first sine wave A is 90°, that is the phase of the second sine wave B

[0022] When the received signal is out of phase with the test signal, it is determined that the value of, if When it is from 0 to 180° or from 270° to 360°, calculate that when the phase of the first sine wave A is 90°, that is the phase of the second sine wave B If When it is from 180° to 270°, calculate that when the phase of the first sine wave A is 90°, that is the phase of the second sine wave B

[0023] The above If it is less than 0, add 360° until it is within 0 to 360°. If it is greater than if it is less than 0, subtract 360° until it is within 0 to 360°.

[0024] Step 4: Calculate according to the formula If or 180°, the line for inputting the test signal corresponds to the line for receiving the signal; if or 90°, it means that the input line does not correspond to the received line.

[0025] Step 5: Repeat the above steps until all lines are corresponding.

[0026] To implement the above method, a system as Figure 1 described is designed. The system is divided into two parts: a host and a slave. The slave can work in a single-machine mode or a dual-machine mode. When working in the single-machine mode, it can realize the detection of single-end short circuit and open circuit of the cable; when working in the dual-machine mode, it is used for the host to detect the line. The slave mainly sends test signals to the host. The host needs to work with the assistance of the slave to realize the double-end short circuit, open circuit and line matching test of the cable. After the test is completed, the test results are displayed on the LED screen.

[0027] The slave is mainly composed of a signal output end and a signal feedback input end. The signal output end of each wire core corresponds one-to-one with the signal feedback end. When working, the MCU, according to a certain coding rule, sequentially sends current detection signals to each wire core through the signal output end, and at the same time detects the corresponding feedback end of the signal output end, and gives the detection result according to the feedback signal or switches the detection signal to transition to the next wire core test.

[0028] The main unit mainly consists of a signal detection end and a feedback signal control end. During operation, the MCU scans the signal detection end to determine which wire core is in the test signal transmission state currently; the feedback signal control end is used to control the on / off state of the test signal. After the detection of the current wire core is completed, the test signal is briefly cut off to notify the slave unit to switch the detection signal and transition to the detection of the next wire core.

[0029] The system can achieve the fault detection and line numbering of multiple wire cores. The number of wire cores for testing is theoretically unlimited, but the actual detection is controlled by the number of I / O interfaces of the system. It can be expanded through an I / O port expansion chip according to the actual situation. Generally, the number of wire cores in a cable in the power system does not exceed 24 cores. Therefore, the maximum wire connection capacity designed for this system is 24 cores.

[0030] Both the main unit and the slave unit of this system are equipped with 24 wiring terminals, numbered in sequence from 1# to 24#. When the system works in the wire connection mode, at the slave unit end, the wire cores are connected to the terminal block in ascending order of the wiring terminal numbers, and labels identical to the wiring terminal numbers are attached to the wire cores. At the same time, the wire connection test signal transmission mode is selected on the slave unit; at the main unit end, only the wire cores need to be connected to the wiring terminals and then the test can be started. The detection process is completed instantaneously, and the wiring terminal number and the wire core number connected to this terminal are correspondingly displayed on the LED screen of the main unit. The construction personnel only need to complete the wire connection function according to the display result on the screen.

[0031] The present invention is not limited to the above embodiments. All technical solutions formed by equivalent substitution fall within the protection scope required by the present invention.

Claims

1. A method for identifying a power cable, characterized in that, It includes the following steps: Step 1: Input a test signal from a certain line at one end of the cable to be measured. The test signal is modulated by a first sine wave A and a second sine wave B, and the frequency ratio of the first sine wave A to the second sine wave B is 2:3; Step 2: Receive a signal from a certain line at the other end of the cable to be tested, compare it with the test signal, and detect the phase of the first sine wave A and the phase of the second sine wave B Step 3: When the received signal is in phase with the test signal, it is determined that value, if is between 0 and 90°, calculate the phase of the second sine wave B when the phase of the first sine wave A is 90°, that is at this time If is between 90° and 360°, calculate the phase of the second sine wave B when the phase of the first sine wave A is 90°, that is at this time wherein, it is defined that is the phase value when the phase of the first sine wave A is 90°; When the received signal is in antiphase with the test signal, it is determined that the value, if is between 0 and 180° or between 270° and 360°, calculate the phase of the second sine wave B when the phase of the first sine wave A is 90°, that is at this time, the phase of the second sine wave B If is between 180° and 270°, calculate the phase of the second sine wave B when the phase of the first sine wave A is 90°, that is at this time, the phase of the second sine wave B Step 4: Calculate according to the formula If or 180°, the line for inputting the test signal corresponds to the line for receiving the signal; if or 90°, it indicates that the input line does not correspond to the receiving line; Step 5: Repeat the above steps until all lines are corresponding completed.

2. The power cable identification method according to claim 1, wherein: In the said step 3 If it is less than 0, add 360° to make it fall within the range of 0 to 360°. If it is greater than or less than 0, subtract 360° to make it fall within the range of 0 to 360°.

3. The power cable identification method according to claim 1, wherein: The frequency of the first sine wave A is 800 Hz, and the frequency of the second sine wave B is 1200 Hz.

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