A non-in-service cable theft prevention online monitoring and early warning method

Abstract

The present application relates to a kind of non-in-service cable theft prevention online monitoring and early warning method, comprising the following steps: by exciting voltage module, the preset size of direct current voltage is output to the A phase terminal and B phase terminal of the near end of non-in-service cable;Current signal is obtained by current detection module at the C phase terminal of the near end of non-in-service cable, and specific current value is obtained based on current signal;Current value of current detection module (4) is analyzed by server, to realize the process of theft prevention monitoring and early warning.Compared with prior art, the present application has the beneficial effects of theft prevention monitoring and early warning, multiple power supply modes, detection loop construction, analysis of current value and accurate calculation of cable equivalent resistance.

Description

Technical Field

[0001] This invention relates to cable anti-theft monitoring technology, and in particular to an online monitoring and early warning method for non-operational cables. Background Technology

[0002] Cables, as crucial equipment for power transmission, play a vital role in the stability and reliability of power systems. However, cables not in operation are highly susceptible to theft due to prolonged periods of inactivity and lack of supervision, causing direct and indirect economic losses to power companies and users. Therefore, effectively monitoring and providing early warning of theft of cables not in operation has become an urgent problem to be solved.

[0003] Currently, cable anti-theft devices based on power line carrier communication technology and vibration sensors exist on the market. However, these devices have some problems. Anti-theft devices based on power line carrier communication technology consist of a transmitter and a reflector, involving many components, resulting in high cost and complex installation. Furthermore, the end reflector is easily damaged, causing the device to malfunction. Vibration signal-based monitoring has a limited range, suitable for monitoring fixed installation points such as transformers, but unsuitable for monitoring long-distance cables, and suffers from high false alarm and false negative rates. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the existing technology and provide an online monitoring and early warning method for theft prevention of off-line cables. This method has the advantages of theft prevention monitoring and early warning, multiple power supply methods, detection circuit construction, analysis of current value and accurate calculation of cable equivalent resistance, low cost and easy implementation.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] This invention provides an online monitoring and early warning method for preventing theft of non-operational cables, comprising the following steps:

[0007] S1: Output a preset DC voltage to the A-phase and B-phase terminals near the non-operational cable via the excitation voltage module;

[0008] S2: Obtain the current signal fed back from the C-phase end of the non-operational cable near the current detection module, and obtain the specific current value based on the current signal;

[0009] S3: The server compares the current value of the current detection module with the preset standard value to achieve the process of anti-theft monitoring and early warning.

[0010] Furthermore, S1 also includes setting a three-connector wire at the other end of the non-operational cable. The three connection terminals of the three-connector wire are respectively connected to the A-phase end, B-phase end and C-phase end of the far end of the non-operational cable, so as to realize the parallel connection of the A-phase conductor and the B-phase conductor, and then the series connection of the C-phase conductor.

[0011] Furthermore, in S1, the excitation voltage module is powered by a battery or a photovoltaic module.

[0012] Furthermore, in S2, the current detection module is powered by a battery or a photovoltaic module.

[0013] Furthermore, the power supply can be controlled by the power management module, which regulates the power supply from the battery or photovoltaic modules.

[0014] Furthermore, the terminating resistance R in the detection circuit constructed in S1 and S2 is 10 to 50 Ω, and the wiring resistance R0 of the three interconnecting wires in the detection circuit is 5 to 20 Ω.

[0015] Furthermore, in S3, the process of comparing the current value of the current detection module with the preset standard value to achieve the anti-theft monitoring and early warning is as follows:

[0016] If the circuit current is lower than 95% of the reference current, it is considered that one phase has been stolen.

[0017] If the circuit current is greater than 110% of the reference current, the cable is considered to have been deliberately short-circuited in three phases, posing a risk of theft.

[0018] Furthermore, in the detection loops constructed in S1 and S2, the formula for calculating the loop current is:

[0019]

[0020]

[0021] Among them: I R U is the loop detection current, U is the excitation voltage, L is the equivalent cable distance, and R is the current detected in the loop. 总 R is the equivalent resistance of the circuit. A =R B =R C R represents the resistance value per phase per kilometer of the cable, R is the terminal resistance of the device, and R0 is the wiring resistance. The resistance values ​​of phases A, B, and C are the same.

[0022] Furthermore, when the very beginning of the cable is short-circuited, the cable's equivalent resistance is 0.

[0023] Furthermore, if the cable is short-circuited at the 1 / 2 mark, there is no end-connection resistance R0, and the equivalent resistance of the cable is:

[0024]

[0025] If the cable is short-circuited at 2 / 3 of its length, there is no end-connection resistance R0, and the equivalent resistance of the cable is:

[0026]

[0027] Compared with the prior art, the present invention has the following beneficial effects.

[0028] Anti-theft monitoring and early warning: By outputting a preset DC voltage to the end of the non-operational cable through the excitation voltage module, and by acquiring and analyzing the current signal through the current detection module, the anti-theft monitoring and early warning of the cable can be realized.

[0029] Multiple power supply options: The excitation voltage module and current detection module can be powered by batteries or photovoltaic modules, providing multiple power supply options and increasing the system's flexibility and reliability.

[0030] Detection loop construction: By connecting the three-way connector to the far end of the non-operational cable, the A-phase conductor, the B-phase end, and the C-phase conductor are connected in series, thus constructing a complete detection loop and improving the accuracy and reliability of monitoring.

[0031] Analyzing current values: By comparing the current values ​​obtained by the current detection module with preset standard values ​​through the server, it can be determined whether the cable has been stolen or deliberately short-circuited in three phases, further improving the accuracy of monitoring.

[0032] Cable equivalent resistance calculation: Different formulas for calculating cable equivalent resistance are provided according to different short-circuit locations of the cable. The cable equivalent resistance can be accurately calculated according to the actual situation, which further improves the accuracy of monitoring. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the structure of the online monitoring and early warning system for anti-theft of non-operating cables in this invention;

[0034] Figure 2 This is a schematic diagram of the detection host in this invention;

[0035] Figure 3 This is a schematic diagram of the three-connection wiring configuration in this invention;

[0036] Figure 4 This is a schematic diagram of the detection principle in this invention.

[0037] In the diagram: 1. Housing, 2. Power management module, 3. Excitation voltage module, 4. Current detection module, 5. Off-line cable, 6. Three-way connector, 7. Server, 8. Battery, 9. User terminal, 10. Solar panel, 11. Communication module. Detailed Implementation

[0038] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. Component models, material names, connection structures, control methods, algorithms, and other features not explicitly described in this technical solution are considered common technical features disclosed in the prior art.

[0039] Example 1

[0040] The online monitoring and early warning method for preventing theft of non-operational cables includes the following steps:

[0041] S1: Output a preset DC voltage to the A-phase and B-phase terminals of the non-operational cable 5 near the excitation voltage module 3;

[0042] It also includes placing a three-connector 6 at the other end of the non-operational cable 5. The three connection terminals of the three-connector 6 are respectively connected to the A-phase terminal, B-phase terminal and C-phase terminal at the far end of the non-operational cable 5, so as to realize the parallel connection of the A-phase conductor and the B-phase conductor, and then the series connection of the C-phase conductor.

[0043] The excitation voltage module 3 is powered by a storage battery 8 or a photovoltaic module.

[0044] S2: The current signal fed back from the C-phase end of the non-operational cable 5 near the current detection module 4 is obtained, and the specific current value is obtained based on the current signal.

[0045] The current detection module 4 is powered by the battery 8 or the photovoltaic module.

[0046] The power supply is controlled by the power management module 2, which regulates the power supply from the battery 8 or the photovoltaic module.

[0047] The terminating resistance R in the detection circuit constructed in S1 and S2 is 10 to 50 Ω, and the wiring resistance R0 of the three-connected wire 6 in the detection circuit is 5 to 20 Ω.

[0048] S3: The server 7 compares the current value of the current detection module 4 with the preset standard value to realize the process of anti-theft monitoring and early warning.

[0049] The process of comparing the current value of current detection module 4 with the preset standard value to achieve the anti-theft monitoring and early warning is as follows:

[0050] If the circuit current is lower than 95% of the reference current, it is considered that one phase has been stolen.

[0051] If the circuit current is greater than 110% of the reference current, the cable is considered to have been deliberately short-circuited in three phases, posing a risk of theft.

[0052] In the detection loops constructed in S1 and S2, the formula for calculating the loop current is:

[0053]

[0054]

[0055] Among them: I R U is the loop detection current, U is the excitation voltage, L is the equivalent cable distance, and R is the current detected in the loop. 总 R is the equivalent resistance of the circuit. A =R B =R C R represents the resistance value per phase per kilometer of the cable, R is the terminal resistance of the device, and R0 is the wiring resistance. The resistance values ​​of phases A, B, and C are the same.

[0056] In principle:

[0057] The electrical parameters of power cables mainly include primary and secondary parameters, with resistance, capacitance, and inductance constituting the main components. Modeling off-line cables eliminates the need for operating voltage, current, and grounding systems, allowing low-voltage detection circuits to be directly applied to the entire cable for testing. The loop current monitoring principle of this invention is as follows: The three-phase (A, B, C) or single-phase conductors of the off-line cable are connected in series or parallel on one side of the cable end. A monitoring module is installed on the conductors and sheath on the other side. The monitoring module periodically sends a DC excitation voltage and simultaneously detects the loop current signal to detect the state of the monitored cable. The equivalent circuit is as follows: Figure 4 As shown.

[0058] The formula for calculating cable circuit current is:

[0059]

[0060]

[0061] Among them: I R U is the loop detection current, U is the excitation voltage, L is the equivalent cable distance, and R is the current detected in the loop. 总 R is the equivalent resistance of the circuit. A =R B =R C R represents the resistance value per phase per kilometer of the cable, R is the terminal resistance of the device, and R0 is the wiring resistance. The resistance values ​​of phases A, B, and C are the same.

[0062] Based on the above calculation method, the cable loop current can be calculated.

[0063] The monitoring module consists of a DC excitation power supply and a sampling resistor. During a single measurement cycle, the excitation voltage source emits a steady-state DC voltage signal, which generates a corresponding current signal in the circuit according to Ohm's law. The two are linearly related. During each detection and recording cycle, the current value can be read. This set of current values ​​is linearly proportional to the preset excitation voltage value and inversely proportional to the resistance of the cable under test and the front and terminal resistance of the device.

[0064] During the installation of the device, based on the cable specifications and length, the theoretical value of the loop current can first be calculated using the calculation formula. At the same time, the initial measured value of the loop current of the cable under test can be obtained. Usually, due to errors in length and resistance, there is a certain deviation between the theoretical value and the measured value of the loop circuit. Therefore, the loop current warning value after the device is installed should be calculated with reference to the initial measured value.

[0065] The early warning and monitoring device is powered by photovoltaic solar energy at 18V DC, and is also equipped with lead-acid batteries as backup power. It also retains an AC 220V power supply interface. Power switching is automatically performed by the built-in power management module.

[0066] The device has a built-in excitation voltage module that outputs a 10V DC voltage to the cable under test through the R terminating resistor. The current detection module determines whether the current exceeds the threshold by sampling the circuit current. If the threshold is exceeded, an alarm message is sent to the management personnel via group SMS / WeChat, and the device alarm light flashes.

[0067] When conducting online monitoring of cables not in operation, the conductor cores at both ends of phases A and B are first connected in parallel with copper / aluminum wire, and then connected in series with the conductor core of phase C to form a current loop. The A-phase and C-phase conductors on one side are then connected to an early warning monitoring device. During testing, the cable parameters and length are first entered through a WeChat mini-program parameter configuration interface. Then, the device is activated, outputting a 10V DC excitation voltage to the cable end. Finally, the cable's condition is detected by measuring the loop current.

[0068] Cable power failure detection function

[0069] The early warning monitoring device also has a power failure detection function. If thieves remove the device before stealing it, and the device fails to detect the circuit current at regular intervals, it will immediately send an abnormal alarm message to the users.

[0070] The early warning monitoring device is based on the principle of loop current detection. The magnitude of the loop current is related to the loop resistance, including cable resistance, terminal resistance, wiring resistance, cable length, and wiring method.

[0071] To facilitate on-site installation and wiring, this solution uses a three-core cable with two parallel connections and one series connection. At the other end of the cable, each of the three phases (A, B, and C) is connected in series with a resistor of equal value. Figure 3 As shown.

[0072] The online monitoring and early warning system for theft prevention of non-operational cables in this invention includes a detection host, a three-way connector 6, a photovoltaic module, and a server 7, as detailed below. Figure 1 and Figure 2 .

[0073] The testing host includes a housing 1 and a power management module 2 housed within the housing 1, an excitation voltage module 3 connected to the power management module 2, and a current detection module 4 connected to the output terminal of the excitation voltage module 3. The excitation voltage module 3 is connected to the A-phase and B-phase terminals near the end of the off-line cable 5, and the current detection module 4 is connected to the C-phase terminal near the end of the off-line cable 5. The excitation voltage module 3 outputs a preset DC voltage to the cable under test, and the current detection module 5 acquires the value of the loop current. The power management module 2 uses a mainstream power management chip.

[0074] The three-connector 6 is located at the other end of the non-operational cable 5. The three connection terminals of the three-connector 6 are respectively connected to the A-phase terminal, B-phase terminal and C-phase terminal at the far end of the non-operational cable 5, so as to realize the parallel connection of the A-phase conductor and the B-phase conductor, and then the series connection of the C-phase conductor.

[0075] The photovoltaic module is connected to the power management module 2 and is used to power the detection host.

[0076] Server 7 is connected to the detection host and is used to compare the current value of current detection module 4 with the preset standard value, thereby realizing anti-theft monitoring and early warning.

[0077] The testing host also includes a storage battery 8, which is connected to the power management module 2.

[0078] Power management module 2 is also connected to 220V AC mains power. When neither battery 8 nor photovoltaic module can output the preset operating voltage, power management module 2 switches to AC mains power supply.

[0079] The off-line cable anti-theft online monitoring and early warning system also includes a user terminal 9, which is communicatively connected to the server 7 and used to adjust the calculation parameters in the server 7 and obtain monitoring and early warning status information.

[0080] The photovoltaic module includes a solar panel 10.

[0081] The excitation voltage module 3 is used to output a DC excitation voltage of 1-50V. The current detection module 4 includes a current sensor. The off-line cable anti-theft online monitoring and early warning system also includes a communication module 11, which is connected to both the excitation voltage module 3 and the current detection module 4, and is also communicatively connected to the server 7.

[0082] The terminating resistance R in the detection circuit of the detection host is 10 to 50 Ω, and the connection resistance R0 of the three-connected wire 6 in the detection circuit is 5 to 20 Ω.

[0083] In practice:

[0084] Taking the 8128-22 crossover cable of Yangpeng as an example, the cable model is YJV-3*400mm. 2 The cable is 0.7856 km long, with a resistance of 0.0621 Ω / km, an excitation voltage of 12V, a terminating resistor R of 30Ω, and a wiring resistor R0 of 10Ω. Under normal circumstances, the loop current is calculated using the following formula:

[0085]

[0086]

[0087] Among them: I R U is the loop detection current, U is the excitation voltage, L is the equivalent cable distance, and R is the current detected in the loop. 总 R is the equivalent resistance of the circuit. A =R B =R C R represents the resistance value per phase per kilometer of the cable, R is the terminal resistance of the device, and R0 is the wiring resistance. The resistance values ​​of phases A, B, and C are the same.

[0088] According to the calculation formula, the theoretical reference current for a cable circuit under normal circumstances is:

[0089]

[0090] 1. If, in the case of a parallel connection of phases A and B, any one of the three phases of the cable is stolen, then:

[0091] R 总 =2×(L×R) C +R0)=20.09Ω

[0092]

[0093] I R ′ =90%I R

[0094] Considering the numerical fluctuations caused by interference, if the loop current is lower than 95% of the reference current at a certain moment, it is considered that one of the phase cables in the AB parallel connection has been stolen.

[0095] 2. If the cable is short-circuited in the middle

[0096] ① Short circuit at the very beginning of the cable

[0097] If the cable is short-circuited at its very beginning, the cable's equivalent resistance is 0, and the loop current is:

[0098]

[0099] ② Short circuit at 1 / 2 point of the cable

[0100] If the cable is short-circuited at 1 / 2, there is no end-connection resistance R0, and the equivalent resistance of the cable is:

[0101]

[0102]

[0103] ③ Short circuit at 2 / 3 of the cable

[0104] If the cable is short-circuited at 2 / 3 of its length, there is no end-connection resistance R0, and the equivalent resistance of the cable is:

[0105]

[0106]

[0107] The calculation results show that the current changes are very large no matter where the cable is artificially short-circuited in three phases. This is because the cable is short-circuited in the middle and the end connection resistance R0 is cut off, which greatly reduces the equivalent resistance of the line and causes the loop current to surge.

[0108] Considering the numerical fluctuations caused by interference, if the loop current is greater than 110% of the reference current at a certain moment, i.e., 321.96mA, it is considered that the cable may have been deliberately short-circuited in three phases, and there is a risk of theft.

[0109] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method for online monitoring and early warning of theft prevention of off-line cables, characterized in that, Includes the following steps: S1: Output a preset DC voltage to the A-phase end and B-phase end of the non-operational cable (5) near the excitation voltage module (3); also includes setting a three-connection wire at the other end of the non-operational cable (5), and the three connection terminals of the three-connection wire are respectively connected to the A-phase end, B-phase end and C-phase end of the non-operational cable (5) at the far end, so as to realize the parallel connection of the A-phase conductor and the B-phase conductor, and then the series connection of the C-phase conductor; S2: Obtain the current signal fed back from the C-phase end of the non-operational cable (5) near the current detection module (4), and obtain the specific current value based on the current signal; S3: The server (7) compares the current value of the current detection module (4) with the preset standard value to realize anti-theft monitoring and early warning; the specific comparison method is as follows: if the circuit current is lower than 95% of the reference current, it is considered that one phase has been stolen; if the circuit current is greater than 110% of the reference current, it is considered that the cable has been deliberately short-circuited in three phases and there is a risk of theft.

2. The method for online monitoring and early warning of theft prevention of non-operational cables according to claim 1, characterized in that, In S1, the excitation voltage module (3) is powered by a battery (8) or a photovoltaic module.

3. The method for online monitoring and early warning of theft prevention of non-operational cables according to claim 1, characterized in that, In S2, the current detection module (4) is powered by a battery (8) or a photovoltaic module.

4. The online monitoring and early warning method for anti-theft of non-operational cables according to claim 2 or 3, characterized in that, The power management module (2) regulates the power supply from the battery (8) or the photovoltaic module.

5. The method for online monitoring and early warning of theft prevention of non-operational cables according to claim 1, characterized in that, The terminating resistance R in the detection circuit constructed in S1 and S2 is 10 to 50 Ω, and the wiring resistance R0 of the three interconnecting wires in the detection circuit is 5 to 20 Ω.

6. The method for online monitoring and early warning of theft prevention of non-operational cables according to claim 1, characterized in that, In the detection loops constructed in S1 and S2, the formula for calculating the loop current is: ， ， Where: I R is the loop test current, U is the excitation voltage, L is the equivalent distance of the cable, R 总 is the loop equivalent resistance, R A = R B = R C is the resistance value of each phase per kilometer of the cable, R is the terminal resistance of the device, R0 is the wiring resistance, and ABC are the same for the three phases.

7. The method for online monitoring and early warning of theft prevention of non-operational cables according to claim 6, characterized in that, When the very beginning of the cable is short-circuited, the cable's equivalent resistance is 0. If the cable is short-circuited at the 1 / 2 mark, there is no end-connection resistance R0, and the equivalent resistance of the cable is: ， If the cable is short-circuited at 2 / 3 of its length, there is no end-connection resistance R0, and the equivalent resistance of the cable is: 。

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