System for monitoring the sheath of a cable

Abstract

This disclosure relates to the field of monitoring technology, and in particular to a monitoring system for a cable sheath. The monitoring system includes: a first current sensing circuit coupled to a first end of the cable sheath and configured to output a first current sensing signal based on the first end of the cable sheath; a first voltage sensing circuit coupled to the first end of the cable sheath and configured to output a first voltage sensing signal based on the first end of the cable sheath; and a logic control circuit coupled to the first current sensing circuit and the first voltage sensing circuit and configured to output an alarm signal when the first current sensing signal is greater than a current threshold, or when the first voltage sensing signal is greater than a voltage threshold; the alarm signal is used to indicate that there is an abnormality in the cable sheath.

Description

Technical Field

[0001] This disclosure relates to the field of monitoring technology, and in particular to a monitoring system for cable sheaths. Background Technology

[0002] With the continuous and rapid growth of installed capacity of new energy photovoltaic power generation, the structure of power transmission networks is becoming increasingly complex, and the phenomenon of line crossings is becoming more and more prominent. In order to meet the demand for power transmission, the engineering applications of overhead line crossings and high-voltage buried cable crossings are becoming more and more frequent.

[0003] With the large-scale commissioning of high-voltage cable lines of 110kV and above, the grounding reliability of cable sheaths has become one of the key factors affecting the safe and stable operation of the power grid. In the actual operation and maintenance of high-voltage cable lines, the common practice is to install sheath grounding boxes at the cable line towers to limit the induced voltage on the cable sheath. This technical solution can only reduce the losses after a fault occurs in the high-voltage cable line to a certain extent, and cannot monitor and prevent the cable's operating conditions in the early stages of a fault.

[0004] Therefore, we look forward to an improved technical solution that can solve the above-mentioned technical problems. Summary of the Invention

[0005] To address the aforementioned technical problems, this disclosure provides a monitoring system for cable sheaths.

[0006] This disclosure provides a cable sheath monitoring system, comprising: a first current sensing circuit coupled to a first end of the cable sheath and configured to monitor the current at the first end of the cable sheath to output a first current sensing signal; a first voltage sensing circuit coupled to the first end of the cable sheath and configured to monitor the voltage at the first end of the cable sheath to output a first voltage sensing signal; and a logic control circuit coupled to the first current sensing circuit and the first voltage sensing circuit to acquire the first current sensing signal and the first voltage sensing signal, wherein the logic control circuit is configured to output an alarm signal when the first current sensing signal is greater than a current threshold or the first voltage sensing signal is greater than a voltage threshold; wherein the alarm signal is used to indicate that the cable sheath is in an abnormal operating condition.

[0007] In one feasible embodiment, the system further includes: a first temperature sensing circuit coupled to a first end of the cable sheath and configured to monitor the temperature of the first end of the cable sheath to output a first temperature sensing signal; a logic control circuit coupled to the first temperature sensing circuit to acquire the first temperature sensing signal, and the logic control circuit is further configured to output the alarm signal when the first temperature sensing signal is greater than a first temperature threshold.

[0008] In one feasible embodiment, the system further includes: a second current sensing circuit coupled to a second end of the cable sheath, configured to monitor the current at the second end of the cable sheath to output a second current sensing signal; a second voltage sensing circuit coupled to a second end of the cable sheath, configured to monitor the voltage at the second end of the cable sheath to output a second voltage sensing signal; and a logic control circuit coupled to the second current sensing circuit and the second voltage sensing circuit to acquire the second current sensing signal and the second voltage sensing signal, wherein the logic control circuit is further configured to output the alarm signal if the second current sensing signal is greater than the current threshold or the second voltage sensing signal is greater than the voltage threshold.

[0009] In one feasible embodiment, the system further includes: a second temperature sensing circuit coupled to a second end of the cable sheath, configured to monitor the temperature of the second end of the cable sheath to output a second temperature sensing signal; the logic control circuit coupled to the second temperature sensing circuit to acquire the second temperature sensing signal, and the logic control circuit further configured to output the alarm signal when the second temperature sensing signal is greater than a first temperature threshold.

[0010] In one feasible embodiment, the system further includes: an ambient temperature sensing circuit configured to output an ambient temperature sensing signal based on the ambient temperature; the logic control circuit is coupled to the ambient temperature sensing circuit to acquire the ambient temperature sensing signal, and the logic control circuit is further configured to output an alarm signal when a first temperature difference signal is greater than a second temperature threshold or a second temperature difference signal is greater than the second temperature threshold; wherein the first temperature difference signal is the value of the first temperature sensing signal minus the value of the ambient temperature sensing signal, and the second temperature difference signal is the value of the second temperature sensing signal minus the value of the ambient temperature sensing signal.

[0011] In one feasible embodiment, the first end of the cable sheath is coupled to a direct grounding box, and the logic control circuit is specifically configured to: output a first sub-alarm signal when the first current sensing signal and the second current sensing signal are both equal to the current threshold, the first voltage sensing signal and the second voltage sensing signal are both greater than the voltage threshold, the first temperature sensing signal and the second temperature sensing signal are both less than the first temperature threshold, and the first temperature difference signal is less than the second temperature threshold; wherein, the first sub-alarm signal is used to characterize an abnormality in the direct grounding box.

[0012] In one feasible embodiment, the logic control circuit is further configured to output a second sub-alarm signal when both the first current sensing signal and the second current sensing signal are greater than the current threshold, the first voltage sensing signal is 0, the second voltage sensing signal is less than the voltage threshold, the first temperature sensing signal is greater than the first temperature threshold, the second temperature sensing signal is less than the first temperature threshold, and the first temperature difference signal is greater than the second temperature threshold; wherein the second sub-alarm signal is used to characterize the multi-point grounding of the cable sheath.

[0013] In one feasible embodiment, the second end of the cable sheath is coupled to the grounding box of the protector, and the logic control circuit is further configured to output a third sub-alarm signal when the first current sensing signal and the second current sensing signal are both greater than the current threshold, the first voltage sensing signal and the second voltage sensing signal are both 0, the first temperature sensing signal and the second temperature sensing signal are both greater than the first temperature threshold, and the first temperature difference signal and the second temperature difference signal are both greater than the second temperature threshold; wherein, the third sub-alarm signal is used to characterize the abnormality of the grounding box of the protector.

[0014] In one feasible embodiment, the logic control circuit is a remote terminal unit; the remote terminal unit is coupled to the second current sensing circuit, the second voltage sensing circuit and the second temperature sensing circuit via an optical fiber.

[0015] In one feasible embodiment, the logic control circuit is further configured to collect two or more of the first current sensing signal, the first voltage sensing signal, the first temperature sensing signal, the second current sensing signal, the second voltage sensing signal, the second temperature sensing signal, and the ambient temperature sensing signal at preset intervals to determine whether to output the alarm signal.

[0016] The technical solution provided in this disclosure has the following advantages compared with the prior art: The monitoring system provided in this disclosure constructs an abnormal operating condition judgment logic by comprehensively considering the current, induced voltage, and temperature change characteristics of the cable sheath under different operating conditions. This logic covers common abnormal operating conditions under the single-end grounding mode of the metal sheath of a single-core cable. Based on this judgment logic, the logic control circuit compares and analyzes the collected current, induced voltage, and temperature data of the cable sheath to determine the current operating status of the cable sheath. When an abnormal operating condition is detected, an alarm signal is issued promptly, achieving effective monitoring of the cable sheath. Attached Figure Description

[0017] The accompanying drawings, which are incorporated in and form a part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure.

[0018] To more clearly illustrate the technical solutions in the embodiments of this disclosure or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a cable sheath monitoring system provided according to some embodiments. Detailed Implementation

[0020] To better understand the above-mentioned objectives, features, and advantages of this disclosure, the solutions disclosed herein will be further described below. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other.

[0021] In this document, the use of "configured to" implies open and inclusive language, which does not exclude devices configured to perform additional tasks or steps. In describing some embodiments, the term "coupled" and its derivative expressions may be used. For example, the term "coupled" may be used in describing some embodiments to indicate that two or more components have direct physical or electrical contact. However, the term "coupled" may also refer to two or more components that do not have direct contact with each other but still cooperate or interact with each other. The embodiments disclosed herein are not necessarily limited to the content of this document.

[0022] Unless the context otherwise requires, throughout the specification and claims, the term "comprise" and its other forms, such as the third-person singular "comprises" and the present participle "comprising," are interpreted as open-ended and encompassing, meaning "including, but not limited to." In the description of the specification, terms such as "one embodiment," "some embodiments," "exemplary embodiments," "example," "specific example," or "some examples," etc., are intended to indicate that a particular feature, structure, material, or characteristic associated with that embodiment or example is included in at least one embodiment or example of this disclosure. The illustrative representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics mentioned may be included in any suitable manner in any one or more embodiments or examples.

[0023] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of embodiments of this disclosure, unless otherwise stated, "a plurality of" means two or more.

[0024] "A and / or B" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone, where A and B can be singular or plural. The use of "based on" implies openness and inclusivity, because processes, steps, calculations, or other actions "based on" one or more of the stated conditions or values ​​may in practice be based on additional conditions or values ​​beyond those stated.

[0025] Numerous specific details are set forth in the following description in order to provide a full understanding of this disclosure, but this disclosure may also be implemented in other ways different from those described herein; obviously, the embodiments in the specification are only some, and not all, of the embodiments of this disclosure.

[0026] With the continuous and rapid growth of installed capacity of new energy photovoltaic power generation, the structure of power transmission networks is becoming increasingly complex, and the phenomenon of line crossings is becoming more prominent. The grounding reliability of cable sheaths has become one of the key factors affecting the safe and stable operation of the power grid. During on-site operation and maintenance, relying on infrared thermal imagers to observe the temperature of cable sheath grounding boxes cannot accurately determine the actual operating conditions of the cable sheath grounding boxes or potential hidden dangers such as grounding deterioration and poor contact. At the same time, the diagnosis of cable and cable sheath conditions in related technologies mainly focuses on periodic tests of the main insulation, and is constrained by planned power outages, making continuous monitoring impossible. This makes it difficult to detect and warn of potential grounding hazards in cable sheaths in a timely manner.

[0027] In view of this, the present disclosure provides a monitoring system for cable sheaths, such as Figure 1 As shown. Figure 1 This is a cable sheath monitoring system provided according to some embodiments.

[0028] The monitoring system 100 is coupled to the cable sheath 201. The monitoring system 100 includes a first sensing device 110 and a logic control circuit 130.

[0029] The first sensing device 110 is coupled to the first end of the cable sheath 201. The first sensing device 110 is configured to monitor the first end of the cable sheath 201 to output a first current sensing signal TA1 and a first voltage sensing signal TV1.

[0030] In this embodiment, the first sensing device 110 includes a first current sensing circuit 111 and a first voltage sensing circuit 112.

[0031] The first current sensing circuit 111 is coupled to the first end of the cable sheath 201. The first current sensing circuit 111 is configured to monitor the current at the first end of the cable sheath 201 and output a first current sensing signal TA1 based on the current at the first end of the cable sheath 201.

[0032] The first voltage sensing circuit 112 is coupled to the first end of the cable sheath 201. The first voltage sensing circuit 112 is configured to monitor the voltage at the first end of the cable sheath 201 and output a first voltage sensing signal TV1 based on the voltage at the first end of the cable sheath 201.

[0033] For example, the first current sensing circuit 111 is selected from a current sensor, and the first voltage sensing circuit 112 is selected from a voltage sensor.

[0034] The logic control circuit 130 is coupled to the first sensing device 110 to acquire the first current sensing signal TA1 and the first voltage sensing signal TV1.

[0035] In this embodiment, the logic control circuit 130 is coupled to the first current sensing circuit 111 to acquire the first current sensing signal TA1, and the logic control circuit 130 is coupled to the first voltage sensing circuit 112 to acquire the first voltage sensing signal TV1.

[0036] The logic control circuit 130 is configured to output an alarm signal if the first current sensing signal TA1 is greater than a current threshold or the first voltage sensing signal TV1 is greater than a voltage threshold. For example, the current threshold is 0A and the voltage threshold is 50V.

[0037] The alarm signal is used to indicate that the cable sheath 201 is in an abnormal operating condition. The logic control circuit, for example 130, is selected from an RTU (Remote Terminal Unit). The logic control circuit 130 is also configured to output the alarm signal to the control room via 4G wireless communication.

[0038] In some embodiments, the first sensing device 110 is further configured to monitor a first end of the cable sheath 201 to output a first temperature sensing signal T1.

[0039] In this embodiment, the first sensing device 110 further includes a first temperature sensing circuit 113, which is coupled to the first end of the cable sheath 201.

[0040] The first temperature sensing circuit 113 is configured to monitor the temperature of the first end of the cable sheath 201 and output a first temperature sensing signal T1 based on the temperature of the first end of the cable sheath 201.

[0041] Logic control circuit 130 is coupled to first temperature sensing circuit 113 to acquire first temperature sensing signal T1. Logic control circuit 130 is also configured to output an alarm signal if the first temperature sensing signal T1 is greater than a first temperature threshold. First temperature sensing circuit 113 is, for example, selected from a fiber optic temperature measurement module. Exemplarily, the first temperature threshold is 70°C.

[0042] In some embodiments, the monitoring system 100 further includes a second sensing device 120, which is coupled to a second end of the cable sheath 201. The second sensing device 120 is configured to monitor the second end of the cable sheath 201 to output a second current sensing signal TA2 and a second voltage sensing signal TV2.

[0043] In this embodiment, the second sensing device 120 includes a second current sensing circuit 121 and a second voltage sensing circuit 122.

[0044] The second current sensing circuit 121 is coupled to the second end of the cable sheath 201. The second current sensing circuit 121 is configured to monitor the current at the second end of the cable sheath 201 and output a second current sensing signal TA2 based on the current at the second end of the cable sheath 201.

[0045] The second voltage sensing circuit 122 is coupled to the second end of the cable sheath 201. The second voltage sensing circuit 122 is configured to monitor the voltage at the second end of the cable sheath 201 and output a second voltage sensing signal TV2 based on the voltage at the second end of the cable sheath 201.

[0046] For example, the second current sensing circuit 121 is selected from a current sensor, and the second voltage sensing circuit 122 is selected from a voltage sensor.

[0047] The logic control circuit 130 is coupled to the second sensing device 120 to acquire the second current sensing signal TA2 and the second voltage sensing signal TV2.

[0048] In this embodiment, the logic control circuit 130 is coupled to the second current sensing circuit 121 to acquire the second current sensing signal TA2, and the logic control circuit 130 is coupled to the second voltage sensing circuit to acquire the second voltage sensing signal TV2.

[0049] The logic control circuit 130 is configured to output an alarm signal if the second current sensing signal TA2 is greater than a current threshold or the second voltage sensing signal TV2 is greater than a voltage threshold. For example, the current threshold is 0A and the voltage threshold is 50V.

[0050] In some embodiments, the second sensing device is further configured to monitor the second end of the cable sheath 201 to output a second temperature sensing signal T2.

[0051] In this embodiment, the second sensing device 120 further includes a second temperature sensing circuit 123, which is coupled to the second end of the cable sheath 201.

[0052] The second temperature sensing circuit 123 is configured to monitor the temperature of the second end of the cable sheath 201 and output a second temperature sensing signal T2 based on the temperature of the second end of the cable sheath 201.

[0053] Logic control circuit 130 is coupled to second temperature sensing circuit 123 to acquire second temperature sensing signal T2. Logic control circuit 130 is also configured to output an alarm signal if the second temperature sensing signal T2 exceeds a first temperature threshold. Second temperature sensing circuit 123 is, for example, selected from a fiber optic temperature measurement module. Exemplarily, the first temperature threshold is 70°C.

[0054] In some embodiments, the first sensing device 110 further includes an ambient temperature sensing circuit 114, which is configured to output an ambient temperature sensing signal T0 based on the ambient temperature.

[0055] Logic control circuit 130 is coupled to ambient temperature sensing circuit 114 to acquire ambient temperature sensing signal T0. Logic control circuit 130 is also configured to output an alarm signal if a first temperature difference signal T10 is greater than a second temperature threshold. The first temperature difference signal T10 is the value of the first temperature sensing signal T1 minus the value of the ambient temperature sensing signal T0. For example, the second temperature threshold is 30°C.

[0056] In some embodiments, the second sensing device 120 further includes an ambient temperature sensing circuit 124, which is configured to output an ambient temperature sensing signal T0 based on the ambient temperature.

[0057] The logic control circuit 130 is coupled to the ambient temperature sensing circuit 124 to acquire the ambient temperature sensing signal T0. The logic control circuit 130 is also configured to output an alarm signal when the second temperature difference signal T20 is greater than a second temperature threshold. The second temperature difference signal T20 is the value of the second temperature sensing signal T2 minus the value of the ambient temperature sensing signal T0.

[0058] In some embodiments, the logic control circuit 130 is further configured to acquire two or more of the following signals at preset intervals: a first current sensing signal TA1, a second current sensing signal TA2, a first voltage sensing signal TV1, a second voltage sensing signal TV2, a first temperature sensing signal T1, a second temperature sensing signal T2, and an ambient temperature sensing signal T0, and to determine whether to output an alarm signal based on two or more of the following signals: a first current sensing signal TA1, a second current sensing signal TA2, a first voltage sensing signal TV1, a second voltage sensing signal TV2, a first temperature sensing signal T1, a second temperature sensing signal T2, and an ambient temperature sensing signal T0.

[0059] In some embodiments, the logic control circuit 130 is coupled to the second sensing device 120 via an optical fiber 140. The logic control circuit 130 is coupled, for example, to at least one of the second current sensing circuit 121, the second voltage sensing circuit 122, the second temperature sensing circuit 123, and the ambient temperature sensing circuit 124 via the optical fiber 140. The optical fiber 140 is laid underground, for example, along with a cable.

[0060] The following combination Figure 1 The monitoring system 100 for cable sheath 201 and its working process according to one embodiment of the present disclosure are described.

[0061] The first end of the cable sheath 201 is coupled to the direct grounding box 202, and the first end of the cable sheath 201 is grounded, for example. The first sensing device 110 and the logic control circuit 130 are, for example, located inside the direct grounding box 202.

[0062] The second end of the cable sheath 201 is coupled to the protector grounding box 203. The protector 204 is located inside the protector grounding box 203, and the first end of the protector 204 is coupled to the second end of the cable sheath 201. The second end of the protector 204 is grounded. The second sensing device 120 is located, for example, inside the protector grounding box 203.

[0063] In this embodiment, the example of a 110kV single-core high-voltage cable with cable sheath 201 is used, and it is applied to the single-end grounding mode of the single-core cable metal sheath.

[0064] For example, the cable can also be selected from a three-phase three-single-core cable, and its grounding method is the same as... Figure 1 They are basically the same, so I will not go into details.

[0065] When the cable sheath 201 is in normal working condition, and the entire length of the cable sheath 201, the direct grounding box 202, and the protector grounding box 203 are all in normal working condition, the sensing signals collected by the logic control circuit 130 have the following characteristics:

[0066] Under normal operating conditions, with single-end direct grounding, the cable sheath 201 has no circulating current loss, so both the first current sensing signal TA1 and the second current sensing signal TA2 are equal to the current threshold of 0. The first end of the cable sheath 201 in the direct grounding box 202 is directly grounded, so the first voltage sensing signal TV1 is equal to 0. The second end of the cable sheath 201 in the protector grounding box 203 is grounded through the protector 204. Since the protector 204 limits the induced voltage, the second voltage sensing signal TV2 is greater than 0 and less than the voltage threshold of 50V. Because there is no circulating current heating, the temperature of the cable sheath 201 is only affected by the ambient temperature and / or slight heat dissipation from the cable body. Therefore, the first temperature sensing signal T1 is equal to the second temperature sensing signal T2, and both the first temperature sensing signal T1 and the second temperature sensing signal T2 are less than the first temperature threshold of 70℃. The first temperature difference signal T10 is equal to the first temperature sensing signal T1 minus the ambient temperature sensing signal T0, which is less than the second temperature threshold of 30℃.

[0067] Under the condition that the direct grounding box 202 fails, the sensing signals collected by the logic control circuit 130 have the following characteristics:

[0068] Under the failure condition of the direct grounding box 202, the cable sheath 201 has no effective grounding discharge channel and cannot form a circulating current or leakage current. Therefore, both the first current sensing signal TA1 and the second current sensing signal TA2 are equal to the current threshold of 0. The induced voltage of the cable sheath 201 cannot be released through the ground at the first end of the cable sheath 201, forming a floating voltage on the cable sheath 201. Therefore, the first voltage sensing signal TV1 is equal to the second voltage sensing signal TV2, and both the first voltage sensing signal TV1 and the second voltage sensing signal TV2 are greater than the voltage threshold of 50V. Since no current flows through the cable sheath 201, no Joule heat is generated. Therefore, the first temperature sensing signal T1 is equal to the second temperature sensing signal T2, and both the first temperature sensing signal T1 and the second temperature sensing signal T2 are less than the first temperature threshold of 70°C. The first temperature difference signal T10 is equal to the first temperature sensing signal T1 minus the ambient temperature sensing signal T0, which is less than the second temperature threshold of 30°C. In this case, the logic control circuit 130 outputs a first sub-alarm signal, which is used to characterize the abnormality of the direct grounding box 202.

[0069] Under the condition of multiple grounding points in the cable sheath 201, the sensing signals collected by the logic control circuit 130 have the following characteristics:

[0070] In the case of multi-point grounding of cable sheath 201, in addition to the first end of cable sheath 201 being directly grounded, cable sheath 201 also includes an additional grounding point, thus forming a sheath circulating current loop. At this time, the first current sensing signal TA1 is equal to the second current sensing signal TA2, and both the first current sensing signal TA1 and the second current sensing signal TA2 are greater than the current threshold of 0. In the direct grounding box 202, the first end of cable sheath 201 remains grounded, so the first voltage sensing signal TV1 is equal to 0. In the protector grounding box 203, the second end of cable sheath 201 remains grounded through protector 204, so the second voltage sensing signal TV2 is greater than 0 and less than the voltage threshold of 50V. The circulating current in the cable sheath 201 mainly flows through the first end, generating significant Joule heating. The temperature at the first end of the cable sheath 201 is significantly higher than the ambient temperature. Therefore, the first temperature sensing signal T1 is greater than the first temperature threshold of 70°C, the first temperature difference signal T10 is equal to the first temperature sensing signal T1 minus the ambient temperature sensing signal T0, the first temperature difference signal T10 is greater than the second temperature threshold of 30°C, and the second temperature sensing signal T2 is less than the first temperature threshold of 70°C. In this situation, the logic control circuit 130 outputs a second sub-alarm signal, which is used to characterize multiple grounding points in the cable sheath 201.

[0071] Under the condition of protector 204 breakdown failure, the sensing signals collected by logic control circuit 130 have the following characteristics:

[0072] When protector 204 fails due to breakdown, protector 204 is equivalent to a short-circuit conductor. The first end of cable sheath 201 is directly grounded, and the second end of cable sheath 201 is also directly grounded, forming a circulating current loop throughout the entire cable sheath 201. Therefore, the first current sensing signal TA1 is equal to the second current sensing signal TA2, and both the first current sensing signal TA1 and the second current sensing signal TA2 are greater than the current threshold of 0. Since the first end of cable sheath 201 is directly grounded, the first voltage sensing signal TV1 is equal to 0. Since the second end of cable sheath 201 is also directly grounded, the second voltage sensing signal TV2 is equal to 0. Because circulating current flows through the entire cable sheath 201, a large amount of Joule heat is generated at the first and second ends of the cable sheath 201. Therefore, the first temperature sensing signal T1 is greater than the first temperature threshold of 70°C, and the second temperature sensing signal T2 is also greater than the first temperature threshold of 70°C. The first temperature sensing signal T1 and the second temperature sensing signal T2 are significantly higher than the ambient temperature. The first temperature difference signal T10 is equal to the first temperature sensing signal T1 minus the ambient temperature sensing signal T0, and the first temperature difference signal T10 is greater than the second temperature threshold of 30°C. The second temperature difference signal T20 is equal to the second temperature sensing signal T2 minus the ambient temperature sensing signal T0, and the second temperature difference signal T20 is also greater than the second temperature threshold of 30°C. Under these circumstances, the logic control circuit 130 outputs a third sub-alarm signal, which is used to characterize an abnormality in the protector grounding box 203.

[0073] The monitoring system 100 provided in this embodiment constructs an abnormal operating condition judgment logic by comprehensively considering the current, induced voltage, and temperature change characteristics of the cable sheath 201 under different operating conditions. This logic covers common abnormal operating conditions under the single-end grounding mode of the single-core cable metal sheath. Based on this judgment logic, the logic control circuit 130 compares and analyzes the collected current, induced voltage, and temperature data of the cable sheath 201 to determine the current operating status of the cable sheath 201. When an abnormal operating condition is detected, an alarm signal is issued in a timely manner, thereby achieving effective monitoring of the cable sheath 201.

[0074] Furthermore, the logic control circuit 130 performs a comprehensive judgment based on six data features from both ends of the cable sheath 201: a first current sensing signal TA1, a second current sensing signal TA2, a first voltage sensing signal TV1, a second voltage sensing signal TV2, a first temperature sensing signal T1, and a second temperature sensing signal T2. Compared to traditional methods that rely on a single variable, this monitoring system 100 significantly improves the accuracy of abnormal operating condition judgment.

[0075] Furthermore, the current threshold, voltage threshold, first temperature threshold, and second temperature threshold used in the monitoring system 100 are simple and effective, requiring no complex simulation data training, and are characterized by small data volume and high reliability. The monitoring system 100 also has advantages such as clear judgment logic, simplicity and reliability, low implementation cost, and low complexity.

[0076] In some embodiments, the logic control circuit 130 periodically collects current, induced voltage and temperature data of the cable sheath 201 at preset intervals, and sequentially completes the four stages of information collection, information processing, information transmission and real-time monitoring, thereby providing reliable data support for the refined operation and maintenance of the cable system.

[0077] The above description is merely a specific embodiment of this disclosure, enabling those skilled in the art to understand or implement it. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this disclosure. Therefore, this disclosure is not to be limited to the embodiments described herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A system for monitoring the condition of a cable sheath, characterised in that, include: A first current sensing circuit, coupled to a first end of the cable sheath, is configured to monitor the current at the first end of the cable sheath to output a first current sensing signal. A first voltage sensing circuit, coupled to a first end of the cable sheath, is configured to monitor the voltage at the first end of the cable sheath to output a first voltage sensing signal. A logic control circuit, coupled to the first current sensing circuit and the first voltage sensing circuit, acquires the first current sensing signal and the first voltage sensing signal. The logic control circuit is configured to output an alarm signal when the first current sensing signal exceeds a current threshold or the first voltage sensing signal exceeds a voltage threshold. The alarm signal is used to indicate that the cable sheath is in an abnormal operating condition.

2. The monitoring system of claim 1, wherein, Also includes: A first temperature sensing circuit, coupled to a first end of the cable sheath, is configured to monitor the temperature of the first end of the cable sheath to output a first temperature sensing signal. The logic control circuit is coupled to the first temperature sensing circuit to acquire the first temperature sensing signal, and the logic control circuit is further configured to output the alarm signal when the first temperature sensing signal is greater than a first temperature threshold.

3. The monitoring system of claim 2, wherein, Also includes: A second current sensing circuit, coupled to the second end of the cable sheath, is configured to monitor the current at the second end of the cable sheath to output a second current sensing signal. A second voltage sensing circuit, coupled to the second end of the cable sheath, is configured to monitor the voltage at the second end of the cable sheath to output a second voltage sensing signal. The logic control circuit is coupled to the second current sensing circuit and the second voltage sensing circuit to acquire the second current sensing signal and the second voltage sensing signal. The logic control circuit is also configured to output the alarm signal when the second current sensing signal is greater than the current threshold or the second voltage sensing signal is greater than the voltage threshold.

4. The monitoring system of claim 3, wherein, Also includes: A second temperature sensing circuit, coupled to the second end of the cable sheath, is configured to monitor the temperature of the second end of the cable sheath to output a second temperature sensing signal. The logic control circuit is coupled to the second temperature sensing circuit to acquire the second temperature sensing signal, and the logic control circuit is further configured to output the alarm signal when the second temperature sensing signal is greater than the first temperature threshold.

5. The monitoring system of claim 4, wherein, Also includes: An ambient temperature sensing circuit is configured to output an ambient temperature sensing signal based on the ambient temperature. The logic control circuit is coupled to the ambient temperature sensing circuit to acquire the ambient temperature sensing signal. The logic control circuit is further configured to output an alarm signal if either the first temperature difference signal is greater than a second temperature threshold or the second temperature difference signal is greater than the second temperature threshold. The first temperature difference signal is the value of the first temperature sensing signal minus the value of the ambient temperature sensing signal, and the second temperature difference signal is the value of the second temperature sensing signal minus the value of the ambient temperature sensing signal.

6. The monitoring system of claim 5, the first end of the cable shield coupled with a direct ground box, characterized by, The logic control circuit is specifically configured as follows: When both the first current sensing signal and the second current sensing signal are equal to the current threshold, both the first voltage sensing signal and the second voltage sensing signal are greater than the voltage threshold, both the first temperature sensing signal and the second temperature sensing signal are less than the first temperature threshold, and the first temperature difference signal is less than the second temperature threshold, a first sub-alarm signal is output; wherein... The first sub-alarm signal is used to characterize the abnormality of the direct grounding box.

7. The monitoring system of claim 5, wherein, The logic control circuit is further configured to output a second sub-alarm signal when both the first current sensing signal and the second current sensing signal are greater than the current threshold, the first voltage sensing signal is 0, the second voltage sensing signal is less than the voltage threshold, the first temperature sensing signal is greater than the first temperature threshold, the second temperature sensing signal is less than the first temperature threshold, and the first temperature difference signal is greater than the second temperature threshold; wherein... The second sub-alarm signal is used to characterize the multi-point grounding of the cable sheath.

8. The monitoring system of claim 5, the second end of the cable shield coupled with a protector grounding box, characterized by, The logic control circuit is further configured to output a third sub-alarm signal when both the first current sensing signal and the second current sensing signal are greater than the current threshold, both the first voltage sensing signal and the second voltage sensing signal are 0, both the first temperature sensing signal and the second temperature sensing signal are greater than the first temperature threshold, and both the first temperature difference signal and the second temperature difference signal are greater than the second temperature threshold; wherein... The third sub-alarm signal is used to characterize an abnormality in the protector's grounding box.

9. The monitoring system of claim 5, wherein, The logic control circuit is a remote terminal unit; The remote terminal unit is coupled to the second current sensing circuit, the second voltage sensing circuit, and the second temperature sensing circuit via optical fiber.

10. The monitoring system of claim 5, wherein, The logic control circuit is further configured to collect two or more of the first current sensing signal, the first voltage sensing signal, the first temperature sensing signal, the second current sensing signal, the second voltage sensing signal, the second temperature sensing signal, and the ambient temperature sensing signal at preset intervals to determine whether to output the alarm signal.

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