Method and apparatus for monitoring current of grounding wires of armored and shielded cables in strong electromagnetic environment

Abstract

A method and apparatus for monitoring the current of grounding wires of armored and shielded cables in a strong electromagnetic environment. In the method, the sum current of armor layer grounding wires of M cables in a terminal box and the sum current of shield layer grounding wires are respectively collected, primary and secondary grounding copper bar potentials of the terminal box and the grounding current of an adjacent terminal box are collected; a potential difference alarm can be implemented; and on the basis of whether the potential difference alarm is implemented, different criteria are used to respectively implement an alarm for the circulating current of a cable loop in the terminal box.

Description

Method and device for monitoring current of armored shielded cable grounding wire in strong electromagnetic environment

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on July 20, 2023, with application number 202310893346.8. The entire contents of the above application are incorporated by reference into this application. Technical Field

[0002] The present application belongs to the field of online monitoring of electrical equipment and circuits in substations, for example, relates to a method and device for monitoring the current of the grounding wire of an armored shielded cable in a strong electromagnetic environment. Background Art

[0003] Dry-type air-core reactors are widely used in ultra-high voltage (UHV) substations. Their magnetic leakage can cause localized strong magnetic areas within the substation. When these areas form loops, the leakage magnetic flux generates circulating currents, causing heat and even cable burns. In recent years, numerous incidents of cable fires and ground grid smoke emanating from dry-type reactors near 220 kV and above substations have occurred, posing significant risks to the safe and stable operation of the substations. The dense concentration of cables within terminal boxes near reactors makes current loops more likely. Furthermore, these terminal boxes are within the range of strong electromagnetic pulse interference, creating a transient strong electromagnetic radiation environment with an electric field strength exceeding 1 kV / m. Therefore, monitoring the cables within terminal boxes in such strong electromagnetic environments is necessary and beneficial.

[0004] Monitoring armored shielded cables in strong electromagnetic environments at substations primarily involves visual inspections. Currently, there are no dedicated monitoring methods for armored shielded secondary cable grounding wires. Traditionally, substation operators conduct manual inspections, such as by inspecting the terminal box and observing the cables and grounding wires for visual abnormalities or a burning odor. Infrared temperature measurement is also used. Substation operators use handheld infrared temperature measurement devices to measure the temperature of armored shielded cables and related grounding wires, checking for excessive temperatures at the cables, grounding wires, and related connections. These methods are inherently non-real-time. Both visual inspections and infrared temperature measurement require manual labor and are conducted within the terminal box or protective screen near the grounding wires. Even 1000 kV UHV stations with high inspection frequencies can only be inspected once or twice a day, and the maximum inspection frequency for power supply maintenance is four times a day. Therefore, the several hours between inspections is sufficient time for the entire process from abnormal cable heating to fire. The aforementioned monitoring methods have limitations in accuracy. Visual inspections are highly subjective, and the ability to spot problems depends on the operator's skill level, mental state, and the stage of the fault, making it difficult to accurately identify faults. Infrared temperature measurement is slightly less susceptible to subjective factors than visual inspections, but it still depends on whether the temperature measurement location is obscured and the fault's current stage of development at the time of measurement, making accurate fault detection difficult.

[0005] Summary of the Invention

[0006] This application proposes a method for monitoring the grounding current of armored shielded cables in a strong electromagnetic environment. The method monitors the grounding current of M armored shielded cables in a terminal box, including:

[0007] Collect the armor layer grounding wire and current, shield layer grounding wire and current of the M cables in the terminal box, the primary grounding copper bar potential and the secondary grounding copper bar potential of the terminal box, and the grounding current of the adjacent terminal box;

[0008] The potential difference is obtained by using the collected primary grounding copper bus potential and the secondary grounding copper bus potential, and a potential difference alarm is issued in response to the potential difference being greater than or equal to the potential difference alarm value; when no potential difference alarm is issued, a cable loop current alarm is issued in response to the armor layer grounding wire and current and the shield layer grounding wire and current being greater than or equal to the corresponding overcurrent alarm value, and the sum of the armor layer grounding wire and current and the shield layer grounding wire and current being less than or equal to the circulating current alarm value; when a potential difference alarm is issued, the overcurrent alarm value and the circulating current alarm value are corrected, and a cable loop current alarm is issued in the terminal box in response to the armor layer grounding wire and current and the shield layer grounding wire and current being greater than or equal to the corresponding corrected overcurrent alarm value, and the sum of the armor layer grounding wire and current and the shield layer grounding wire and current being less than or equal to the corrected circulating current alarm value;

[0009] In response to the grounding current of the adjacent terminal box being greater than or equal to the first current alarm value, the grounding current alarm value of the terminal box is set to the first value; in response to the grounding current of the adjacent terminal box being greater than or equal to the second current alarm value and the grounding current increment of the adjacent terminal box being greater than or equal to the current increment alarm value, the grounding current alarm value of the terminal box is set to the second value; in response to the grounding current of the terminal box being greater than the grounding current alarm value, a terminal box grounding current alarm is issued; wherein, the first current alarm value is greater than the second current alarm value.

[0010] This application also proposes a current monitoring device for armored shielded cable grounding wires in a strong electromagnetic environment, comprising: an acquisition module, a monitoring module, and an alarm module;

[0011] The data acquisition module is configured to acquire data of the armor layer grounding wire and current, the shield layer grounding wire and current of the M cables in the terminal box, the primary grounding copper bar potential and the secondary grounding copper bar potential of the terminal box, and the grounding current of the adjacent terminal box;

[0012] The monitoring module includes: potential difference alarm unit, terminal box ground current alarm unit, cable ground wire overcurrent alarm unit, cable loop current alarm unit; among them,

[0013] a potential difference alarm unit configured to obtain a potential difference by using the collected potentials of the primary grounding copper busbar and the secondary grounding copper busbar, and to call an alarm module to generate a potential difference alarm in response to the potential difference being greater than or equal to a potential difference alarm value;

[0014] The cable loop current alarm unit is configured to, when no potential difference alarm is given, call the alarm module to issue a cable loop current alarm in the terminal box in response to the armor layer grounding wire and current and the shield layer grounding wire and current being respectively greater than or equal to the corresponding overcurrent alarm value, and the sum of the armor layer grounding wire and current and the shield layer grounding wire and current being less than or equal to the circulating current alarm value; in the event of a potential difference alarm, correct the overcurrent alarm value and the circulating current alarm value, and call the alarm module to issue a cable loop current alarm in the terminal box in response to the armor layer grounding wire and current and the shield layer grounding wire and current being respectively greater than or equal to the corresponding corrected overcurrent alarm value, and the sum of the armor layer grounding wire and current and the shield layer grounding wire and current being less than or equal to the corrected circulating current alarm value;

[0015] The terminal box ground current alarm unit is configured to set the ground current alarm value of the terminal box to a first value in response to the ground current of the adjacent terminal box being greater than or equal to the first current alarm value; and to set the ground current alarm value of the terminal box to a second value in response to the ground current of the adjacent terminal box being greater than or equal to the second current alarm value;

[0016] The cable grounding wire overcurrent alarm unit is configured to respond to the armor layer grounding wire and current or the shielding layer grounding wire and current being greater than or equal to the corresponding overcurrent alarm value, calling the alarm module to issue an armor layer grounding wire overcurrent alarm or a shielding layer grounding wire overcurrent alarm; wherein, the armor layer grounding wire and current correspond to the armor layer overcurrent alarm value, and the shielding layer grounding wire and current correspond to the shielding layer overcurrent alarm value.

[0017] The alarm module is configured to send out a terminal box potential difference alarm signal after a set delay after the potential difference alarm criterion is met, send out a cable shielding layer overcurrent alarm signal after a set delay after the shielding layer grounding wire overcurrent alarm criterion is met, send out a cable armor layer overcurrent alarm signal after a set delay after the armor layer grounding wire overcurrent alarm criterion is met, send out a cable loop current alarm signal in the terminal box after a set delay after the cable loop current alarm criterion in the terminal box is met; in response to the grounding current of the adjacent terminal box being greater than or equal to the first current alarm value, send out a terminal box grounding current alarm signal after a set delay; in response to the grounding current of the adjacent terminal box being greater than or equal to the second current alarm value, send out a terminal box grounding current alarm signal after a set delay. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] FIG1 is a schematic diagram of grounding of an armored shielded cable according to an embodiment of the present application;

[0019] FIG2 is a flow chart of a method for monitoring the ground wire current of an armored shielded cable in a strong electromagnetic environment proposed in an embodiment of the present application;

[0020] FIG3 is a schematic diagram of a current monitoring device for an armored shielded cable grounding wire in a strong electromagnetic environment in an embodiment of the present application. DETAILED DESCRIPTION

[0021] Extensive maintenance data indicates that cable fires near dry-type reactors generally meet the following two conditions: 1) The heating cable is located near the dry-type reactor, thus being exposed to a strong electromagnetic environment. 2) A loop (e.g., insulation wear between the armor and shielding layers, or a short circuit in the armor or shielding grounding wires) has occurred due to a problem (e.g., poor cable installation workmanship). Some cable fires also meet a third condition: a potential difference between the primary and secondary grounds. Conditions 1 and 2 are generally necessary for a fire to occur. Simultaneously meeting condition 3 can lead to a more complex heating situation, with multiple cables heating simultaneously. If this heating is not detected promptly, it can cause the cable grounding wire to heat up and even burn related cables.

[0022] Substations utilize extensive armored shielded cables. As shown in Figure 1, cable #1 in the terminal box consists of a shield and armor layer. The shield is typically grounded at both ends, connecting to the secondary grounding grid via a shield grounding wire, a secondary grounding busbar, and a grounding copper cable. Currently, there are no standardized grounding methods for the armor layer; the mainstream method is to connect both ends to the primary grounding grid via an armor grounding wire and a primary grounding busbar.

[0023] In a non-limiting embodiment, the analysis is based on the use of double-grounded armored shielded cables. If single-side grounding of the armor layer is used, the possibility of some cable grounding wires forming loops is reduced at the expense of a certain anti-interference effect. You can also refer to the monitoring solution deployed in the embodiment of this application.

[0024] In a strong electromagnetic environment, factors that cause fire hazards in armored shielded cables include potential difference, circulating current and ground current. Therefore, the embodiments of this application provide detailed descriptions of the potential difference alarm, cable loop circulating current alarm and ground current alarm.

[0025] Based on the above analysis, the embodiment of the present application proposes a method for monitoring the ground wire current of an armored shielded cable in a strong electromagnetic environment. As shown in FIG2 , the ground wire current of M armored shielded cables in a terminal box is monitored, including:

[0026] Step 1: Collect the armor layer grounding wire and current, shield layer grounding wire and current of M cables in the terminal box, collect the primary grounding copper bar potential and secondary grounding copper bar potential of the terminal box, and collect the grounding current of the adjacent terminal box.

[0027] For example, the shield grounding current of cable #1 in the switch field terminal box is recorded as I p1 , the armor layer grounding wire current is recorded as I k1 When there are M armored shielded cables in the terminal box, the grounding current of the shield layer of each cable is I p1 , I p2 ,…,I pM , the grounding current of the armor layer of each cable is I k1 , I k2 ,…,I kM ; Then the shielding grounding wire of M cables and the current I P , armor layer grounding wire and current I K They satisfy the following relationships respectively:

[0028] Where, I P is the shield grounding wire and current, I K For the armor layer grounding wire and current.

[0029] Considering that when several different cables in the same terminal box have serious leakage at the same time, their respective armor layer grounding wires are in different loops, and the probability of phase cancellation of the armor layer grounding current is small, for economic considerations, the armor layer grounding wire and current collection method is adopted. Similarly, the shield layer grounding wire also adopts the current collection method.

[0030] Among the connection points between the secondary grounding busbar of the terminal box and the secondary grounding grid, the connection point closest to the terminal box is used as the potential reference point. Based on the potential reference point, the potential of the connection point between the grounding end of the terminal box body and the primary grounding busbar is measured as the primary grounding busbar potential, and the potential of the secondary grounding busbar is measured as the secondary grounding busbar potential. The current flowing from the grounding end of the box body of the adjacent terminal box into the primary grounding busbar is measured as the grounding current of the adjacent terminal box.

[0031] In actual projects, there is a potential difference on the primary grounding copper busbar. Therefore, the potential of the starting point closest to the terminal box body is used as the primary grounding copper busbar potential to accurately reflect the potential difference of the terminal box. In a non-limiting embodiment, the potential of the primary grounding copper busbar is used as the potential of the connection point between the terminal box body ground terminal and the primary grounding copper busbar.

[0032] For example, the sampling frequency is 1ms per data point.

[0033] Step 2: Use the collected potential to obtain the potential difference, and issue a potential difference alarm when the potential difference is not less than the potential difference alarm value; when there is no potential difference alarm, if the armor layer grounding wire and current and the shield layer grounding wire and current are not less than the corresponding overcurrent alarm value, and the sum of the armor layer grounding wire and current and the shield layer grounding wire and current is not greater than the circulating current alarm value, then issue a cable loop circulating current alarm in the terminal box; when the potential difference alarm is issued, the overcurrent alarm value and the circulating current alarm value are corrected, and if the armor layer grounding wire and current and the shield layer grounding wire and current are not less than the corresponding corrected overcurrent alarm value, and the sum of the armor layer grounding wire and current and the shield layer grounding wire and current is not greater than the corrected circulating current alarm value, then issue a cable loop circulating current alarm in the terminal box;

[0034] When the grounding current of the adjacent terminal box is not less than the first current alarm value, the grounding current alarm value of the terminal box is set to the first value (high value); when the grounding current of the adjacent terminal box is not less than the second current alarm value and the grounding current increment of the adjacent terminal box is not less than the current increment alarm value, the grounding current alarm value of the terminal box is set to the second value (low value); when the grounding current of the terminal box is greater than the grounding current alarm value, the terminal box grounding current alarm is issued; wherein, the first current alarm value is greater than the second current alarm value.

[0035] The impact of the grounding current of the adjacent box on the fire hazard of this box is integrated into the judgment criteria through the setting of the grounding current alarm value of the terminal box. By setting high and low values, the impact of the grounding current of the adjacent terminal box on this terminal box is fully reflected. Because when the grounding current of the adjacent terminal box is large (not less than the first current alarm value), it is only necessary to judge whether to alarm based on the grounding current of the terminal box, and it is configured not to be easy to alarm; when the grounding current of the adjacent terminal box is small, it is necessary to judge whether to alarm based on the grounding current and grounding current increment of the terminal box, and it is configured to be easy to alarm.

[0036] If the armor layer grounding wire and current or the shield layer grounding wire and current are not less than the corresponding overcurrent alarm value, an armor layer grounding wire overcurrent alarm or a shield layer grounding wire overcurrent alarm is issued;

[0037] The armor layer grounding wire and current correspond to the armor layer overcurrent alarm value, and the shield layer grounding wire and current correspond to the shield layer overcurrent alarm value.

[0038] For example, the terminal box leakage alarm includes five criteria, as follows:

[0039] 1) Potential difference alarm criterion |U I -U II |≥U T1

[0040] Among them, U I The potential of the primary grounding copper busbar of the terminal box.

[0041] Among them, U II The potential of the secondary grounding copper busbar of the terminal box.

[0042] Among them, U T1 It is the alarm value of the potential difference between the primary and secondary grounds of the terminal box. The empirical value is 1V.

[0043] After the potential difference alarm criterion is met, the signal "potential difference alarm near XX terminal box" is issued after the set delay t3 (generally 30 seconds).

[0044] 2) Criteria for overcurrent of box grounding current

[0045] In actual projects, the adjacent terminal box is the terminal box that is adjacent to the monitored terminal box in terms of grounding network. Usually, it is the terminal box in the adjacent equipment compartment.

[0046] When the ground current of the adjacent terminal box satisfies the following relationship, the adjacent terminal box does not have a "box ground current overcurrent alarm" and the ground current alarm value of the terminal box is set to 1: I J ≥k1I T1 ;

[0047] When the ground current of the adjacent terminal box satisfies the following relationship, the "Box Ground Current Overcurrent Alarm" appears in the adjacent terminal box, and the ground current alarm value of the terminal box is set to 0: I J ≥k2I T1 And ΔI J ≥I T2 ;

[0048] In the box grounding current overcurrent criterion proposed in the embodiment of the present application, when the grounding current of the adjacent terminal box does not have an overcurrent alarm, the alarm of the monitored terminal box uses a high value, that is, it is not easy to alarm. When the grounding current of the adjacent terminal box has an overcurrent alarm, the alarm of the monitored terminal box uses a low value, which is easier to alarm.

[0049] Among them, I J is the grounding current of the adjacent terminal box, ΔI J is the ground current increment of the adjacent terminal box,

[0050] I T1 It is the alarm value when the ground current of the adjacent terminal box exceeds the limit. The empirical value is 15A. T2 It is the alarm value of the ground current increment of the adjacent terminal box, and the empirical value is 5A;

[0051] k1 and k2 are the first coefficient and the second coefficient respectively, and satisfy k2∈[1, k1], k1 is a real number greater than 1. In a non-limiting embodiment, k1 is a real number greater than 1, such as 2; k2∈[1, k1], for example, 1.5;

[0052] k1I T1 is the first current alarm value,

[0053] k2I T1 is the second current alarm value,

[0054] When there is no "box grounding current overcurrent alarm" in the nearby terminal box, the signal "this box grounding current overcurrent alarm" is issued after the judgment criteria are met and the set delay t1 (the empirical value is 30 seconds).

[0055] When the "box grounding current overcurrent alarm" appears in the nearby terminal box, the signal "XX terminal box grounding current overcurrent alarm" is issued after the judgment criteria are met and the set delay t2 (the empirical value is 15 seconds).

[0056] 3) Shielding layer grounding wire overcurrent criterion I P ≥k P I T3

[0057] Among them, I T3 k is the shield grounding wire alarm value, P is the shield grounding wire current coefficient, which is a real number greater than 1.

[0058] After the judgment criteria are met, the signal "cable shielding layer overcurrent alarm" is issued after the set delay t4 (usually 15 seconds).

[0059] 4) Overcurrent criterion for armored grounding wire I K ≥k K I T4

[0060] Among them, I T4 is the armor layer grounding wire alarm value, k K is the armor layer grounding wire current coefficient, which is a real number greater than 1.

[0061] After the judgment criteria are met, the signal "cable armor layer overcurrent alarm" is issued after the set delay t4 (generally 15 seconds).

[0062] 5) Criteria for cable loop current in terminal box

[0063] In a strong electromagnetic environment, if the cable grounding wires in the box form a loop for some reason, they can easily overheat and cause a fire. Based on on-site emergency repair practices, the sum of the armor layer grounding wire current and the shield layer grounding wire current, or the presence of high overcurrent in either the shielding wire or the armor layer grounding wire, is not the root cause of the loop current. Therefore, the criterion proposed in the embodiments of this application is "the sum of the armor layer grounding wire current and the shield layer grounding wire current is not greater than the loop current alarm value."

[0064] The criteria for the circulating current of the cable loop in the terminal box are as follows:

[0065] 5.1) When the potential difference alarm criteria are not met

[0066] Generally, the loop is caused by the damage of cable insulation, which generates current in a strong electromagnetic environment. Therefore, the situation where multiple cables are damaged at the same time is not considered.

[0067] Where, I K is the armor layer grounding wire and current, I P is the shield grounding wire and current, I T3 is the shield ground wire alarm value, I T4 is the armor layer ground wire alarm value, I T5 is the circulation alarm value, k P is the shield grounding wire current coefficient, which is a real number greater than 1, k K is the armor layer grounding wire current coefficient, which is a real number greater than 1.

[0068] Among them, I T5 Used to determine whether one or several armor layer grounding wires and shield layer grounding wires in the terminal box are in the same circuit. The value is generally less than 5A.

[0069] 5.2) When the potential difference alarm criteria are met

[0070] When the potential difference alarm occurs, there may be some problems in the ground network. According to practical experience, it is necessary to consider the possibility of insulation damage in multiple cables at the same time or at similar times. At this time, due to the influence of partial current phase cancellation, I P , I K At the same time, considering the leakage of multiple cables at the same time, more unbalanced currents need to be considered, so |I P +I K |The constraints need to be relaxed, then:

[0071] Among them, k U The influence coefficient of potential difference on the alarm value is 0.5.

[0072] After the judgment criteria are met, a signal "cable loop current alarm in the terminal box" is issued after a set delay t5 (generally 15 seconds).

[0073] There are many causes of fire, so the criteria are different. Each criterion is independent of each other and can quickly obtain a judgment result. The invention that the inventor wants to protect is the innovation of the criteria, such as the criterion of no more than the circulating current, the combined criterion of potential difference and circulating current, and the setting of the grounding alarm value of the adjacent terminal box relative to the terminal box itself. All of these are proposed based on the summary of on-site maintenance experience.

[0074] The current monitoring of the armored shielded cable grounding wire in a strong electromagnetic environment proposed in the embodiment of the present application has a wide coverage. The proposed criteria are discovered during on-site maintenance and emergency repairs, and are accurate and effective for monitoring the armored shielded cable grounding wire in strong electromagnetic environments such as dry-type reactor sites.

[0075] The embodiment of the present application establishes potential difference alarm criteria, box grounding current overcurrent criteria, shielding layer grounding wire overcurrent criteria, armor layer grounding wire overcurrent criteria and cable loop current criteria in the terminal box through analysis of terminal box grounding current characteristics and field data collection; among them, in the box grounding current overcurrent criteria, the impact of the grounding overcurrent of the adjacent terminal box on the terminal box is fully considered, and different alarm values ​​are set to achieve alarm reliability and accuracy under different grounding current environments; in the cable loop current criteria in the terminal box, the potential difference alarm is introduced to improve the judgment logic to meet the actual situation of loops caused by damaged cable insulation, and avoid false alarms and missed alarms.

[0076] The impact of the grounding current of the adjacent box on the fire hazard of this box is integrated into the judgment criteria through the setting of the grounding current alarm value of the terminal box. By setting high and low values, the impact of the grounding current of the adjacent terminal box on this terminal box is fully reflected. Because when the grounding current of the adjacent terminal box is large (not less than the first current alarm value), it is only necessary to judge whether to alarm based on the grounding current of the terminal box, and it is configured not to be easy to alarm; when the grounding current of the adjacent terminal box is small, it is necessary to judge whether to alarm based on the grounding current and grounding current increment of the terminal box, and it is configured to be easy to alarm.

[0077] The method for collecting current and voltage in the embodiment of the present application is easy to implement in engineering and will not cause any impact on the operation and construction of existing equipment.

[0078] The embodiment of the present application also proposes a device for monitoring the current of the ground wire of an armored shielded cable in a strong electromagnetic environment, comprising: a collection module, a monitoring module, and an alarm module;

[0079] The data acquisition module is configured to acquire data of the armor layer grounding wire and current, the shield layer grounding wire and current of the M cables in the terminal box, the primary grounding copper bar potential and the secondary grounding copper bar potential of the terminal box, and the grounding current of the adjacent terminal box;

[0080] The monitoring module includes: potential difference alarm unit, terminal box ground current alarm unit, cable ground wire overcurrent alarm unit, cable loop current alarm unit; among them,

[0081] A potential difference alarm unit is configured to obtain a potential difference by using the collected potential, and to call an alarm module to generate a potential difference alarm when the potential difference is not less than a potential difference alarm value;

[0082] The cable loop current alarm unit is configured to, when there is no potential difference alarm, call the alarm module to issue a cable loop current alarm in the terminal box if both the armor layer grounding wire current and the shield layer grounding wire current are not less than the corresponding overcurrent alarm value, and the sum of the armor layer grounding wire current and the shield layer grounding wire current is not greater than the circulating current alarm value; when a potential difference alarm is issued, the overcurrent alarm value and the circulating current alarm value are corrected, and if both the armor layer grounding wire current and the shield layer grounding wire current are not less than the corresponding corrected overcurrent alarm value, and the sum of the armor layer grounding wire current and the shield layer grounding wire current is not greater than the corrected circulating current alarm value, call the alarm module to issue a cable loop current alarm in the terminal box;

[0083] The terminal box ground current alarm unit is configured to set the ground current alarm value of the terminal box to a first value when the ground current of the adjacent terminal box is not less than the first current alarm value; and to set the ground current alarm value of the terminal box to a second value when the ground current of the adjacent terminal box is not less than the second current alarm value;

[0084] The cable grounding wire overcurrent alarm unit is configured to call the alarm module to issue an armor layer grounding wire overcurrent alarm or a shield layer grounding wire overcurrent alarm if the armor layer grounding wire and current or the shield layer grounding wire and current are not less than the corresponding overcurrent alarm value; wherein, the armor layer grounding wire and current correspond to the armor layer overcurrent alarm value, and the shield layer grounding wire and current correspond to the shield layer overcurrent alarm value.

[0085] The alarm module is configured to send out a terminal box potential difference alarm signal after a set delay after the potential difference alarm criterion is met, send out a cable shielding layer overcurrent alarm signal after a set delay after the shielding layer grounding wire overcurrent alarm criterion is met, send out a cable armoring layer overcurrent alarm signal after a set delay after the armoring layer grounding wire overcurrent alarm criterion is met, send out a cable loop current alarm signal in the terminal box after a set delay after the cable loop current alarm criterion in the terminal box is met, send out a terminal box grounding current alarm signal after a set delay when the grounding current of the adjacent terminal box is not less than the first current alarm value; send out a terminal box grounding current alarm signal after a set delay when the grounding current of the adjacent terminal box is not less than the second current alarm value.

[0086] The embodiments of the present application provide a method and device for monitoring the grounding wire current of an armored shielded cable in a strong electromagnetic environment. Based on the analysis of the grounding current characteristics of the terminal box and the collection of on-site data, a complete method for monitoring the grounding wire current of the cable in the terminal box is proposed, which avoids the heating and fire of the terminal box caused by the strong magnetic environment, and the situation in the early stage where the mechanism was unclear and there was no appropriate monitoring means, thereby comprehensively improving the monitoring level of the cables in the terminal box of the substation.

[0087] As shown in Figure 3, the armored shielded cable grounding wire current monitoring device in a strong electromagnetic environment is equipped with an acquisition module for collecting the parameters required for the five criteria of the terminal box leakage alarm.

[0088] The method proposed in the embodiment of the present application can also be used to monitor the grounding wire current of armored shielded cables in conventional electromagnetic environments.

[0089] The present disclosure may be a system, method and / or computer program product. The computer program product may include a computer-readable storage medium carrying computer-readable program instructions for causing a processor to implement various aspects of the present disclosure.

[0090] A computer-readable storage medium may be a tangible device that can hold and store instructions for use by an instruction execution device. A computer-readable storage medium may be, for example, but not limited to, an electrical storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination thereof. Examples of computer-readable storage media (a non-exhaustive list) include: a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM) or flash memory, a static random access memory (SRAM), a portable compact disc read-only memory (CD-ROM), a digital versatile disc (DVD), a memory stick, a floppy disk, a mechanical encoding device, such as a punch card or a raised structure in a groove on which instructions are stored, and any suitable combination thereof. The computer-readable storage medium used herein is not to be construed as a transient signal per se, such as a radio wave or other freely propagating electromagnetic wave, an electromagnetic wave propagating through a waveguide or other transmission medium (e.g., light pulses through a fiber optic cable), or an electrical signal transmitted through wires.

[0091] The computer-readable program instructions described herein can be downloaded from a computer-readable storage medium to each computing / processing device, or downloaded to an external computer or external storage device via a network, such as the Internet, a local area network, a wide area network, and / or a wireless network. The network can include copper transmission cables, fiber optic transmission, wireless transmission, routers, firewalls, switches, gateway computers, and / or edge servers. The network adapter card or network interface in each computing / processing device receives the computer-readable program instructions from the network and forwards the computer-readable program instructions to be stored in the computer-readable storage medium in each computing / processing device.

[0092] The computer program instructions for performing the operations of the present disclosure may be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine-dependent instructions, microcode, firmware instructions, state setting data, or source code or object code written in any combination of one or more programming languages, including object-oriented programming languages ​​such as Smalltalk, C++, and conventional procedural programming languages ​​such as "C" or similar programming languages. The computer-readable program instructions may be executed entirely on the user's computer, partially on the user's computer, as a separate software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In the case of a remote computer, the remote computer may be connected to the user's computer via any type of network, including a local area network (LAN) or a wide area network (WAN), or may be connected to an external computer (e.g., via the Internet using an Internet service provider). In some embodiments, by utilizing state information of computer-readable program instructions to personalize an electronic circuit, such as a programmable logic circuit, a field programmable gate array (FPGA), or a programmable logic device (PLA), the electronic circuit can execute the computer-readable program instructions to implement various aspects of the present disclosure.

[0093] Finally, it should be noted that the above embodiments are only used to illustrate the embodiments of the present application and not to limit them. Although the present application has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present application can still be modified or replaced by equivalents, which should all be included in the scope of protection of the claims of this application.

Claims

1. A method for monitoring the grounding wire current of an armored shielded cable in a strong electromagnetic environment, monitoring the grounding wire current of M armored shielded cables in a terminal box, comprising: Collect the armor layer grounding wire and current, shield layer grounding wire and current of M cables in the terminal box, collect the primary grounding copper bar potential and secondary grounding copper bar potential of the terminal box, and the grounding current of the adjacent terminal box; The potential difference is obtained by using the collected primary grounding copper busbar potential and the secondary grounding copper busbar potential, and a potential difference alarm is issued in response to the potential difference being greater than or equal to a potential difference alarm value; When there is no potential difference alarm, in response to the armor layer grounding wire and current and the shield layer grounding wire and current being respectively greater than or equal to the corresponding overcurrent alarm value, and the sum of the armor layer grounding wire and current and the shield layer grounding wire and current being less than or equal to the circulating current alarm value, a cable loop circulating current alarm is issued in the terminal box; when there is a potential difference alarm, the overcurrent alarm value and the circulating current alarm value are corrected, and in response to the armor layer grounding wire and current and the shield layer grounding wire and current being respectively greater than or equal to the corresponding corrected overcurrent alarm value, and the sum of the armor layer grounding wire and current and the shield layer grounding wire and current being less than or equal to the corrected circulating current alarm value, a cable loop circulating current alarm is issued in the terminal box; In response to the grounding current of the adjacent terminal box being greater than or equal to the first current alarm value, the grounding current alarm value of the terminal box is set to the first value; in response to the grounding current of the adjacent terminal box being greater than or equal to the second current alarm value and the grounding current increment of the adjacent terminal box being greater than or equal to the current increment alarm value, the grounding current alarm value of the terminal box is set to the second value; In response to the grounding current of the terminal box being greater than the grounding current alarm value, a terminal box grounding current alarm is issued; wherein the first current alarm value is greater than the second current alarm value.

2. The method for monitoring the grounding current of an armored shielded cable in a strong electromagnetic environment according to claim 1 further comprises: In response to the armor layer grounding wire and current or the shield layer grounding wire and current being greater than or equal to the corresponding overcurrent alarm value, an armor layer grounding wire overcurrent alarm or a shield layer grounding wire overcurrent alarm is issued; Among them, the armor layer grounding wire and current correspond to the armor layer overcurrent alarm value, and the shield layer grounding wire and current correspond to the shield layer overcurrent alarm value.

3. The method for monitoring the grounding current of an armored shielded cable in a strong electromagnetic environment according to claim 1 or 2, wherein: The shield grounding wire and current I of M cables P , armor layer grounding wire and current I K They satisfy the following relationships respectively: In the formula, I p1 ,I p2 ,…,I pM is the cable shield grounding wire current, I k1 ,I k2 ,…,I kM is the grounding wire current of the cable armor layer.

4. The method for monitoring the grounding current of an armored shielded cable in a strong electromagnetic environment according to claim 3, wherein: The criteria for the shield ground wire overcurrent alarm are as follows: I P ≥k P I T3 The criteria for overcurrent alarm of armor layer grounding wire are as follows: I K ≥k K I T4 In the formula, I T3 is the shield ground wire alarm value, I T4 is the armor layer ground wire alarm value, k P is the current coefficient of the shield grounding wire, which is a real number greater than 1. k K is the current coefficient of the armor layer grounding wire, which is a real number greater than 1.

5. The method for monitoring the grounding current of an armored shielded cable in a strong electromagnetic environment according to claim 4 further comprises: When the shielding layer grounding wire overcurrent alarm criterion is met, the cable shielding layer overcurrent alarm signal is issued after a set delay; When the overcurrent alarm criteria for the armor layer grounding wire are met, the cable armor layer overcurrent alarm signal is issued after a set delay.

6. The method for monitoring the grounding current of an armored shielded cable in a strong electromagnetic environment according to claim 1 further comprises: Among the connection points between the secondary grounding copper bar of the terminal box and the secondary grounding grid, the connection point closest to the terminal box is used as the potential reference point; According to the potential reference point, the potential of the connection point between the grounding terminal of the terminal box and the primary grounding copper busbar is measured as the primary grounding copper busbar potential, and the potential of the secondary grounding copper busbar is measured as the secondary grounding copper busbar potential. The current flowing from the grounding terminal of the adjacent terminal box into the primary grounding copper busbar is measured as the grounding current of the adjacent terminal box.

7. The method for monitoring the grounding current of an armored shielded cable in a strong electromagnetic environment according to claim 6, wherein: The criteria for potential difference alarm are as follows: |In I -IN II |≥U T1 In the formula, U I The potential of the primary grounding copper bar of the terminal box. U II The potential of the secondary grounding copper bar of the terminal box. U T1 It is the potential difference alarm value.

8. The method for monitoring the grounding current of an armored shielded cable in a strong electromagnetic environment according to claim 7 further comprises: When the potential difference alarm criterion is met, a terminal box potential difference alarm signal is issued after a set delay.

9. The method for monitoring the grounding current of an armored shielded cable in a strong electromagnetic environment according to claim 7 further comprises: When there is no potential difference alarm, the cable loop current alarm in the terminal box is triggered when the armor layer grounding wire and current, shield layer grounding wire and current meet the following relationship: In the formula, I K is the armor layer grounding wire and current, I P For the shield ground wire and current, I T3 is the shield ground wire alarm value, I T4 is the armor layer ground wire alarm value, I T5 is the circulation alarm value, k P is the current coefficient of the shield grounding wire, which is a real number greater than 1. k K is the current coefficient of the armor layer grounding wire, which is a real number greater than 1.

10. The method for monitoring the grounding current of an armored shielded cable in a strong electromagnetic environment according to claim 9, further comprising: When the potential difference alarm occurs, the cable loop current alarm in the terminal box is triggered when the armor layer grounding wire and current, the shield layer grounding wire and current meet the following relationship: In the formula, k U is the influence coefficient of potential difference on the alarm value.

11. The method for monitoring the ground wire current of an armored shielded cable in a strong electromagnetic environment according to claim 9 or 10, further comprising: When the cable loop current alarm criterion in the terminal box is met, the cable loop current alarm signal in the terminal box is issued after a set delay.

12. The method for monitoring the grounding current of an armored shielded cable in a strong electromagnetic environment according to claim 1, wherein: When the ground current of the adjacent terminal box satisfies the following relationship, the ground current alarm value of the terminal box is set to 1: I J ≥k1I T1 When the ground current of the adjacent terminal box satisfies the following relationship, the ground current alarm value of the terminal box is set to 0: I J ≥k2I T1 and ΔI J ≥I T2 In the formula, I J is the grounding current of the adjacent terminal box, ΔI J is the ground current increment of the adjacent terminal box, k1 and k2 are the first coefficient and the second coefficient respectively, and they satisfy k2∈[1, k1], k1 is a real number greater than 1, I T1 It is the alarm value when the ground current of the adjacent terminal box exceeds the limit. i T1 is the first current alarm value, k 2 T1 is the second current alarm value, I T2 It is the ground current increment alarm value of the adjacent terminal box.

13. The method for monitoring the grounding current of an armored shielded cable in a strong electromagnetic environment according to claim 12 further comprises: In response to the ground current of the adjacent terminal box being greater than or equal to the first current alarm value, a ground current alarm signal of the terminal box is issued after a set delay; In response to the grounding current of the adjacent terminal box being greater than or equal to the second current alarm value, a grounding current alarm signal of the adjacent terminal box is issued after a set delay.

14. A device for monitoring the grounding current of an armored shielded cable in a strong electromagnetic environment, used to implement the method according to any one of claims 1 to 13, the device comprising: Collection module, monitoring module, alarm module; The acquisition module is configured to acquire the armor layer grounding wire and current, the shield layer grounding wire and current of the M cables in the terminal box, the primary grounding copper bar potential and the secondary grounding copper bar potential of the terminal box, and the grounding current of the adjacent terminal box; The monitoring module includes: potential difference alarm unit, terminal box ground current alarm unit, cable ground wire overcurrent alarm unit, cable loop current alarm unit; among them, A potential difference alarm unit is configured to obtain a potential difference by using the collected potential of the primary grounding copper busbar and the collected potential of the secondary grounding copper busbar, and in response to the potential difference being greater than or equal to a potential difference alarm value, call an alarm module to generate a potential difference alarm; The cable loop current alarm unit is configured to, when there is no potential difference alarm, call the alarm module to issue a cable loop current alarm in the terminal box in response to the armor layer grounding wire and current and the shield layer grounding wire and current being respectively greater than or equal to the corresponding overcurrent alarm value, and the sum of the armor layer grounding wire and current and the shield layer grounding wire and current being less than or equal to the circulating current alarm value; in the case of a potential difference alarm, correct the overcurrent alarm value and the circulating current alarm value, and call the alarm module to issue a cable loop current alarm in the terminal box in response to the armor layer grounding wire and current and the shield layer grounding wire and current being respectively greater than or equal to the corresponding corrected overcurrent alarm value, and the sum of the armor layer grounding wire and current and the shield layer grounding wire and current being less than or equal to the corrected circulating current alarm value; A terminal box grounding current alarm unit, configured to set the grounding current alarm value of the terminal box to a first value in response to the grounding current of the adjacent terminal box being greater than or equal to the first current alarm value; and to set the grounding current alarm value of the terminal box to a second value in response to the grounding current of the adjacent terminal box being greater than or equal to the second current alarm value; The cable grounding wire overcurrent alarm unit is configured to call the alarm module to issue an armor layer grounding wire overcurrent alarm or a shield layer grounding wire overcurrent alarm in response to the armor layer grounding wire and current or the shield layer grounding wire and current being greater than or equal to the corresponding overcurrent alarm value; wherein the armor layer grounding wire and current correspond to the armor layer overcurrent alarm value, and the shield layer grounding wire and current correspond to the shield layer overcurrent alarm value; The alarm module is set to send out a terminal box potential difference alarm signal after a set delay after the potential difference alarm criterion is met, send out a cable shielding layer overcurrent alarm signal after a set delay after the shielding layer grounding wire overcurrent alarm criterion is met, send out a cable armoring layer overcurrent alarm signal after a set delay after the armoring layer grounding wire overcurrent alarm criterion is met, and send out a terminal box after a set delay after the cable loop current alarm criterion in the terminal box is met. Inner cable loop circulating current alarm signal; in response to the grounding current of the adjacent terminal box being greater than or equal to the first current alarm value, a grounding current alarm signal of the terminal box is issued after a set delay; in response to the grounding current of the adjacent terminal box being greater than or equal to the second current alarm value, a grounding current alarm signal of the adjacent terminal box is issued after a set delay.

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