High-voltage cable joint monitoring system

Abstract

The utility model discloses a high-voltage cable joint monitoring system, which comprises a shielding layer current acquisition part and a shielding layer current display part, the shielding layer current acquisition part adopts a through-core current transformer, and the shielding layer current display part adopts a multifunctional display ampere meter; the cable joint pull-off detection device has the advantages of being simple in structure, convenient to install and low in cost, the operation state of the cable joint can be analyzed and judged through data of the ammeter screen behind the cabinet in the operation period, manpower and material resources for cable maintenance are reduced, in the actual production environment, cable joint pull-off is a process, and production efficiency is improved. The difficulty of fault processing and the influence on operation power supply after abnormal conditions are found in the initial stage are small, the system monitors current data of the shielding layer, the pull-off degree of the cable connector is quantified by comparing the ratio of the load current to the shielding current, the abnormal conditions of the cable connector can be found in the initial pull-off stage through data analysis, and the safety of the cable connector is guaranteed. And fault processing and stable operation power supply are facilitated.

Description

Technical Field

[0001] This utility model relates to the technical field of high-voltage cable intermediate joint monitoring technology, specifically to a high-voltage cable joint monitoring system. A real-time monitoring device has been developed to address issues such as electrical disconnection and continuity in the shielding layer of ring network cables. This reduces the failure rate of 35kV ring network cables, improves the stability of urban rail transit power supply, and addresses the low accuracy of traditional cable fault detection methods. By analyzing the current between the shielding layers between two stations, the shielding current is detected in real time, effectively reducing and preventing partial discharge, heating, and even breakdown at the intermediate joints. Background Art

[0002] In urban rail transit power supply systems, the main power supply ring network primarily delivers power to stations along the line via 35kV AC cables. Cable joints are a vulnerable link in the power supply system. Due to temperature and environmental fluctuations, problems such as joint detachment and insulation breakdown can occur. Therefore, the operating status of cable joints requires regular inspection.

[0003] The traditional detection method is to manually walk up to the overhead line and use the naked eye and a thermometer to detect the condition. This method is labor-intensive, inefficient, and involves a harsh working environment. It is dangerous, and the status monitoring of the intermediate cable joints is not accurate, and real-time monitoring is not possible. Utility Model Content

[0004] In order to overcome the problems of traditional detection methods that require manual labor to walk on the elevated line and use the naked eye and thermometers, such as large workload, low efficiency, harsh working environment, danger, low accuracy, and inability to achieve real-time monitoring, the utility model provides a high-voltage cable joint monitoring system.

[0005] The technical solution adopted by the utility model to achieve the above purpose is: comprising a shielding layer current acquisition part and a shielding layer current display part; the shielding layer current acquisition part adopts a core-through current transformer, and the shielding layer current display part adopts a multi-function display ammeter.

[0006] This system passes the shielded wires of phases A, B, and C of the 35kV ring network cable through three through-core current transformers (CTs). After passing through the CTs, the shielded wires are secured to the ground busbar. The CTs are mounted inside the rear of the 35kV switchgear cabinet. The CTs are connected to a multi-function ammeter, which monitors the current in the ring network cable shield. The multi-function ammeter's power supply is connected to the 220V AC power supply in the substation wall. The multi-function ammeter is also mounted on the rear of the 35kV switchgear cabinet.

[0007] Working principle:

[0008] The shield layer of the 35kV ring network cable is grounded at both ends, forming a loop with the earth. When the 35kV ring network cable is operating normally, the three-phase load current flows through the cable's internal core wires, generating an alternating magnetic field. Consequently, an induced electromotive force is generated on the shield layer. The induced current in the shield layer passes through the shield grounding wire in the 35kV switchgear of the substation at both ends, through the grounding copper busbar, and flows through the earth to form a loop. This induced current is generated in the shield layer, which in turn generates a magnetic field that offsets the external interference magnetic field, thereby achieving a shielding effect. At this time, the shield current of the three-phase cable is respectively passed through the core of the three core-through current transformers of this system. The secondary current induced by the core-through current transformer is transmitted to the multi-function display ammeter.

[0009] The induced current in the shield layer varies with the magnitude of the three-phase load current, following the same pattern as the load current. When a 35kV phase cable connector is disconnected or the insulation is damaged, the impedance of the shield layer loop increases significantly, causing the induced current in the shield layer of that phase to drop significantly, resulting in a significant difference in the load and shield current ratios of the other two phases. Operators can determine if the middle connector of that cable segment has disconnected by observing the data displayed by the multi-function display ammeter behind the 35kV cabinet.

[0010] The cable joint monitoring system uses the characteristic of induced current in the cable shielding layer to measure and monitor the induced current flowing through the shielding layer, allowing operators to monitor the operating status of the ring network cable joints in real time.

[0011] The beneficial effects of the utility model are:

[0012] The system has a simple structure, is easy to install and has low cost. During operation, the operating status of the cable connector can be judged through data analysis on the ammeter screen behind the cabinet, reducing the manpower and material resources for cable maintenance.

[0013] In actual production environments, cable connector pull-out is a process. The difficulty of troubleshooting and the impact on operational power supply after the initial abnormality is discovered are relatively small. The system monitors the shield layer current data and quantifies the degree of cable connector pull-out by comparing the ratio of load current to shield current. Through data analysis, the abnormal state of the cable connector can be discovered in the early stage of pull-out, which is conducive to fault handling and stable operational power supply. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a schematic diagram of a high voltage cable joint monitoring system;

[0015] Figure 2 It is an operation flow chart of a high voltage cable joint monitoring system. DETAILED DESCRIPTION

[0016] like Figure 1 and Figure 2As shown, the utility model is a high-voltage cable joint monitoring system, including a shielding layer current acquisition part and a shielding layer current display part; the shielding layer current acquisition part adopts a core-through current transformer, and the shielding layer current display part adopts a multi-function display ammeter.

[0017] This system passes the shielded wires of phases A, B, and C of the 35kV ring network cable through three through-core current transformers (CTs). After passing through the CTs, the shielded wires are secured to the ground busbar. The CTs are mounted inside the rear of the 35kV switchgear cabinet. The CTs are connected to a multi-function ammeter, which monitors the current in the ring network cable shield. The multi-function ammeter's power supply is connected to the 220V AC power supply in the substation wall. The multi-function ammeter is also mounted on the rear of the 35kV switchgear cabinet.

[0018] Working principle:

[0019] The shield layer of the 35kV ring network cable is grounded at both ends, forming a loop with the earth. When the 35kV ring network cable is operating normally, the three-phase load current flows through the cable's internal core wires, generating an alternating magnetic field. Consequently, an induced electromotive force is generated on the shield layer. The induced current in the shield layer passes through the shield grounding wire in the 35kV switchgear of the substation at both ends, through the grounding copper busbar, and flows through the earth to form a loop. This induced current is generated in the shield layer, which in turn generates a magnetic field that offsets the external interference magnetic field, thereby achieving a shielding effect. At this time, the shield current of the three-phase cable is respectively passed through the core of the three core-through current transformers of this system. The secondary current induced by the core-through current transformer is transmitted to the multi-function display ammeter.

[0020] The induced current in the shield layer varies with the magnitude of the three-phase load current, following the same pattern as the load current. When a 35kV phase cable connector is disconnected or the insulation is damaged, the impedance of the shield layer loop increases significantly, causing the induced current in the shield layer of that phase to drop significantly, resulting in a significant difference in the load and shield current ratios of the other two phases. Operators can determine if the middle connector of that cable segment has disconnected by observing the data displayed by the multi-function display ammeter behind the 35kV cabinet.

[0021] The cable joint monitoring system uses the characteristic of induced current in the cable shielding layer to measure and monitor the induced current flowing through the shielding layer, allowing operators to monitor the operating status of the ring network cable joints in real time.

Claims

1. A high-voltage cable joint monitoring system, characterized by: It includes a shielding layer current acquisition part and a shielding layer current display part; the shielding layer current acquisition part adopts a core-through current transformer, and the shielding layer current display part adopts a multi-function display ammeter; this system passes the shielding wires of the three phases A, B, and C of the 35kV ring network cable through three core-through current transformers respectively. After the shielding wires pass through the core-through current transformers, they are fixed to the grounding busbar, and the core-through current transformers are connected to the multi-function display ammeter.

2. A high-voltage cable joint monitoring system according to claim 1, characterized in that: The core-through current transformer is fixed inside the rear of the 35kV switch cabinet.

3. The high-voltage cable joint monitoring system according to claim 1, characterized in that: The multifunctional display ammeter is fixed behind the 35kV switch cabinet.

4. A high-voltage cable joint monitoring system according to claim 1, characterized in that: The power line of the multifunctional display ammeter adopts the AC 220V power supply of the wall in the substation.

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