CN201229389Y - Cable sheath insulation on-line monitoring device - Google Patents

Abstract

The utility model relates to a monitoring device, in particular to an on-line monitoring device for cable sheath insulation. The grounding box is connected to the ground terminal, the signal output terminal of the signal detection device is connected to the input terminal of the central processing unit, and the data display device is connected to the display output terminal of the central processing unit. The utility model has the advantage of detecting the current of the direct ground terminal by using the principle that the current of the direct ground terminal must produce abnormal changes after the metal sheath ground fault causes a circulating current. It can effectively judge and find the grounding fault in the insulating sheath, or other grounding faults, so as to detect system defects as early as possible, and take necessary measures to repair the cable in time to prevent cable faults and further expansion of faults, and improve the reliability of power supply It is of great significance for the maintenance of cables.

Description

On-line monitoring device for cable sheath insulation

technical field

The utility model relates to a monitoring device, in particular to an on-line monitoring device for cable sheath insulation.

Background technique

The metal sheath of 110-220KV high-voltage cross-linked cables is usually directly grounded at one end, and the other end is grounded through a protector. As shown in Figure 1, the protector is a lightning arrester with a zinc oxide valve plate. It is low resistance at high pressure and high resistance at low pressure. The protector only realizes grounding when the valve plate is low resistance when the cable is hit by high voltage. After the cable constitutes an AC transmission circuit, an induced potential will be generated between the cable conductor-core wire and the metal sheath. Inductive potential will be generated on the layer. Under normal circumstances, the metal sheath of the cable has only a single point grounding-direct grounding terminal. Therefore, although there is an induced potential on the metal sheath, since no closed loop is formed, no circulating current will be formed to affect the cable. of normal operation. However, when the cable is running, due to the long running distance, after any point of the insulating sheath on it is damaged due to various influences, the metal sheath at the corresponding point will be exposed and form a grounding point, which causes the metal sheath to be damaged. There are more than two or even multiple grounding points on the ground, and a closed loop will be formed between two or more grounding points. Referring to Figure 2, since there is an induced potential in the metal sheath, and the resistance of the metal sheath is very small, so A larger circulation will be generated on the closed circuit. On the one hand, this circulating current will generate heat in the cable, resulting in a decrease in the actual carrying capacity of the cable and consuming a lot of energy; on the other hand, there is a current flowing around the grounding point, which causes soil denaturation and increases electrical corrosion, so that the metal sheath will It will slowly perforate, and moisture will enter the cable through it, and cause the cable line to fail, reducing the service life of the cable. Due to the long production cycle of EHV cables, the cable laying and accessory installation are also relatively complicated, and the recovery period after a fault occurs is long, which seriously affects the reliability of power supply.

Contents of the invention

The purpose of this utility model is to provide an on-line monitoring device for cable sheath insulation that prevents cable line failures and improves the reliability of cable power supply based on the shortcomings of the prior art.

The utility model is achieved through the following approaches:

The on-line monitoring device for cable sheath insulation has a structure that includes a signal detection device, a central processing unit, and a data display device. It is connected with the input end of the central processing unit, and the data display device is connected with the display output end of the central processing unit.

When the cable is in normal operation, a certain capacitive current flows through the direct grounding end. If there is a metal sheath grounding fault that causes a circulating current, the current at the direct grounding end will inevitably change abnormally. By detecting the current at the direct grounding end, the protection of the protection can be realized. Layer insulation monitoring. The utility model adopts the above principle, connects the signal detection device to the direct grounding end of the cable, collects the current data of the direct grounding end of the cable, then processes the collected data through the central processing unit, and finally displays the collected current through the data display device When the current is abnormal, it can be judged that there is a ground fault in the insulating sheath, or there is another ground fault, so as to repair the cable in time to prevent the cable fault and further expansion of the fault, and improve the reliability of power supply. Cable maintenance is of great significance.

The utility model can be further specifically described as:

The central processing unit includes a converter and a processor. The signal input end of the converter is connected to the signal detection device, the output end of the converter is connected to the data display device, and the other output end of the converter is connected to the processor.

Since the signal collected by the signal detection device is an analog signal, it needs to be converted into a digital signal by a converter, and then displayed by a data display device, which is convenient for visually monitoring the current change of the direct grounding end of the cable.

It also includes a phase detector, which is inserted between the signal detection device and the central processing unit, that is, the input end of the phase detector is connected to the signal detection device, and the output end is connected to the central processing unit.

The phase detector is a kind of current phase identifier. Since the phase of the sheath circulation generated when the insulation sheath fault occurs is different from that of the capacitive current at the direct grounding end of the cable during normal operation, the use of a phase detector can facilitate the detection of the current at the direct grounding end of the cable. Phase situation, to provide detailed current variation of the direct grounding end of the cable, including magnitude and phase data.

The data display device includes a capacitive current display device and a sheath circulation display device, both of which are respectively connected with the display output terminals of the central processing unit.

When a cable ground fault occurs, two currents will appear at the direct ground terminal, namely the capacitive current in normal operation and the faulty sheath circulation. Displaying the two separately can provide a more detailed current change situation.

Also includes an alarm device, which is connected with the central processing unit.

The alarm device can be a sound alarm or a light signal alarm. When the central processing unit receives the detected current data, it compares the data with the set reference data. Once the detected current data deviates from the set reference data by a certain Outside the range, an alarm will be issued through the alarm device. The alarm device can be implemented remotely to notify the abnormality of the monitoring personnel's data, which can avoid personnel's 24-hour monitoring, resulting in a waste of human resources.

The utility model can also be further specifically:

It also includes a voltage detection device, which is electrically connected to the grounding box of the cable protector, the signal output end of the voltage detection device is connected to a processing device, and the output end of the processing device is connected to an alarm device.

During the normal operation of the cable, a voltage is generated at the protective ground terminal, and this voltage is proportional to the core current. If there is a sheath ground fault, the sheath circulation will inevitably cause abnormal changes in the voltage of the protector ground terminal. The detection can realize the monitoring of the insulation condition of the sheath.

The signal collected by the voltage detection device is processed by the processing device. At the same time, the processing device includes a judgment and comparison device to compare the detected voltage signal with the reference value in the processing device. When the detected signal deviates from the reference value within a certain range , the processing device will give an alarm through the alarm device, prompting that a ground fault occurs in the insulation of the cable sheath.

This is a voltage monitoring device (including a voltage detecting device, a processing device and an alarm), which can be used alone as an on-line monitoring device for cable sheath insulation. However, it is different from the principle and structure of the previous circulating current monitoring device (signal detection device, central processing unit and data display device), the value of the circulating current generated due to the grounding of the cable is relatively large, and the monitoring sensitivity is also high. Relatively speaking, the voltage change of the protector caused by the ground fault is relatively small, and the monitoring sensitivity is relatively low, so the voltage monitoring device is generally used as an auxiliary monitoring device for the circulating current monitoring device.

To sum up, the utility model has the advantage that it provides an online monitoring device for the insulation of the cable sheath, which utilizes the principle that the current at the direct ground end will inevitably change abnormally after the ground fault of the metal sheath causes a circulating current. current is detected. After the abnormal current is found during monitoring, it can effectively judge and find the grounding fault of the insulation sheath, or the occurrence of other grounding faults, so as to detect system defects as early as possible, and take necessary measures to repair the cable in time to prevent cable faults and The further expansion of faults improves the reliability of power supply, which is of great significance to the maintenance of cables.

Description of drawings

Fig. 1 shows the grounding schematic diagram of the cable metal sheath in the prior art described in the utility model background technology;

FIG. 2 is a schematic diagram of the principle of a closed circuit in the metal sheath when a fault occurs and grounding is described in the background technology of the present invention.

Fig. 3 is a schematic diagram of a circuit for monitoring by using faults to generate circulating currents in the on-line monitoring device for cable sheath insulation described in the embodiment of the present invention;

Fig. 4 is a schematic circuit diagram of the on-line monitoring device for cable sheath insulation described in the present invention, which utilizes faults to generate voltage anomalies for monitoring.

Below in conjunction with embodiment the utility model is described further.

specific embodiment

Best practice:

With reference to accompanying drawing 3, the mark explanation in the figure is as follows:

A: grounding box protector; B: signal detection device; C: cable core to sheath capacitance; D: protector grounding point; E: metal sheath direct grounding point; F: fault point; G: fault grounding point; K: phase detector; L: central processing unit; M: sheath circulation display device; N: capacitance current display device; P: alarm device; R1, R2: metal sheath resistance; r: fault point grounding resistance.

The cable sheath insulation online monitoring device is a circulating current monitoring device, including a signal detection device B, a central processing unit L, a data display device, a phase detector K and an alarm device P, and the signal acquisition terminal of the signal detection device B is connected to the The cable is directly connected to the ground terminal of the grounding box, the signal output terminal of the signal detection device B is connected to the input terminal of the central processing unit L through the phase detector K, and the data display device is connected to the display output terminal of the central processing unit. The data display device includes a capacitive current display device N and a sheath circulation display device M, both of which are connected to the display output terminals of the central processing unit L respectively; The signal output end is electrically connected.

When the cable is in normal operation, a certain capacitive current flows through the direct grounding point E. When a grounding fault occurs on the metal sheath and a circulating current is generated, the current at the direct grounding point E will inevitably change abnormally. Connect the signal detection device B to the direct point of the cable. Grounding point, collect the current data of the direct grounding point of the cable, then process the collected data through the phase detector K and the central processing unit L, and finally display the collected different currents through the data display device, including the sheath circulation and capacitance Current, when the sheath circulation occurs, it can be judged that there is a ground fault in the insulation sheath, or other ground faults occur, and the cable should be repaired in time to prevent the cable fault and further expansion of the fault.

With reference to accompanying drawing 4, each mark in the figure is explained as follows:

A: grounding box protector; C: cable core to sheath capacitance; D: protector grounding point; E: metal sheath direct grounding point; F: fault point; G: fault grounding point; Q: voltage measuring device; Y: processing device; U: voltage display device; P: alarm device; R1, R2: metal sheath resistance; r: fault point grounding resistance.

The above cable sheath online monitoring device can also be a voltage monitoring device, including a voltage detection device Q, which is electrically connected to the grounding box of the cable protector, and the signal output terminal of the voltage detection device Q is connected to a processing device Y, The output terminal of the processing device Y is connected to an alarm device P, and a display output terminal of the processing device Y is electrically connected to a voltage display device U.

During the normal operation of the cable, a voltage is generated at the protective ground terminal, and this voltage is proportional to the core current. If there is a sheath ground fault, the sheath circulation will inevitably cause abnormal changes in the voltage of the protector ground terminal. The detection can also realize the monitoring of the insulation condition of the sheath. Due to the grounding of the cable, the value of the circulating current generated is relatively large, and the sensitivity of monitoring is also high. Relatively speaking, the voltage change of the protector caused by the ground fault is relatively small, and the monitoring sensitivity is relatively low, so the voltage monitoring device is generally used as an auxiliary monitoring device for the aforementioned circulating current monitoring device.

All the devices B, K, L, M, N, P, Q, U, and Y mentioned above can be commercially available products, and the central processing unit only needs to be modified in a targeted manner. For example, the central processor L can adopt NXP80C51 series single-chip microcomputer, or the central processor of INTEL; M, N can adopt the existing digital display screen with data line, can adopt the products produced in Western Regions, etc.; phase detector K can adopt American A phase detector with chip model PDP-201 produced by SYNERGY.

The undescribed part of the utility model is the same as the prior art.

Claims (6)

1. The on-line monitoring device for cable sheath insulation is characterized in that it includes a signal detection device, a central processing unit, and a data display device. The signal acquisition end of the signal detection device is connected to the ground terminal of the cable direct grounding box, and the signal output of the signal detection device is The terminal is connected with the input terminal of the central processing unit, and the data display device is connected with the display output terminal of the central processing unit. 2. The on-line monitoring device for cable sheath insulation according to claim 1, wherein the central processing unit includes a converter and a processor, the signal input end of the converter is connected to the signal detection device, and the output end of the converter Connect the data display device, and connect the other output end of the converter to the processor. 3. The on-line monitoring device for cable sheath insulation according to claim 1, characterized in that it also includes a phase detector, which is inserted between the signal detection device and the central processing unit, that is, the input end of the phase detector is connected to The signal detection device is connected with the central processing unit at the output end. 4. The on-line monitoring device for cable sheath insulation according to claim 1, wherein the data display device includes a capacitive current display device and a sheath circulation display device, both of which are respectively connected to the display output terminals of the central processing unit. 5. The on-line monitoring device for cable sheath insulation according to claim 1, further comprising an alarm device connected to the signal output terminal of the central processing unit. 6. The on-line monitoring device for cable sheath insulation according to claim 1, characterized in that it also includes a voltage detection device, which is electrically connected to the grounding box of the cable protector, and the signal output terminal of the voltage detection device is connected to a processing device, the output terminal of the processing device is connected with an alarm device.

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