On-line monitoring method and device for insulating state of power cable

A technology of insulation status and power cables, applied in the direction of testing dielectric strength, etc., can solve problems such as unsolvable grounding methods and DC signal loading, limited to well-shielded laboratories, and unsuitable for high-voltage power systems

Inactive Publication Date: 2011-02-16
HUAZHONG UNIV OF SCI & TECH
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Problems solved by technology

From the specific analysis of these technologies, the DC component method is suitable for the on-line monitoring of cable insulation systems of various voltage levels, but due to the interference of stray currents and the difficulty of extracting small currents, it is not suitable for practical applications in power systems; The superposition method is suitable for the monitoring of the low-voltage cable insulation system, but it is not suitable for the practical application of the high-volta...

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  • On-line monitoring method and device for insulating state of power cable
  • On-line monitoring method and device for insulating state of power cable
  • On-line monitoring method and device for insulating state of power cable

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Embodiment Construction

[0015] In the present invention, the current sensor is set on the grounding wire of the cable, and the current transformer converts the current signal into a voltage signal by connecting a small resistance, and is connected to a filter amplifier circuit. The circuit filters out the required low-frequency current and voltage signals, amplifies them by a certain factor, and then sends them to the A / D converter. The microcomputer control module then sends the current and voltage digital signals obtained from the A / D converter to the GSM / GPRS data transmission module ( DTU), GSM / GPRS DTU sends the current signal, voltage signal and line number to the GSM / GPRS DTU in the monitoring room, and the GSM / GPRS DTU in the monitoring room finally transmits the signal to the monitoring host through the serial port. After the monitoring host receives the current and line number information of each cable, it first stores it in the database and displays it, and then analyzes and judges the info...

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Abstract

The invention discloses on-line monitoring method and device for the insulating state of a power cable. Two factors are mainly considered for the monitoring of the insulating state of the cable, wherein one factor is a low-frequency current value generated by low-frequency oscillation of a power system; and the other factor is a cable medium loss factor value acquired by calculating the phase angle difference between a low-frequency voltage signal and the current signal, which is generated by the oscillation of the power system and seeking an arctangent value. If any one of the two factors is greater than the corresponding insulated safety threshold, the cable has the insulated ageing hidden trouble. By using the low-frequency signal to monitor, the invention has high detection precision and can remarkably reflect the ageing state of the cable; and in addition, the extra superposition power supply is avoided, so that the invention avoids the damage to the safety of a power grid.

Description

technical field [0001] The invention relates to the field of on-line monitoring of power equipment, in particular to an on-line monitoring device for the insulation state of a power cable. Background technique [0002] There are offline detection method and online monitoring method for cable insulation monitoring. The test of offline detection method needs to be carried out with power failure. After the power failure, the status of the cable is inconsistent with that in operation, which affects the accuracy of judgment; the offline detection method is a periodic inspection, not continuous monitoring at any time. It has greater blindness, resulting in greater waste of manpower and material resources, and even unnecessary insulation damage. For example, in the insulation preventive test, since the AC polyethylene cable insulation cannot use the DC withstand voltage test, the AC withstand voltage test or the resonance withstand voltage test must be used, but these equipment ar...

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Application Information

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IPC IPC(8): G01R31/12
Inventor 陈俊武陈爱文周凯
Owner HUAZHONG UNIV OF SCI & TECH
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