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On-line monitoring system for current and carrying capacity of cable sheath

A technology of sheath current and cable sheath, which is applied in the field of online monitoring system of cable sheath current and ampacity, and can solve the problems of increased error between calculation results and actual results, misdiagnosis of cable operation, etc.

Inactive Publication Date: 2014-07-23
STATE GRID CORP OF CHINA +2
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AI Technical Summary

Problems solved by technology

Ignoring the leakage current will increase the error between the calculated results and the actual results, and it is easy to misdiagnose the cable operation when performing fault diagnosis under the condition of high loop impedance

Method used

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  • On-line monitoring system for current and carrying capacity of cable sheath
  • On-line monitoring system for current and carrying capacity of cable sheath
  • On-line monitoring system for current and carrying capacity of cable sheath

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Embodiment approach

[0027] Refer to attached figure 1 , The cable line adopts the cross-connection mode of direct grounding at both ends, and the connection mode of the metal sheath is as follows: A1-B2, B1-C2, C1-A2; B3-C4, C3-A4, A3-B4. The induced current flowing in the metal sheath is as figure 2 as shown, respectively represent the induced currents in the three sheath loops, Respectively represent the current carrying capacity in the three-phase cable, Indicates the cable segment length, ,..., ,..., Respectively represent the respective induced voltage and impedance in the corresponding nine cable segments, representing the ground resistance. pass image 3 The sum of the induced currents in the three loops can be obtained as shown in Equation (1):

[0028]

[0029] The induced voltage in formula (1) can be calculated by formula (2):

[0030]

[0031] in Indicates the self-inductance coefficient of the three-phase cable, Indicates the mutual inductance coefficient be...

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Abstract

The invention relates to an on-line monitoring system for the current and carrying capacity of a cable sheath, belonging to the field of a power cable on-line monitoring technology. The technical scheme is as follows: firstly, setting a plurality of different measurement points, intersecting and interconnecting clamp current sensors sleeved on the inlet wire of an earth box under the condition that a cable electrically operates, and acquiring the sheath current signals; obtaining the cable capacity data by a clamp current sensor sleeved on a cable body; secondly, synchronously acquiring the sheath current signals and the capacity data through the clamp current sensor sleeved on the cable body; thirdly, uploading the acquired sheath current signals and the capacity data to an upper computer for theoretical calculation; and fourthly, comparing the sheath current signals acquired in real time and expected sheath current values under a non-fault condition, and simultaneously comparing the sheath current values of the different measuring points so as to position, early warn and reminder faults. According to the on-line monitoring system, the current which flows through a power cable metal sheath can be monitored on line, so that the reliable basis can be provided for the faults in the process of diagnosing the cable.

Description

technical field [0001] The invention relates to an on-line monitoring system for cable sheath current and ampacity, in particular to a method for synchronously measuring power cable sheath current and ampacity and simulating and calculating the expected value of sheath current at each measurement point under fault and non-fault states The invention belongs to the technical field of power cable on-line monitoring. Background technique [0002] When both ends of the medium and high voltage cables are grounded at the same time or through cross interconnection, a closed loop is formed between the cable sheath and the ground. The sum of the induced current generated by the induced voltage in this circuit and the leakage current generated in the cable insulation is called the sheath current. At present, in the calculation method of the cable sheath current in the background technology, the current induced by the induced voltage in the cable metal sheath is regarded as the sheath ...

Claims

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Application Information

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IPC IPC(8): G01R31/08G01R19/00G06F19/00
Inventor 袁燕岭周灏郝乾陈昕袁继军任建国杨志才甘景福孙超穆勇王玉坚肖寒韩丹刘轩明刘长亮
Owner STATE GRID CORP OF CHINA
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