CN-121995159-A - Cable insulation aging monitoring method for AC/DC mixed signals

Abstract

The invention provides a cable insulation aging monitoring method of an alternating current-direct current mixed signal aiming at the change process of a transient state and a steady state of cable insulation aging, which is based on Hall alternating current and TMR (Tunnel Magneto Resistance) direct current combined on-line monitoring, realizes the comprehensive detection function of chronic insulation aging defects caused by ground short circuit faults and long-term operation, and verifies the effectiveness and the practical feasibility of the method by utilizing experiments and simulation under a complex topological structure. The invention has great practical value and can solve the problem of nonlinear operation and maintenance of the 10kV cable.

Inventors

• YANG BO
• TANG FEI
• ZUO WEINING
• MA PENGTAO
• ZHANG LIZHEN
• WANG JIAN
• YANG XIN

Assignees

• 国网甘肃省电力公司庆阳供电公司

Dates

Publication Date

20260508

Application Date

20241104

Claims (3)

1. 1. A cable insulation aging monitoring method for an alternating current/direct current mixed signal is characterized in that an alternating current cable signal adopts a Hall monitoring mode, a non-contact measurement mode is adopted, the problem that a distribution cable is difficult to install is solved, and a high-magnetic material is selected as a coil, so that magnetism gathering and linearity measurement performances are greatly improved.
2. 2. The method for monitoring insulation aging of the cable of the alternating current-direct current mixed signal according to claim 1, wherein the direct current selects a TMR leakage current detection mode, and insulation capacitance can be effectively monitored by measuring insulation leakage current. The output effect linearity is high, and the open loop type installation is convenient.
3. 3. The method for monitoring the insulation aging of the cable of the alternating current-direct current mixed signal according to claim 1 is characterized in that the design mode is monitored by adopting an alternating current-direct current integrated sensing device, the design concepts of intensification, low power consumption, miniaturization and the like are adopted, a sampling input and two independent signal output integrated sensor forms are formed, the monitoring of transient state and steady state fault current can be simultaneously realized, and the operation state of the cable can be comprehensively known in real time.

Description

Cable insulation aging monitoring method for AC/DC mixed signals Technical Field The application belongs to the field of cable fault monitoring, and particularly relates to a cable insulation aging monitoring method for an alternating current-direct current mixed signal. Background The underground cable has a severe working environment, is extremely easy to be insulated and aged under the action of multiple stresses such as electricity, heat, machinery and the like, and finally causes line faults to jeopardize the reliable operation of the power distribution network. The proportion of cable-related faults in medium voltage distribution networks is up to 59%, with approximately half of the faults caused by the cable body. At present, most researches focus on timely cutting off after cable faults occur to avoid occurrence of cascading faults, but regional faults are still difficult to avoid, and the protection mode is more passive. If the high-precision sensing of the state of the cable can be realized in the operation process, the cable can be overhauled and replaced when the serious aging phenomenon occurs, so that the operation and maintenance of the system are changed from 'passive' to 'active', the occurrence of faults is avoided fundamentally, and the reliability of the system is improved. The state sensing of the power distribution network cable mainly comprises the following two aspects of 1) judging whether the cable is aged or severely failed or not through an online monitoring method, and 2) positioning local aging so as to realize targeted overhaul. Serious faults such as short circuit, breakage, overvoltage, overload and the like can be easily detected by the abrupt large pulse of alternating current. The change of leakage current electrical parameters in the long-term operation aging process of cable insulation is weak, and great difficulty exists in realizing online and accurate perception of the leakage current electrical parameters. Therefore, the invention can monitor larger alternating current fault current and weak leakage current caused by insulation aging. Disclosure of Invention The application aims to solve the problem of on-line monitoring of insulation ageing defects of an AC/DC hybrid power distribution cable. In order to achieve the above purpose, the application provides a cable insulation aging monitoring method for an alternating current-direct current mixed signal. In order to realize insulation aging monitoring of the AC/DC cable, reasonable on-line monitoring means are respectively provided. The method based on the on-line measurement of the electrical parameters mainly measures the dielectric loss tangent or leakage current of the cable insulation. Common dielectric loss angle online measurement methods comprise a zero crossing comparison method, a grounding box lead current measurement method, a double-end electrical quantity measurement method, a system transient response analysis method and the like. The essence of the method is to establish a relation between the measurable electric quantity of the cable system and the dielectric loss angle, and to reversely push the dielectric loss angle by measuring the relevant electric quantity. However, the change of the dielectric loss angle tends to be smaller during the insulation aging process, and the change of the relevant electrical quantity caused by the change is weaker, so that the monitoring precision is lower. A small measurement error may cause a great error in the estimated dielectric loss tangent value, making the related method difficult to use in a practical system. In contrast, the leakage current of the insulation of the measurement cable can directly reflect the insulation state without complex calculation, so that the monitoring precision can be improved. Compared with the prior art, the invention has the advantages that: According to the 10kV cable aging comprehensive condition analysis, the cable insulation aging characteristic can be represented as transient and steady state changes, the transient aging is generally caused by abrupt changes of load current (such as fault ground short circuit and the like), abrupt current amplitude changes can be generated in cable alternating current signals, and the cable can be judged to have a transient ground fault. And secondly, the cable is gradually aged in the long-term operation process due to factors such as the cable structure, tunnel environmental influence, load change and the like, and the aging process is a process accumulation quantity and shows the characteristic of gradual change. The common mode direct current signal source is injected, weak direct current signals can be detected by utilizing TMR electromagnetic detection leakage current, and therefore steady-state aging process parameters of the cable are judged. The two AC/DC monitoring parameters are used as criteria of the cable insulation aging process, so that the cable insulation operation state can