CN112924824A - Cable insulation state monitoring method based on carbonization channel evolution process - Google Patents

Cable insulation state monitoring method based on carbonization channel evolution process Download PDF

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CN112924824A
CN112924824A CN202110120167.1A CN202110120167A CN112924824A CN 112924824 A CN112924824 A CN 112924824A CN 202110120167 A CN202110120167 A CN 202110120167A CN 112924824 A CN112924824 A CN 112924824A
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cable
decay parameter
decay
fault
monitoring
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CN112924824B (en
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张文海
瞿科
肖先勇
楚恬歆
张姝
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Sichuan University
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/12—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing
    • G01R31/1227—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing of components, parts or materials
    • G01R31/1263—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing of components, parts or materials of solid or fluid materials, e.g. insulation films, bulk material; of semiconductors or LV electronic components or parts; of cable, line or wire insulation
    • G01R31/1272—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing of components, parts or materials of solid or fluid materials, e.g. insulation films, bulk material; of semiconductors or LV electronic components or parts; of cable, line or wire insulation of cable, line or wire insulation, e.g. using partial discharge measurements
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y04—INFORMATION OR COMMUNICATION TECHNOLOGIES HAVING AN IMPACT ON OTHER TECHNOLOGY AREAS
    • Y04S—SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS
    • Y04S10/00—Systems supporting electrical power generation, transmission or distribution
    • Y04S10/50—Systems or methods supporting the power network operation or management, involving a certain degree of interaction with the load-side end user applications
    • Y04S10/52—Outage or fault management, e.g. fault detection or location

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  • General Physics & Mathematics (AREA)
  • Testing Of Short-Circuits, Discontinuities, Leakage, Or Incorrect Line Connections (AREA)

Abstract

The invention discloses a cable insulation state monitoring method based on a carbonization channel evolution process, which comprises the following steps: s1, sampling a fault current signal of the cable by using a fault recorder or an electric energy quality device to obtain a fault current sequence; s2, obtaining a plurality of decay parameters according to the fault current sequence by adopting a decay parameter extraction algorithm; s3, using a decay parameter with the frequency corresponding to 1500-3000 Hz as a decay parameter of the last monitored cable state, reflecting the cable insulation equivalent resistance based on the decay parameter, and monitoring the cable insulation state; the invention solves the problems that the prior monitoring device has high investment cost in the early stage, has higher requirement on the sampling frequency of signals and is easily influenced by the environment.

Description

Cable insulation state monitoring method based on carbonization channel evolution process
Technical Field
The invention relates to the field of power line control, in particular to a cable insulation state monitoring method based on a carbonization channel evolution process.
Background
The cable has the advantages of high reliability, strong durability, small occupied area and the like, and is widely applied to urban power distribution networks. As the cable's insulation performance gradually degrades over its operating time, domestic and foreign research and related data measurements suggest that transient, intermittent and self-clearing early failures occur before permanent failures occur in the cable. During early faults, the cable may generate an arc whose ablative action accelerates the deterioration of the cable insulation state.
At present, methods for monitoring the insulation state of a cable are mainly divided into two types of methods based on electrical quantity and non-electrical quantity, and mainly comprise the following steps: partial discharge, dielectric loss, polarization current, temperature, etc. The monitoring means need to be provided with a special monitoring device, and the early investment cost is high; and the requirement on the sampling frequency of the signal is high, and the signal is easily influenced by the environment.
Disclosure of Invention
Aiming at the defects in the prior art, the cable insulation state monitoring method based on the carbonization channel evolution process solves the problems that the prior monitoring device is high in investment cost in the early stage, high in requirement on the sampling frequency of signals and easy to be influenced by the environment.
In order to achieve the purpose of the invention, the invention adopts the technical scheme that: a cable insulation state monitoring method based on a carbonization channel evolution process comprises the following steps:
s1, sampling a fault current signal of the cable by using a fault recorder or an electric energy quality device to obtain a fault current sequence;
s2, obtaining a plurality of decay parameters according to the fault current sequence by adopting a decay parameter extraction algorithm;
s3, using the decay parameter with the frequency corresponding to 1500-3000 Hz as the decay parameter of the last monitored cable state, reflecting the cable insulation equivalent resistance based on the decay parameter, and monitoring the cable insulation state.
Further, the decay parameter extraction algorithm in step S2 is specifically:
solving decay parameters by least squares method so that
Figure BDA0002921745810000021
Minimum, where ε is the cost functionN is the length of the fault current sequence, i (N) is the data of the nth sampling point in the fault current sequence, AkFor the k-th amplitude component, δkIs the k-th decay parameter of the sample,
Figure BDA0002921745810000022
is the k-th phase component, fkIs the kth frequency component, j is an imaginary number, and Δ t is the sampling period.
Further, the decay parameter of the monitored cable state in step S2 is calculated by the following formula:
Figure BDA0002921745810000023
wherein, delta is decay parameter of monitoring cable state, L is sum of line mode inductance of cable and zero mode inductance of fault line, sbThe constant coefficient of the arc resistance of the cable when the arc current is larger than the arc current threshold value is shown, R is the sum of the line mode resistance of the cable and the zero mode resistance of a fault line, and R is the carbonization channel resistance of the cable.
In conclusion, the beneficial effects of the invention are as follows: the state of the cable is analyzed through the waveform disturbance data, so that not only can high-grade application of a large amount of power quality monitoring data be realized, but also the cable insulation state can be analyzed off-line or on-line in practical engineering, and the serious consequences of unplanned power failure caused by explosion and fire of the cable can be avoided.
Drawings
FIG. 1 is a flow chart of a cable insulation status monitoring method based on a carbonization channel evolution process;
FIG. 2 is a circuit model diagram;
FIG. 3 is a graph showing the variation trend of the verification decay parameter of the power distribution network along with the resistance of the carbonization channel.
Detailed Description
The following description of the embodiments of the present invention is provided to facilitate the understanding of the present invention by those skilled in the art, but it should be understood that the present invention is not limited to the scope of the embodiments, and it will be apparent to those skilled in the art that various changes may be made without departing from the spirit and scope of the invention as defined and defined in the appended claims, and all matters produced by the invention using the inventive concept are protected.
As shown in fig. 1, a cable insulation state monitoring method based on a carbonization channel evolution process includes the following steps:
s1, sampling a fault current signal of the cable by using a fault recorder or an electric energy quality device to obtain a fault current sequence;
s2, obtaining a plurality of decay parameters according to the fault current sequence by adopting a decay parameter extraction algorithm;
the decay parameter extraction algorithm in the step S2 specifically includes:
solving decay parameters by least squares method so that
Figure BDA0002921745810000031
Minimum, where ε is the cost function, N is the fault current sequence length, i (N) is the data at the nth sample point in the fault current sequence, AkFor the k-th amplitude component, δkIs the k-th decay parameter of the sample,
Figure BDA0002921745810000032
is the k-th phase component, fkIs the kth frequency component, j is an imaginary number, and Δ t is the sampling period.
The decay parameter of the monitored cable state in step S2 is calculated by the formula:
Figure BDA0002921745810000033
wherein, delta is decay parameter of monitoring cable state, L is sum of line mode inductance of cable and zero mode inductance of fault line, sbThe constant coefficient of the arc resistance of the cable when the arc current is larger than the arc current threshold value is shown, R is the sum of the line mode resistance of the cable and the zero mode resistance of a fault line, and R is the carbonization channel resistance of the cable.
S3, using the decay parameter with the frequency corresponding to 1500-3000 Hz as the decay parameter of the last monitored cable state, reflecting the cable insulation equivalent resistance based on the decay parameter, and monitoring the cable insulation state.
The certification process of the scheme of the application: the cable fault changes the electrical characteristics of the cable, and for the fault on the cable, a circuit model is constructed, as shown in fig. 2, and according to the circuit model and the electrical characteristics of each element, a differential equation can be established:
Figure BDA0002921745810000041
Figure BDA0002921745810000042
wherein L is the sum of the line mode inductance of the cable and the zero mode inductance of the fault line, uCIs the voltage of a capacitance to ground, sbIs the constant coefficient of the arc resistance of the cable when the arc current is larger than the arc current threshold value, R is the carbonization channel resistance of the cable, C is the capacitance to ground, R is the sum of the line mode resistance of the cable and the zero mode resistance of a fault line, u is the sum of the line mode resistance of the cable and the zero mode resistance of the fault linefFor a failed virtual power supply, ithCritical value for arc current segmentation, iarcIs the arc current, sbArc resistance R for cablearcConstant coefficient when the arc current is larger than the critical value of the arc current, b is a proportionality coefficient, uarcIs the arc voltage.
Solving this differential equation yields:
Figure BDA0002921745810000043
where i (t) is fault current, ωfIs a high frequency component frequency, omega is a power frequency, UmTo the fault point voltage amplitude before fault, theta0For the phase of the voltage at the fault point before the fault, B1And B2Is constant and is related to the initial state of the fault;
from the above differential equation, it is possible to obtain
Figure BDA0002921745810000044
Therefore, the i (t) includes a delta term, and the delta term is in a linear relationship with r, and the i (t) is discretized to obtain:
Figure BDA0002921745810000051
transforming cos, sin trigonometric functions to exponential form, which can be equivalently replaced by:
Figure BDA0002921745810000052
thus, δ can be estimated from the i (n) sequence by a learning algorithmkThe value is obtained.
The trend of the decay parameters along with the resistance of the carbonization channel is verified by establishing the distribution network shown in fig. 3, and table 1 corresponds to the decay parameters extracted under different carbonization channels.
TABLE 1
Carbonized channel resistance r/omega Decay parameter delta
50 967
100 976
150 1045
200 1105
400 1239
600 1302
800 1338

Claims (3)

1. A cable insulation state monitoring method based on a carbonization channel evolution process is characterized by comprising the following steps:
s1, sampling a fault current signal of the cable by using a fault recorder or an electric energy quality device to obtain a fault current sequence;
s2, obtaining a plurality of decay parameters according to the fault current sequence by adopting a decay parameter extraction algorithm;
s3, using the decay parameter with the frequency corresponding to 1500-3000 Hz as the decay parameter of the last monitored cable state, reflecting the cable insulation equivalent resistance based on the decay parameter, and monitoring the cable insulation state.
2. The cable insulation state monitoring method based on the carbonization channel evolution process as claimed in claim 1, wherein the decay parameter extraction algorithm in step S2 is specifically:
solving decay parameters by least squares method so that
Figure FDA0002921745800000011
Minimum, where ε is the cost function, N is the fault current sequence length, i (N) is the data at the nth sample point in the fault current sequence, AkFor the k-th amplitude component, δkIs the k-th decay parameter of the sample,
Figure FDA0002921745800000012
is the k-th phase component, fkIs the kth frequency component, j is an imaginary number, and Δ t is the sampling period.
3. The method for monitoring the insulation state of the cable based on the evolution process of the carbonization channel as claimed in claim 1, wherein the decay parameter for monitoring the state of the cable in the step S2 is calculated by the following formula:
Figure FDA0002921745800000013
wherein, delta is decay parameter of monitoring cable state, L is sum of line mode inductance of cable and zero mode inductance of fault line, sbThe constant coefficient of the arc resistance of the cable when the arc current is larger than the arc current threshold value is shown, R is the sum of the line mode resistance of the cable and the zero mode resistance of a fault line, and R is the carbonization channel resistance of the cable.
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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114578186A (en) * 2022-02-28 2022-06-03 四川大学 Cable early fault severity evaluation method based on volt-ampere characteristic analysis

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CN104764966A (en) * 2015-04-20 2015-07-08 河北工业大学 Test simulation device for simulating alternating current arc faults
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CN107765150A (en) * 2017-10-18 2018-03-06 福州大学 Intelligent electric arc fault simulation system and operating method
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JPH04328473A (en) * 1991-04-30 1992-11-17 Tokyo Electric Power Co Inc:The Testing apparatus for withstand voltage of power cable
US6128169A (en) * 1997-12-19 2000-10-03 Leviton Manufacturing Co., Inc. Arc fault detector with circuit interrupter and early arc fault detection
CN104764966A (en) * 2015-04-20 2015-07-08 河北工业大学 Test simulation device for simulating alternating current arc faults
CN105425127A (en) * 2015-12-16 2016-03-23 国家电网公司 Analytical calculation method for creepage trace on surface of organic material insulator
CN107765150A (en) * 2017-10-18 2018-03-06 福州大学 Intelligent electric arc fault simulation system and operating method
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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114578186A (en) * 2022-02-28 2022-06-03 四川大学 Cable early fault severity evaluation method based on volt-ampere characteristic analysis
CN114578186B (en) * 2022-02-28 2023-03-31 四川大学 Cable early fault severity evaluation method based on volt-ampere characteristic analysis

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