CN113311284A - High-voltage cable sheath circulating current fault discrimination method based on fault characteristic curve - Google Patents
High-voltage cable sheath circulating current fault discrimination method based on fault characteristic curve Download PDFInfo
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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
- G01R31/08—Locating faults in cables, transmission lines, or networks
- G01R31/081—Locating faults in cables, transmission lines, or networks according to type of conductors
- G01R31/083—Locating faults in cables, transmission lines, or networks according to type of conductors in cables, e.g. underground
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- 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
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Abstract
The invention discloses a high-voltage cable sheath circulating current fault judging method based on a fault characteristic curve, which comprises the following steps of: step 1, establishing a two-dimensional coordinate system consisting of load current and cable sheath circulating current, calculating a fault characteristic curve between the load current and the cable sheath circulating current according to high-voltage cable operation parameters, and dividing fault areas according to the fault characteristic curve; step 2, collecting the load current and the cable sheath circulating current of the high-voltage power cable in real time, and calculating the collected load current and the collected cable sheath circulating current amplitude; and 3, judging whether a coordinate point formed by the cable load current and the sheath circulating current falls in a fault area divided by the fault characteristic curve or not, and further judging whether the high-voltage cable has a fault or not. The fault discrimination method can improve the speed of high-voltage cable fault recognition, has low requirements on hardware cache and resources, and is easy to integrate into a sheath circulating current monitoring device.
Description
Technical Field
The invention belongs to the technical field of high-voltage cable on-line monitoring, and particularly relates to a high-voltage cable sheath circulating current fault discrimination method based on a fault characteristic curve.
Background
With the wider and wider application of high-voltage cables in urban power grid construction, the demand for online monitoring of corresponding high-voltage cables is also increasing. The on-line monitoring of the grounding circulation of the cable sheath is one of the important means for on-line monitoring of the high-voltage cable, and has the functions of monitoring whether the high-voltage cable is in an abnormal operation state caused by aging, artificial damage, insulation breakdown and the like in the operation process, giving an early warning in advance, and preventing the occurrence of power failure accidents caused by further single-phase or multi-phase grounding short circuit faults.
At present, the on-line monitoring of the sheath circulating current of the high-voltage cable is mainly focused on a monitoring stage, and the judgment of the grounding circulating current of the cable is mainly carried out by the following two methods: 1) and uploading the circulating current monitoring data to a data center server for storage, and judging whether the cable is in a normal operation state or not by combining analysis software with database data. The discrimination method is based on a large amount of operation data for analysis, has high accuracy, but is complex and cannot monitor faults in real time to give early warning. 2) Fault diagnosis is carried out through an online monitoring device, generally, overrun judgment is adopted, and when circulating current exceeds a certain limit value, alarm information is sent out. The method is simple and has high real-time performance, but the induced voltage on the cable sheath is related to the load current, so that the magnitude of the circulating current is influenced, comprehensive fault diagnosis and analysis are lacked, and false alarm or false alarm is easy to occur.
In summary, the ground loop fault discrimination method needs to have both real-time performance and accuracy, and can only play a due role in engineering application if the theoretical scientificity and the practical feasibility of the discrimination method are guaranteed.
Disclosure of Invention
The invention aims to provide a high-voltage cable sheath circulating current fault judging method based on a fault characteristic curve, which can improve the speed of high-voltage cable fault identification, has low requirements on hardware cache and resources and is easy to integrate into a sheath circulating current monitoring device.
In order to achieve the above purpose, the solution of the invention is:
a high-voltage cable sheath circulating current fault discrimination method based on a fault characteristic curve comprises the following steps:
step 1, establishing a two-dimensional coordinate system consisting of load current and cable sheath circulating current, calculating a fault characteristic curve between the load current and the cable sheath circulating current according to high-voltage cable operation parameters, and dividing fault areas according to the fault characteristic curve;
step 2, collecting the load current and the cable sheath circulating current of the high-voltage power cable in real time, and calculating the collected load current and the collected cable sheath circulating current amplitude;
and 3, judging whether a coordinate point formed by the cable load current and the sheath circulating current falls in a fault area divided by the fault characteristic curve or not, and further judging whether the high-voltage cable has a fault or not.
In the two-dimensional coordinate system established in step 1, the X axis represents the load current, and the Y axis represents the sheath circulating current.
In the step 1, the fault area is an upper half area formed by a fault characteristic curve and a sheath circulating current coordinate axis.
In the step 1, the operation parameters of the high-voltage cable include the operation voltage of the cable, the capacitance current, the length of the cable section and the load current.
In step 1, the fault characteristic curve is a broken line or a curve having a specific functional relationship.
After the scheme is adopted, the two-dimensional coordinate system is established by adopting two electrical parameters of the load current and the sheath circulation, the fault characteristic curve is obtained through calculation, and the fault area is divided by taking the fault characteristic curve as a boundary, so that the fault is identified; under different operating conditions, the load current and the sheath circulating current can correspond to a certain coordinate point in a two-dimensional coordinate system, and whether the cable breaks down or not can be judged according to whether the coordinate point at the current moment falls into a fault area or not.
The key point of the invention is to determine a fault characteristic curve and divide a fault area. The induced voltage in the whole sheath loop is the vector sum of the induced voltages of the segmented cables, but in practice, even in a cross-connection grounding mode, the lengths of the three segments of cables cannot be completely equal, a certain induced voltage is generated, the induced voltage is related to the load current, and the impedance value in the loop is a fixed value, so that the functional relation between the sheath loop current and the load current in normal operation can be obtained. The functional relationship curve can be used as the boundary of the fault area, namely a fault characteristic curve. When the position of the coordinate point monitored in real time exceeds the characteristic curve, the cable can be judged to have a fault. Further, if the fault area can be divided more finely according to the specific fault type in the fault area, the fault type of the cable can be judged more accurately.
The fault area of the method can be calculated and determined in advance, so that the real-time fault discrimination calculation amount is not large, the method can be integrated in a cable sheath circulating current on-line monitoring device, and the method is easy to popularize and implement.
Drawings
FIG. 1 is a flow chart of a system implementing a fault discrimination method;
FIG. 2 is a diagram illustrating a fault characteristic curve and a fault region.
Detailed Description
The technical solution and the advantages of the present invention will be described in detail with reference to the accompanying drawings.
The invention provides a high-voltage cable sheath circulating current fault judging method based on a fault characteristic curve, which comprises the following steps of:
s1, establishing a two-dimensional coordinate system consisting of the load current and the sheath circulating current, wherein the load current is used as an X axis, and the sheath circulating current is used as a Y axis; calculating fault characteristic curve between the high-voltage cable and the cable according to the operation parameters (including cable operation voltage, capacitance current, cable segment length and load current) of the high-voltage cableDividing fault areas by using the characteristic curve; the fault characteristic curve can be composed of a broken line or a curve with a specific functional relationship; the fault area is characterized by a characteristic curve and a sheath circulating current coordinate axis IhThe upper half area is formed as follows: when the actually measured load current and sheath circulating current coordinate point is positioned in the fault area, the insulation of the cable can be judged to have a fault; conversely, when the coordinate point is positioned outside the fault area, the cable can be considered to run normally;
in general, the sheath current is induced by the capacitive current IcThe cable sheath induction current and the leakage current, wherein the capacitance current is related to the load voltage and the cable section length, and the cable is kept unchanged after operation; the induced current of the cable sheath is related to the length of the cable section and the induced voltage of the cable sheath, the induced voltage of the cable sheath is induced by the load current, and the values are different when the load current is different; the leakage current can be ignored under normal conditions, and even when a cable has a major fault and generates a large leakage current, the corresponding relay protection system can act, which does not belong to the consideration range of the invention. Under the known conditions of cable length, electric parameters, grounding mode of a metal sheath of the cable, operating voltage grade of the cable and the like, the functional relation between sheath circulating current and load current during normal operation of the cable can be used as a fault characteristic curve, and a fault area divided by taking the fault characteristic curve as a boundary can be determined.
S2, acquiring the load current and the cable sheath circulating current of the high-voltage power cable in real time through the on-site mounted on-line monitoring device for the cable sheath circulating current, and calculating the acquired load current and the amplitude of the cable sheath circulating current;
and S3, judging whether a coordinate point formed by the cable load current and the sheath circulating current falls in a fault area divided by the fault characteristic curve, and further judging whether the high-voltage cable has insulation faults caused by mechanical damage, aging, breakdown and the like.
The whole fault discrimination process is integrated in the cable sheath circulation on-line monitoring device, and on-line real-time fault discrimination can be realized.
In order to make the method for determining the circulating current fault of the cable sheath more clear, the cross-connection grounding method is taken as an example for detailed description. As shown in fig. 1, which is a flow chart of the determination process of the present invention, the ground loop fault determination process is implemented in a ground loop online monitoring device, when a cable is abnormal, a fault determination result is uploaded to a background monitoring system for alarming and displaying, and an operator can obtain the fault determination result at the first time and perform maintenance in time.
For the cross-interconnect grounding mode, the fault characteristic curves and boundaries are as follows:
wherein, IhFor sheath circulating current in normal operation, ILFor load current, IgThe load current value at the inflection point.
ICIs a capacitance current, ICJ ω CU, ω is power frequency angular frequency, and C is the equivalent capacitance of cable core to the sheath, and U is cable operating voltage. It can be seen that the capacitance current is only related to parameters such as the cable operation voltage level and the cable segment length, and when the cable operation voltage and the cable segment length are kept unchanged, the capacitance current is also kept unchanged.
And k is a braking coefficient and is related to the length of the segmented cable, the impedance distribution parameter of the cable sheath and the unbalance degree of the three-phase load current. The three-phase load current in the high-voltage cable generally has a small phase difference, so the parameters are fixed values, the coefficient k is constant, the characteristic curve is a straight line, and the numerical value of the specific coefficient k can be obtained through simulation calculation or according to experimental tests. In practical application, if specific parameters cannot be obtained, the braking coefficient can be not more than 0.1 according to industry experience.
IlmtThe maximum current allowed by the metal sheath of the cable is determined according to the cable operation regulations of each region, the value is generally not more than 100A, and when the sheath current change value exceeds the value, an alarm must be given.
According to the above conditions, the fault characteristic curve and the fault region division diagram of the present embodiment can be obtained as shown in fig. 2.
And then, judging the positions of sheath circulating current and load current in a two-dimensional coordinate system under the current operation condition in real time through the real-time load current and sheath circulating current values acquired by the cable sheath circulating current on-line monitoring device, monitoring the position change condition, judging that the current cable is abnormal when the position point falls into a fault area and the time exceeds a set fixed value, and sending alarm information by the on-line monitoring device.
The above embodiments are only for illustrating the technical idea of the present invention, and the protection scope of the present invention is not limited thereby, and any modifications made on the basis of the technical scheme according to the technical idea of the present invention fall within the protection scope of the present invention.
Claims (5)
1. A high-voltage cable sheath circulating current fault discrimination method based on a fault characteristic curve is characterized by comprising the following steps:
step 1, establishing a two-dimensional coordinate system consisting of load current and cable sheath circulating current, calculating a fault characteristic curve between the load current and the cable sheath circulating current according to high-voltage cable operation parameters, and dividing fault areas according to the fault characteristic curve;
step 2, collecting the load current and the cable sheath circulating current of the high-voltage power cable in real time, and calculating the collected load current and the collected cable sheath circulating current amplitude;
and 3, judging whether a coordinate point formed by the cable load current and the sheath circulating current falls in a fault area divided by the fault characteristic curve or not, and further judging whether the high-voltage cable has a fault or not.
2. The method for discriminating a circulating current fault of a high voltage cable according to claim 1, wherein: in the two-dimensional coordinate system established in the step 1, the X axis represents the load current, and the Y axis represents the sheath circulating current.
3. The method for discriminating a circulating current fault of a high voltage cable based on a fault characteristic curve as claimed in claim 2, wherein: in the step 1, the fault area is an upper half area formed by a fault characteristic curve and a sheath circulating current coordinate axis.
4. The method for discriminating a circulating current fault of a high voltage cable according to claim 1, wherein: in the step 1, the high-voltage cable parameters include cable operating voltage, capacitance current, cable segment length and load current.
5. The method for discriminating a circulating current fault of a high voltage cable according to claim 1, wherein: in the step 1, the fault characteristic curve is a broken line or a curve with a specific functional relationship.
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Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102866289A (en) * | 2012-09-05 | 2013-01-09 | 山东康威通信技术股份有限公司 | Power cable sheath grounding current fault analysis method |
| CN105004907A (en) * | 2015-04-20 | 2015-10-28 | 江苏省电力公司常州供电公司 | Power cable intersect cross connection grounding system grounding current monitoring and evaluating method |
| CN109375028A (en) * | 2018-08-27 | 2019-02-22 | 许继集团有限公司 | A method and device for identifying disconnection of high-voltage power cable sheath current sensor |
| CN109444661A (en) * | 2018-11-21 | 2019-03-08 | 山东康威通信技术股份有限公司 | A kind of mixed power transmission line shorted to earth On-line Fault monitoring system and localization method |
| CN110763957A (en) * | 2018-07-24 | 2020-02-07 | 长沙理工大学 | A new method for online monitoring of medium voltage cable insulation faults |
| CN112067946A (en) * | 2020-09-17 | 2020-12-11 | 郑州中聖电子科技有限公司 | Cable sheath fault monitoring device and method for broadcasting synchronous signals by multiple Rogowski coils |
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2020
- 2020-02-26 CN CN202010118944.4A patent/CN113311284B/en active Active
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102866289A (en) * | 2012-09-05 | 2013-01-09 | 山东康威通信技术股份有限公司 | Power cable sheath grounding current fault analysis method |
| CN105004907A (en) * | 2015-04-20 | 2015-10-28 | 江苏省电力公司常州供电公司 | Power cable intersect cross connection grounding system grounding current monitoring and evaluating method |
| CN110763957A (en) * | 2018-07-24 | 2020-02-07 | 长沙理工大学 | A new method for online monitoring of medium voltage cable insulation faults |
| CN109375028A (en) * | 2018-08-27 | 2019-02-22 | 许继集团有限公司 | A method and device for identifying disconnection of high-voltage power cable sheath current sensor |
| CN109444661A (en) * | 2018-11-21 | 2019-03-08 | 山东康威通信技术股份有限公司 | A kind of mixed power transmission line shorted to earth On-line Fault monitoring system and localization method |
| CN112067946A (en) * | 2020-09-17 | 2020-12-11 | 郑州中聖电子科技有限公司 | Cable sheath fault monitoring device and method for broadcasting synchronous signals by multiple Rogowski coils |
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