CN115825534A - Phase calibration cable sheath layer circulating current monitoring method and system - Google Patents

Phase calibration cable sheath layer circulating current monitoring method and system Download PDF

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CN115825534A
CN115825534A CN202310155065.2A CN202310155065A CN115825534A CN 115825534 A CN115825534 A CN 115825534A CN 202310155065 A CN202310155065 A CN 202310155065A CN 115825534 A CN115825534 A CN 115825534A
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current
phase
cable
sheath layer
grounding
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CN115825534B (en
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曹京荥
陈杰
孙蓉
杨景刚
谭笑
李陈莹
张伟
周立
胡丽斌
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Electric Power Research Institute of State Grid Jiangsu Electric Power Co Ltd
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Electric Power Research Institute of State Grid Jiangsu Electric Power Co Ltd
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Abstract

A phase-calibrated cable sheath layer circulating current monitoring method is characterized by comprising the following steps: step 1, current collection is carried out on a three-phase high-voltage cable body by adopting a first mutual inductor so as to obtain first current; step 2, adopting a second mutual inductor to collect current of the coaxial cable when a sheath layer lead of the three-phase high-voltage cable is connected into the cross interconnection grounding box so as to obtain second current; step 3, calculating and obtaining three-phase sheath layer current and minimum core current based on the first current and the second current; phase calibration is carried out between the three-phase grounding circulating current and the minimum core current; and 4, judging the defects of the cable grounding system by taking the maximum grounding circular current, the circular current three-phase deviation proportion and the circular current core proportion as standards. The invention fully overcomes the influence of phase deviation, and calibrates the amplitude and the phase angle of the current to be analyzed, thereby ensuring the accuracy of the defect judgment result.

Description

Phase calibration cable sheath layer circulating current monitoring method and system
Technical Field
The invention relates to the field of power systems, in particular to a method and a system for monitoring circulating current of a cable sheath layer through phase calibration.
Background
The high-voltage cable grounding system has a complex operating environment, can effectively find whether the cable cross-connection grounding system has the defects of multipoint grounding, overhigh circulating current and the like through circulating current detection, and can eliminate the defects in time so as to avoid local overheating and accelerated aging of a line. Conventional techniques typically employ a current transformer to perform the circulating current test from the location of the coaxial cable.
For example, in the background art document CN113640574A, an online monitoring device and a monitoring method for ground circulation of a tunnel cable sheath are disclosed, wherein a first current transformer is installed at a ground of a high-voltage cable sheath layer ground box or a cross-connection box, each signal input channel of a current acquisition device acquires the ground circulation and the cable core current of the current sheath layer, analyzes and calculates the running state of a cable, and sends out circulation warning information based on that the digital ground circulation of the cable sheath layer is greater than the ground circulation threshold of the cable sheath layer.
However, in the prior art, the main component of the current collected by the current transformer is generally only roughly determined according to the position of the current transformer, and the minor component is completely ignored in the analysis calculation. Therefore, the components of the superposed current collected by the current transformer are not accurately analyzed, so that the test process is not accurate enough, and the problem of misjudgment of the test conclusion is easy to occur.
Furthermore, because the coaxial cable contains a two-core or multi-core structure, the superposed current collected by the current transformer has the problem of superposition of current vectors from a plurality of different sources. The maximum amplitude of the superposed current obtained by testing of the current transformer cannot be accurately used for analyzing the sheath layer circulation of the high-voltage cable. If the phase angle deviation of the superposed current is simply ignored, interference is brought to the test, and the problems of inaccurate test and misjudgment of conclusion exist.
In view of the foregoing, a method and a system for monitoring a circulating current of a cable sheath layer with phase calibration are needed.
Disclosure of Invention
In order to solve the defects in the prior art, the invention provides a method and a system for monitoring the circulating current of a cable sheath layer through phase calibration.
The invention adopts the following technical scheme.
The invention relates to a phase calibration method for monitoring circulating current of a cable sheath layer, which comprises the following steps: step 1, current collection is carried out on a three-phase high-voltage cable body by adopting a first mutual inductor so as to obtain first current; step 2, adopting a second mutual inductor to collect current of the coaxial cable when a sheath layer lead of the three-phase high-voltage cable is connected into the cross interconnection grounding box so as to obtain second current; step 3, calculating and obtaining three-phase sheath layer current and minimum core current based on the first current and the second current; phase calibration is carried out between the three-phase grounding circulation current and the minimum core current; and 4, judging the defects of the cable grounding system by taking the maximum grounding circular current, the circular current three-phase deviation proportion and the circular current core proportion as standards.
Preferably, the number of the first mutual inductors is three, and the first mutual inductors are respectively arranged on the three-phase high-voltage cable body so as to respectively collect superposed currents of core currents and sheath layer currents on the ABC three phases
Figure SMS_1
、
Figure SMS_2
And
Figure SMS_3
(ii) a The number of the second transformers is three, and the second transformers are respectively arranged on the three-phase coaxial cables to respectively collect the cross circulation currents on the ABC three phases
Figure SMS_4
、
Figure SMS_5
And
Figure SMS_6
。
preferably, the current collection is based on sampling interval collection of instantaneous amplitude of superimposed current or cross-circulating current.
Preferably, the grounding current of the three-phase sheath layer and the current of the three-phase wire core are calculated based on the amplitude and the phase angle of the three-phase superposed current and the amplitude and the phase angle of the three-phase cross circulating current.
Preferably, ABC three-phase sheath current
Figure SMS_7
、
Figure SMS_8
And
Figure SMS_9
satisfy the requirement of
Figure SMS_10
Wherein, the matrix
Figure SMS_11
Is a current direction matrix in a cross-connect, and has
Figure SMS_12
，
Figure SMS_13
For the current to be shunted by the grounding lead, and has
Figure SMS_14
。
Preferably, the amplitude and phase angle of the current of the three-phase sheath layer are respectively
Figure SMS_15
Wherein, the first and the second end of the pipe are connected with each other,
Figure SMS_16
is any one of three phases of ABC,
Figure SMS_17
and
Figure SMS_18
respectively according to ABC order
Figure SMS_19
The front and back adjacent phases of the phase are,
Figure SMS_20
time of flight
Figure SMS_21
Time of flight
Figure SMS_22
，
Figure SMS_23
Time of flight
Figure SMS_24
；
Figure SMS_25
、
Figure SMS_26
Respectively, the modes of the superposed currents of the corresponding phases,
Figure SMS_27
、
Figure SMS_28
respectively the phase angle of the superposed current of the corresponding phase,
Figure SMS_29
and
Figure SMS_30
respectively, the mode and phase angle of the ground lead branch current.
Preferably, the three-phase core current of the high-voltage cable is solved according to the calculated three-phase sheath layer grounding current.
Preferably, the maximum ground circulating current is
Figure SMS_31
When the maximum grounding circulating current is larger than a first threshold value, judging that the cable grounding system has defects; the circulation three-phase deviation ratio is
Figure SMS_32
When the circulation three-phase deviation proportion is larger than a second threshold value, judging that the cable grounding system has defects; the ratio of the circulating line core is
Figure SMS_33
Wherein, in the step (A),
Figure SMS_34
and when the ratio of the circulating line core is larger than a third threshold value, judging that the cable grounding system has defects.
Preferably, the first threshold is 200A, the second threshold is 2, and the third threshold is 50%.
In a second aspect, the present invention relates to a phase-calibrated cable sheath layer circulating current monitoring system, which is used for implementing the steps of the method in the first aspect of the present invention.
Compared with the prior art, the method and the system for monitoring the circulating current of the cable sheath layer through phase calibration respectively collect the currents of the high-voltage cable body and the coaxial cable connected with the sheath layer through the first mutual inductor and the second mutual inductor, and realize the judgment of the defects of the grounding system through the phase calibration. The invention fully overcomes the influence of phase deviation, and calibrates the amplitude and the phase angle of the current to be analyzed, thereby ensuring the accuracy of the defect judgment result.
The beneficial effects of the invention also include:
1. according to the invention, after the first mutual inductor and the second mutual inductor are deployed at proper positions, each component of the current acquired by the mutual inductors is accurately analyzed, so that the current state of the actual test can be fully restored in the process of analyzing and processing the acquired current data. The problem that partial fault and defect conditions are difficult to eliminate for a long time because the secondary current component is ignored is prevented.
2. In the invention, on the basis of analyzing each component of the current, phase deviation existing between three phases and between different current components is further considered. Meanwhile, the phase angle of one current is used as a reference phase angle, the calculation of the phase angles of other currents is realized, and the actual values of the alternating current components are restored through the calculation, so that the accuracy of the judgment basis in defect judgment is ensured.
3. The invention adopts a software layer calculation mode to realize conversion operation and solution of the direct measurement result of the mutual inductor, and realizes more accurate output of the conversion operation result after considering the phase deviation of each superposed component in the measurement current.
Drawings
FIG. 1 is a schematic diagram illustrating steps of a method for monitoring circulating current of a phase-calibrated cable sheath layer according to the present invention;
fig. 2 is a schematic structural diagram of a phase-calibrated cable sheath layer circulating current monitoring system according to the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. The described embodiments of the invention are only some of the embodiments of the invention and not all of them. All other embodiments of the invention that are not described in the present application and are obtained by the embodiments of the invention described in the present application without creative efforts should be included in the protection scope of the present application by those of ordinary skill in the art.
Fig. 1 is a schematic step diagram of a phase-calibrated cable sheath layer circulating current monitoring method according to the present invention. As shown in fig. 1, a first aspect of the present invention relates to a phase-calibrated cable sheath layer circulating current monitoring method, which includes steps 1 to 4.
Step 1, current collection is carried out on a three-phase high-voltage cable body by adopting a first mutual inductor so as to obtain first current.
Fig. 2 is a schematic structural diagram of a phase-calibrated cable sheath layer circulating current monitoring system according to the present invention. As shown in FIG. 2, the invention adopts different transformers respectively arranged at different positions in the system to collect the current condition of the cable.
First, the first transformer may be disposed on the high voltage cable body, and the measurement of the total current on the high voltage cable body is achieved by surrounding the single-phase high voltage cable body.
In the prior art, such measurement would typically approximate the measurement result to the core current of the high voltage cable, because the core current of the high voltage cable, as a good electrical conductor, has a larger flow of current than the current of the sheath layer on the outside of the core of the high voltage cable. Therefore, in the prior art, the current of the sheath layer can be neglected. In the invention, in order to judge the defects more accurately, the collected first current is regarded as the superposition of the core current of each phase line and the current of the sheath layer.
And 2, adopting a second mutual inductor to collect current of the coaxial cable when the sheath layer lead of the three-phase high-voltage cable is connected into the cross interconnection grounding box so as to obtain second current.
It is understood that the second transformer of the present invention may be disposed on the coaxial cable to which the sheath layer is connected. The specific connection method can be referred to the method in the prior art.
The second current obtained here may be understood as a superposition of a plurality of currents in the coaxial cable, and specifically, for example, a coaxial cable to which a sheath lead of an a-phase high-voltage cable is connected may include a cross current from the C-phase and a cross current flowing into the B-phase. Therefore, when three-phase sheath layer circulation has phase deviation, the actual magnitude of the single-phase sheath layer current cannot be accurately judged by adopting a simple superposition algorithm. This causes a problem that the criterion is liable to fail in the defect judgment.
The present invention improves upon the above-described problems.
Preferably, the number of the first transformers is three, and the first transformers are respectively arranged on the three-phase high-voltage cable body to respectively collect superposed currents of core currents and sheath currents on three phases
Figure SMS_35
、
Figure SMS_36
And
Figure SMS_37
(ii) a The number of the second transformers is three, and the second transformers are respectively arranged on the three-phase coaxial cables to respectively collect the cross circulation currents on the three phases
Figure SMS_38
、
Figure SMS_39
And
Figure SMS_40
。
as described above, the present invention collects a plurality of superimposed currents through the first and second transformers. It should be noted that, since the present invention can be designed as a real-time online monitoring system, the superposed current and the cross-loop current collected here can be instantaneous values at different sampling times.
And 3, calculating and obtaining three-phase sheath layer current and minimum core current based on the first current and the second current. Phase calibration is carried out between the three-phase grounding circulation current and the minimum core current.
Preferably, the current collection is based on sampling interval collection of instantaneous amplitude of superimposed current or cross-circulating current.
The instantaneous amplitude here cannot be considered as a simple superposition of the various current components, since there is a phase deviation of indeterminate magnitude between the various current components. Therefore, in order to actually recover the current criterion to be used from the various current components, the amplitude and the phase angle of each current component are further solved in the invention.
Preferably, the grounding current of the three-phase sheath layer and the current of the three-phase wire core are calculated based on the amplitude and the phase angle of the three-phase superposed current and the amplitude and the phase angle of the three-phase cross circulating current.
The specific calculation method is as follows:
three-phase sheath current
Figure SMS_41
、
Figure SMS_42
And
Figure SMS_43
satisfy the requirement of
Figure SMS_44
Wherein, the matrix
Figure SMS_45
Is a current direction matrix in a cross-connect, and has
Figure SMS_46
，
Figure SMS_47
For the current to be shunted by the grounding lead, and has
Figure SMS_48
。
And solving the equation, and obtaining the amplitude and the phase angle of the grounding current of the three-phase sheath layer according to the superposed current and the cross circulation.
Specifically, since the currents are all vector values, the present invention derives the above formula as the relationship between the two-dimensional vector phase angle and the amplitude value in consideration of the characteristics of the three-phase currents
Figure SMS_49
And
Figure SMS_50
in the context of the present formula, the expression,
Figure SMS_51
、
Figure SMS_52
and
Figure SMS_53
the phase angles of the currents of the three-phase sheath layers are respectively solved by the formula, so that the values of the currents of the three-phase sheath layers can be known.
Preferably, the amplitude and phase angle of the current of the three-phase sheath layer are respectively
Figure SMS_54
Wherein the content of the first and second substances,
Figure SMS_55
is any one of three phases of ABC,
Figure SMS_56
and
Figure SMS_57
respectively according to ABC order
Figure SMS_58
The adjacent phases of the phases are in front of and behind,
Figure SMS_59
time of flight
Figure SMS_60
，
Figure SMS_61
Time of flight
Figure SMS_62
，
Figure SMS_63
Time-piece
Figure SMS_64
；
Figure SMS_65
、
Figure SMS_66
Respectively, the modes of the superposed currents of the corresponding phases,
Figure SMS_67
、
Figure SMS_68
respectively the phase angle of the superposed current of the corresponding phase,
Figure SMS_69
and
Figure SMS_70
respectively, the mode and phase angle of the ground lead branch current. Furthermore, after the grounding current of the three-phase sheath layer is obtained, the method can further calculate the accurate current of the three-phase wire core, namely the current of the sheath layer is planed from the high-voltage cableThe current thereafter.
Because the sheath layer current and the three-phase core current have the same phase relation, the current amplitude can be calculated according to the detection value of the first mutual inductor, and the three-phase core current is finally obtained.
And 4, judging the defects of the cable grounding system by taking the maximum grounding circular current, the circular current three-phase deviation proportion and the circular current core proportion as standards.
After the value of the current is obtained in the calculation step 3, the system defect can be accurately judged according to a certain judgment standard.
Preferably, the maximum ground circulating current is
Figure SMS_71
When the maximum grounding circulation is larger than a first threshold, judging that the cable grounding system has defects; the circulation three-phase deviation ratio is
Figure SMS_72
When the circulation three-phase deviation ratio is larger than a second threshold value, judging that the cable grounding system has defects; the ratio of the circulating line core is
Figure SMS_73
Wherein, in the step (A),
Figure SMS_74
and when the ratio of the circulating line core is larger than a third threshold value, judging that the cable grounding system has defects.
In the invention, different defect types of the system are judged by respectively selecting a plurality of different modes. For example, when the maximum ground circulating current is too large, it can be considered that there is a case where the sheath layer of the single-phase cable in the system is seriously damaged. If the proportion of the circulating three-phase deviation is too large, the fault such as abnormal damage or aging of part of the sheath layer can exist. If the proportion of the circulating line core is higher, the problem of abnormal grounding of the system can occur.
Preferably, the first threshold value is 200A, the second threshold value is 2, and the third threshold value is 50%.
The invention can set the specific value of the criterion of different judging modes according to experience, and can modify the value of the criterion according to the condition of the cross interconnection grounding box.
In an embodiment of the present invention, a test is performed on a section of high voltage cable having a cross-connection grounding box, and test results of a first transformer and a second transformer are shown in table 1.
Table 1 high-voltage cable cross-connection grounding test data table
Figure SMS_75
Because ABC phases have a symmetrical relationship, the current level on the cable with the same axis C is not tested in this embodiment. The test result can be directly obtained by an oscilloscope and other instruments. In a second aspect, the present invention relates to a phase-calibrated cable sheath layer circulating current monitoring system, which is used for implementing the steps of the method in the first aspect of the present invention.
It will be appreciated that the output ports of the first and second sensors in the present invention may be connected to a multi-port oscilloscope apparatus or similar waveform sampling and processing device to carry out the steps of the method described in the first aspect of the present invention.
It is understood that the waveform sampling and processing device includes hardware structures and/or software modules for executing the functions of the method provided by the embodiments of the present application. Those of skill in the art will readily appreciate that the present application is capable of hardware or a combination of hardware and computer software implementing the various illustrative algorithm steps described in connection with the embodiments disclosed herein. Whether a function is performed as hardware or computer software drives hardware depends upon the particular application and design constraints imposed on the solution. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present application.
In the embodiment of the present application, the waveform sampling and processing apparatus may be divided into functional modules according to the above method, for example, each functional module may be divided corresponding to each function, or two or more functions may be integrated into one processing module. The integrated module can be realized in a hardware mode, and can also be realized in a software functional module mode. It should be noted that, in the embodiment of the present application, the division of the module is schematic, and is only one logic function division, and there may be another division manner in actual implementation.
The device comprises at least one processor, a bus system and at least one communication interface. The processor may be a central processing unit, field programmable gate array, application specific integrated circuit, or other hardware replacement. The memory may be a read-only memory, other types of static storage devices that may store static information and instructions, a random access memory, or other types of dynamic storage devices that may store information and instructions, and so forth. The memory may be self-contained and coupled to the processor via a bus. The memory may also be integrated with the processor. The hard disk may be a mechanical disk or a solid state disk, and the like, which is not limited in the embodiment of the present invention. And an interface card in the hard disk module communicates with the hard disk. The storage node communicates with the interface card of the hard disk module, thereby accessing the hard disk in the hard disk module.
In the above embodiments, the present invention may be implemented in whole or in part by software, hardware, or any combination thereof. When implemented using a software program, may be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer instructions. The procedures or functions described in accordance with the embodiments of the present application are all or partially generated upon loading and execution of computer program instructions on a computer.
Compared with the prior art, the method and the system for monitoring the circulating current of the cable sheath layer through phase calibration respectively collect the currents of the high-voltage cable body and the coaxial cable connected with the sheath layer through the first mutual inductor and the second mutual inductor, and realize the judgment of the defects of the grounding system through the phase calibration. The invention fully overcomes the influence of phase deviation, and calibrates the amplitude and the phase angle of the current to be analyzed, thereby ensuring the accuracy of the defect judgment result.
Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention and not for limiting the same, and although the present invention is described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: modifications and equivalents may be made to the embodiments of the invention without departing from the spirit and scope of the invention, which is to be covered by the claims.

Claims (10)

1. A phase-calibrated cable sheath layer circulating current monitoring method is characterized by comprising the following steps:
step 1, current collection is carried out on a three-phase high-voltage cable body by adopting a first mutual inductor so as to obtain first current;
step 2, adopting a second mutual inductor to collect current of the coaxial cable when a sheath layer lead of the three-phase high-voltage cable is connected into the cross interconnection grounding box so as to obtain second current;
step 3, calculating and obtaining three-phase sheath layer current and minimum core current based on the first current and the second current;
phase calibration is carried out between the three-phase grounding circulating current and the minimum core current;
and 4, judging the defects of the cable grounding system by taking the maximum grounding circular current, the circular current three-phase deviation proportion and the circular current core proportion as standards.
2. A method for monitoring a circulating current of a phase-calibrated cable sheath according to claim 1, wherein:
the number of the first mutual inductors is three, and the first mutual inductors are respectively arranged on the three-phase high-voltage cable body so as to respectively collect superposed currents of core currents and sheath layer currents on the ABC three phases
Figure QLYQS_1
、
Figure QLYQS_2
And
Figure QLYQS_3
；
the number of the second transformers is three, the second transformers are respectively arranged on the three-phase coaxial cables and are used for respectively collecting the crossed circulation currents on the ABC three phases
Figure QLYQS_4
、
Figure QLYQS_5
And
Figure QLYQS_6
。
3. a method for monitoring a circulating current of a phase-calibrated cable sheath according to claim 2, wherein:
the current collection is based on sampling interval collection superposition current or instantaneous amplitude of cross circulation.
4. A method for monitoring a circulating current of a phase-calibrated cable sheath according to claim 3, wherein:
and calculating the grounding current of the three-phase sheath layer and the current of the three-phase core based on the amplitude and the phase angle of the three-phase superposed current and the amplitude and the phase angle of the three-phase crossed circulating current.
5. A method for monitoring circulating current of a phase-calibrated cable sheath according to claim 4, wherein:
the ABC three-phase sheath layer current
Figure QLYQS_7
、
Figure QLYQS_8
And
Figure QLYQS_9
satisfy the requirement of
Figure QLYQS_10
Wherein, the matrix
Figure QLYQS_11
Is a current direction matrix in a cross-connect, and has
Figure QLYQS_12
，
Figure QLYQS_13
For the current to be branched to the ground lead, and has
Figure QLYQS_14
。
6. A method for monitoring a phase-calibrated cable sheath circulating current according to claim 5, wherein:
the amplitude and the phase angle of the three-phase sheath layer current are respectively
Figure QLYQS_15
Wherein the content of the first and second substances,
Figure QLYQS_16
is any one of three phases of ABC,
Figure QLYQS_17
and
Figure QLYQS_18
are respectively asThe adjacent phases before and after the i phase according to the ABC sequence,
Figure QLYQS_19
time of flight
Figure QLYQS_20
，
Figure QLYQS_21
Time-piece
Figure QLYQS_22
，
Figure QLYQS_23
Time of flight
Figure QLYQS_24
；
Figure QLYQS_25
、
Figure QLYQS_26
Respectively, the modes of the superposed currents of the corresponding phases,
Figure QLYQS_27
、
Figure QLYQS_28
respectively the phase angle of the superposed current of the corresponding phase,
Figure QLYQS_29
and
Figure QLYQS_30
respectively, the mode and phase angle of the ground lead branch current.
7. A method for monitoring a circulating current of a phase-calibrated cable sheath according to claim 6, wherein:
and solving the three-phase core current of the high-voltage cable according to the calculated three-phase sheath layer grounding current.
8. A method for monitoring a circulating current of a phase-calibrated cable sheath according to claim 7, wherein: the maximum ground circulating current is
Figure QLYQS_31
When the maximum grounding circulating current is larger than a first threshold value, judging that the cable grounding system has defects;
the circulation three-phase deviation proportion is
Figure QLYQS_32
When the circulation three-phase deviation proportion is larger than a second threshold value, judging that the cable grounding system has defects;
the ratio of the circulating line core is
Figure QLYQS_33
Wherein, in the step (A),
Figure QLYQS_34
and when the proportion of the circulating line core is larger than a third threshold value, judging that the cable grounding system has defects.
9. A method for monitoring a phase-calibrated cable sheath circulating current according to claim 8, wherein:
the first threshold is 200A, the second threshold is 2, and the third threshold is 50%.
10. The utility model provides a phase calibration's cable sheath layer circulation current monitored control system which characterized in that:
the system is adapted to implement the steps of the method of any one of claims 1-9.
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