CN115453256A - Defect diagnosis and positioning method and device for cable cross-connection grounding system - Google Patents
Defect diagnosis and positioning method and device for cable cross-connection grounding system Download PDFInfo
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- CN115453256A CN115453256A CN202210816081.7A CN202210816081A CN115453256A CN 115453256 A CN115453256 A CN 115453256A CN 202210816081 A CN202210816081 A CN 202210816081A CN 115453256 A CN115453256 A CN 115453256A
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
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Abstract
The invention discloses a defect diagnosis and positioning method and a device of a cable cross-connection grounding system, wherein the method comprises the following steps: constructing a goat horn reverse-connection defect library; respectively carrying out synchronous acquisition on three-phase load current and three-phase grounding circulating current; three-phase grounding circulation conversion is carried out to obtain six groups of grounding circulation data; determining the correct 'goat' direction of the cross interconnection unit; acquiring the ratio of the absolute value of the difference value of the first-end and tail-end grounding circulation currents to the larger value of the first-end and tail-end grounding circulation currents; when the ratio exceeds a preset value, performing outer protection layer damage diagnosis on the current cable section; and when the ratio is not over, calling the defect library to perform circulation characteristic comparison, and outputting the reason and the position of the reversed defect of the horn switch. The method provided by the invention can be used for diagnosing whether the cable cross-connection grounding system has the defect of reverse connection of the claw and the defect of damage of the outer sheath under the state of electrification and without opening the cross-connection grounding box, so that the influence of the damage of the outer sheath on the diagnosis of the defect of reverse connection of the claw is eliminated, and the diagnosis accuracy of the defect of reverse connection of the claw is improved.
Description
Technical Field
The invention relates to the technical field of power cables, in particular to a method and a device for diagnosing and positioning defects of a cable cross-connection grounding system in an electrified way.
Background
With the acceleration of urban development process, overhead lines are gradually replaced by cables, and long-distance cable lines are more and more. At present, single-core cables are mostly adopted for 110kV and above-ground cables, and metal sheath cross interconnection grounding modes are mostly adopted for long-distance single-core transmission cables.
The cross-connection grounding system has the possibility of system defects during installation, maintenance or operation, such as a 'claw' reverse connection defect, a cable outer protective layer damage defect, a cross-connection transposition failure defect, a cross-connection box water inlet defect and a cross-connection box inner protector breakdown defect caused by inconsistent connection modes of two insulating joint grounding columns in the same cross-connection unit and inner and outer cores of a coaxial cable.
The defects of cross interconnection transposition failure, water inlet of a cross interconnection box and breakdown of a protector in the cross interconnection box can be found by opening the cross interconnection box in a charged state to check and test.
For the "dog-ear" anti-fault, there are two grounded posts on the copper shell of an insulated joint in the cross-connect unit, here called M-post near the inspection path and N-post near the wall. In a normal cross interconnection unit, six insulation joints are all connected with the outer core of the coaxial grounding cable through M columns or all connected with the outer core of the coaxial grounding cable through N columns, if the connection is inconsistent, normal offset of loop induction voltage cannot be realized, and the defect of reverse connection is commonly called as 'claw'. For the defects, the traditional diagnosis method is to perform conduction tests of inner and outer cores of the coaxial grounding cable after power failure.
For the defect of the damaged outer sheath of the cable, the damaged outer sheath can lead to multipoint grounding of the metal sheath, and the original grounding mode is disturbed, so that the line fault can be caused. For the defects, the traditional diagnosis mode is to perform an outer sheath direct current withstand voltage test after power failure to judge whether the defects exist, and then find out damaged points through an outer sheath fault accurate fixed point test in a power failure state.
Therefore, at present, power failure diagnosis needs to be adopted for all the defects, on one hand, power failure needs to be carried out for a long time, a large amount of manpower and material resources are wasted, on the other hand, due to the limitation of the power failure time, part of cable lines have to operate with defects, and further circulation loss is increased, current-carrying capacity is reduced, insulation aging is caused, and even a main insulation fault is caused.
Disclosure of Invention
To overcome the above-mentioned deficiencies of the prior art, the present invention provides a method and apparatus for diagnosing and positioning defects of a cross-connect grounding system for cables, which solves at least one of the above-mentioned problems.
According to an aspect of the present specification, there is provided a method for diagnosing and locating defects of a cable cross-connect grounding system, including:
constructing a 'horn-shaped' reverse connection defect library, wherein the defect library comprises a topological structure and circulation characteristics corresponding to each defect;
synchronously collecting three-phase load current and three-phase grounding circulation current at six measuring positions in the cross interconnection unit respectively;
converting three-phase grounding circulation currents obtained at other five measuring positions according to the three-phase load current obtained at the first measuring position to obtain six groups of grounding circulation data to be compared;
judging the correct 'goat' direction of the cross-connection unit according to the grounding circulation of the M column and the N column of the insulation joint connected with the two cross-connection boxes respectively;
acquiring the ratio of the absolute value of the difference value of the head-end grounding circulation of each cable segment in the cross interconnection unit to the larger value of the head-end grounding circulation;
when the ratio exceeds a preset value, performing outer protection layer damage diagnosis on the current cable section;
and when the ratio does not exceed the preset value, calling a defect library to perform circulation characteristic comparison, and outputting the reason and the position of the reversed defect of the horn switch.
According to the technical scheme, whether the cable cross-connection grounding system has the defect of reverse connection of the 'goat' horn and the defect of damage of the outer sheath is diagnosed in the charged state without opening the cross-connection grounding box, the accurate determination of the current at the head end and the tail end of the cable section is realized through the direction determination of the 'goat' horn, and the defect matching is carried out after the live diagnosis and the repair of the damage of the outer sheath is judged through the comparison of the current at the head end and the tail end, so that the influence of the damage of the outer sheath on the diagnosis of the reverse connection defect of the 'goat' horn is eliminated, and the diagnosis accuracy of the reverse connection defect of the 'goat' horn is improved.
According to the technical scheme, when the defect that the 'claw' is reversely connected is diagnosed, the defect library is called to compare the circulation characteristics, the position of the reverse connection of the 'claw' of the insulating joint is pre-judged, the defect reason is judged, the defect position is positioned, and the conversion from power failure diagnosis to live diagnosis is completed.
According to the technical scheme, under the premise that the cross-connection grounding box is not opened, the diagnosis of the reversed connection defect of the 'horn' and the damage defect of the outer protective layer is realized, the defect position can be positioned, targeted power failure maintenance is realized after power failure, the power failure time is shortened, the defect removal difficulty is reduced, and the power supply reliability is improved.
Furthermore, there are two connection modes of the copper bars of the cross interconnection box of the cross interconnection unit, each copper bar connection mode corresponds to 21 defect conditions, and the defects in 42 and the topological structures and the circulation characteristics corresponding to each defect are prestored in the defect library.
As a further technical scheme, after the outer protective layer is diagnosed to be damaged, the damaged position of the outer protective layer is positioned and electrified to repair; then calling a defect library to compare circulation characteristics, and outputting the reason and the position of the reversed defect of the horn.
Because the diagnosis precision of the reversed connection defect of the goat's horn can be influenced by the damage of the outer protective layer, whether the damage diagnosis and repair of the outer protective layer of the current cable section are needed or not is judged by comparing the currents at the head end and the tail end of the cable section, so that the influence of the possible damage of the outer protective layer on the diagnosis precision of the reversed connection defect of the goat's horn is reduced.
As a further technical scheme, if the damage of the outer protective layer is not diagnosed, a defect library is called to carry out circulation characteristic comparison, and the reason and the position of the defect of the reversed connection of the horn are output.
As a further technical solution, the method further comprises:
for each insulating joint, acquiring the absolute value of the difference between the M column current of the small-sequence cross interconnection box and the N column current of the large-sequence cross interconnection box as a first current difference, and acquiring the absolute value of the difference between the N column current of the small-sequence cross interconnection box and the M column current of the large-sequence cross interconnection box as a second current difference;
comparing the first current difference with the second current difference, and taking the connection mode corresponding to the smaller one of the first current difference and the second current difference as a preliminary judgment result of the direction of the claw of the corresponding insulated joint;
after the 'goat' directions of the six insulation joints are preliminarily judged, if the 'goat' directions of four or more insulation joints are consistent, the 'goat' directions of the four or more insulation joints are taken as the 'goat' directions of all the insulation joints in the current cross interconnection unit.
Specifically, if the M-pillars connect the small-order side grounding boxes, the a of the small-order cross-connect box is not considered in the case that there may be a "cavel" reverse connection N 、B N And C N The current values should be respectively cross-connected with A of the large serial number cross-connection box M 、B M 、C M The current values being close, i.e. A of the cross-bar N A of cross-connection box with large serial number M Is less than A of the small-order cross-connection box M A of cross-connection box with large serial number N The absolute value of the difference of (a).
As a further technical scheme, when a cross interconnection unit is found to have an abnormal circulating current defect, six groups of three-phase load currents and three-phase grounding circulating currents of the unit are collected on site, wherein the grounding circulating currents at two direct grounding boxes are measured on a three-phase grounding cable, and the grounding circulating currents at two cross interconnection boxes are respectively measured at two 'goat' corners of an insulation connector connected with the two cross interconnection boxes respectively.
Specifically, each direct grounding box measures a group of grounding circulation respectively, M columns of the insulation joints connected with each group of cross interconnection boxes measure a group of grounding circulation, N columns measure a group of grounding circulation, and finally six groups of grounding circulation data are obtained.
As a further technical scheme, after the 'claw' direction is determined, the grounding circulation corresponding to the head and the tail of each cable section in the cross interconnection unit is obtained, the ratio of the absolute value of the difference value of the grounding circulation of the head and the tail of each cable section to the larger value of the grounding circulation of the head and the tail is respectively obtained, and the ratio is compared with a preset value for judgment.
Further, the preset value may be 0-5%. If the ratio is within the range, the defect library can be directly called for circulation characteristic comparison. If the ratio exceeds the range, the damaged defect of the outer protective layer needs to be positioned and repaired first, and then the influence of the damaged defect of the outer protective layer on the diagnosis precision of the reversed defect of the goat horn is avoided.
As a further technical solution, the outer sheath breakage diagnosis further includes:
installing a plurality of current sensors at equal intervals on a cable section with an outer protection layer damaged, and synchronously acquiring current data acquired by the current sensors, wherein the data comprises current magnitude and phase;
comparing current data between adjacent current sensors, and if the vector difference of the current data of two adjacent current sensors is larger than a preset current value, mounting the current sensors on the cable sections limited by the two adjacent current sensors at equal intervals again;
and repeating the steps of synchronously acquiring the current data acquired by the current sensors and comparing the current data between the adjacent current sensors until the distance of the cable sections limited by the two adjacent current sensors with the vector difference of the current data larger than the preset current value is smaller than the preset distance, and manually determining the damage point of the outer protective layer within the preset distance.
As a further technical scheme, five to eight current sensors for positioning the damage points of the outer protective layer are arranged; the preset current value is set to be 0A-1A; the preset distance is set to be 2-3 m.
According to an aspect of the present specification, there is provided a defect diagnosing and locating apparatus for a cable cross-connection grounding system, including: the three clamp-shaped ammeters are used for collecting three-phase grounding circulation; three load ammeters are used for collecting three-phase load current; the synchronous timing module is used for sending a synchronous signal to the clamp ammeter and the load ammeter; the wireless transmission module is used for transmitting the three-phase load current and the three-phase grounding circulating current to the handheld terminal;
the handheld terminal is provided with: the handheld terminal is configured with: the input module is used for displaying the field acquisition current data and converting the grounding circulation; the 'claw' direction determining module is used for determining the correct 'claw' direction of the cross interconnection unit according to the grounding circulation currents of the M column and the N column of the insulation joint connected with the two cross interconnection boxes respectively; the current comparison module is used for acquiring the ratio of the absolute value of the difference value of the head-end grounding circulation of each cable section in the cross interconnection unit to the larger value of the head-end grounding circulation, and comparing the ratio with a preset value; the defect comparison module is used for comparing and matching the measured grounding circulation with circulation characteristics in a defect library; the outer protective layer damage diagnosis module is used for carrying out outer protective layer damage diagnosis on the current cable section when the ratio exceeds a preset value; and the output module is used for outputting the reason and the position of the reversed defect of the 'horn' connection.
As a further technical solution, the outer sheath breakage diagnosis module includes: the current sensors are used for synchronously acquiring current data of the cable line; the comparison module is used for comparing current data between the adjacent current sensors and judging whether the vector difference of the current data of the two adjacent current sensors is larger than a preset current value or not; and the data synchronization module is used for sending a synchronization signal to all the current sensors.
Furthermore, the plurality of current sensors are flexible current sensors, the comparison module and the data synchronization module are configured on a controller where one of the current sensors is located, and the controller is connected with the handheld terminal.
Compared with the prior art, the invention has the beneficial effects that:
(1) The method diagnoses whether the cable cross-connection grounding system has the defect of reverse connection of the cleat and the defect of damage of the outer sheath in a charged state without opening the cross-connection grounding box, realizes accurate determination of the current of the head end and the tail end of the cable section by determining the correct direction of the cleat of the cross-connection unit, judges whether to perform failure diagnosis of the outer sheath and then performs defect matching by comparing the current of the head end and the tail end, thereby eliminating the influence of the damage of the outer sheath on the diagnosis of the reverse connection defect of the cleat and improving the accuracy of the diagnosis of the reverse connection defect of the cleat.
(2) When the 'goat' horn reverse connection defect is diagnosed, the invention pre-judges the reverse connection position of the insulating joint 'goat' by calling the defect library to carry out circulation characteristic comparison, realizes the judgment of defect reasons and the positioning of the defect position, and finishes the conversion from power failure diagnosis to live diagnosis.
(3) According to the invention, on the premise of not opening the cross interconnection grounding box, the diagnosis of the reversed connection defect of the cleat and the damage defect of the outer protective layer is realized, and the defect position can be positioned, so that targeted power failure maintenance is realized after power failure, the power failure time is shortened, the defect removal difficulty is reduced, and the power supply reliability is improved.
Drawings
Fig. 1 is a schematic diagram of a cross-connect cell according to an embodiment of the present invention.
FIG. 2 is a flowchart of a defect diagnosis and location method according to an embodiment of the invention.
Fig. 3 (a) - (b) illustrate two connection modes of copper bars in the cross-connect box according to the embodiment of the invention.
FIG. 4 is J according to an embodiment of the present invention 2A And (4) an equivalent circuit diagram when the circuit is reversed.
FIG. 5 is J according to an embodiment of the present invention 1A And J 1B Schematic diagram when reverse.
FIG. 6 shows J according to an embodiment of the present invention 1A And J 1B And (4) an equivalent circuit diagram when the circuit is reversed.
Fig. 7 (a) - (c) are graphs of three loop induced voltage phasors according to an embodiment of the present invention.
FIG. 8 is a drawing of J in accordance with an embodiment of the present invention 1A And J 2A Schematic diagram when reverse.
FIG. 9 is a drawing of J according to an embodiment of the present invention 1A And J 2A And (4) an equivalent circuit diagram when the circuit is reversed.
FIG. 10 is a drawing of J according to an embodiment of the present invention 1A And J 2B Schematic diagram when reverse.
FIG. 11 shows a J according to an embodiment of the present invention 1A And J 2B And (5) connecting the equivalent circuit diagram in the reverse direction.
FIG. 12 is J according to an embodiment of the present invention 1A And J 2C Schematic diagram when reverse.
FIG. 13 is J according to an embodiment of the present invention 1A And J 2C And (5) connecting the equivalent circuit diagram in the reverse direction.
FIG. 14 shows an embodiment of the invention for J 2A Reverse case programming schematic.
FIG. 15 is a schematic diagram of the outer sheath breakage diagnosis positioning according to the embodiment of the invention.
Detailed Description
The technical solutions of the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings, and it is to be understood that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without any inventive step, are within the scope of the present invention.
According to one aspect of the present disclosure, a method for diagnosing and positioning defects of a cable cross-connection grounding system is provided, so as to diagnose whether a "cavel" connection reversal defect and an outer sheath breakage defect exist in the cable cross-connection grounding system in a state of being electrified and not opening a cross-connection grounding box, eliminate an influence of the outer sheath breakage on the diagnosis of the "cavel" connection reversal defect, and improve the diagnosis accuracy of the "cavel" connection reversal defect.
As shown in fig. 1, in one cross-connection unit, two cross-connection boxes are connected to six insulated connectors through six coaxial ground cables, respectively. Three insulated joints connected with the 2# cross interconnection box are respectively numbered J according to the phase 1A 、J 1B And J 1C And three insulation joints connected with the 3# cross interconnection box are respectively numbered J according to the phase 2A 、J 2B And J 2C . For convenience of observation, the inner core and the outer core of the coaxial grounding cable are separately drawn in fig. 1, the inner core is the wire core of the coaxial grounding cable, and the outer core is the copper wire shielding layer of the coaxial grounding cable.
Two grounding columns are arranged on a copper shell of one insulating joint, wherein the grounding column close to the inspection channel is called an M column, and the grounding column close to the wall is called an N column. In a normal cross-connect unit, the six insulated contacts are either all M-posts connected to the outer core of the coaxial ground cable or all N-posts connected to the outer core of the coaxial ground cable.
As shown in fig. 2, the method of the present invention comprises:
The copper bar connection modes of the cross interconnection box of the cross interconnection unit are two, each copper bar connection mode corresponds to 21 defect conditions, and the defects in the 42 and the topological structures and the circulation characteristics corresponding to the defects are prestored in the defect library.
The defect library covers the case that 12 kinds of 1 insulating joint 'goat' are connected reversely and 30 kinds of 2 insulating joint 'goat' are connected reversely simultaneously, and covers all common 'goat' reverse defect types.
The defect library comprises 42 subprograms, each subprogram corresponds to a defect condition, and the characteristics which the 6 groups of loop data should have under the defect condition are described by using a programming language and summarized according to the characteristic that the currents of the series circuits are equal everywhere and the loop relations of different loops analyzed by the actual topological structure of the cross-interconnection grounding system under the defect condition. The method comprises the steps of establishing a topological structure and loop circulation relation library of 42 defect conditions, judging which collected circulation value is in accordance with the topological structure and loop circulation relation of which condition, judging which condition causes the defect, finally displaying the defect reason and position on an output unit, and providing a schematic diagram of a defect cross interconnection unit.
The defect library is established according to the following steps:
the analysis is carried out under the assumed ideal condition, and the ideal condition comprises that the whole line of the line is laid in a delta shape, the lengths of three cross interconnection sections in the cross interconnection units are equal, the load current of three phase line cores is balanced, and the like. In addition, there are two ways for connecting copper bars of the cross-connect box, as shown in fig. 3 (a) - (b), a classification study is first conducted on the condition that the "cavel" is reversely connected in the second arrangement way.
(1) One "cavel" is connected reversely
J 2A The equivalent circuit in the case of reverse connection is shown in fig. 4:
U Ai 、U Bi 、U Ci (i =1,2, 3) inducing a voltage (V), Z for each of the metal sheaths of the cross-connect sections s 、R e Respectively the self-impedance of the metal protective layer and the earth leakage resistance (omega), R 1 And R 2 The grounding resistances (omega) of the 1# and 2# direct grounding boxes are respectively.
In the ideal case, and U Ai 、U Bi And U Ci Equal size, U Bi Phase U Ai Lags behind by 120 DEG, while U Ci Phase ratio U Bi With a lag of 120. Is provided with a U A ＝U A1 ＝U A2 ＝U A3 ，U B ＝U B1 ＝U B2 ＝U B3 ，U C ＝U C1 ＝U C2 ＝U C3 。
The conclusion is that the cross-connect sheetThe element is divided into three loops, I 1 、I 2 And I 3 Currents of three loops, I 1 ＝0， I 3 ＝-2I 2 I.e. the first loop current is 0, the third loop current is twice as large as the second loop current. Considering that it is impossible to achieve the ideal situation in reality, J 2A In the reverse defect, the first loop circulation is normal, and the third loop circulation is about 2 times larger than that of the second loop circulation. The measured values of the cases in the existing literature really meet the characteristics, and the scientificity of realizing the defect electrification diagnosis by using the method is proved.
The conditions that other 5 joints are singly reversely connected by the horn are respectively analyzed, and the circulation characteristic and J are found 2A The reverse is similar: in three loops of the cross interconnection unit, the loop current of one loop is normal, and the loop current of the other two loops is 2 times of the size.
(2) Two sheep horns are connected reversely
The two cases of opposite connection of the sheep horn are divided into three categories: two 'cavels' connected with the same cross interconnection box are reversely connected, two 'cavels' in the same phase are reversely connected, and two 'cavels' in different phases are reversely connected with different grounding boxes.
(2.1) two 'horns' connected by the same cross-connection box are connected reversely
The class of defects comprises six cases, J respectively 1A And J 1B Simultaneously reverse connection, J 1A And J 1C Simultaneously reverse connection, J 1B And J 1C Simultaneously reverse connection and J 2A And J 2B Simultaneously reverse connection, J 2A And J 2C Are simultaneously connected inversely and J 2B And J 2C And simultaneously reverse connection. Below with J 1A And J 1B The analysis is performed in the case of reverse connection.
A schematic diagram of the cross-connect cell in this case is shown in fig. 5.
The cross-connect unit is divided into three loops: a first circuit A1-C1, a second circuit B1-A2-B3, and a third circuit B2-C3-A3-C2. The equivalent circuit is shown in fig. 6:
first loop ground loop:
second loop ground circulating current:
third loop ground loop:
the three-loop induced voltage phasor diagram is shown in fig. 7.
From phasor analysis it can be derived:
due to R 1 +R 2 +R e Ratio Z S Much larger, so the second loop current is the smallest of the three loop currents.
Considering the actual situation, it is concluded that in this case the cross-connect element is divided into three loops, the second loop current is the smallest and the first loop current is about 2 times that of the third loop.
To J 1A And J 1C Reverse connection, J 1B And J 1C Reverse connection, J 2A And J 2B Reverse connection, J 2A And J 2C Reverse and J 2B And J 2C Similar analysis is carried out on the condition of reverse connection, and the circulation characteristic is found to be similar to J 1A And J 1B Reverse connectionSimilarly: the cross interconnection unit is divided into three loops, and the loop current size of the two loops with larger loop current presents a 2-time relationship.
(2.2) two opposite horns of the same phase
This type of defect comprises three cases, J respectively 1A And J 2A Simultaneously reverse connection, J 1B And J 2B Simultaneously reverse connection, J 1C And J 2C And simultaneously reverse. Below with J 1A And J 2A The analysis is performed in the case of simultaneous reverse.
A schematic diagram of the cross-interconnect cell in this case is shown in fig. 8.
The cross-connect unit is divided into three loops: a first loop A1-B1, a second loop C1-B2-A2-C2-B3, and a third loop A3-C3. The equivalent circuit diagram in this case is shown in fig. 9:
the following can be obtained by combining the circuit principle with phasor analysis:
first loop ground connection circulation:
second loop ground circulating current:
third loop ground loop:
by comparison, the first loop current in the three loops is the minimum.
Considering the actual situation, the conclusion is that in this case, the cross-connected unit is divided into three loops, the first loop has the smallest current, and the second loop and the third loop have basically the same current.
Are respectively paired with J 1B And J 2B Are simultaneously connected inversely and J 1C And J 2C In the case of simultaneous reversalSimilar analysis shows that the circulation characteristics are similar to J 1A And J 1B At the same time, the connection is reverse similar: the cross interconnection unit is divided into three loops, and the two loops with larger loop current are basically equal in size.
(2.3) different cross-connecting boxes and two 'sheep-horns' of different phases are connected reversely
The class of defects comprises six cases, J respectively 1A And J 2B Simultaneously reverse connection, J 1A And J 2C Simultaneously reverse connection, J 1B And J 2A Simultaneously reverse connection and J 1B And J 2C Simultaneously reverse connection, J 1C And J 2A Are simultaneously connected inversely and J 1C And J 2B And simultaneously reverse connection. The six cases can be divided into two types according to the phase sequence of two phases connected reversely at the 2# and 3# cross-connection boxes, and the positive sequence type comprises J 1A And J 2B Simultaneously reverse connection, J 1B And J 2C Are simultaneously connected inversely and J 1C And J 2A Three types of simultaneous reverse connection, negative sequence type including J 1A And J 2C Simultaneously reverse connection, J 1B And J 2A Are simultaneously connected inversely and J 1C And J 2B And connecting the three types at the same time.
(2.3.1) Positive sequence class
With J 1A And J 2B The analysis is performed in the case of reverse connection.
A schematic diagram of the cross-connect cell in this case is shown in fig. 10.
The cross-connect unit is divided into four loops: a first loop A1-C1, a second loop B1-C2-A3, a third loop A2-B2, and a fourth loop B3-C3. The equivalent circuit diagram in this case is shown in fig. 11:
first loop ground connection circulation:
second loop ground circulating current:
third loop ground loop:
fourth loop ground circulating current:
considering the practical situation, the conclusion is that the cross-connected unit is divided into four loops in the situation, the current of the second loop is normal, and the current of the first loop, the second loop and the third loop are basically equal in magnitude.
Are respectively paired with J 1B And J 2C Are simultaneously connected inversely and J 1C And J 2A Similar analysis is carried out on the condition of simultaneous reverse connection, and the circulation characteristic is found to be J 1A And J 2B At the same time, the reverse connection is similar: the cross interconnection unit is divided into four loops, wherein the loop current of one loop is normal, and the loop current of the other three loops is basically equal in size.
(2.3.2) negative sequence class
With J 1A And J 2C The analysis is performed in the case of simultaneous reverse.
A schematic diagram of the cross-interconnect cell in this case is shown in fig. 12.
The cross-connect unit is divided into three loops: a first loop A1-C1, a second loop B1-C2-B2-A2-B3, and a third loop A3-C3. The equivalent circuit diagram in this case is shown in fig. 13:
first loop ground loop:
second loop ground circulating current:
third loop ground loop:
in consideration of practical situations, the conclusion is that in the situation, the cross interconnection unit is divided into four loops, the current of the second loop is normal, and the current of the first loop and the current of the third loop are basically equal in magnitude.
Are respectively paired with J 1B And J 2A Are simultaneously connected inversely and J 1C And J 2B Similar analysis is carried out on the condition of simultaneous reverse connection, and the circulation characteristic is found to be J 1A And J 2C At the same time, the connection is reverse similar: the cross interconnection unit is divided into three loops, wherein one loop has normal circulation, and the circulation sizes of the other two loops are basically equal.
The same idea is adopted to research the reverse connection defect of the 'cavel' in the first copper bar arrangement mode in fig. 3, and the result shows that the result is slightly different from the first one, and the circulation characteristics of the reverse connection defect of the 'cavel' in the two arrangement modes are respectively shown in tables 1 and 2:
TABLE 1 circulation characteristics of defects in the first copper bar arrangement
TABLE 2 circulation characteristics of defects in the second copper bar arrangement
In conjunction with the topology of each case, programming can be performed, such as for J 2A The reverse case, as shown in fig. 14, the first loop of circulation: a = d = h = k = o = r, the error is within 5%, and the above five values should all be less than 50A. A second circuit: b = e = i = l = m = g = f = c, with an error within 5%. A third loop: j = p = q = n, and the average value of the third loop circulation is 1.9-2.1 times the average value of the second loop circulation.
And 2, synchronously acquiring the three-phase load current and the three-phase grounding circulating current at six measuring positions in the cross interconnection unit respectively.
The apparatus for data acquisition includes: the three load ammeters are used for respectively acquiring three-phase load currents of the cable line; and the three clamp-shaped ammeters are used for respectively collecting three-phase grounding circulation. And all the load ammeters and the clamp-on ammeters synchronously acquire time signals respectively through synchronization.
When the abnormal circulation defect of one cross interconnection unit is found, six groups of three-phase load current and three-phase grounding circulation of the unit are collected on site, wherein the grounding circulation at two direct grounding boxes is measured on a three-phase grounding cable, and the grounding circulation at the two cross interconnection boxes is measured at two 'sheep-horn' positions of an insulation joint connected with the two cross interconnection boxes respectively.
Specifically, each direct grounding box respectively measures a group of grounding circulation, M columns of the insulation joints connected with each group of cross interconnection boxes measure a group of grounding circulation, N columns measure a group of grounding circulation, and finally six groups of grounding circulation data are obtained.
And 3, converting the three-phase grounding circulation currents obtained at the other five measuring positions according to the three-phase load current obtained at the first measuring position to obtain six groups of grounding circulation data to be compared.
Because the grounding loop current and the load current are in a positive proportional relation, the last five groups of grounding loop current data can be converted into loop current data under the condition that the load is the same as that of the first group of grounding loop current data according to the load current proportion. The converted circular current data are automatically presented in four tables of the handheld terminal, as shown in tables 3-6.
TABLE 3# direct grounding box circulation detection data table
TABLE 4# Cross-Linked Box Loop flow test data sheet
TABLE 5 # Cross-Linked Box Loop flow test data sheet
TABLE 6 # direct grounding box circulation detection data table
And 4, determining the 'claw' direction of each insulation joint according to the grounding circulation of the M column and the N column of the insulation joint respectively connected with the two cross interconnection boxes.
Further comprising: step 4.1, for each insulating joint, acquiring the absolute value of the difference between the M column current of the small-sequence cross interconnection box and the N column current of the large-sequence cross interconnection box as a first current difference, and acquiring the absolute value of the difference between the N column current of the small-sequence cross interconnection box and the M column current of the large-sequence cross interconnection box as a second current difference;
step 4.2, comparing the first current difference with the second current difference, and taking the connection mode corresponding to the smaller one of the first current difference and the second current difference as the direction of the goat's horn of the corresponding insulated joint;
and 4.3, after preliminarily judging the directions of the 'goat' of the six insulation joints, if the directions of the 'goat' of four or more insulation joints are consistent, taking the directions of the 'goat' of the four or more insulation joints as the directions of the 'goat' of all the insulation joints in the current cross interconnection unit.
Specifically, if the M-pillars connect the small-order side grounding boxes, the a of the small-order cross-connect box is not considered in the case that there may be a "cavel" reverse connection N 、B N And C N The current values should be respectively cross-connected with A of the large serial number cross-connection box M 、B M 、C M The current value being close, i.e.A of small-sequence cross-connection box N A of cross-connection box with large serial number M Is less than A of the small-order cross-connection box M A of cross-connection box with large serial number N The absolute value of the difference of (a).
In practical work, the condition that three or more insulating joints in one unit are reversely connected by the lambdoidal angle is a small probability event, so that when four or more insulating joints are judged to be connected with the small-serial-number side cable metal sheath by the M column, the correct direction of the insulating joint of the unit is considered to be that the M column is connected with the small-serial-number side cable metal sheath, and vice versa.
After the direction of the 'goat' is determined, the circulation data corresponding to the head end and the tail end of the 9-section cable can be known. For example, if it is determined that M columns are connected to the small-sequence-number-side grounding box, the head-end grounding circulation currents are respectively the circulation current of phase a at the 1# direct grounding box and the circulation current of phase a at the 2# cross-connection box for the a cable segment A1 M Circulation, and for the A2 section, the first and the last grounding circulation are respectively A at the 2# cross-connection box N Circulation and 3# Cross-connect Box A M And (4) circulating.
And 5, acquiring the ratio of the absolute value of the difference value of the head and tail end grounding circulation of each cable section in the cross interconnection unit to the larger value of the head and tail end grounding circulation.
After the direction of the 'goat' is determined, the grounding circulation corresponding to the head end and the tail end of each cable section in the cross interconnection unit is obtained, the ratio of the absolute value of the difference value of the grounding circulation of the head end and the tail end of each cable section to the larger value of the grounding circulation of the head end and the tail end is respectively obtained, and the ratio is compared with a preset value.
Further, the preset value may be 0% to 5%. If the ratio is within the range, the defect library can be directly called to carry out circulation characteristic comparison. If the ratio exceeds the range, the damaged defect of the outer protective layer needs to be positioned and repaired, and then the influence of the damaged defect of the outer protective layer on the diagnosis precision of the reversed defect of the goat horn is avoided.
As an embodiment, the effective values of the head-end grounding circulation currents of the 9-section cables are respectively compared to define the difference of the head-end current and the tail-end currentThe larger ratio of the absolute value to the two is the relative error of the head-to-tail ground current. For example, if phase A at 1# directly grounded tank circulates and phase A at 2# cross-connect tank N If the relative error of the circulating current exceeds 5%, judging that the cable section A1 has the defect of outer sheath damage, and needing to enter an outer sheath damage positioning mode to further position the defect point. If not more than 5%, judging the insulation joint J 1A The possibility of reverse connection of the goat horn exists, and the comparison is carried out in a defect library comparison stage.
And 6, when the ratio does not exceed the preset value, calling a defect library to compare circulation characteristics, judging whether the 'goat' reverse connection defect exists, and if so, outputting the reason and the position of the 'goat' reverse connection defect.
And 7, when the ratio exceeds a preset value, performing outer protection layer damage diagnosis on the current cable section.
For a cable section judged to have the defect of outer sheath damage, as shown in fig. 15, 5 current sensors are installed on the cable body at equal distance, and in practice, the length of one cable in the cross interconnection unit is generally 300m-500m, so the direct distance between two adjacent sensors is about 100 m.
The magnitude and the phase position of the current are collected by each sensor, and the collected actual current is the vector sum of the load current passing through the wire core and the grounding circulation passing through the metal sheath because the sensors are arranged on the body, and the synchronous time synchronization unit ensures that the 5 sensors collect data at the same moment.
If the outer protective layer is not damaged, the currents collected by the 5 sensors are completely equal. If an outer protection layer damage point exists between the sensors 1 and 2, and a metal sheath at the point is grounded, the currents collected by the sensors 1 and 2 have difference, if the vector difference is larger than 1A, the outer protection layer damage point exists between the sensors 1 and 2, the steps are repeated on the cable between the sensors 1 and 2, the circulation is carried out, the length of the cable with the damage point is continuously reduced, and finally when the length reaches about 2m, the damage point can be found through a manual inspection mode.
After the outer protective layer is diagnosed to be damaged, the damaged position of the outer protective layer is positioned and electrified to be repaired; then calling a defect library to carry out circulation characteristic comparison, judging whether the 'goat' anti-reversal defect exists, and if so, outputting the reason and the position of the 'goat' anti-reversal defect.
Because the damage of the outer protective layer can influence the diagnosis precision of the reversed connection defect of the cleat, whether the damage diagnosis of the outer protective layer needs to be carried out on the current cable section or not is judged by comparing the current of the head end and the current of the cable section, and if the damage diagnosis of the outer protective layer exists, the damage defect positioning and the repair of the outer protective layer are carried out firstly so as to reduce the influence of the possible damage of the outer protective layer on the defect diagnosis precision.
If the damage of the outer protective layer is not diagnosed, calling a defect library to carry out circulation characteristic comparison, judging whether the 'horn' reverse connection defect exists or not, and if so, outputting the reason and the position of the 'horn' reverse connection defect.
And 7, calling a defect library to compare circulation characteristics when the ratio does not exceed a preset value, and outputting the reason and the position of the reversed defect of the ' goat ' horn '. And matching the detected grounding loop data with the topological structure and the loop characteristics of 42 defect conditions to judge whether the claw connection reverse defect exists or not, and if the claw connection reverse defect exists, judging which insulation joints claw are reversely connected according to a matching result.
According to an aspect of the present specification, there is provided a defect diagnosis and location apparatus for a cable cross-connect grounding system, comprising: the three clamp-shaped ammeters are used for collecting three-phase grounding circulation; three load ammeters are used for collecting three-phase load current; the synchronous timing module is used for sending a synchronous signal to the clamp ammeter and the load ammeter; the wireless transmission module is used for transmitting the three-phase load current and the three-phase grounding circulating current to the handheld terminal;
the handheld terminal is provided with: the handheld terminal is provided with: the input module is used for displaying the field acquisition current data and converting the grounding circulation; the 'claw' direction determining module is used for determining the correct 'claw' direction of the cross interconnection unit according to the grounding circulation of the M column and the N column of the insulation joint connected with the two cross interconnection boxes respectively; the current comparison module is used for acquiring the ratio of the absolute value of the difference value of the head-end grounding circulation of each cable section in the cross interconnection unit to the larger value of the head-end grounding circulation, and comparing the ratio with a preset value; the defect comparison module is used for comparing and matching the measured grounding circulation with circulation characteristics in a defect library; the outer protection layer damage diagnosis module is used for carrying out outer protection layer damage diagnosis on the current cable section when the ratio exceeds a preset value; and the output module is used for outputting the reason and the position of the reversed defect of the 'horn' connection.
The outer jacket damage diagnostic module includes: the current sensors are used for synchronously acquiring current data of the cable line; the comparison module is used for comparing current data between the adjacent current sensors and judging whether the vector difference of the current data of the two adjacent current sensors is larger than a preset current value or not; and the data synchronization module is used for sending a synchronization signal to all the current sensors.
As an implementation manner, the external protection layer damage diagnosis module includes 5 flexible current sensors for measuring vector sum of load current and ground loop current, the data synchronization module includes 5 controllers and optical fibers, the 5 controllers convert collected electrical signals into optical signals, the optical signals are gathered to the third controller through the optical fibers (the third controller is located in the middle position of the 5 controllers, and the lengths of the optical fibers from the other 4 controllers are equal), the third controller gathers, and realizes a synchronous time synchronization function, so as to ensure that the 5 sensors synchronously collect current signals; and the comparison module is used for judging the position of the outer sheath damage point according to the acquired data. The third controller is connected with the handheld terminal through Bluetooth so as to transmit the summarized data and the comparison result to the handheld terminal; or, the comparing module can also be configured in a handheld terminal to directly compare the summarized data.
As shown in fig. 15, the data collected by two adjacent sensors are subtracted to obtain the vector difference of the grounding circulation of two adjacent measurement points, and if the vector difference is greater than or equal to 1A, it is determined that the cable between the two sensors has the outer sheath damage point. Then 5 sensors are arranged at equal intervals between the two sensors, the operation is repeated, finally, the damaged point is determined within the range of about 2 meters, and then the damaged point is found out by manually checking the 2m cable.
In the description of the present specification, reference to the description of "one embodiment", "certain embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" or the like means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and these modifications or substitutions do not depart from the essence of the corresponding technical solutions.
Claims (10)
1. The defect diagnosis and positioning method of the cable cross-connection grounding system is characterized by comprising the following steps:
constructing a 'goat' horn-connected reverse defect library, wherein the defect library comprises a topological structure and circulation characteristics corresponding to each defect;
respectively and synchronously acquiring three-phase load current and three-phase grounding circulation at six measuring positions in the cross interconnection unit;
converting three-phase grounding circulation currents obtained at other five measuring positions according to the three-phase load current obtained at the first measuring position to obtain six groups of grounding circulation data to be compared;
determining the correct 'goat' horn direction of the cross interconnection unit according to the grounding circulation currents of the M column and the N column of the insulation joint connected with the two cross interconnection boxes respectively;
acquiring the ratio of the absolute value of the difference value of the head-end grounding circulation of each cable section in the cross interconnection unit to the larger value of the head-end grounding circulation;
when the ratio exceeds a preset value, performing outer protection layer damage diagnosis on the current cable section;
and when the ratio does not exceed the preset value, calling a defect library to perform circulation characteristic comparison, and outputting the reason and the position of the reversed defect of the horn.
2. The method for diagnosing and locating the defects of the cross-connect grounding system of the cable as claimed in claim 1, wherein after the outer sheath is diagnosed to be damaged, the damaged position of the outer sheath is located and the live repair is performed; then calling a defect library to compare circulation characteristics, judging whether the defect of 'goat' turning back exists or not, and outputting the reason and the position of the defect of 'goat' turning back.
3. The method as claimed in claim 2, wherein if the outer sheath is not diagnosed as damaged, the defect library is called to perform circulation characteristic comparison to determine whether the defect of "cavel" reversal connection exists, and if so, the cause and position of the defect of "cavel" reversal connection are output.
4. The method of claim 1, further comprising:
for each insulating joint, acquiring the absolute value of the difference between the M column current of the small-sequence cross interconnection box and the N column current of the large-sequence cross interconnection box as a first current difference, and acquiring the absolute value of the difference between the N column current of the small-sequence cross interconnection box and the M column current of the large-sequence cross interconnection box as a second current difference;
comparing the first current difference with the second current difference, and taking the connection mode corresponding to the smaller of the first current difference and the second current difference as the direction of the 'goat' horn of the corresponding insulating joint;
after the 'goat' directions of the six insulation joints are determined, if the 'goat' directions of four or more insulation joints are consistent, the 'goat' directions of the four or more insulation joints are taken as the correct 'goat' directions of the current cross interconnection unit.
5. A method for diagnosing and locating defects in a cross-connect grounding system for cables according to claim 1, wherein six sets of three-phase load currents and three-phase grounding loops of a cross-connect unit are collected on site when a loop anomaly defect is found in the unit, wherein the grounding loops at two direct grounding boxes are measured on a three-phase grounding cable, and the grounding loops at two cross-connect boxes are measured at two "sheeps" of an insulation joint to which the two cross-connect boxes are respectively connected.
6. The method for diagnosing and locating the defects of the cable cross-connection grounding system according to claim 1, wherein after the direction of the ' goat ' horn ' is determined, the grounding loop current corresponding to the head end and the tail end of each cable section in the cross-connection unit is obtained, the ratio of the absolute value of the difference value of the grounding loop current of the head end and the tail end of each cable section to the larger value of the grounding loop current of the head end and the tail end is respectively obtained, and the ratio is compared with a preset value for judgment.
7. The method of claim 1, wherein the diagnosing of the outer jacket failure further comprises:
installing a plurality of current sensors at equal intervals on a cable section with an outer protective layer damaged, and synchronously acquiring current data acquired by the current sensors;
comparing current data between adjacent current sensors, and if the vector difference of the current data of two adjacent current sensors is larger than a preset current value, mounting the current sensors on a cable segment limited by the two adjacent current sensors at equal intervals again;
and repeating the steps of synchronously acquiring the current data acquired by the current sensors and comparing the current data between the adjacent current sensors until the distance of the cable sections limited by the two adjacent current sensors with the vector difference of the current data larger than the preset current value is smaller than the preset distance, and manually determining the damage point of the outer protective layer within the preset distance.
8. The method of claim 7, wherein the current sensors for outer sheath breakage diagnosis are set to five to eight; the preset current value is set to be 0-1A; the preset distance is set to be 2-3 m.
9. A device for diagnosing and positioning defects of a cable cross-connection grounding system is characterized by comprising: the three clamp-shaped ammeters are used for collecting three-phase grounding circulation; three load ammeters are used for acquiring three-phase load current; the synchronous timing module is used for sending a synchronous signal to the clamp-on ammeter and the load ammeter; the wireless transmission module is used for transmitting the three-phase load current and the three-phase grounding circulating current to the handheld terminal;
the handheld terminal is provided with: the input module is used for displaying the field acquisition current data and converting the grounding circulation; the 'claw' direction determining module is used for determining the 'claw' direction of each insulating joint according to the grounding circulating currents of the M column and the N column of the insulating joint respectively connected with the two cross interconnection boxes; the current comparison module is used for acquiring the ratio of the absolute value of the difference value of the head-end grounding circulation of each cable section in the cross interconnection unit to the larger value of the head-end grounding circulation, and comparing the ratio with a preset value; the defect comparison module is used for comparing and matching the measured grounding circulation with circulation characteristics in a defect library; the outer protective layer damage diagnosis module is used for carrying out outer protective layer damage diagnosis on the current cable section when the ratio exceeds a preset value; and the output module is used for outputting whether the 'goat' reverse connection defect exists or not, and outputting the specific reason and the position of the defect if the 'goat' reverse connection defect exists.
10. The apparatus for diagnosing and locating defects in a cross-connect cable grounding system of claim 9, wherein said outer sheath failure diagnosis module comprises: the current sensors are used for synchronously acquiring current data of the cable line; the comparison module is used for comparing current data between the adjacent current sensors and judging whether the vector difference of the current data of the two adjacent current sensors is larger than a preset current value or not; and the data synchronization module is used for sending a synchronization signal to all the current sensors.
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| CN115856708A (en) * | 2023-02-28 | 2023-03-28 | 江苏省电力试验研究院有限公司 | Cross interconnection grounding test method and system using coaxial cable |
| CN117630613A (en) * | 2024-01-25 | 2024-03-01 | 南京九维测控科技有限公司 | Cable insulation fault positioning method based on grounding circular flow fitting curve |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN115856708A (en) * | 2023-02-28 | 2023-03-28 | 江苏省电力试验研究院有限公司 | Cross interconnection grounding test method and system using coaxial cable |
| CN117630613A (en) * | 2024-01-25 | 2024-03-01 | 南京九维测控科技有限公司 | Cable insulation fault positioning method based on grounding circular flow fitting curve |
| CN117630613B (en) * | 2024-01-25 | 2024-04-26 | 南京九维测控科技有限公司 | Cable insulation fault positioning method based on grounding circular flow fitting curve |
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