CN112415237A - Main transformer low-voltage side pipe bus direct-current resistance measurement auxiliary device and parameter calculation method thereof - Google Patents

Main transformer low-voltage side pipe bus direct-current resistance measurement auxiliary device and parameter calculation method thereof Download PDF

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Publication number
CN112415237A
CN112415237A CN202011487299.XA CN202011487299A CN112415237A CN 112415237 A CN112415237 A CN 112415237A CN 202011487299 A CN202011487299 A CN 202011487299A CN 112415237 A CN112415237 A CN 112415237A
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spring
contact finger
main transformer
voltage side
support body
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钱聪
张佳剑
冯新民
曹军
揣振国
王国华
袁进
钱林清
陈超
周鹏程
陈昊
张兆君
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Maintenance Branch of State Grid Jiangsu Electric Power Co Ltd
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Maintenance Branch of State Grid Jiangsu Electric Power Co Ltd
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R1/00—Details of instruments or arrangements of the types included in groups G01R5/00 - G01R13/00 and G01R31/00
    • G01R1/02—General constructional details
    • G01R1/04—Housings; Supporting members; Arrangements of terminals
    • G01R1/0408—Test fixtures or contact fields; Connectors or connecting adaptors; Test clips; Test sockets
    • G01R1/0425—Test clips, e.g. for IC's
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R15/00—Details of measuring arrangements of the types provided for in groups G01R17/00 - G01R29/00, G01R33/00 - G01R33/26 or G01R35/00
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
    • G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant

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Abstract

The invention provides a main transformer low-voltage side pipe bus direct current resistance measurement auxiliary device and a parameter calculation method thereof, wherein the device comprises a support body which is a U-shaped opening, a concave surface of the U-shaped opening of the support body is respectively provided with a first contact finger and a second contact finger, and the first contact finger and the second contact finger are respectively arranged on the left side and the right side of the concave surface of the support body and are fixed on the support body; the first contact finger and the second contact finger are both elastic and arc-shaped, and the arc-shaped concave surfaces of the first contact finger and the second contact finger are in the same direction as the concave surface of the bracket body; the outer side of the support body relative to the concave surface is provided with a wiring terminal. The invention can be well clamped on the pipe bus or the pipe bus holding clamp through the matching of the support body and the elastic contact finger, ensures a more fit contact surface, can realize the direct current resistance measurement of the main transformer low-voltage side reactive pipe bus by matching with other contact devices on the site, ensures the measurement precision, is convenient for the site maintenance operation, and reduces the damage of the maintenance operation to the equipment to be maintained.

Description

Main transformer low-voltage side pipe bus direct-current resistance measurement auxiliary device and parameter calculation method thereof
Technical Field
The invention relates to a main transformer low-voltage side pipe bus direct-current resistance measurement auxiliary device and a parameter calculation method thereof, and belongs to the technical field of power detection.
Background
An electrically conductive circuit is always formed by several components, two parts of which are electrically conductive by being brought into contact with each other by means of a mechanical connection, the contact surfaces of which become electrically conductive contact surfaces. In substations, whether transformers, switches or busbars, such electrically conductive contact surfaces are numerous. The contact surfaces of the electrical contacts are always covered with poorly conducting substances, and the increase in resistance that occurs for this reason is referred to as the surface resistance. Such substances are oxides, sulfides, dust, dirt, oil films, water films, etc. The oxide is mostly a semiconductor and has a high resistivity, and any metal surface that is polished to a very smooth surface by the naked eye is actually rough and uneven, and when the two metal surfaces are brought into contact with each other, only a few protruding points (facets) are actually in contact, and only a small portion of the spots of the metal or metalloid contact can conduct electricity. When current passes through these small conductive spots, the current lines necessarily shrink. The current lines contract, the current path flowing through the vicinity of the conductive spot increases, the effective conductive cross section decreases, and the resistance value increases accordingly. This additional resistance caused by the contraction of the current line is called a contraction resistance, and is another component constituting the contact resistance. The main phenomenon of the current passing through the electrical contact of two conductors is the local high temperature at the contact. This occurs because there is an additional resistance at the electrical contact, called the contact resistance, which includes the surface resistance and the pinch resistance described above.
In recent years, several forced shutdown events of equipment caused by contact surface heating occur in the range of an electric power system, and the reason for the forced shutdown events is that the contact resistance of a conductive contact surface is not well controlled, so that the contact resistance rises and generates heat. Therefore, the system text needs to take a plurality of measures to control the occurrence of the heat defect.
The contact resistance measurement is carried out on the lap joint surface of the low-voltage side pipe bus of the 500kV main transformer and the hoop, and the test item is always a key test item for measuring the contact resistance in the transformer substation. The outer diameter of the pipe bus is large and is not suitable for a wire clamp equipped with a loop resistance meter, and the current field can only press a wire clamp mouth on the pipe bus, so that data measurement is obviously inaccurate, even if process links such as a contact surface and the like meet requirements, the requirements of 10u omega specified by a company are often not met, operation risks such as ascending, scaffold use and the like are increased, or a special tool for parameter calculation is used for measuring a certain pipe bus, but the universality is easily reduced.
Disclosure of Invention
The invention aims to provide a special test fixture for clamping a pipe bus or a pipe bus aiming at the problem that a wire clamp provided by the existing loop resistance meter does not adapt to the outer diameter of the pipe bus.
In order to achieve the technical purpose, the invention adopts the following technical scheme.
The invention provides a main transformer low-voltage side pipe bus direct current resistance measurement auxiliary device which comprises a support body, wherein the support body is provided with a U-shaped opening, a concave surface of the U-shaped opening of the support body is respectively provided with a first contact finger and a second contact finger, and the first contact finger and the second contact finger are respectively arranged on the left side and the right side of the concave surface of the support body and are fixed on the support body; the first contact finger and the second contact finger are both elastic and arc-shaped, and the arc-shaped concave surfaces of the first contact finger and the second contact finger are in the same direction as the concave surface of the bracket body; and the outer side of the bracket body relative to the concave surface is provided with a wiring terminal.
Furthermore, a first spring is arranged between the first contact finger and the bracket body, one end of the first spring is connected with the first contact finger, and the other end of the first spring is connected with the bracket body; and a second spring is arranged between the second contact finger and the support body, one end of the second spring is connected with the second contact finger, the other end of the second spring is connected with the support body, and the first spring corresponds to the second spring in position.
Furthermore, one end of the U-shaped opening of the bracket body is connected with an operating rod.
Further, the support body comprises a left support and a right support, and the left support and the right support are connected and fixed through a connecting piece.
Furthermore, one end of the U-shaped opening of the support body further comprises a bending part, and the bending part and the support body are of an integrated structure.
Further, the first contact finger and the second contact finger are riveted on the bracket body through a rivet.
Further, the first spring and the second spring are riveted on the bracket body through rivets.
On the other hand, in order to provide a parameter calculation method of the device, the invention also provides a parameter calculation method of the auxiliary device for measuring the direct current resistance of the main transformer low-voltage side pipe bus, which comprises the following steps: the U-shaped opening of the device is divided into two ranges of phi 160-phi 200 and phi 200-260.
Further, torsion springs are selected as the first spring and the second spring, and the parameter determination method of the first spring and the second spring is as follows:
(1) determining a force value parameter: determining the clamping force of the contact points according to the diameter of the pipe nut and the diameter of the pipe nut clamp;
(2) determining a torque parameter: according to the overall dimension of the device, primarily determining torsion arms of the springs, adopting a double-torsion-spring structure, so that the torque born by each spring is half of the total torque, and determining the installation torque T1And operating torque T2；
(3) Determining other parameter requirements, including: determining the material according to the actual service life requirement;
determining the allowable bending stress of the selected spring, wherein the method comprises the following steps: the cycle characteristic γ is calculated as:
Figure BDA0002839692720000041
determination of the cycling characteristics γ and 10 in the manual7Ordinate of the intersection of the lines, according to the ordinate and the tensile strength R of the materialmDetermines the allowable bending stress [ sigma ] of the spring](ii) a The diameter d of the steel wire material is calculated,
Figure BDA0002839692720000042
where T is the torque per spring, KbIs the intermediate variable(s) of the variable,
according to the inner diameter D of the spring1And the diameter d of the steel wire material determines the convolution ratio C, and the formula is as follows
Figure BDA0002839692720000043
Wherein D is the spring pitch diameter: d ═ D1+d；
The spring rate T' and the torsional deformation angle theta are calculated according to the following formulas1Theta and DEG2°，
Figure BDA0002839692720000044
Figure BDA0002839692720000045
Figure BDA0002839692720000046
The effective number of turns n of the spring is calculated by the following formula,
Figure BDA0002839692720000047
e is the elastic modulus of the material; l1The length of the torsion arm at one side of the torsion spring; l2The length of the torsion arm at the other side of the torsion spring;
according to the experimental bending stress sigmasThen test torque TsAnd the variation angle theta under the test torquesThe calculation formula is as follows:
Figure BDA0002839692720000051
Figure BDA0002839692720000052
Dnis the spring pitch diameter; n is the number of effective turns of the spring,
calculating the diameter D' of the guide rod according to the following formula:
Figure BDA0002839692720000053
D′＝0.9(D1-ΔDs)
calculating the free length H0The formula is as follows:
H0＝(nt+d)+L0，
L0the length of the torque arm on the axis is n, and the number of effective turns of the spring is n; t is the spring pitch, and the spring expansion length L is calculated by the formula: l ≈ pi Dn + L1，L1Is the torque arm length.
Further, the fatigue life of the spring is determined by the following method:
Figure BDA0002839692720000054
wherein sigmamaxMaximum allowable bending stress of spring, sigmaminAnd determining the minimum allowable bending stress of the spring, respectively determining the ratio of the maximum allowable bending stress of the spring to the allowable stress of the material selected by the spring, and determining the fatigue life of the spring according to the comparison result.
The invention has the following beneficial technical effects:
the auxiliary device for measuring the direct current resistance of the main transformer low-voltage side pipe bus can be well clamped on the pipe bus or the pipe bus clamp through the matching of the support body and the elastic contact finger, a more attached contact surface is ensured, the direct current resistance of the main transformer low-voltage side pipe bus can be measured through matching with other on-site contact devices, the measurement precision is ensured, the on-site maintenance operation is facilitated, and the damage of the maintenance operation to equipment to be repaired is reduced.
Through the design that increases the spring, further strengthened the block power, through set up the connecting rod on the support body, make things convenient for the on-the-spot maintenance operation, improve the accuracy of measuring return circuit resistance data, improve maintenance quality and efficiency.
Drawings
Fig. 1 is a schematic structural diagram of an auxiliary device according to an embodiment of the present invention;
FIG. 2 is a schematic structural diagram of an auxiliary device according to another embodiment of the present invention;
FIG. 3 is a general view of a 500kV main transformer low-voltage side pipe bus;
FIG. 4 is a contact surface measuring point of a part A in a general view schematic diagram of a low-voltage side pipe bus of a 500kV main transformer;
FIG. 5 is a contact surface measuring point of a B part in a general view schematic diagram of a low-voltage side pipe bus of a 500kV main transformer;
FIG. 6 is a contact surface measuring point of a C position in a general view schematic diagram of a low-voltage side pipe bus of a 500kV main transformer;
FIG. 7 is a contact surface measuring point at a D position in a general view schematic diagram of a low-voltage side pipe bus of a 500kV main transformer;
FIG. 8 is a schematic diagram of an application of a specific embodiment of the present invention;
FIG. 9 is a schematic view of the measurement dimensions of the bus bar and the bus bar clamp;
FIG. 10 is a spring diagram of an embodiment;
in the figure: 1: a stent body; 2: a first contact finger; 3: a second finger; 4: a first spring: 5: a second spring; 6: a wiring terminal; 7: an operating lever; 8: a bending part; 9: a connecting member; 10: a serrated surface.
Detailed Description
The invention is further described below with reference to the figures and the specific examples. In order to better understand the technical solution of the present invention, the following further describes the measurement of the contact resistance of the mother tube.
In the description of the present invention, it is to be understood that the terms "inside", "outside", "upper", "top", "lower", "left", "right", "vertical", "horizontal", "parallel", "bottom", "inner", "outer", and the like indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience of description and simplicity of description, and do not indicate or imply that the referenced devices or elements must have a particular orientation, be constructed in a particular orientation, and be operated, and therefore, should not be taken as limiting the scope of the present invention.
Fig. 3 is a general view of a 500kV main transformer low-voltage side pipe bus of a certain 500kV substation, and fig. 4-7 show a method and a jig for testing contact resistance of conductive contact surfaces of 4 (a-D) different types of clasps and wire clamps in fig. 3, i.e., measuring the clamping position of the jig. Where the a site measurement points are shown in fig. 4: the female clamp of embracing of pipe (g point) -double fastener (s point), the anchor clamps of g point need the centre gripping on the outer fringe that the female clamp of embracing of pipe was held, shows B position measuring point in figure 5: mother tube (point m) -mother tube clamp (point g), the measurement points at the C site are shown in fig. 6: tube bus (m point) -bus tie line clamp (x point), D site measurement point is shown in fig. 7: pipe bus (point m) -single line clamp (point d).
The invention provides an auxiliary device for measuring the direct current resistance of a main transformer low-voltage side reactive pipe bus, namely a measuring clamp, aiming at the pipe bus holding clamp (g point) in fig. 4, the pipe bus (m point) in fig. 5, the pipe bus (m point) in fig. 6 and the pipe bus (m point).
The following are specific examples.
Example 1: a main transformer low-voltage side reactive tube bus direct current resistance measurement auxiliary device comprises a support body 1, wherein the support body 1 is a U-shaped opening, a concave surface of the U-shaped opening of the support body 1 is respectively provided with a first contact finger 2 and a second contact finger 3, and the first contact finger 2 and the second contact finger 3 are respectively arranged on the left side and the right side of the support body 1 and fixed on the support body 1; the first contact finger 2 and the second contact finger 3 are both elastic and arc-shaped, and the arc-shaped concave surfaces of the first contact finger 2 and the second contact finger are in the same direction as the concave surface of the bracket body 1; and the outer side of the bracket body 1 relative to the concave surface is provided with a wiring terminal 6.
Because the shape of the pipe bus and the shape of the pipe bus clamp are basically consistent and are all round pipe shapes, the support body 1 is a U-shaped opening in the embodiment, and two elastic contact fingers are arranged on two sides of the support body 1. Because touch and indicate to possess certain elasticity, it has certain margin to press from both sides at the female or female embracing of pipe through touching the finger block when support body 1, guarantees the contact surface of laminating more, and other contact devices of cooperation scene can realize having guaranteed the measuring to main transformer low-voltage side idle tubular bus direct current resistance, and the convenience on-the-spot maintenance operation reduces the injury of maintenance operation to waiting to repair equipment. The size of the opening of the clamp can be designed by those skilled in the art according to the actual situation. When in use, the test wire is connected through the wiring terminal 6.
Because this anchor clamps need be to some, need certain mechanical strength again, still must compromise the requirement of "light in weight" simultaneously, support body 1 and the optional copper of sense finger or aluminum alloy material.
The embodiment further comprises the following steps: a first spring 4 is arranged between the first contact finger 2 and the bracket body 1, one end of the first spring 4 is connected with the first contact finger 2, and the other end is connected with the bracket body 1; a second spring 5 is arranged between the second contact finger 3 and the support body 1, one end of the second spring 5 is connected with the second contact finger 3, the other end of the second spring is connected with the support body 1, and the first spring 4 corresponds to the second spring 5 in position.
This embodiment has guaranteed certain pressure of touching through setting up the spring, makes auxiliary device block on female or female the embracing of pipe is pressed from both sides well, and the test principle torsion spring according to anchor clamps is as working spring. Preferably, a general-purpose carbon steel wire is selected.
Example 2: on the basis of the above embodiment, one end of the U-shaped opening of the bracket body 1 in this embodiment is connected with the operating rod 7. The operating rod 7 is additionally arranged, so that the convenience of the site is improved, the accuracy of measuring the resistance data of the loop is improved, and the overhauling quality and efficiency are improved.
Optionally, the bracket body 1 includes a left bracket and a right bracket (as shown in fig. 2), and the left bracket and the right bracket are connected and fixed by a connecting piece 9. Optionally, the left and right brackets are riveted to the connecting piece 9.
Optionally, one end of the U-shaped opening of the bracket body 1 further includes a bending portion 8, and the bending portion 8 and the bracket body 1 are of an integral structure. Through setting up the portion of bending 8, make things convenient for 1 block of support body to advance female or female clamp of embracing of pipe. As shown in fig. 2, in the specific embodiment, one end of the U-shaped opening of the bracket body 1 is connected to an operating rod 7, and the other end of the U-shaped opening is provided with a bent portion 8.
Optionally, the first contact finger 2 and the second contact finger 3 are riveted to the bracket body 1 by a rivet.
Optionally, the first spring 4 and the second spring 5 are riveted to the bracket body 1 by rivets.
In order to further increase the friction force between the first contact finger 2 and the second contact finger 3 and the pipe nut or the pipe nut holding clamp, in a specific embodiment, the concave surfaces of the inner sides of the first spring 4 and the second spring 5 are both provided with sawtooth surfaces 10.
The invention provides an auxiliary device for measuring direct current resistance of a main transformer low-voltage side reactive tube bus, which comprises the following application methods: the application method comprises the following steps: when the reactive circuit resistance is measured, one circuit resistance meter, two groups of test lines, two main transformer low-voltage side reactive tube bus direct-current resistance measurement auxiliary devices (which have the functions of being like a same-tube bus clamp or a bus clamp) and one power wire coil are required to be prepared. Two groups of test wires are respectively connected to an auxiliary device for measuring the direct current resistance of the main transformer low-voltage side passive tube bus, and two persons cooperate to hang two tube bus clamps at a measured position, as shown in fig. 8, wherein a loop resistance meter is in the prior art. The auxiliary device for measuring the direct current resistance of the main transformer low-voltage side reactive pipe bus can be well clamped on the pipe bus or a pipe bus holding clamp through the matching of the support body 1 and the elastic contact fingers, a more attached contact surface is ensured, the direct current resistance measurement of the main transformer low-voltage side reactive pipe bus can be realized through matching with other on-site contact devices, the measurement precision is ensured, the on-site maintenance operation is facilitated, and the damage of the maintenance operation to equipment to be repaired is reduced.
Through the design that increases the spring, further strengthened the block power, through set up the connecting rod on support body 1, make things convenient for the on-the-spot maintenance operation, improve the accuracy of measuring return circuit resistance data, improve maintenance quality and efficiency.
The design test fixture (namely the main transformer low-voltage side reactive tube bus direct current resistance measurement auxiliary device) must know the relevant dimension of the test object in detail, and for this reason, the bus power failure opportunity is utilized to carry out field test on the relevant dimension (the units used in the text are all mm).
1) Measuring the circumference of the pipe mother: c550 mm and the calculated diameter Φ is about 175mm, see fig. 9.
2) Measuring the perimeter of the bus clamp: 780mm, calculated diameter Φ about 248mm, width 190mm, see fig. 9.
Embodiment 3. a parameter calculation method of an auxiliary device for measuring direct current resistance of a main transformer low-voltage side reactive tube bus, wherein the auxiliary device adopts the device provided by the above embodiment, and the parameter calculation method comprises the following steps:
according to the measured data (as shown in FIG. 9), the diameter phi 175 of the pipe bus and the outer diameter phi 248 of the bus clamp are designed to be within the measuring range phi 175-phi 248. A certain margin is reserved at present, the design is carried out according to phi 160-phi 260, namely, the measurement range is suitable for phi 160-phi 260 pipe nuts and clasps.
According to the structural form of fig. 1, the compression amount of the contact finger springs on the two sides needs to be more than 50mm, if the springs are designed according to the minimum pipe trunk diameter phi 160 and certain contact finger pressure is ensured, when the maximum pipe trunk diameter phi 260 is measured, the compression amount of the single-side spring exceeds 50mm, the contact finger pressure is hundreds of newtons, and the great pressure can cause difficult operation, so that the measurement fails.
Based on the above considerations, the opening size of the clamp is now divided into two steps: phi 160-phi 200 and phi 200-260, and the design description is only given in the first grade of phi 160-phi 200.
Selection of (A) materials
The clamp needs to be conductive, needs certain mechanical strength and also has the requirement of light weight, and related materials are listed in table 1 for comparison.
Based on the parameters listed in Table 1, 2-series and 7-series aluminum alloys are suitable in view of strength, conductivity, hardness, weight, and the like.
TABLE 1 comparison of several Material Performance parameters
Figure BDA0002839692720000121
Design of spring
The spring is a key element of the clamp, and the torsion spring is selected as a working spring according to the test principle of the clamp.
1) Determination of basic parameters
(1) Force value determination
The diameter of the bus is measured to be phi 175 and the diameter of the bus clamp is measured to be phi 248, the clamping force of a contact point during measurement is not less than 25N, the value is large as much as possible, the oxide layer is favorably removed, the clamping force is too large, the operation is not favorable, and 28N is selected.
(2) Torque determination
The torsion arm of the spring is preliminarily determined to be 60 according to the external dimension of the clamp, and the torque born by each spring is half of the total torque (14 × 60 ═ 840n.mm) by adopting a double torsion spring structure. Determination of the mounting torque (pretension) T1＝300N.mm，
Working torque T2＝840N.mm。
(3) Other parameter requirements
The spring structure type is NVI single-arm torsion dense right-handed spring, the right-handed torsion is performed in the clockwise direction, and the working torsion deformation angle theta is equal to theta DEG2°-θ1The structure is required to be compact in size, wherein the angle is 53 degrees, the inner diameter is larger than or equal to 7mm, the length of the torsion arm is 60mm, (the influence of the long torsion arm on the torsion deformation angle needs to be considered). The fatigue life N is more than 10 ten thousand times.
2) Selection of materials
And selecting a carbon steel wire group C for general use according to the actual service life requirement. According to the working torque T2The material diameter d is 1.8mm to 2.2mm, 840N mm. Examining the handbook to obtain the material with the elastic modulus E being 206X 103MPaThe tensile strength R of the material is found by the related handbookm＝1760MPa～1660MPaTaking Rm＝1710MPa。
3) Selecting allowable bending stress of spring
The spring is subjected to a dynamic load, according to a cycle characteristic γ:
Figure BDA0002839692720000131
in the manual,. gamma.0.35 and 107The ordinate of the line intersection point is approximately 0.57, the allowable bending stress is
[σ]＝0.57Rm＝0.57×1710＝974.7MPa
4) Diameter of steel wire
Calculating the diameter of the steel wire material according to a formula, and taking Kb＝1
Figure BDA0002839692720000132
Taking d as 2mm basically conforms to the original hypothesis and conforms to the GB/T1358 series of values. Look-up table tensile strength Rm＝1710MPa，[σ]＝0.57Rm＝0.57×1710＝974.7MPa
5) Diameter of spring
Inner diameter of spring D17mm, then D2＝D1+2d＝7+2×2＝11mm
The pitch diameter of the spring: d ═ D1+d＝7+2＝9mm
The winding ratio C:
Figure BDA0002839692720000141
6) spring rate and torsional deflection angle
Calculated according to a formula
Figure BDA0002839692720000142
Calculated according to a formula
Figure BDA0002839692720000143
Figure BDA0002839692720000144
7) Effective number of turns of spring
Considering the influence of the long torque arm on the torque deformation angle, calculating by a formula
Figure BDA0002839692720000145
Get n equal to 9 circles
8) According to the experimental bending stress sigmas＝0.78Rm＝0.78×1710＝1334MPaThen test torque TsAnd the variation angle theta under the test torquesCalculation of degree:
Figure BDA0002839692720000146
Figure BDA0002839692720000147
Figure BDA0002839692720000148
then 0.2 thetas°≤θ1，2°≤0.8θsAnd (4) meeting the characteristic requirements.
9) Diameter of guide rod
Calculating the diameter D' of the guide rod according to a formula:
Figure BDA0002839692720000151
D′＝0.9(D1-ΔDs)＝0.9(7-0.29)＝6.04mm
the diameter D' of the guide rod is 6 mm.
10) Fatigue strength check
Calculated by a formula, K is takenb1, obtaining:
Figure BDA0002839692720000152
Figure BDA0002839692720000153
thereby to obtain
Figure BDA0002839692720000154
Where 0.11 is the ratio of the minimum stress at which the spring is used to the allowable stress of the material selected for the spring. 0.31 is the ratio of the maximum stress at which the spring is used to the allowable stress of the material selected for the spring.
The ratio is less than 1, which shows that the stress of the spring in use is less than the allowable stress of the selected material of the spring, and the fatigue life of the spring is longer.
The curve in the manual is a test (verification) curve, and the calculated value falls in a certain area, which indicates that the fatigue life meets the corresponding value in the area.
From the curves in the manual, it can be seen that the points (0.11,0.31) are at γ ═ 0.35 and 106Below the intersection point of the action lines, the fatigue life N of the spring is shown>10 ten thousand times.
11) Free length and spring extension length
The free length is calculated according to the formula:
H0the length of the torque arm on the axis line is (9 multiplied by 2+4) + (6 multiplied by 2-4) 30mm, and the spring expansion length is calculated according to the formula:
l ≈ pi Dn + torque arm length 3.14 × 9 × 9+ (60+30+12) ═ 356.34mm
12) Spring working diagram the spring working diagram is shown in fig. 10, and the technical requirements in the diagram are as follows:
a. spring end structure type: an NVI single-arm bending torsion spring;
b. rotating direction: d, rotating rightwards;
c. effective circle number: n is 9 circles;
d. surface treatment: brushing antirust paint;
e. the manufacturing technical conditions are as follows: the rest is according to the second-level precision of GB/T1239.3.
13) The spring parameters are shown in table 2.
TABLE 2 design parameters of the springs
Figure BDA0002839692720000161
The invention analyzes the conductive contact surface structure type of primary equipment in the jurisdiction range and a method for measuring and processing the contact resistance. The invention researches the working condition of measuring the resistance, designs and processes the contact surface resistance tool clamp for measuring the bus or the bus clamp. The successful development of the device can practically solve the field difficulty, facilitate the field maintenance operation, reduce the damage of the maintenance operation to the equipment to be maintained, improve the accuracy of measuring the resistance data of the loop and improve the maintenance quality and efficiency. The device is successfully developed, the measurement of the 500kV main transformer low-voltage side reactive circuit pipe bus and the hoop can be solved, and the device can be popularized in the measurement work of the direct current resistance of the hoop of a 220kV and 110kV open type pipe bus.
It should be understood that the above-described embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the claims of the present invention.

Claims (10)

1. The main direct current resistance measurement auxiliary device of the main transformer low-voltage side pipe is characterized by comprising
The support comprises a support body, a first contact finger and a second contact finger are arranged on the concave surface of the U-shaped opening of the support body respectively, and the first contact finger and the second contact finger are arranged on the left side and the right side of the concave surface of the support body respectively and are fixed on the support body; the first contact finger and the second contact finger are both elastic and arc-shaped, and the arc-shaped concave surfaces of the first contact finger and the second contact finger are in the same direction as the concave surface of the bracket body; the outer side of the bracket body, which is opposite to the concave surface, is provided with a wiring terminal; a first spring is arranged between the first contact finger and the bracket body, one end of the first spring is connected with the first contact finger, and the other end of the first spring is connected with the bracket body; and a second spring is arranged between the second contact finger and the support body, one end of the second spring is connected with the second contact finger, the other end of the second spring is connected with the support body, and the first spring corresponds to the second spring in position.
2. The auxiliary device for measuring the direct current resistance of the main transformer low-voltage side pipe bus according to claim 1, wherein one end of the U-shaped opening of the bracket body is connected with an operating rod.
3. The auxiliary device for measuring the direct current resistance of the main transformer low-voltage side pipe bus according to claim 1, wherein the bracket body comprises a left bracket and a right bracket, and the left bracket and the right bracket are fixedly connected through a connecting piece.
4. The auxiliary device for measuring the direct current resistance of the main transformer low-voltage side pipe bus according to claim 1, wherein one end of the U-shaped opening of the support body further comprises a bent portion, and the bent portion and the support body are of an integral structure.
5. The auxiliary device for measuring the direct current resistance of the main transformer low-voltage side pipe bus according to claim 1, wherein the first contact finger and the second contact finger are riveted on the bracket body through rivets.
6. The auxiliary device for measuring the direct current resistance of the main transformer low-voltage side pipe bus according to claim 1, wherein concave surfaces of the first contact finger and the second contact finger are provided with sawtooth surfaces.
7. The auxiliary device for measuring the direct current resistance of the main transformer low-voltage side pipe bus according to claim 1, wherein the first spring and the second spring are riveted on the bracket body through rivets.
8. The parameter calculation method of the auxiliary device for measuring the direct current resistance of the main transformer low-voltage side pipe bus is characterized in that the auxiliary device for measuring the direct current resistance of the main transformer low-voltage side pipe bus is the device according to any one of claims 1 to 7, and the parameter calculation method comprises the following steps: the U-shaped opening of the device is divided into two ranges of phi 160-phi 200 and phi 200-260.
9. The parameter calculation method of the auxiliary device for measuring the direct current resistance of the main transformer low-voltage side pipe bus according to claim 8, wherein torsion springs are selected as the first spring and the second spring, and the parameter determination method of the first spring and the second spring is as follows:
(1) determining a force value parameter: determining the clamping force of the contact points according to the diameter of the pipe nut and the diameter of the pipe nut clamp;
(2) determining a torque parameter: according to the overall dimension of the device, primarily determining torsion arms of the springs, adopting a double-torsion-spring structure, so that the torque born by each spring is half of the total torque, and determining the installation torque T1And operating torque T2；
(3) Determining other parameter requirements, including: determining the material according to the actual service life requirement;
determining the allowable bending stress of the selected spring, wherein the method comprises the following steps: the cycle characteristic γ is calculated as:
Figure FDA0002839692710000021
determination of the cycling characteristics γ and 10 in the manual7Ordinate of the intersection of the lines, according to the ordinate and the tensile strength R of the materialmDetermines the allowable bending stress [ sigma ] of the spring](ii) a The diameter d of the steel wire material is calculated,
Figure FDA0002839692710000031
where T is the torque per spring, KbIs the intermediate variable(s) of the variable,
according to the inner diameter D of the spring1And the diameter d of the steel wire material determines the convolution ratio C, and the formula is as follows
Figure FDA0002839692710000032
Wherein D is the spring pitch diameter: d ═ D1+d；
The spring rate T' and the torsional deformation angle theta are calculated according to the following formulas1Theta and DEG2°，
Figure FDA0002839692710000033
Figure FDA0002839692710000034
Figure FDA0002839692710000035
The effective number of turns n of the spring is calculated by the following formula,
Figure FDA0002839692710000036
e is the elastic modulus of the material; l1The length of the torsion arm at one side of the torsion spring; l2The length of the torsion arm at the other side of the torsion spring;
according to the experimental bending stress sigmasThen test torque TsAnd the variation angle theta under the test torquesThe calculation formula is as follows:
Figure FDA0002839692710000041
Figure FDA0002839692710000042
dn is the spring pitch diameter; n is the number of effective turns of the spring,
calculating the diameter D' of the guide rod according to the following formula:
Figure FDA0002839692710000043
D′＝0.9(D1-ΔDs)
calculating the free length H0The formula is as follows:
H0＝(nt+d)+L0，
L0the length of the torque arm on the axis is n, and the number of effective turns of the spring is n; t is the pitch of the spring and,
calculating the expansion length L of the spring according to the formula: l ≈ pi Dn + L1，L1Is the torque arm length.
10. The parameter calculation method for the main transformer low-voltage side tubular bus direct current resistance measurement auxiliary device according to claim 9, wherein the fatigue life of the spring is determined by the following method:
Figure FDA0002839692710000044
wherein sigmamaxMaximum allowable bending stress of spring, sigmaminAnd determining the minimum allowable bending stress of the spring, respectively determining the ratio of the maximum allowable bending stress of the spring to the allowable stress of the material selected by the spring, and determining the fatigue life of the spring according to the comparison result.
CN202011487299.XA 2020-12-16 2020-12-16 Main transformer low-voltage side pipe bus direct-current resistance measurement auxiliary device and parameter calculation method thereof Pending CN112415237A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113851864A (en) * 2021-09-26 2021-12-28 国网辽宁省电力有限公司抚顺供电公司 Tube bus flexible connection and hoop downlead node direct current resistance measuring device

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113851864A (en) * 2021-09-26 2021-12-28 国网辽宁省电力有限公司抚顺供电公司 Tube bus flexible connection and hoop downlead node direct current resistance measuring device
CN113851864B (en) * 2021-09-26 2023-09-22 国网辽宁省电力有限公司抚顺供电公司 Direct-current resistance measuring device for flexible connection of tubular bus and down-lead node of anchor ear

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