CN113030795A - Pre-detection device and method before insulation test of stator winding of internal water-cooled generator - Google Patents

Pre-detection device and method before insulation test of stator winding of internal water-cooled generator Download PDF

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CN113030795A
CN113030795A CN202110273892.2A CN202110273892A CN113030795A CN 113030795 A CN113030795 A CN 113030795A CN 202110273892 A CN202110273892 A CN 202110273892A CN 113030795 A CN113030795 A CN 113030795A
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sink
ground
phase
water
switch
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CN113030795B (en
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张晓鹏
韩金华
郑豫生
刘秀明
牟义革
武震宇
黄卫华
田自强
孙彬
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Huazhong Electric Power Test Research Institute China of Datang Corp Science and Technology Research Institute Co Ltd
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Huazhong Electric Power Test Research Institute China of Datang Corp Science and Technology Research Institute Co Ltd
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
    • G01R31/72—Testing of electric windings
    • 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
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/12—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing
    • G01R31/1227—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing of components, parts or materials
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/34—Testing dynamo-electric machines
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
    • G01R31/52—Testing for short-circuits, leakage current or ground faults

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  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Tests Of Circuit Breakers, Generators, And Electric Motors (AREA)

Abstract

The invention relates to a pre-detection device and method before insulation test of stator winding of water-cooled generator, the technical scheme is that the device comprises a shell, the surface of the shell is respectively provided with a display and an operation key, the side surface of the shell is provided with a wiring row for connecting with a test contact of the stator winding of the water-cooled generator, the wiring row is respectively provided with 7 wiring terminals for respectively connecting seven measuring points of A, B, C three phases of stator winding of the water-cooled generator, excitation end water inlet and water collecting pipe, steam end water outlet and water collecting pipe, sleeve pipe water outlet and water collecting pipe and the ground, a pre-detection circuit is arranged in the shell, a set of complete pre-detection fault diagnosis process is designed, and provides various fault diagnosis criteria, practice proves that possible fault reasons can be rapidly judged, and a corresponding inspection range and a corresponding inspection method are provided, so that the method has great guiding significance for field work.

Description

Pre-detection device and method before insulation test of stator winding of internal water-cooled generator
Technical Field
The invention relates to a portable pre-detection device and a pre-detection method before insulation test of a stator winding of a water-cooled generator.
Background
At present, when alternating current and direct current voltage withstand tests are carried out on stator windings of water-cooled generators with water collection pipes which can be opened in a grounded mode and insulation resistance tests before a unit is started, insulation resistance of the water collection pipes to the ground of a motor with the water collection pipes which are not in a dead-grounded mode is measured under the condition that water flows through the motor, and the results accord with the requirements of a manufacturer for carrying out subsequent insulation tests such as insulation resistance, direct current voltage withstand, leakage current and alternating current voltage withstand. The insulation resistance of the catchment pipe to the ground and the winding to the catchment pipe before the alternating current/direct current voltage withstand test is generally called as 'pre-detection' before the insulation test of the stator winding of the water-cooled generator. Meanwhile, after the generator set is overhauled and before the generator set is started to run, insulation resistance testing is carried out on a stator winding of the generator before the stator winding is tested, pre-testing is carried out, and the insulation resistance testing is qualified after the pre-testing result meets the requirement, so that the generator set can be started and connected to the grid.
Some faults often occur in the process of carrying out on-site 'pre-detection', so that the test result is not in accordance with the requirements, and serious consequences such as incapability of carrying out subsequent tests, delay of unit overhaul work, incapability of normally starting up the unit and the like mainly comprise the following problems:
1. relevant requirements for "Pre-detection" in standards
According to GB 50150 and 2016 Electrical device installation engineering electrical equipment handover test standard and DL/T596 and 1996 electrical equipment preventive test procedure, for a motor with a non-dead-grounded water collecting pipe, the insulation resistance of a winding and the water collecting pipe are respectively measured, a shielding method is adopted to eliminate the influence of water when the insulation resistance of the winding is measured, and the measurement result meets the regulations of a manufacturing plant. That is, in the generator transfer and preventive tests, before insulation tests such as dc withstand voltage, leakage current, and ac withstand voltage are performed, the resistance value of the winding to the water collection pipe and the resistance value of the water collection pipe to the ground are measured in advance.
2. "Pre-detection" method and procedure
The pre-detection generally comprises two items of resistance measurement of a water collecting pipe to the ground and resistance measurement of a winding to the water collecting pipe, and the detection process is simple in principle and roughly as follows:
1) and (3) measuring the resistance of the water collecting pipe to the ground: firstly, the universal meter is adjusted to a resistance gear, and the resistance value of the water collecting pipe to the ground is measured by the meter probe.
2) Measuring the resistance of the winding to the water collecting pipe: part of experienced high voltage testers further measured the resistance of the windings to the water header (i.e., the resistance of the circuit water) using a multimeter.
The stator winding is formed by connecting a plurality of stator bars in series and parallel, each stator bar is formed by a plurality of hollow copper wires and solid copper wires, an insulating layer is coated on the surface of each stator bar, and stator internal cooling water flows in the hollow copper wires.
3. Significance and Effect of "Pre-detection
When the pre-detection result before the insulation test of the generator stator winding is abnormal, the subsequent test cannot be carried out according to the regulation requirement, and even the capacity of the test equipment is insufficient, the subsequent test result is unqualified and the like. According to many years of working experience, the probability of occurrence of abnormal conditions of a test result in the process of 'pre-detection' is about 30-50%, sometimes the fault reasons are relatively simple, the experience of field testers is relatively rich, the reasons can be quickly checked and processed, and often the fault reasons cannot be quickly found out under the conditions that the fault conditions are relatively complex, the fault point positions are relatively hidden, the processing workload is relatively large, or the experience of the testers is not enough, and the equipment loops and structures of equipment managers are not clear, so that the overhaul period of a generator is delayed by 3-5 working days or even longer, or the generator set cannot be started according to rule requirements due to low insulation when the generator set is started, the production and operation of the generator set are influenced, and the problems greatly disturb the field testers. Specific examples are as follows:
1. 60-100T-shaped thermocouples are generally welded on the water outlet and water collecting pipe, when one or more temperature measuring elements and one point in a loop thereof are damaged in a ground-to-ground insulation manner, the whole ground-to-ground insulation of the water collecting pipe is possibly low, but the temperature measuring elements and leads are more in number, the temperature measuring elements and the leads are difficult to loosen along the water pipe in a bundle and fix, and the external part of the water collecting pipe is difficult to check in a groove box or a corner, so that the searching workload is large;
2. the water inlet and outlet catchment pipe all has insulating flange near the generator shell, this flange insulation is by the insulating sheath of several bolts, insulating gasket and the insulating cover between the flange mouth, insulating pad is constituteed, the insulating problem of any one of them subassembly can all lead to catchment pipe whole insulating to ground on the low side, interior cold water must be emptied during the disassembly, wash, dry all foregoing insulating parts with the special washing liquid that conductivity is extremely low, spare part that still need to be renewed when necessary, this work load is also great, and also difficult judgement leads to catchment pipe insulating specifically to which insulating part on the low side before and after disassembling.
4. Problems that may arise in "Pre-detection
Although the principle and method of "pre-detection" are relatively simple, there are many problems that may occur in the actual "pre-detection" process on site, and the fault is divided into multiple types according to the root cause and the position of the fault, and sometimes the multiple types of faults are superimposed together, so the situation is relatively complex, and the summary is as follows:
1) because a digital multimeter is usually used in field pre-detection, the battery capacity of the digital multimeter is very small, under the condition of water passing, if the polarization potential of internal cold water is higher, the polarization potential of the water collecting pipe is superposed with the output voltage of the multimeter, so that the data deviation of the insulation resistance of the water collecting pipe to the ground measured by the multimeter is larger, for example, the insulation resistance difference measured by the multimeter in the forward direction and the reverse direction is too large, even the highest value and the lowest value respectively reach infinity or zero, and the data are seriously distorted;
2) similar to the former situation, when the polarization potential of the inner cooling water is higher, if a universal meter is used for measuring the insulation resistance of the winding to the water collecting pipe, the phenomenon that the test data is higher or lower can also be caused, so that the estimation of a tester on the capacity of a test instrument is deviated, and adverse results are caused to subsequent test work;
3) when the insulation resistance of each insulation flange or insulation support of the water collecting pipe is low, the measured insulation leakage current of the stator winding is large (the large insulation leakage current can cause the measured insulation resistance to be low, so that the false appearance that the insulation of a tested product is unqualified is caused, and the insulation resistance may be qualified actually);
4) when the insulation resistance of a temperature measuring element welded on the water collecting pipe and a temperature measuring wire of the temperature measuring element is low, the measured insulation leakage current of the stator winding is large;
5) the insulation damage of the test wire or the disconnection of the test wire can cause the measured insulation leakage current of the stator winding to be larger;
6) poor contact, broken wire or damaged lead wire insulation and the like in the middle link of a single or a plurality of water collecting pipe lead wires can cause larger insulation leakage current of the stator winding.
Therefore, improvement and innovation of pre-detection before insulation test of the stator winding of the water-cooled generator are imperative.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a device and a method for pre-detecting a stator winding of a water-cooled generator before an insulation test, which can effectively solve the problems of more interference factors and inaccurate test results in the pre-detection process before the insulation test of the stator winding of the water-cooled generator.
In order to achieve the purpose, the technical scheme of the invention is as follows:
a pre-detection device before insulation test of stator winding of water-cooled generator includes shell, display and operation key are set on surface of shell, connection row for connecting test connection point of stator winding of water-cooled generator is set on side surface of shell, 7 connection terminals for connecting with A, B, C three-phase, excitation end water inlet and water collecting pipe, steam end water outlet and water collecting pipe, sleeve water outlet and water collecting pipe, earth seven measurement points are set on connection row, pre-detection circuit is set in shell, pre-detection circuit includes power module, ammeter, voltmeter, first switch K1, second switch K2 and controller, one electrode of power module is connected with one end of ammeter, another end of ammeter is connected with movable contact of first switch K1 through first output switch M1, static contact of first switch K1 is 7, the power supply module is respectively connected with 7 binding posts of the wire bank, the other electrode of the power supply module is connected with a movable contact of a second change-over switch K2 through a second output switch M2, 7 stationary contacts of the second change-over switch K2 are respectively connected with 7 binding posts of the wire bank, two ends of a voltmeter are respectively connected with movable contact sides of a first change-over switch K1 and a second change-over switch K2, signal output ends of an ammeter and the voltmeter are respectively connected with a signal output end of a controller, an output end of the controller is respectively connected with an input end of a display, a control end of a first output switch M1, a controller end of a first change-over switch K1, a control end of a second output switch M2 and a controller end of a second change-over switch K2, and an output end of an operation key is connected with an input end of the controller, wherein:
the power supply module is an adjustable direct current stabilized power supply, the output voltage range is direct current 0V-500V, the controller end of the power supply module is connected with the output end of the controller, and the output direct current voltage value of the power supply module is adjusted through the controller;
the first output switch M1 and the second output switch M2 are used for switching on or off the pre-detection circuit, and corresponding operations are carried out through the controller;
the first change-over switch K1 and the second change-over switch K2 are used for adjusting a contact point accessed to the pre-detection circuit, and the moving contacts of the first change-over switch K1 and the second change-over switch K2 are adjusted to be correspondingly switched by the controller;
the ammeter is used for collecting the current value of the pre-detection circuit, namely the current between the measuring points of the pre-detection circuit, and transmitting the current data to the controller for fault judgment;
the voltmeter is used for collecting the voltage between the first change-over switch K1 and the second change-over switch K2, namely the voltage between the measuring points of the access pre-detection circuit, and transmitting the voltage data to the controller for fault judgment;
the controller is used for receiving current data acquired by the ammeter and voltage data acquired by the voltmeter, dividing the voltage by the current to obtain corresponding resistance data, and judging the fault type according to the resistance data.
The controller is the prior art, such as a PLC controller, a single chip controller and the like.
The display is used for displaying the data information acquired by the controller or displaying the fault type acquired by the controller;
the operation keys are used for inputting instructions to the controller.
A pre-detection method before insulation test of a stator winding of a water-cooled generator based on a pre-detection device comprises the following steps:
s1: 7 binding posts on the wiring row of the pre-detection device are respectively connected with seven measuring points of a three-phase junction of a stator winding A, B, C of the water-cooled generator, a first water collecting pipe junction (excitation end water inlet water collecting pipe), a second water collecting pipe junction (steam end water outlet water collecting pipe), a third water collecting pipe junction (sleeve water outlet water collecting pipe) and a ground junction, and detection is started;
s2: turning on the first output switch M1 and the second output switch M2, controlling the first switch K1 to be connected to the A-phase connection point and controlling the second switch K2 to be connected to the B-phase connection point;
s3: adjusting the output voltage of the power supply module to a preset voltage value;
s4: the voltmeter measures the voltage U between the A phase contact and the B phase contactA-BCurrent I between A phase contact and B phase contact of ammeterA-BObtaining the resistance R between the phase A contact and the phase B contact through the formula R ═ U/IA-B；
S5: after the test is finished, reducing the output voltage of the power supply module to zero;
s6: controlling the first switch K1 to connect to the B phase connection point and the second switch K2 to connect to the A phase connection point, repeating the steps S3-S5, and measuring the voltage U between the B phase connection point and the A phase connection pointB-ACurrent I between phase B and phase AB-AAnd calculating to obtain the resistance R between the B phase contact point and the A phase contact pointB-A；
S7: changing the contact point, repeating the steps S2-S6 to obtain: u shapeB-C、UC-B、UC-A、UA-C、USink 1-ground、UFloor-sink 1、USink 2-ground、UGround-sink 2、USink 3-ground、UGround-sink 3And IB-C、IC-B、IC-A、IA-C、ISink 1-ground、IFloor-sink 1、ISink 2-ground、IGround-sink 2、ISink 3-ground、IGround-sink 3(ii) a Wherein, UB-CRepresenting the measured voltage, U, between the B and C phase junctionsC-BRepresenting the measured voltage between the C-phase contact point and the B-phase contact point, and so on; u shapeSink 1-groundRepresenting the measured voltage between the junction of the first catchment pipe and the earth connection, UFloor-sink 1The measured voltage between the earth junction and the first water collecting pipe junction is represented, and the rest can be done; i isB-CThe current between the B phase contact point and the C phase contact point is measured, and the like; i isSink 1-groundRepresenting the measured current between the first water collecting pipe joint and the earth joint, and so on; sequentially calculating to obtain RB-C、RC-B、RC-A、RA-C、RSink 1-ground、RFloor-sink 1、RSink 2-ground、RGround-sink 2、RSink 3-ground、RGround-sink 3Wherein R isB-CRepresenting the resistance between the B phase contact point and the C phase contact point, and so on; rSink 1-groundRepresenting the resistance between the first water collecting pipe joint and the earth joint, and so on;
s8: calculating the water resistance R of the stator winding single-phase and opposite catchment pipes according to the measured valuesPhase-sink：
RPhase-sink＝(RA-B+RB-A+RB-C+RC-B+RC-A+RA-C)/12
S9: the first output switch M1 and the second output switch M2 are switched on, the first switch K1 is controlled to be connected to all the junction points of the water collecting pipes simultaneously, the second switch K2 is controlled to be connected to the ground junction point, the output voltage of the power supply module is adjusted to be 0 in a preset voltage value, and the voltmeter measures the voltage U between the first switch K1 and the second switch K2Summary of the invention；
S10: controlling the second switch K2 to be connected to all the junction points of the water collecting pipes at the same time, controlling the first switch K1 to be connected to the ground junction point, adjusting the output voltage of the power supply module to a preset voltage value of 0, and measuring the voltage U between the first switch K1 and the second switch K2 by a voltmeterGround-summaryAfter the test is finished, reducing the output voltage of the power supply module to zero;
s11: and (3) fault judgment:
a. if R isSink n-groundAnd REarth-sink nThe larger value of the two is less than 10 times of the smaller value, and the two are both between 30k omega and 500k omega, the branch of the water collecting pipe is judged to be normally insulated to the ground;
wherein R isSink n-groundAnd RFloor-sink 1In which n is 1, 2, 3, such as RSink 1-groundAnd RFloor-sink 1In the two, RSink 1-groundIs a large value, RFloor-sink 1Is a smaller value, RSink 1-ground/RFloor-sink 1If the current collector is less than 10 and both the current collector and the current collector are between 30k omega and 500k omega, the first water collecting pipe branch is normally insulated to the ground, and the branch has a low possibility of having an insulation weak point;
b. if R isSink n-groundAnd REarth-sink nIf the number of the branches is less than 30k omega, judging that the branch of the water collecting pipe has an insulation weak point;
wherein R isSink n-groundAnd REarth-sink nIn which n is 1, 2, 3, such as RSink 2-groundAnd RGround-sink 2If the number of the branches is less than 30k omega, the second water collecting pipe branch is judged to have an insulation weak point; the method proposes to carry out key investigation on the ground insulation of the relevant parts of the water collecting pipe branches, and the main investigation directions sequentially comprise the following steps from large to small according to the fault occurrence probability: the branch water collecting pipe is insulatedThe flange (including the insulating cover of the fastening bolt, insulating pad), temperature measuring element and its temperature measuring line (including two parts inside and outside the machine) arranged along the surface of the branch catchment pipe, each insulating support of the branch catchment pipe, the lead wire of the branch catchment pipe (including the test line itself);
c. if R isSink n-groundAnd REarth-sink nAre all greater than 500k omega and RSink n-groundAnd REarth-sink nIf the deviation is less than 10%, judging that the branch water collecting pipe is higher in insulation;
wherein R isSink n-groundAnd REarth-sink nIn which n is 1, 2, 3, such as RSink 3-groundAnd RGround-sink 3Are both greater than 500k and RSink 3-groundAnd RGround-sink 3If the deviation is less than 10%, it is determined that the insulation of the branch of the third header is too high, there may be a broken line, a loose joint, or a wrong lead-out terminal of the connected header, and it is necessary to check whether the lead-out terminal of the header and the test line of the branch header of the pre-tester are broken or connected in a false manner, and determine whether the lead-out terminal of the connected branch header is correct (due to the fact that there are many terminals on the temperature measurement connection line or the tester is not familiar with the drawing, the phenomenon of wrong connection of the terminals may occur).
d. If U isSummary of the inventionOr UGround-summaryIs greater than 100mV or RSink n-groundAnd REarth-sink nThe larger of the two is greater than ten times the smaller, and RSink n-groundOr REarth-sink nIf the internal cooling water polarization potential is higher than 500k omega, judging that the internal cooling water polarization potential is higher;
wherein R isSink n-groundAnd REarth-sink nIn which n is 1, 2, 3, such as RSink 2-groundAnd RGround-sink 2In the two, RSink 2-groundIs a large value, RGround-sink 2Is a smaller value, RSink 2-ground/RGround-sink 2If the polarization potential of the inner cooling water is higher than 10 and one of the polarization potential and the other polarization potential is 500k omega, judging that the polarization potential of the inner cooling water is higher;
also such as USummary of the inventionIf the absolute value of the voltage is 640mV, judging that the polarization potential of the internal cooling water is higher, suggesting to check the conductivity and the copper ion content of the internal cooling water, and confirming whether various parameters of water quality are qualified, wherein the insulated water conduit is possibly knocked when the conductivity or the copper ions are overhigh and other water quality parameters are abnormal;if the preliminary detection is still needed, it is recommended to adopt a high-voltage measurement mode to reduce the influence of polarization potential.
e. If U isSummary of the inventionOr UGround-summaryIf the absolute values of the voltages are less than 100mV, judging that the polarization potential of the internal cooling water is normal;
the step S9 fault judgment further includes judgment of whether the capacity of the instrument before the dc withstand voltage test meets the test requirement, where the criterion is as follows:
f. if R isPhase-sinkIf the voltage is less than 300k omega, judging that the inter-phase water resistance of the stator winding is too small; the controller prompts that the capacity of the required direct-current withstand voltage test instrument is higher, and the conductivity of cold water in the stator and copper ions need to be further reduced or whether the capacity of the instrument meets the requirement of the direct-current withstand voltage test is calculated according to the test voltage.
g. If R isPhase-sinkIf the resistance is more than 300k omega, judging that the inter-phase water resistance of the stator winding meets the requirement; a dc withstand voltage test can be performed.
The preset voltage value of the step S3 is 0-500V, and preferably, the preset voltage value of the step S3 is 0V, 1V, 24V, 100V, 250V and 500V.
The specific output voltage can be set to 500V gear, 250V gear, 100V gear, 24V gear, 1V gear and 0V gear, when the test is carried out in all gears, if the output current exceeds 1A, the instrument automatically drops to 24 gears for testing, and if the output current still exceeds 1A in the 24V gear, the instrument drops to 1V gear for testing, so that the test instrument and the tested circuit are prevented from being damaged under the condition that the resistance of the tested circuit is too low or metallic grounding occurs.
Compared with the prior art, the method has the following beneficial technical effects:
1) the invention provides a method for pre-detecting before insulation test of a water-cooled generator, designs a set of complete pre-detection fault diagnosis process, provides various fault diagnosis criteria, can quickly judge possible fault reasons through practice, provides a corresponding detection range and a corresponding method, and has great guiding significance for field work.
2) Abandons the traditional method of measuring the water resistance (U) of each winding to the water collection pipea-sink、Ub-sink、Uc-sink) The method for judging whether the capacity of instrument meets the requirement is easily affected by polarization potential, and the method adopts forward and reverse measurement of water resistance between three phases, and then calculates the average value as the test value of the interphase water resistance of stator winding, namely RPhase-sink＝(RA-B+RB-A+RB-C+RC-B+RC-A+RA-C) And/12, calculating the average value of the water resistance of the winding to the water collecting pipe, wherein the actual measurement loop is UA—B＝(UA-sink+Usink-B) Therefore, the positive and negative polarization potentials of the two water loops are offset, and the measurement influence of the polarization potentials on the water resistance of the single-phase water collecting pipe of the stator winding is greatly reduced.
3) The device can adopt a high-capacity direct current power supply with high voltage of 500V and highest output current of 3-100mA for pre-detection at most, effectively improves the signal amplitude, reduces the signal-to-noise ratio and greatly improves the accuracy of a test result.
4) The device can adopt a prefabricated program to carry out full-automatic measurement on the main water collecting pipe and each branch thereof, greatly simplifies the processes of repeated switching of test contacts, switching of the positive and negative polarities of the multimeter, manual operation and the like of testers, and obviously improves the test efficiency.
5) The method determines various types of criteria, greatly improves the efficiency of fault diagnosis of the tester, and solves the problems of insufficient experience of the tester, field wiring errors and the like.
6) The device has the advantages of small volume, light weight, convenient use and good anti-interference effect, and is an innovation on an electrical test tool.
Drawings
FIG. 1 is a schematic structural diagram of a pre-detection apparatus according to the present invention.
FIG. 2 is a schematic circuit diagram of the pre-detection circuit of the present invention.
Fig. 3 is a schematic view of the connection of the water collection pipe.
FIG. 4 is a schematic diagram of an equivalent circuit of a water collecting pipe connection, wherein R1Water (W)、R2Water (W)……R9Water (W)The equivalent water resistance of the water in the insulated water conduit is shown.
Detailed Description
The following detailed description of embodiments of the present invention is provided in connection with the accompanying drawings and examples.
The on-site water collecting pipe is generally provided with 3 water collecting pipe branches, which comprise a first water collecting pipe (excitation end water inlet water collecting pipe) for water inlet, a second water collecting pipe (steam end water outlet water collecting pipe) for water outlet and a third water collecting pipe (casing pipe water outlet water collecting pipe), as shown in figure 3, the connecting structure of the first water collecting pipe and the second water collecting pipe is schematically shown, in the figure, a first water collecting pipe 1a is communicated with a second water collecting pipe 1b sequentially through a first insulating water conduit 3a, a stator bar 4 made of an air-core copper wire and a first insulating water conduit 3b, the insulating water conduits and the stator bars between the first water collecting pipe 1a and the second water collecting pipe 1b are divided into three groups (taking 60 ten thousand of Ha-power machines as an example, the total number of three-phase stator bars is 84), the three groups are divided into three groups on average and respectively used as A, B, C stator windings, the outer surfaces of the three-phase stator windings are wrapped with insulating layers, and stator internal cooling water flows through the inside of the air-core copper wire; as shown in fig. 2, one end of the stator bar is used as a junction (measuring point) of A, B, C three phases, the tube walls of the first catchment tube 1a, the second catchment tube 1b and the third catchment tube 1c are respectively led out with junctions (measuring points) as a first catchment tube junction 2a, a second catchment tube junction 2b and a third catchment tube junction 2c which are in one-to-one correspondence, the three catchment tube junctions can be led out to a temperature measuring terminal board 7 through a catchment tube leading-out wire 6, so that the wiring detection is convenient, and the preliminary detection is carried out by connecting A, B, C three-phase junctions, the catchment tube junctions and the ground through the preliminary detection device.
Taking the detection between the phase-A contact and the phase-B contact as an example, the controller controls the first switch K1 to switch on the terminal connected with the phase-A contact, and controls the second switch K2 to switch on the terminal connected with the phase-B contact, and switches on the first output switch M1 and the second output switch M2 to form a loop, wherein the loop is a power module-the first output switch M1-the first switch K1-the phase-A contact-a water resistance R2Water (W)Second catchment-water resistance R4Water (W)-phase B contact-second transfer switch K2-second output switch M2-power supply module, voltmeter to measure voltage U between phase a contact and phase B contactA-BThe ammeter measures the current I between the phase A contact and the phase B contactA-BObtaining the phase A connection through the formula R ═ U/IResistance R between point and B phase contact pointA-B；
Taking the detection between the B junction and the second water collecting pipe 1B as an example, the controller controls the first switch K1 to switch on the binding post connected with the B junction, and controls the second switch K2 to switch on the binding post connected with the second water collecting pipe junction 2B, and the first output switch M1 and the second output switch M2 are conducted to form a loop, and the loop is a power module, namely the first output switch M1, the first switch K1, the B junction, a water resistance R4Water (W)Second water collection pipe connection 2B, second changeover switch K2, second output switch M2, power supply module, voltmeter to measure the voltage U between B connection and second water collection pipe connection 2BB-sink 2The ammeter measures the current I between the B junction and the second water collecting pipe junction 2BB-sink 2The resistance R between the B junction and the second header junction 2B is obtained by the formula R ═ U/IB-sink 2(ii) a And so on.
Example 1
After the Guangxi H power plant #2 generator is overhauled, before a generator stator winding direct-current withstand voltage and leakage current test is carried out, the voltage, the current and the insulation resistance between each water collecting pipe branch and the ground are respectively measured positively and negatively by the method, and the data of the first water collecting pipe branch are as follows: rSink 1-ground＝153kΩ(24.2V/158μA)/RFloor-sink 1209k Ω (24.1V/115 μ a), data of the second header branch: rSink 2-ground＝112kΩ(23.7V/212μA)/RGround-sink 2147k Ω (23.8V/162 μ a), third header branch data: rSink 3-ground＝2.3kΩ(23.0V/10.0mA)/RGround-sink 39.8k omega (23.4V/2.4mA), the test result shows that the forward and reverse ground resistance of the third catchment pipe branch is less than 30k, the condition of 'criterion b' is met, the third catchment pipe branch is judged to have an insulation weak point, the ground insulation resistance is abnormally low, the fault range prompted by the instrument is gradually checked, and finally the fault is finally found out because the insulation damage of the water outlet temperature measuring line on the catchment pipe branch is caused by the fact that the whole temperature measuring line is not fixed firmly and slightly vibrates and wears in operation, and finally the insulation damage of the temperature measuring line is caused, and because the water outlet temperature measuring point is a T-shaped thermocouple, the temperature measuring line and the temperature measuring line are directly welded on the catchment pipe branch, so the temperature measuring line and the temperature measuring line are directly welded on theThe water collecting pipe is communicated, after the temperature measuring wire is damaged in an insulation way, under the condition that the oil pollution in the machine is serious, the temperature measuring wire and the generator shell (which is a grounding body) are lower in insulation, and after the insulation damage is repaired, the branch earth insulation resistance of the water collecting pipe is tested to rise to RSink 3-ground＝96kΩ/RGround-sink 3＝125kΩ。
Example 2
After a stator bar of a #2 generator of the Hunan J power plant is replaced, before a DC withstand voltage and leakage current test after repair is carried out, the DC voltage values between a water collecting pipe and the ground are respectively U through forward and reverse testing by the method of the inventionSummary of the invention＝-135mV、UGround-summary142mV, the absolute values are all more than 100mV, the polarization potential of the internal cooling water is judged to be higher, the difference between the detected internal cooling water conductivity and the normal running stator internal cooling water quality requirements (the conductivity is less than 1.5 mu S/cm, and the copper ion is less than 20 mu g/L) is larger, after the working personnel processes the water quality, the conductivity is reduced to 0.6 mu S/cm and the copper ion is reduced to 37 mu g/L (the copper ion is still not reduced to the standard requirement range, but the difference is obviously smaller), and the direct current voltage values between the retest catchment pipe and the ground are respectively USummary of the invention＝-31mV、UGround-summary＝34mV。
Example 3
Before a direct-current withstand voltage test is carried out in the overhaul of a #1 generator of a Hunan Y power plant, a universal meter is used for testing the resistance of a stator winding single-phase pair water collecting pipe between 202 and 338k omega, the resistance is estimated according to the minimum value, when the voltage is increased to 55kV, the total leakage current is about 272mA, the requirement of the capacity of the test can be met by preliminarily judging a 300mA/60kV direct-current high-voltage generator, but in the actual voltage increasing process, when the voltage is increased to 40kV, the total leakage current reaches 238mA, when the voltage is increased to 55kV, the total leakage current is expected to reach 327mA, and the capacity of a test. After the test is stopped, the voltage is increased to 500V by the method of the invention, and the inter-phase water resistance of the winding is measured to obtain UA-B＝502.6V、UB-A＝496.7V、UB-C＝503.3V、UC-B＝501.1V、UC-A＝497.8V、UA-C502.4V and IA-B＝1.397mA、IB-A＝1.360mA、IB-C＝1.427mA、IC-B＝1.430mA、IC-A＝1.447mA、IA-C1.447mA, and calculating the water resistance R of the stator winding single-phase-to-phase water collection pipe according to the water resistance RPhase-sink＝(RA-B+RB-A+RB-C+RC-B+RC-A+RA-C) The result shows that the deviation of the winding interphase water resistance test data and the large-capacity direct high-power test data is 5% under the condition that the output voltage of the pre-detection device is higher and adopted, the deviation of a universal meter is 20% -91%, and the measurement precision of the stator winding single-phase to catchment pipe water resistance of the pre-detection device is far higher than that of the universal meter.
Through practical application, the invention obtains the same or similar effect, and the specific results are shown in the following table:
table 1 catchment branch n fault diagnosis data table 1
Figure BDA0002975702750000091
Table 2 catchment branch n fault diagnosis data table 2
Figure BDA0002975702750000092
Table 3 catchment branch n fault diagnosis data table 3
Figure BDA0002975702750000101
The device and the method can effectively solve the problems of more interference factors and inaccurate test result in the pre-detection process before the insulation test of the stator winding of the current water-cooled generator, can quickly judge possible fault reasons, provide a corresponding detection range and a corresponding method, and have great guiding significance for field work.

Claims (5)

1. The pre-detection device before insulation test of the stator winding of the water-cooled generator is characterized by comprising a shell (8), wherein the surface of the shell (8) is respectively provided with a display (9) and an operation key (10), the side surface of the shell (8) is provided with a wiring row (11) which is used for being connected with a test contact of the stator winding of the water-cooled generator, the wiring row is respectively provided with 7 wiring terminals which are respectively connected with seven measuring points of A, B, C three phases of the stator winding of the water-cooled generator, an excitation end water inlet and water collecting pipe, a steam end water outlet and water collecting pipe, a sleeve water outlet and water collecting pipe and the ground, a pre-detection circuit is arranged in the shell (8), the pre-detection circuit comprises a power module, an ammeter, a voltmeter, a first change-over switch K1, a second change-over switch K2 and a controller, one electrode of the power module is connected with one end of the ammeter, the other end of the ammeter is connected with the movable contact of a first change-over switch K1 through a first output switch M1, 7 fixed contacts of a first change-over switch K1 are respectively connected with 7 wiring terminals of the wiring bank, the other electrode of the power supply module is connected with the movable contact of a second change-over switch K2 through a second output switch M2, 7 fixed contacts of a second change-over switch K2 are respectively connected with 7 wiring terminals of the wiring bank, two ends of the voltmeter are respectively connected with the movable contact sides of the first change-over switch K1 and the second change-over switch K2, signal output ends of the ammeter and the voltmeter are respectively connected with the signal output end of the controller, output ends of the controller are respectively connected with an input end of the display, a control end of the first output switch M1, a controller end of the first change-over switch K1, a control end of the second output switch M2 and a controller end of the second change-over switch K2, and output ends of the operation keys are connected with the input end of the controller, wherein:
the power supply module is an adjustable direct current stabilized power supply, the output voltage range is direct current 0V-500V, the controller end of the power supply module is connected with the output end of the controller, and the output direct current voltage value of the power supply module is adjusted through the controller;
the first output switch M1 and the second output switch M2 are used for switching on or off the pre-detection circuit, and corresponding operations are carried out through the controller;
the first change-over switch K1 and the second change-over switch K2 are used for adjusting a contact point accessed to the pre-detection circuit, and the moving contacts of the first change-over switch K1 and the second change-over switch K2 are adjusted to be correspondingly switched by the controller;
the ammeter is used for collecting the current value of the pre-detection circuit, namely the current between the measuring points of the pre-detection circuit, and transmitting the current data to the controller for fault judgment;
the voltmeter is used for collecting the voltage between the first change-over switch K1 and the second change-over switch K2, namely the voltage between the measuring points of the access pre-detection circuit, and transmitting the voltage data to the controller for fault judgment;
the controller is used for receiving current data acquired by the ammeter and voltage data acquired by the voltmeter, dividing the voltage by the current to obtain corresponding resistance data, and judging the fault type according to the resistance data.
2. A pre-detection method before insulation test of a stator winding of a water-cooled generator based on a pre-detection device is characterized by comprising the following steps:
s1: 7 binding posts on the wiring row of the pre-detection device are respectively connected with seven measuring points of a three-phase junction of a stator winding A, B, C of the water-cooled generator, a first water collecting pipe junction, a second water collecting pipe junction, a third water collecting pipe junction and a large ground junction, and detection is started;
s2: turning on the first output switch M1 and the second output switch M2, controlling the first switch K1 to be connected to the A-phase connection point and controlling the second switch K2 to be connected to the B-phase connection point;
s3: adjusting the output voltage of the power supply module to a preset voltage value;
s4: the voltmeter measures the voltage U between the A phase contact and the B phase contactA-BCurrent I between A phase contact and B phase contact of ammeterA-BObtaining the resistance R between the phase A contact and the phase B contact through the formula R ═ U/IA-B；
S5: after the test is finished, reducing the output voltage of the power supply module to zero;
s6: controlling the first switch K1 to connect to the B phase connection point and the second switch K2 to connect to the A phase connection point, repeating the steps S3-S5, and measuring the voltage U between the B phase connection point and the A phase connection pointB-ACurrent I between phase B and phase AB-AAnd calculating to obtain the connection point of the B phase and the A phaseResistance between points RB-A；
S7: changing the contact point, repeating the steps S2-S6 to obtain: u shapeB-C、UC-B、UC-A、UA-C、USink 1-ground、UFloor-sink 1、USink 2-ground、UGround-sink 2、USink 3-ground、UGround-sink 3And IB-C、IC-B、IC-A、IA-C、ISink 1-ground、IFloor-sink 1、ISink 2-ground、IGround-sink 2、ISink 3-ground、IGround-sink 3(ii) a Wherein, UB-CRepresenting the measured voltage, U, between the B and C phase junctionsC-BRepresenting the measured voltage between the C-phase contact point and the B-phase contact point, and so on; u shapeSink 1-groundRepresenting the measured voltage between the junction of the first catchment pipe and the earth connection, UFloor-sink 1The measured voltage between the earth junction and the first water collecting pipe junction is represented, and the rest can be done; i isB-CThe current between the B phase contact point and the C phase contact point is measured, and the like; i isSink 1-groundRepresenting the measured current between the first water collecting pipe joint and the earth joint, and so on; sequentially calculating to obtain RB-C、RC-B、RC-A、RA-C、RSink 1-ground、RFloor-sink 1、RSink 2-ground、RGround-sink 2、RSink 3-ground、RGround-sink 3Wherein R isB-CRepresenting the resistance between the B phase contact point and the C phase contact point, and so on; rSink 1-groundRepresenting the resistance between the first water collecting pipe joint and the earth joint, and so on;
s8: calculating the water resistance R of the stator winding single-phase and relative catchment pipe according to the ownership measured valuePhase-sink：
RPhase-sink＝(RA-B+RB-A+RB-C+RC-B+RC-A+RA-C)/12
S9: the first output switch M1 and the second output switch M2 are switched on, the first switch K1 is controlled to be connected to all the junction points of the water collecting pipes simultaneously, the second switch K2 is controlled to be connected to the ground junction point, the output voltage of the power supply module is adjusted to a preset voltage value of 0, and the voltmeter is connected to the power supply moduleThe voltage U between the first switch K1 and the second switch K2 is measuredSummary of the invention；
S10: controlling the second switch K2 to be connected to all the junction points of the water collecting pipes at the same time, controlling the first switch K1 to be connected to the ground junction point, adjusting the output voltage of the power supply module to a preset voltage value of 0, and measuring the voltage U between the first switch K1 and the second switch K2 by a voltmeterGround-summaryAfter the test is finished, reducing the output voltage of the power supply module to zero;
s11: and (3) fault judgment:
a. if R isSink n-groundAnd REarth-sink nThe larger value of the two is less than 10 times of the smaller value, and the two are both between 30k omega and 500k omega, the branch of the water collecting pipe is judged to be normally insulated to the ground;
b. if R isSink n-groundAnd REarth-sink nIf the number of the branches is less than 30k omega, judging that the branch of the water collecting pipe has an insulation weak point;
c. if R isSink n-groundAnd REarth-sink nAre all greater than 500k omega and RSink n-groundAnd REarth-sink nIf the deviation is less than 10%, judging that the branch water collecting pipe is higher in insulation;
d. if U isSummary of the inventionOr UGround-summaryIs greater than 100mV or RSink n-groundAnd REarth-sink nThe larger of the two is greater than ten times the smaller, and RSink n-groundOr REarth-sink nIf the internal cooling water polarization potential is higher than 500k omega, judging that the internal cooling water polarization potential is higher;
e. if U isSummary of the inventionOr UGround-summaryIf the absolute values of the voltages are less than 100mV, the polarization potential of the internal cooling water is judged to be normal.
3. The preliminary testing method according to claim 2, wherein the step S11 fault judgment further comprises judgment before the dc withstand voltage test, and the criteria are as follows:
f. if R isPhase-sinkIf the voltage is less than 300k omega, judging that the inter-phase water resistance of the stator winding is too small;
g. if R isPhase-sinkAnd if the resistance is more than 300k omega, judging that the inter-phase water resistance of the stator winding meets the requirement.
4. The pre-detection method according to claim 2, wherein the preset voltage value of step S3 is 0-500V.
5. The pre-detection method according to claim 4, wherein the preset voltage values of step S3 are 1V, 24V, 100V, 250V and 500V.
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