CN113030795B - 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 PDFInfo
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- CN113030795B CN113030795B CN202110273892.2A CN202110273892A CN113030795B CN 113030795 B CN113030795 B CN 113030795B CN 202110273892 A CN202110273892 A CN 202110273892A CN 113030795 B CN113030795 B CN 113030795B
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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
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- 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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- 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
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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
- G01R31/34—Testing dynamo-electric machines
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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
- G01R31/52—Testing for short-circuits, leakage current or ground faults
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Abstract
The invention relates to a pre-detection device and a method before insulation test of a stator winding of a water-cooled generator, which adopts the technical scheme that the device comprises a shell, wherein 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 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 stator winding A, a stator winding B and a stator winding C of the water-cooled generator, an excitation end water inlet water collecting pipe, a steam end water outlet water collecting pipe, a sleeve water outlet water collecting pipe and the ground, and a pre-detection circuit is arranged in the shell.
Description
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 50150-2016 (Standard for testing Handover of Electrical Equipment in Electrical installation engineering) and DL/T596-1996 (preventive test procedure for Electrical Equipment), the insulation resistance of a winding and a catchment pipe of a motor with a non-dead-grounded catchment pipe is measured respectively, the influence of water is eliminated by adopting a shielding method when the insulation resistance of the winding is measured, and the measurement result meets the regulations of a manufacturing factory. 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) Measuring the ground resistance of the water collecting pipe: 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 a meter needle.
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 "pre-detection" process is divided into multiple types according to the root cause and the position of the fault, and sometimes 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 flowing, if a multimeter is used for measuring the earth resistance of a water collecting pipe when the polarization potential of internal cold water is higher, the polarization potential of the digital multimeter can be superposed with the output voltage of the multimeter, so that the data deviation of the earth insulation resistance of the water collecting pipe 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 internal cooling water is high, 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 the capacity of the tester by a tester 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 low insulation resistance obtained by the test, so that the false impression that the insulation of a tested product is unqualified is caused, and the insulation resistance is possibly 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 lead insulation damage and the like of the middle links of the leads of the single or a plurality of water collecting pipes 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 realize 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 comprises a shell, the surface of the shell is respectively provided with a display and an operation button, the side surface of the shell is provided with a wiring row for connecting with test contacts of the stator winding of the water-cooled generator, the wiring row is respectively provided with 7 wiring terminals for respectively connecting with seven measuring points of a water-cooled generator stator winding A, a water collecting pipe of a excitation end, a water collecting pipe of a steam end, a water collecting pipe of a sleeve pipe and a ground, a pre-detection circuit is arranged in the shell and 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 a movable contact of the first change-over switch K1 through a first output switch M1, the fixed contacts of the first change-over switch K1 are 7 and are respectively connected with 7 binding posts of the wiring bank, the other electrode of the power supply module is connected with the movable contact of the second change-over switch K2 through the second output switch M2, the fixed contacts of the second change-over switch K2 are 7 and are respectively connected with 7 binding posts 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, the signal output ends of the ammeter and the voltmeter are respectively connected with the signal output end of the controller, the output end of the controller is respectively connected with the input end of the display, the control end of the first output switch M1, the controller end of the first change-over switch K1, the control end of the second output switch M2 and the controller end of the second change-over switch K2, and the output end of the operation key is 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 operation is carried out through the controller;
the first change-over switch K1 and the second change-over switch K2 are used for adjusting the contact points 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 through 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 pre-detection circuit is accessed, and the voltage data is transmitted 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 PLC controller, single chip controller etc..
The display is used for displaying the data information acquired by the controller or displaying the fault type acquired by the controller;
the operation key is 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 stator winding A, a stator winding B and a stator winding C of the water-cooled generator, a first water collecting pipe joint (an excitation end water inlet water collecting pipe), a second water collecting pipe joint (a steam end water outlet water collecting pipe), a third water collecting pipe joint (a sleeve water outlet water collecting pipe) and a ground joint, and detection is started;
s2: switching on a first output switch M1 and a second output switch M2, controlling the first change-over switch K1 to be connected to the phase A connecting point, and controlling the second change-over switch K2 to be connected to the phase B connecting 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 phase A contact and the phase B contact A-B Current I between A phase contact and B phase contact of ammeter A-B Obtaining the resistance R between the A-phase contact and the B-phase contact through a formula R = U/I A-B ；
S5: after the test is finished, reducing the output voltage of the power supply module to zero;
s6: controlling the first change-over switch K1 to be connected to the B phase contact and the second change-over switch K2 to be connected to the A phase contact, repeating the steps S3-S5, and measuring the voltage U between the B phase contact and the A phase contact B-A Current I between phase B and phase A B-A And calculating to obtain the resistance R between the B phase contact point and the A phase contact point B-A ；
S7: changing the contact point, and repeating the steps S2-S6 to respectively obtain: u shape B-C 、U C-B 、U C-A 、U A-C 、U Sink 1-ground 、U Floor-sink 1 、U Sink 2-ground 、U Floor-sink 2 、U Sink 3-ground 、U Floor-sink 3 And I B-C 、I C-B 、I C-A 、I A-C 、I Sink 1-ground 、I Floor-sink 1 、I Hui 2-ground 、I Floor-sink 2 、I Sink 3-ground 、I Ground-sink 3 (ii) a Wherein, U B-C Representing the measured voltage, U, between phase B and phase C C-B The measured voltage between the C-phase contact and the B-phase contact is represented, and so on; u shape Sink 1-ground Representing the measured voltage between the junction of the first catchment pipe and the earth connection, U Floor-sink 1 The measured voltage between the earth junction and the first water collecting pipe junction is represented, and the rest can be done; i is B-C The current between the B phase contact point and the C phase contact point is measured, and the like; i is Sink 1-ground The measured current between the first water collecting pipe joint and the ground joint is shown, and the like; sequentially calculating to obtain R B-C 、R C-B 、R C-A 、R A-C 、R Sink 1-ground 、R Floor-sink 1 、R Sink 2-ground 、R Floor-sink 2 、R Sink 3-ground 、R Ground-sink 3 Wherein R is B-C Representing the resistance between the B phase contact point and the C phase contact point, and so on; r is Sink 1-ground Representing 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 values Phase-sink ：
R Phase-sink ＝(R A-B +R B-A +R B-C +R C-B +R C-A +R A-C )/12
S9: switching on the first output switch M1 and the second output switch M2, controlling the first switch K1 to be connected to all the junction points of the water collecting pipes simultaneously, controlling the second switch K2 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 voltmeter Summary of the invention ；
S10: controlling the second diverter switch K2 to be connected to all catchments simultaneouslyThe tube joint controls the first switch K1 to be connected to the earth joint, the output voltage of the power supply module is adjusted to a preset voltage value of 0, and the voltmeter measures the voltage U between the first switch K1 and the second switch K2 Ground-summary After the test is finished, reducing the output voltage of the power supply module to zero;
s11: and (3) fault judgment:
a. if R is Sink n-earth And R Earth-sink n The 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 water collecting pipe branch is judged to be normally insulated to the ground;
wherein R is Sink n-earth And R Floor-sink 1 In which n is 1, 2, 3, such as R Sink 1-ground And R Floor-sink 1 In the two, R Sink 1-ground Is a large value, R Floor-sink 1 Is a smaller value, R Sink 1-ground /R Floor-sink 1 If 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 is Sink n-ground And R Earth-sink n If 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 is Sink n-earth And R Earth-sink n In which n is 1, 2, 3, such as R Sink 2-ground And R Ground-sink 2 If the number of the branches is less than 30k omega, judging that the second water collecting pipe branch has 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 comprises an insulating flange (comprising a fastening bolt insulating sleeve and an insulating pad), a temperature measuring element and a temperature measuring line (comprising an internal part and an external part) which are arranged along the surface of the branch water collecting pipe, insulating supports of the branch water collecting pipe and a lead of the branch water collecting pipe (comprising the test line per se);
c. if R is Sink n-ground And R Earth-sink n Are all greater than 500k omega and R Sink n-earth And R Earth-sink n If the deviation is less than 10%, judging that the branch water collecting pipe is higher in insulation;
wherein R is Sink n-ground And R Earth-sink n In which n is 1, 2, 3, such as R Sink 3-ground And R Floor-sink 3 Are both greater than 500k and R Sink 3-ground And R Ground-sink 3 If 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 is present Summary of the invention Or U Ground-summary Is greater than 100mV or R Sink n-earth And R Earth-sink n The larger of the two is greater than ten times the smaller, and R Sink n-ground Or R Earth-sink n If the polarization potential is larger than 500k omega, judging that the polarization potential of the internal cooling water is higher;
wherein R is Sink n-ground And R Earth-sink n In which n is 1, 2, 3, such as R Hui 2-ground And R Floor-sink 2 In the two, R Hui 2-ground Is a large value, R Floor-sink 2 Is a smaller value, R Hui 2-ground /R Ground-sink 2 If 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 U Summary of the invention If the absolute value of the voltage is 640mV, judging that the polarization potential of the internal cooling water is higher, advising to check the conductivity and the copper ion content of the internal cooling water, and determining whether all parameters of the water quality are qualified, wherein the insulated water conduit is likely to be knocked when the conductivity or the copper ions are overhigh and other water quality parameters are abnormal; if the preliminary detection is still needed, a high voltage measurement mode is recommended to reduce the polarization potential influence.
e. If U is Summary of the invention Or U Ground-summary If 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 of fault judgment further includes judging 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 is Phase-sink If the voltage is less than 300k omega, judging that the inter-phase water resistance of the stator winding is too small; controller promptingThe 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 is Phase-sink If 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, 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 pipe a-sink 、U b-sink 、U c-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 R Phase-sink ＝(R A-B +R B-A +R B-C +R C-B +R C-A +R A-C ) /12, calculating the average value of the water resistance of the winding pair water collecting pipe, and actually measuring the loop to be U A—B ＝(U A-sink +U sink-B ) So that the polarization potentials of the two water circuits are positively and negatively offset each otherThe measurement influence of the polarization potential on the water resistance of the stator winding single-phase relative water collecting pipe 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 circuit schematic 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 header connection, wherein R1 Water (W) 、R2 Water (W) ……R9 Water (I) The equivalent water resistance of the water in the insulated water conduit is shown.
Detailed Description
The following detailed description of the present invention is provided in connection with the accompanying drawings and examples.
The field water collecting pipe is generally provided with 3 water collecting pipe branches, and comprises a first water collecting pipe (excitation end water inlet water collecting pipe) for feeding water, a second water collecting pipe (steam end water outlet water collecting pipe) for discharging water and a third water collecting pipe (sleeve water outlet water collecting pipe), as shown in fig. 3, the connection structure schematic diagram of the first water collecting pipe and the second water collecting pipe is shown, in the diagram, the first water collecting pipe 1a is communicated with the second water collecting pipe 1B sequentially through a first insulating water guiding pipe 3a, a stator bar 4 made of hollow copper wires and a first insulating water guiding pipe 3B, the insulating pipes and the stator bars between the first water collecting pipe 1a and the second water collecting pipe 1B are provided with a plurality of groups (taking 60 ten thousand Ha-power machines as an example, the total number of the three-phase stator bars is 84), the insulating pipes and the insulating bars are evenly divided into three groups which are respectively used as stator windings A, B and C, the outer surfaces of the three-phase stator windings are wrapped with insulating layers, and inner-phase stator water flows in the hollow copper wires; as shown in figure 2, one end of the stator bar is used as a joint (measuring point) of three phases A, B and C, the pipe walls of the first catchment pipe 1a, the second catchment pipe 1B and the third catchment pipe 1C are respectively led out with joints (measuring points) as a first catchment pipe joint 2a, a second catchment pipe joint 2B and a third catchment pipe joint 2C which are in one-to-one correspondence, and the three catchment pipe joints can be led out to a temperature measurement terminal board 7 through a catchment pipe leading-out wire 6 to facilitate wiring detection, so that the pre-detection device is used for carrying out 'pre-detection' on the three-phase joints A, B and C, the catchment pipe joints and the ground.
Taking the detection between the phase A contact and the phase B contact as an example, the controller controls the first change-over switch K1 to switch on the terminal connected with the phase A contact, and controls the second change-over 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 change-over switch K1, the phase A contact and the water resistance R2 Water (I) Second catchment pipe-water resistance R4 Water (I) -phase B contact-second diverter switch K2-second output switch M2-power module, voltmeter measuring voltage U between phase a contact and phase B contact A-B The ammeter measures the current I between the phase A contact and the phase B contact A-B Obtaining the resistance R between the A-phase contact and the B-phase contact through a formula R = U/I A-B ；
Taking the detection between the B junction and the second water collection pipe 1B as an example, the controller controls the first change-over switch K1 to switch on the binding post connected with the B junction, and simultaneously controls the second change-over switch K2 to switch on the binding post connected with the second water collection pipe junction 2B, 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 change-over switch K1-the B junction-the water resistance R4 Water (W) Second water collecting pipe junction 2b second change-over switch K2 second output switch M2 power supplyA module, a voltmeter for measuring the voltage U between the joint B and the joint 2B of the second water collecting pipe B-Hui 2 The ammeter measures the current I between the B junction and the second water collecting pipe junction 2B B-Hui 2 Obtaining the resistance R between the joint B and the joint 2B of the second water collecting pipe by the formula R = U/I B-Hui 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: r is Sink 1-ground ＝153kΩ(24.2V/158μA)/R Floor-sink 1 =209k Ω (24.1V/115 μ a), data of the second water header branch: r Hui 2-ground ＝112kΩ(23.7V/212μA)/R Floor-sink 2 =147k Ω (23.8V/162 μ a), third header branch data: r Sink 3-ground ＝2.3kΩ(23.0V/10.0mA)/R Ground-sink 3 =9.8k Ω (23.4V/2.4 mA), 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 satisfied, the third catchment pipe branch is judged to have 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 found out because the insulation damage of the effluent temperature measuring line on the catchment pipe branch is caused by the weak fixation of the whole temperature measuring line and slight vibration and abrasion during operation, and the insulation damage of the temperature measuring line is finally caused because the effluent temperature measuring point is a T-type thermocouple and is directly welded on the catchment pipe branch, so the temperature measuring line is communicated with the catchment pipe, after the insulation damage of the temperature measuring line, under the condition of serious oil pollution in the machine, the insulation of the temperature measuring line and the generator shell is low, after the insulation damage is repaired, the ground insulation resistance of the catchment pipe branch is tested to rise to R Sink 3-ground ＝96kΩ/R Floor-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 between a water collecting pipe and the ground is tested in a forward and reverse direction by the method of the inventionRespectively has a value of U Summary of the invention ＝-135mV、U Ground-summary =142mV, the absolute values are all larger than 100mV, the polarization potential of the internal cooling water is judged to be higher, the electrical conductivity of the internal cooling water is checked to be 4.7 mu S/cm, the copper ions are checked to be 368 mu g/L, the difference between the electrical conductivity of the internal cooling water and the water quality requirement (the electrical conductivity is smaller than 1.5 mu S/cm, and the copper ions are smaller than 20 mu g/L) of the internal cooling water of the stator in normal operation is larger, after a worker treats the water quality, the electrical conductivity is reduced to be 0.6 mu S/cm, the copper ions are reduced to be 37 mu g/L (the copper ions are not reduced to the standard required range, but the difference is obviously smaller), and the direct current voltage values between the retest water collection pipe and the ground are respectively U Summary of the invention ＝-31mV、U Ground-summary ＝34mV。
Example 3
Before a direct-current withstand voltage test is carried out in the overhaul of a #1 generator of a Y power plant in Hunan province, a universal meter is used for testing the resistance of a single-phase counter catchment pipe of a stator winding between 202 and 338k omega, according to the minimum value estimation, when the voltage is increased to 55kV, the total leakage current is about 272mA, the direct-current high-voltage generator of 300mA/60kV can meet the test capacity requirement by preliminary judgment, 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 predicted to reach 327mA, and the capacity of a test instrument is insufficient. 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 U A-B ＝502.6V、U B-A ＝496.7V、U B-C ＝503.3V、U C-B ＝501.1V、U C-A ＝497.8V、U A-C =502.4V and I A-B ＝1.397mA、I B-A ＝1.360mA、I B-C ＝1.427mA、I C-B ＝1.430mA、I C-A ＝1.447mA、I A-C =1.447mA, and the water resistance R of the stator winding single-phase relative water collecting pipe is calculated according to the water resistance R Phase-sink ＝(R A-B +R B-A +R B-C +R C-B +R C-A +R A-C ) The result shows that the deviation of the winding interphase water resistance test data and the large-capacity direct high-power test data back-calculation water resistance value of the pre-detection device is 5 percent under the condition that the output voltage of the pre-detection device is higher and adopted, the deviation of a multimeter is 20 to 91 percent, and the stator of the pre-detection device isThe measurement accuracy of the water resistance of the single-phase opposite catchment pipe of the winding is far higher than that of a universal meter.
Through practical application, the invention achieves the same or similar effect, and the following table shows that:
table 1 catchment branch n fault diagnosis data table 1
Table 2 catchment branch n fault diagnosis data table 2
Table 3 catchment pipe branch n fault diagnosis data table 3
The invention 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 internal water cooling generator, can quickly judge possible fault reasons, provides a corresponding detection range and a corresponding method, and has great guiding significance for field work.
Claims (5)
1. A pre-detection method before insulation test of a stator winding of a water-cooled generator is characterized by comprising the following steps:
s1: respectively connecting 7 wiring terminals on a wiring row of a pre-detection device with seven measuring points of a stator winding A, a stator winding B and a stator winding C of the internal water-cooled generator, a first water collecting pipe joint, a second water collecting pipe joint, a third water collecting pipe joint and a large ground joint, and starting detection;
s2: switching on a first output switch M1 and a second output switch M2, controlling the first change-over switch K1 to be connected to the phase A connecting point, and controlling the second change-over switch K2 to be connected to the phase B connecting 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 contact A-B Current I between A phase contact and B phase contact of ammeter A-B Obtaining the resistance R between the phase A contact point and the phase B contact point through a formula R = U/I A-B ；
S5: after the test is finished, reducing the output voltage of the power supply module to zero;
s6: controlling the first change-over switch K1 to be connected to the B phase connection point and the second change-over switch K2 to be connected 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 point B-A Current I between phase B and phase A B-A And calculating to obtain the resistance R between the B phase contact point and the A phase contact point B-A ；
S7: changing the contact point, and repeating the steps S2-S6 to respectively obtain: u shape B-C 、U C-B 、U C-A 、U A-C 、U Sink 1-ground 、U Floor-sink 1 、U Sink 2-ground 、U Ground-sink 2 、U Sink 3-ground 、U Ground-sink 3 And I B-C 、I C-B 、I C-A 、I A-C 、I Sink 1-ground 、I Floor-sink 1 、I Sink 2-ground 、I Ground-sink 2 、I Sink 3-ground 、I Ground-sink 3 (ii) a Wherein, U B-C Representing the measured voltage, U, between phase B and phase C C-B The measured voltage between the C-phase contact and the B-phase contact is represented, and so on; u shape Sink 1-ground Representing the measured voltage between the junction of the first catchment pipe and the earth connection, U Floor-sink 1 The measured voltage between the earth junction and the first water collecting pipe junction is represented, and the rest can be done; i is B-C The current between the B phase contact point and the C phase contact point is measured, and the like; i is Sink 1-ground Representing the measured current between the first water collecting pipe joint and the earth joint, and so on; sequentially calculating to obtain R B-C 、R C-B 、R C-A 、R A-C 、R Sink 1-ground 、R Floor-sink 1 、R Sink 2-ground 、R Ground-sink 2 、R Sink 3-ground 、R Floor-sink 3 Wherein R is B-C Representing the resistance between the B phase contact point and the C phase contact point, and so on; r Sink 1-ground Representing 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 value Phase-sink ：
R Phase-sink ＝(R A-B +R B-A +R B-C +R C-B +R C-A +R A-C )/12
S9: switching on the first output switch M1 and the second output switch M2, controlling the first switch K1 to be connected to all the water collecting pipe joints simultaneously, controlling the second switch K2 to be connected to the ground joint, adjusting the output voltage of the power supply module to a preset voltage value, and measuring the voltage U between the first switch K1 and the second switch K2 by a voltmeter Summary of the invention ；
S10: controlling the second change-over switch K2 to be connected to all the junction points of the water collecting pipes at the same time, controlling the first change-over switch K1 to be connected to the earth 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 change-over switch K1 and the second change-over switch K2 by a voltmeter Ground-summary After the test is finished, reducing the output voltage of the power supply module to zero;
s11: and (3) fault judgment:
a. if R is Sink n-ground And R Earth-sink n The 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 is Sink n-earth And R Earth-sink n If 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 is Sink n-ground And R Earth-sink n Are all greater than 500k omega and R Sink n-ground And R Earth-sink n If the deviation is less than 10%, judging that the insulation of the branch water collecting pipe is higher;
d. if U is Summary of the invention Or U Ground-summary Is greater than 100mV or R Sink n-earth And R Earth-sink n The larger of the two is greater than ten times the smaller, andR sink n-ground Or R Earth-sink n If the internal cooling water polarization potential is higher than 500k omega, judging that the internal cooling water polarization potential is higher;
e. if U is Summary of the invention Or U Ground-summary If the absolute values of the voltages are less than 100mV, the polarization potential of the internal cooling water is judged to be normal.
2. The preliminary testing method according to claim 1, wherein the step S11 of determining the fault further comprises determining before a dc withstand voltage test, the criteria are as follows:
f. if R is Phase-sink If the voltage is less than 300k omega, judging that the inter-phase water resistance of the stator winding is too small;
g. if R is Phase-sink And if the resistance is more than 300k omega, judging that the inter-phase water resistance of the stator winding meets the requirement.
3. The pre-detection method according to claim 1, wherein the preset voltage value of step S3 is 0-500V.
4. The pre-detection method according to claim 3, wherein the preset voltage values of step S3 are 1V, 24V, 100V, 250V and 500V.
5. A pre-detection device before insulation test of stator winding of water-cooled generator for implementing the pre-detection method of claim 1, characterized in that the pre-detection device comprises a housing (8), the surface of the housing (8) is respectively provided with a display (9) and an operation button (10), the side surface of the housing (8) is provided with a wiring row (11) for connecting with the test connection point of the stator winding of the water-cooled generator, the wiring row is respectively provided with 7 wiring terminals for respectively connecting with the stator winding A, B and C of the water-cooled generator, an excitation end water inlet and water collection pipe, a steam end water outlet and water collection pipe, a sleeve water outlet and water collection pipe and seven ground test points, the housing (8) is internally provided with a pre-detection circuit, 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 a power supply module is connected with one end of an ammeter, the other end of the ammeter is connected with a movable contact of a first change-over switch K1 through a first output switch M1, 7 static contacts of the first change-over switch K1 are respectively connected with 7 wiring terminals of a wiring 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 static contacts of the second change-over switch K2 are respectively connected with 7 wiring terminals of the wiring bank, two ends of a 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 a signal input end of a controller, and output ends of the controller are respectively connected with an input end of a display, a control end of the first output switch M1, a controller end of the first change-over switch K1, the control end of the second output switch M2 and the controller end of the second change-over switch K2 are connected, and the output end of the operation key is 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 switching off the pre-detection circuit, and corresponding operation is carried out through the controller;
the first change-over switch K1 and the second change-over switch K2 are used for adjusting the contact points connected to the pre-detection circuit and adjusting the moving contacts thereof to be correspondingly switched through 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 pre-detection circuit is accessed, and the voltage data is transmitted 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.
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