CN109375077B - Quick test device and method for insulation parameters of electrical equipment - Google Patents
Quick test device and method for insulation parameters of electrical equipment Download PDFInfo
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- CN109375077B CN109375077B CN201811435387.8A CN201811435387A CN109375077B CN 109375077 B CN109375077 B CN 109375077B CN 201811435387 A CN201811435387 A CN 201811435387A CN 109375077 B CN109375077 B CN 109375077B
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- 238000009413 insulation Methods 0.000 title claims abstract description 69
- 238000000034 method Methods 0.000 title claims abstract description 22
- 238000012360 testing method Methods 0.000 title abstract description 10
- 238000005070 sampling Methods 0.000 claims abstract description 42
- 238000005259 measurement Methods 0.000 claims abstract description 37
- 238000010521 absorption reaction Methods 0.000 claims abstract description 13
- 230000010287 polarization Effects 0.000 claims abstract description 11
- 239000003990 capacitor Substances 0.000 claims description 4
- NAWXUBYGYWOOIX-SFHVURJKSA-N (2s)-2-[[4-[2-(2,4-diaminoquinazolin-6-yl)ethyl]benzoyl]amino]-4-methylidenepentanedioic acid Chemical compound C1=CC2=NC(N)=NC(N)=C2C=C1CCC1=CC=C(C(=O)N[C@@H](CC(=C)C(O)=O)C(O)=O)C=C1 NAWXUBYGYWOOIX-SFHVURJKSA-N 0.000 claims description 3
- 230000008859 change Effects 0.000 claims description 3
- 239000004973 liquid crystal related substance Substances 0.000 claims description 3
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 claims description 3
- 239000011159 matrix material Substances 0.000 claims description 3
- 230000004044 response Effects 0.000 claims description 3
- 230000009466 transformation Effects 0.000 claims description 3
- 238000012545 processing Methods 0.000 claims description 2
- 239000012774 insulation material Substances 0.000 claims 1
- 238000004364 calculation method Methods 0.000 abstract description 5
- 238000012935 Averaging Methods 0.000 abstract description 2
- 238000004422 calculation algorithm Methods 0.000 abstract description 2
- 238000005516 engineering process Methods 0.000 abstract description 2
- 238000004088 simulation Methods 0.000 description 9
- 239000011810 insulating material Substances 0.000 description 8
- 230000009471 action Effects 0.000 description 4
- 238000010586 diagram Methods 0.000 description 3
- 230000008569 process Effects 0.000 description 3
- 230000006978 adaptation Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 230000032683 aging Effects 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000004146 energy storage Methods 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 239000011229 interlayer Substances 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
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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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Abstract
The invention provides a device and a method for rapidly measuring insulation parameters of electrical equipment, wherein the device comprises a control circuit module and a main circuit module connected with the control circuit module; after the method is combined with the method, the insulation parameters of the electrical equipment can be rapidly measured, the measurement time of the absorption ratio can be shortened to within 10s from 60s of the traditional method, the measurement time of the polarization index can be shortened to within 100s from 600s of the traditional method, the probability of the high-voltage tester touching the charged body such as the testing end of the device by mistake can be effectively reduced due to the short measurement time in application, the test safety is improved, and the probability of electric shock accidents during the measurement of the insulation parameters is reduced to 1/6 of the prior art; the feedback control technology of the high-voltage power supply enables the measurement voltage to be more stable and the measurement result to be more accurate; according to the invention, the insulation parameters are obtained by adopting a calculation method, a plurality of groups of sampling moments can be selected for calculation and solution respectively, and the test error can be reduced to be within 0.15% by utilizing a numerical algorithm for averaging, so that the accuracy of the measurement result is improved.
Description
Technical Field
The invention relates to the technical field of insulation parameters of electrical equipment, in particular to a device and a method for rapidly measuring the insulation parameters of the electrical equipment.
Background
The insulation resistance of the electrical equipment is the simplest and most basic method for reflecting the insulation state of the electrical equipment, and the defects of local or whole damp and dirt, insulation breakdown, severe overheat aging and the like of the equipment can be effectively discovered by measuring the insulation resistance of the equipment in a high-voltage test. Engineering, absorption ratio K (60 s insulation resistance R 60s Insulation resistance R with 15s 15s Ratio) or polarization index PI (600 s insulation resistance value R 600s Insulation resistance R with 60s 60s The ratio) is also an important index for judging whether the equipment insulation is wet, and the insulation state is more favorable for judging because K and PI are the ratio of two insulation resistances of the same sample and are irrelevant to the insulation size of the electrical equipment. Insulation resistance, absorption ratio and polarization index are all important insulation parameters of electrical equipment.
The insulation resistance, absorption ratio or polarization index is usually calculated by applying a certain direct current voltage to both ends of the insulation to be tested and measuring the leakage current flowing through the insulation to be tested. The insulation of many electrical devices such as transformers, generators, capacitors and oil-filled current transformers is multi-layered, and the equivalent circuit of the insulation of the electrical devices under direct current voltage can be represented by the model shown in fig. 1.
FIG. 1 consists of three parallel branches, R x Representing the insulation resistance of the insulating material, the branch current i under the action of direct current voltage x Is leakage current formed by conductive particles, reflects the volume leakage condition of an insulating material, is relatively stable, and is i as long as the applied direct current voltage U is unchanged x I.e. constant value; resistor R in series q And capacitor C q Represents equivalent parameters of the insulating material under the action of non-uniformity, layering, dirt and other factors, and when the direct current voltage begins to act, the branch current i q The absorption current formed by the interlayer polarization and the dipole polarization can last for several minutes or even hours according to the dielectric properties, the degree of non-uniformity and the structure; c (C) 0 Representing the geometrical capacitance of the insulating material, when the DC voltage starts to act, the branch current i 0 Charging current formed for rapid polarization of electrons and ions, with duration in microsecond order, decaysAt a high speed, FIG. 2 shows the current in the insulating material over time under the action of a DC voltage, and it can be seen that the current i flowing through the insulating material is the sum of the three currents, i.e
i＝i x +i q +i 0 (1)
For high-capacity electrical such as transformers, the absorption phenomenon is obvious when the insulation parameters are measured, and the current i is absorbed q The insulation parameter measurement takes a long time, and how to obtain the insulation parameter of the tested insulation in a short time is an urgent requirement for the insulation parameter measurement of the high-capacity electrical equipment. The invention provides a device and a method for rapidly measuring insulation parameters of electrical equipment by a sampling method, which can effectively shorten the time consumption of insulation parameter measurement and improve the working efficiency.
Disclosure of Invention
In view of the above, the invention provides a device and a method for rapidly measuring insulation parameters of electrical equipment, which can effectively shorten the time consumption of insulation parameter measurement, improve test safety, and have more accurate measurement results and improved measurement accuracy.
In order to achieve the above purpose, the invention provides a device for rapidly measuring insulation parameters of electrical equipment, which comprises a control circuit module and a main circuit module connected with the control circuit module;
the main circuit module comprises a positive input end of a direct current power supply connected with a positive electrode of a storage battery, a negative input end of the direct current power supply connected with a negative electrode of the storage battery, and a power switch tube S 1 The drain electrode of the (B) is connected with the anode of the storage battery, and the power switch tube S 1 Source electrode of (C) is connected with power switch tube S 3 Drain electrode of power switch tube S 3 The source electrode of the power switch tube S is connected with the negative electrode of the storage battery 2 Drain electrode of (C) is connected with power switch tube S 1 Drain electrode of power switch tube S 2 Source electrode of (C) is connected with power switch tube S 4 Drain electrode of power switch tube S 4 Source electrode of (C) is connected with power switch tube S 3 The source electrode of the transformer T primary side a1 terminal is connected with the power switch tube S 1 The b1 terminal of the primary side of the transformer T is connected with the power switch tube S 2 The a2 terminal of the secondary side of the transformer T is connected with the diodeTube D 1 The cathode of the secondary side of the transformer T is connected with a diode D at the b2 terminal 2 Cathode of diode D 2 Cathode of (C) is connected with diode D 4 Anode of diode D 1 Anode of (D) is connected to diode D 2 Anode of diode D 1 Cathode of (C) is connected with diode D 3 Anode of diode D 3 Cathode of (C) is connected with diode D 4 A3 terminal of the inductor L is connected with a diode D 3 The cathode of the inductor L is connected with the resistor R at the b3 terminal 2 B5 terminal of (2), resistance R 2 A5 terminal of (2) is connected with potentiometer R 1 B4 terminal of (2), potentiometer R 1 A4 terminal of (a) is connected with diode D 1 Anode of (2), potentiometer R 1 A high-voltage power supply sampling signal u is led out from the sliding contact end of the (2) S Resistance R 0 B0 terminal of (2) is connected with potentiometer R 1 A4 terminal of (2), resistance R 0 The a0 terminal of (2) leads out a measurement sampling signal u 0 Resistance R 0 A0 terminal of (2), resistance R 2 The b5 terminals of (2) are used for connecting two ends of the tested insulation respectively.
The control circuit module comprises a controller, a keyboard, a display screen and a PWM driving circuit, wherein the keyboard, the display screen and the PWM driving circuit are connected with the controller, and the main circuit module obtains a high-voltage power supply sampling signal u S Measuring the sampled signal u 0 Direct input controller, PWM driving circuit output connect power switch tube S 1 Grid and power switch tube S 2 Grid and power switch tube S 3 Grid and power switch tube S 4 And a gate.
The storage battery is a +12V lithium iron phosphate battery, the direct current power supply is composed of an LM7805 chip, and the power switch tube S 1 Power switch tube S 2 Power switch tube S 3 And a power switch tube S 4 And the power MOSFET is selected, and the transformer T adopts a high-frequency transformer with the transformation ratio of 1:500.
The controller is realized by adopting an STC12C5A60S2 singlechip and a timing and resetting circuit at the periphery of the STC12C5A60S2 singlechip, the keyboard is a4 multiplied by 4 matrix keyboard, the display screen is a Nokia5110 liquid crystal screen, and the PWM driving circuit is formed by adopting an MOS tube driving chip IR 2110.
A method for rapidly measuring insulation parameters of electrical equipment,first, a measurement voltage U is applied to the insulation to be tested, and at t 1 、t 2 And t 3 Time (t) 3 ＞t 2 ＞t 1 > 100 ms), for u respectively 0 Sampling, and sequentially marking the calculated measurement loop current I as I 1 、I 2 And I 3 Due to i 0 The decay time is in the order of microseconds, so i is when three current samples are taken 0 The attenuation is zero, can be ignored, and the expression of the measured loop current i can be obtained by combining the first-order RC circuit zero state response current expression and the expression (1)
Let t 1 、t 2 And t 3 The measured loop current at the moment is substituted into (2) in sequence to obtain the following equation
Equations (3), (4) and (5) are all overrun equations, R can be solved by the three simultaneous cancellation elements x 、R q And C q The formulae (3), (4) and (5) are deformed to obtain
The formula (6) divided by the formula (7)
The formula (7) divided by the formula (8)
The index of both the left and right sides of (9) isTo the power of the operation of (a) to obtain
The combination of the formula (10) and the formula (11) can be obtained
Deforming (12) to obtain
Since formula (13) is represented by R x For the equation of unknown number, for the convenience of solution, the indexes of two sides of the equation are equal, namely, t is satisfied 3 -t 2 ＝t 2 -t 1 The solution is most advantageous when it is the first time t 1 There is no special requirement as long as the third sampling instant t 3 Time t of second sampling 2 And a second sampling instant t 2 Time t of first sampling 1 The difference is equal, at this time
(I 2 R x -U) 2 ＝(I 3 R x -U)(I 1 R x -U) (14)
Solving for R from (14) x The expression is
The index of both the left and right sides of (6) isTo the power of the operation of (a) to obtain
The combination of the formula (7) and the formula (16) can be obtained
Obtainable from (17)
R can be obtained by substituting formula (15) into formula (18) q An expression;
obtainable from (6)
Substituting the formula (15) and the formula (18) into the formula (19), namely obtaining C q Is an expression of (2);
in conclusion, at guarantee t 1 、t 2 And t 3 Satisfy t 3 -t 2 ＝t 2 -t 1 On the premise of (a), for u 0 Sampling for three times, and calculating to obtain measurementLoop current value I 1 、I 2 And I 3 R can be obtained by substituting the above-mentioned components into the following formulas (15), (18) and (19) in order x 、R q And C q Is a numerical value of (2); r is R x 、R q And C q Substituting the formula (2) to obtain an expression of i (t), and obtaining the functional relation of the insulation resistance R of the electrical equipment along with the change of t according to ohm law
R(t)＝U/i(t) (20)
R can be found by substituting t=15s, t=60deg.s, and t=600s into formula (20) 15s 、R 60s And R is 600s Finally, the absorption ratio K and the polarization index PI are obtained.
The storage battery is used for providing a working power supply for the device, the direct current power supply converts +12V direct current power of the storage battery into +5V low voltage direct current, and the direct current power supply is used as a power supply of a control circuit and is used as a power switch tube S 1 Power switch tube S 2 Power switch tube S 3 And a power switch tube S 4 The bridge type full-control inverter circuit is used for converting low-voltage direct current into high-frequency low-voltage alternating current, the transformer T converts the high-frequency low-voltage alternating current into high-frequency high-voltage alternating current, and the diode D 1 Diode D 2 Diode D 3 And diode D 4 An uncontrollable full-bridge rectifying circuit is formed, which is used for converting high-frequency high-voltage alternating current into high-voltage direct current, an inductor L is used for energy storage and filtering, and a potentiometer R 1 And resistance R 2 Forming a high-voltage power supply sampling circuit, and sampling a signal u by the high-voltage power supply S As a feedback signal to the controller, resistor R 0 Form a measuring loop together with the tested insulation, and resist R 0 Voltage sampling is performed at the a0 terminal of (2) to obtain a sampling signal u 0 Input controller, the measured loop current is calculated by ohm's law, i.e. i=u 0 /R 0 。
In addition, the keyboard in the control circuit is used for inputting the measurement voltage U to the controller, the controller outputs a PWM signal with a certain duty ratio to the PWM driving circuit according to the voltage, and then the controller outputs a PWM signal with a certain duty ratio to the PWM driving circuit according to the sampling signal U S The duty ratio of PWM is adjusted in time to form a feedback control link, so that the measurement voltage of the measurement loop is kept U within the error allowable range, and the controller adoptsSample signal u 0 And performing operation processing, calculating insulation parameters of the tested insulation, and displaying measured voltage and information of the measured insulation parameters by a display screen.
According to the invention, the insulation parameter of the electrical equipment can be rapidly measured, the measurement time of the absorption ratio K can be shortened to within 10s from 60s of the traditional method, the measurement time of the polarization index PI can be shortened to within 100s from 600s of the traditional method, and the working efficiency is greatly improved. In the application of the invention, because the measurement time is short, the probability of the high-voltage tester to touch the charged body such as the testing end of the device by mistake can be effectively reduced, the safety of the test is improved, and the probability of electric shock accidents during the measurement of the insulation parameters is reduced to 1/6 of that of the prior art. The feedback control technology of the high-voltage power supply enables the measurement voltage to be more stable and the measurement result to be more accurate. According to the invention, the parameters of the tested insulation are rapidly calculated through signal sampling, so that the energy is saved due to short measurement time, and the endurance of the device is more than 5 times of that of the traditional digital megohmmeter. According to the invention, the insulation parameters are obtained by adopting a calculation method, a plurality of groups of sampling moments can be selected for calculation and solution respectively, and the test error can be reduced to be within 0.15% by utilizing a numerical algorithm for averaging, so that the accuracy of the measurement result is improved.
Drawings
FIG. 1 is an equivalent circuit of an electrical device insulation in the background of the invention;
FIG. 2 is a graph showing the current in an insulating material with time under the action of DC voltage in the background art of the invention;
FIG. 3 is a schematic diagram of the main circuit of the present invention;
FIG. 4 is a schematic diagram of the control principle of the present invention;
FIG. 5 is a simulation model of MATLAB of the present invention;
FIG. 6 is an input diagram of the high voltage power supply of the present invention;
fig. 7 shows the results of MATLAB simulation experiments according to the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to fig. 3 to 7 of the embodiments of the present invention. It will be apparent that the described embodiments are some, but not all, embodiments of the invention. All other embodiments, which are obtained by a person skilled in the art based on the described embodiments of the invention, fall within the scope of protection of the invention.
Example 1
An insulation parameter quick-measuring device of electrical equipment comprises a control circuit module and a main circuit module connected with the control circuit module;
the main circuit module comprises a positive input end of the direct current power supply 1 connected with a positive electrode of a storage battery, a negative input end of the direct current power supply connected with a negative electrode of the storage battery, and a power switch tube S 1 The drain electrode of the (B) is connected with the anode of the storage battery, and the power switch tube S 1 Source electrode of (C) is connected with power switch tube S 3 Drain electrode of power switch tube S 3 The source electrode of the power switch tube S is connected with the negative electrode of the storage battery 2 Drain electrode of (C) is connected with power switch tube S 1 Drain electrode of power switch tube S 2 Source electrode of (C) is connected with power switch tube S 4 Drain electrode of power switch tube S 4 Source electrode of (C) is connected with power switch tube S 3 The source electrode of the transformer T primary side a1 terminal is connected with the power switch tube S 1 The b1 terminal of the primary side of the transformer T is connected with the power switch tube S 2 The a2 terminal of the secondary side of the transformer T is connected with a diode D 1 The cathode of the secondary side of the transformer T is connected with a diode D at the b2 terminal 2 Cathode of diode D 2 Cathode of (C) is connected with diode D 4 Anode of diode D 1 Anode of (D) is connected to diode D 2 Anode of diode D 1 Cathode of (C) is connected with diode D 3 Anode of diode D 3 Cathode of (C) is connected with diode D 4 A3 terminal of the inductor L is connected with a diode D 3 The cathode of the inductor L is connected with the resistor R at the b3 terminal 2 B5 terminal of (2), resistance R 2 A5 terminal of (2) is connected with potentiometer R 1 B4 terminal of (2), potentiometer R 1 A4 terminal of (a) is connected with diode D 1 Anode of (2), potentiometer R 1 A high-voltage power supply sampling signal u is led out from the sliding contact end of the (2) S Resistance R 0 B0 terminal of (2) is connected with potentiometer R 1 A4 terminal of (2), resistance R 0 A0 end of (2)Sub-extraction measurement sampling signal u 0 Resistance R 0 A0 terminal of (2), resistance R 2 The b5 terminals of (2) are used for connecting two ends of the tested insulation respectively.
The control circuit module comprises a controller, a keyboard, a display screen and a PWM driving circuit, wherein the keyboard, the display screen and the PWM driving circuit are connected with the controller, and the main circuit module obtains a high-voltage power supply sampling signal u S Measuring the sampled signal u 0 Direct input controller, PWM driving circuit output connect power switch tube S 1 Grid and power switch tube S 2 Grid and power switch tube S 3 Grid and power switch tube S 4 And a gate.
The storage battery is a +12V lithium iron phosphate battery, the direct current power supply is composed of an LM7805 chip, and the power switch tube S 1 Power switch tube S 2 Power switch tube S 3 And a power switch tube S 4 And the power MOSFET is selected, and the transformer T adopts a high-frequency transformer with the transformation ratio of 1:500.
The controller is realized by adopting an STC12C5A60S2 singlechip and a timing and resetting circuit at the periphery of the STC12C5A60S2 singlechip, the keyboard is a4 multiplied by 4 matrix keyboard, the display screen is a Nokia5110 liquid crystal screen, and the PWM driving circuit is formed by adopting an MOS tube driving chip IR 2110.
A method for quickly measuring the insulating parameters of electric equipment includes such steps as applying a measuring voltage U to the tested insulation, and at t 1 、t 2 And t 3 Time (t) 3 ＞t 2 ＞t 1 > 100 ms), for u respectively 0 Sampling, and sequentially marking the calculated measurement loop current I as I 1 、I 2 And I 3 Due to i 0 The decay time is in the order of microseconds, so i is when three current samples are taken 0 The attenuation is zero, can be ignored, and the expression of the measured loop current i can be obtained by combining the first-order RC circuit zero state response current expression and the expression (1)
Let t 1 、t 2 And t 3 The measured loop current at the moment is substituted into (2) in sequence to obtain the following equation
Equations (3), (4) and (5) are all overrun equations, R can be solved by the three simultaneous cancellation elements x 、R q And C q The formulae (3), (4) and (5) are deformed to obtain
The formula (6) divided by the formula (7)
The formula (7) divided by the formula (8)
The index of both the left and right sides of (9) isTo the power of the operation of (a) to obtain
The combination of the formula (10) and the formula (11) can be obtained
Deforming (12) to obtain
Since formula (13) is represented by R x For the equation of unknown number, for the convenience of solution, the indexes of two sides of the equation are equal, namely, t is satisfied 3 -t 2 ＝t 2 -t 1 The solution is most advantageous when it is the first time t 1 There is no special requirement as long as the third sampling instant t 3 Time t of second sampling 2 And a second sampling instant t 2 Time t of first sampling 1 The difference is equal, at this time
(I 2 R x -U) 2 ＝(I 3 R x -U)(I 1 R x -U) (14)
Solving for R from (14) x The expression is
The index of both the left and right sides of (6) isTo the power of the operation of (a) to obtain
The combination of the formula (7) and the formula (16) can be obtained
Obtainable from (17)
R can be obtained by substituting formula (15) into formula (18) q An expression;
obtainable from (6)
Substituting the formula (15) and the formula (18) into the formula (19), namely obtaining C q Is an expression of (2);
in conclusion, at guarantee t 1 、t 2 And t 3 Satisfy t 3 -t 2 ＝t 2 -t 1 On the premise of (a), for u 0 Sampling for three times, and calculating to obtain a measured loop current value I 1 、I 2 And I 3 R can be obtained by substituting the above-mentioned components into the following formulas (15), (18) and (19) in order x 、R q And C q Is a numerical value of (2); r is R x 、R q And C q Substituting the formula (2) to obtain an expression of i (t), and obtaining the functional relation of the insulation resistance R of the electrical equipment along with the change of t according to ohm law
R(t)＝U/i(t) (20)
R can be found by substituting t=15s, t=60deg.s, and t=600s into formula (20) 15s 、R 60s And R is 600s Finally, the absorption ratio K and the polarization index PI are obtained.
In order to verify the theoretical correctness of the method, as a further specific embodiment of the invention, a simulation model is built in a Simulink function module of MATLAB software. As shown in FIG. 5As shown in FIG. 6, the three-phase AC power supplies are 2886VAC and 50Hz, rectified by a rectifying module, filtered by a capacitor C, and 5000VDC DC is output as a high-voltage power supply, wherein R is in three branches x ＝180GΩ，R q ＝10GΩ，C q ＝1.2nF，C q Initial voltage is zero, C 0 ＝1.2×10 -3 nF, forming sink current i q The branch time constant of (1) is τ=r q ·C q In theory, i after an indefinite period of time q The attenuation can be zero, but the process is generally regarded as ending after the 3 tau to 5 tau absorption process, the simulation ending time is set to 120s in the model, and the simulation experiment result is shown in fig. 7.
As can be seen from fig. 7, the dc power supply maintains 5000VDC, and the current i flowing through the insulating material decays exponentially under the dc voltage, and the decay process is substantially completed at 60 s. In the MATLAB generated experimental data array, 10 sets of time data were randomly extracted, 3 time points per set and t was guaranteed 1 、t 2 And t 3 Satisfy t 3 -t 2 ＝t 2 -t 1 Recording 30 sampling current data corresponding to each time point, and calculating R corresponding to each group of time data according to the formula (15), the formula (18) and the formula (19) x 、R q And C q The values are shown in Table 1.
Table 1 simulation experiment calculation results
From Table 1, R x Average value is 179.7670GΩ, R in simulation model x =180gΩ, experimental error 0.13%; r is R q Average value is 10.0004GΩ, R in simulation model q =10gΩ, experimental error was 0.004%; c (C) q Average value is 1.1998nF, C in simulation model q The experimental error was 0.02%, and it can be seen that the insulation parameter error calculated from the sampling current was extremely small, indicating that the method was correct.
While the foregoing is directed to the preferred embodiments of the present invention, it will be appreciated by those skilled in the art that various modifications and adaptations can be made without departing from the principles of the present invention, and such modifications and adaptations are intended to be comprehended within the scope of the present invention.
Claims (3)
1. An insulation parameter quick-measuring device for electrical equipment is characterized in that: the circuit comprises a control circuit module and a main circuit module connected with the control circuit module;
the main circuit module comprises a positive input end of a direct current power supply connected with a positive electrode of a storage battery, a negative input end of the direct current power supply connected with a negative electrode of the storage battery, and a power switch tube S 1 The drain electrode of the (B) is connected with the anode of the storage battery, and the power switch tube S 1 Source electrode of (C) is connected with power switch tube S 3 Drain electrode of power switch tube S 3 The source electrode of the power switch tube S is connected with the negative electrode of the storage battery 2 Drain electrode of (C) is connected with power switch tube S 1 Drain electrode of power switch tube S 2 Source electrode of (C) is connected with power switch tube S 4 Drain electrode of power switch tube S 4 Source electrode of (C) is connected with power switch tube S 3 The source electrode of the transformer T primary side a1 terminal is connected with the power switch tube S 1 The b1 terminal of the primary side of the transformer T is connected with the power switch tube S 2 The a2 terminal of the secondary side of the transformer T is connected with a diode D 1 The cathode of the secondary side of the transformer T is connected with a diode D at the b2 terminal 2 Cathode of diode D 2 Cathode of (C) is connected with diode D 4 Anode of diode D 1 Anode of (D) is connected to diode D 2 Anode of diode D 1 Cathode of (C) is connected with diode D 3 Anode of diode D 3 Cathode of (C) is connected with diode D 4 A3 terminal of the inductor L is connected with a diode D 3 The cathode of the inductor L is connected with the resistor R at the b3 terminal 2 B5 terminal of (2), resistance R 2 A5 terminal of (2) is connected with potentiometer R 1 B4 terminal of (2), potentiometer R 1 A4 terminal of (a) is connected with diode D 1 Anode of (2), potentiometer R 1 A high-voltage power supply sampling signal u is led out from the sliding contact end of the (2) S Resistance R 0 B0 terminal of (2) is connected with potentiometer R 1 A4 terminal of (2), resistance R 0 A0 terminal lead-out measurement acquisition of (2)Sample signal u 0 Resistance R 0 A0 terminal of (2), resistance R 2 The b5 terminals of (2) are respectively used for connecting two ends of the tested insulation; the control circuit module comprises a controller, a keyboard, a display screen and a PWM driving circuit, wherein the keyboard, the display screen and the PWM driving circuit are connected with the controller, and the main circuit module obtains a high-voltage power supply sampling signal u S Measuring the sampled signal u 0 Direct input controller, PWM driving circuit output connect power switch tube S 1 Grid and power switch tube S 2 Grid and power switch tube S 3 Grid and power switch tube S 4 A gate;
potentiometer R 1 And resistance R 2 Forming a high-voltage power supply sampling circuit, and sampling a signal u by the high-voltage power supply S As a feedback signal to the controller, resistor R 0 Form a measuring loop together with the tested insulation, and resist R 0 Voltage sampling is performed at the a0 terminal of (2) to obtain a sampling signal u 0 An input controller; the keyboard is used for inputting a measurement voltage U to the controller, the controller outputs a PWM signal with a certain duty ratio to the PWM driving circuit according to the voltage, and then the controller outputs a PWM signal with a certain duty ratio to the PWM driving circuit according to the sampling signal U S The duty ratio of PWM is adjusted in time to form a feedback control link, so that the measurement voltage of the measurement loop is kept U within the error allowable range, and the controller samples the signal U 0 Performing operation processing, calculating insulation parameters of tested insulation, and displaying measured voltage and information of the measured insulation parameters on a display screen;
the method for rapidly measuring the insulation parameters of the electrical equipment by using the device comprises the following steps:
applying a measurement voltage U to the tested insulation, and making a current i flowing through the tested insulation be
i＝i x +i q +i 0 (1)，
Wherein i is x Is leakage current, i q Is the absorption current, i 0 In order for the charge current to be sufficient,
and at t 1 、t 2 And t 3 Time t 3 ＞t 2 ＞t 1 > 100ms, respectively to u 0 Sampling, and sequentially marking the calculated measurement loop current I as I 1 、I 2 And I 3 Due to i 0 The decay time is in the order of microseconds, so i is when three current samples are taken 0 The attenuation is zero, can be ignored, and the expression of the measured loop current i can be obtained by combining the current expression of the zero state response of the first-order RC circuit and the expression (1)
Wherein R is x Represents the insulation resistance, R, of the insulation material q And capacitor C q Representing an absorption current equivalent circuit;
let t 1 、t 2 And t 3 The measured loop current at the moment is substituted into (2) in sequence to obtain the following equation
Equations (3), (4) and (5) are all overrun equations, R can be solved by the three simultaneous cancellation elements x 、R q And C q The formulae (3), (4) and (5) are deformed to obtain
The formula (6) divided by the formula (7)
The formula (7) divided by the formula (8)
The index of both the left and right sides of (9) isTo the power of the operation of (a) to obtain
The combination of the formula (10) and the formula (11) can be obtained
Deforming (12) to obtain
Since formula (13) is represented by R x For the equation of unknown number, for the convenience of solution, the indexes of two sides of the equation are equal, namely, t is satisfied 3 -t 2 ＝t 2 -t 1 The solution is most advantageous when it is the first time t 1 There is no special requirement as long as the third sampling instantt 3 Time t of second sampling 2 And a second sampling instant t 2 Time t of first sampling 1 The difference is equal, at this time
(I 2 R x -U) 2 ＝(I 3 R x -U)(I 1 R x -U) (14)
Solving for R from (14) x The expression is
The index of both the left and right sides of (6) isTo the power of the operation of (a) to obtain
The combination of the formula (7) and the formula (16) can be obtained
Obtainable from (17)
R can be obtained by substituting formula (15) into formula (18) q An expression;
obtainable from (6)
Substituting the formula (15) and the formula (18) into the formula (19), namely obtaining C q Is an expression of (2);
to sum upSaid, at guarantee t 1 、t 2 And t 3 Satisfy t 3 -t 2 ＝t 2 -t 1 On the premise of (a), for u 0 Sampling for three times, and calculating to obtain a measured loop current value I 1 、I 2 And I 3 R can be obtained by substituting the above-mentioned components into the following formulas (15), (18) and (19) in order x 、R q And C q Is a numerical value of (2); r is R x 、R q And C q Substituting the formula (2) to obtain an expression of i (t), and obtaining the functional relation of the insulation resistance R of the electrical equipment along with the change of t according to ohm law
R(t)＝U/i(t) (20)
R can be found by substituting t=15s, t=60deg.s, and t=600s into formula (20) 15s 、R 60s And R is 600s Finally, the absorption ratio K and the polarization index PI are obtained.
2. An insulation parameter rapid measurement device for electrical equipment according to claim 1, wherein: the storage battery is a +12V lithium iron phosphate battery, the direct current power supply is composed of an LM7805 chip, and the power switch tube S 1 Power switch tube S 2 Power switch tube S 3 And a power switch tube S 4 All adopt power MOSFET, transformer T adopts the transformation ratio to be 1: 500.
3. An insulation parameter rapid measurement device for electrical equipment according to claim 2, wherein: the controller is realized by adopting an STC12C5A60S2 singlechip and a timing and resetting circuit at the periphery of the STC12C5A60S2 singlechip, the keyboard is a4 multiplied by 4 matrix keyboard, the display screen is a Nokia5110 liquid crystal screen, and the PWM driving circuit is formed by adopting an MOS tube driving chip IR 2110.
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