CN116540030A - Insulation fault monitoring circuit and method based on pulse width change principle - Google Patents
Insulation fault monitoring circuit and method based on pulse width change principle Download PDFInfo
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- CN116540030A CN116540030A CN202310247824.8A CN202310247824A CN116540030A CN 116540030 A CN116540030 A CN 116540030A CN 202310247824 A CN202310247824 A CN 202310247824A CN 116540030 A CN116540030 A CN 116540030A
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- 238000009413 insulation Methods 0.000 title claims abstract description 42
- 238000012544 monitoring process Methods 0.000 title claims abstract description 25
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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
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R29/00—Arrangements for measuring or indicating electric quantities not covered by groups G01R19/00 - G01R27/00
- G01R29/02—Measuring characteristics of individual pulses, e.g. deviation from pulse flatness, rise time or duration
- G01R29/027—Indicating that a pulse characteristic is either above or below a predetermined value or within or beyond a predetermined range of values
- G01R29/0273—Indicating that a pulse characteristic is either above or below a predetermined value or within or beyond a predetermined range of values the pulse characteristic being duration, i.e. width (indicating that frequency of pulses is above or below a certain limit)
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- Y04—INFORMATION OR COMMUNICATION TECHNOLOGIES HAVING AN IMPACT ON OTHER TECHNOLOGY AREAS
- Y04S—SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS
- Y04S10/00—Systems supporting electrical power generation, transmission or distribution
- Y04S10/50—Systems or methods supporting the power network operation or management, involving a certain degree of interaction with the load-side end user applications
- Y04S10/52—Outage or fault management, e.g. fault detection or location
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Abstract
The invention discloses an insulation fault monitoring circuit and method based on a pulse width change principle, wherein the circuit comprises a current transformer iron core, a wire, a measuring coil, an oscillating circuit and a measuring circuit, the method is a current detection method based on pulse width change, the characteristics that inductance current cannot break are utilized, the voltages of positive and negative input ends of a comparator are compared with each other, square wave signals of positive and negative levels are output, the time, the period and the amplitude of the high and low levels of the square wave signals are related to circuit parameters, and the square wave duty ratio and the direct current are obtained through an algorithm according to the difference between the positive and negative levels of the time output by the oscillating circuit. The problem of the insufficient precision of current direct current transformer has been solved to the current insufficient precision of having solved high resistance earth leakage current and has not obviously led to the problem of being difficult to detect, has characteristics such as high integration, interference killing feature are strong, the accuracy is high. Therefore, the invention can play the role of early warning, avoid the ground fault from being continuously worsened, and play an important role in the safe operation of the direct current system.
Description
Technical Field
The invention relates to the technical field of insulation monitoring, in particular to an insulation fault monitoring circuit and method based on a pulse width change principle.
Background
For insulation monitoring of a direct current system, insulation fault line selection of a branch is most difficult to realize, an opening type milliamp-level current transformer with high precision is needed, and the anti-interference capability is high. At present, in the aspect of branch line selection, the main current methods are direct current leakage current and alternating current injection methods. The direct current leakage current method is to judge through measuring the current difference value of the same branch, the positive and negative current counteracts each other when insulation is good, the positive and negative current may not counteract each other when insulation fault exists, when the branch grounding resistance exists, the leakage current is very small, the current transformer with low precision can not be detected, and the open type direct current transformer can not influence the subsequent measurement under the continuous superposition of the residual magnetism due to the residual magnetism problem, after the iron core is magnetized to saturation and demagnetized, the residual magnetization intensity which can not be eliminated naturally still in the same magnetization direction of the residual part can be greatly influenced. The AC injection rule is to add AC signal source between bus and earth, when insulation is good, there is no ground loop, AC signal can not form transmission closed loop, so AC transformer can not detect signal current, when insulation fault exists, AC signal can flow through ground branch and earth to return to signal source, the method can eliminate remanence effect, but cable, power supply equipment and electric equipment of DC system can have distributed capacitance, capacitive reactance can have certain effect on measuring result, and injected AC signal can not be too big, possibly resulting in equipment refusal or misoperation.
In summary, the problem of insufficient precision of the direct current transformer exists at present, the problem of difficult detection caused by the low high-resistance grounding current is not obvious, and the existing detection circuit has low integration, weak interference resistance and low accuracy.
Disclosure of Invention
The insulation fault monitoring circuit and the method based on the pulse width change principle solve the problems in the background technology.
In order to achieve the above purpose, the present invention provides the following technical solutions: an insulation fault monitoring circuit based on a pulse width variation principle comprises a current transformer iron core, a wire, a measuring coil, an oscillating circuit and a measuring circuit; the measuring coil and the lead are wound on the current transformer iron core; the wire is connected with the oscillating circuit, and the measuring coil is respectively connected with the oscillating circuit and the measuring circuit; the measuring circuit is connected with the oscillating circuit; the measuring graph circuit comprises an inductance measuring circuit and a direct current signal measuring circuit, wherein the direct current signal measuring circuit is used for filtering alternating current signals to obtain direct current signals and outputting square waves, and the inductance measuring circuit is used for calculating positive and negative level time.
Preferably, the oscillating circuit comprises a resistor R1, a resistor R2, a resistor R3, a comparator, a capacitor C1 and an inductor L; the inductor L is an inductor with a core, and the capacitor C1 is a filter capacitor for filtering alternating current; the resistor R1 is connected with the comparator and the coil, the inductor L is connected with the other coil, the resistor R1 is further connected with the comparator and the resistor R2, the resistor R2 is further connected with the resistor R3 and the capacitor C1, and the capacitor C1 is further connected with the resistor R3 and the inductor L.
Preferably, the inductance measurement circuit includes a venturi bridge sine wave oscillator, a voltage follower, and an inductance-voltage conversion circuit.
Preferably, the direct current signal measuring circuit consists of a filter circuit, an amplifying circuit and a zeroing circuit.
An insulation fault monitoring method based on a pulse width variation principle is applied to the insulation fault monitoring circuit based on the pulse width variation principle, and comprises the following steps:
s1: by utilizing the characteristic that the inductance current cannot be suddenly changed, the voltages of the positive and negative input ends of the comparator are compared with each other to output positive and negative square wave signals, and the time, period and amplitude of the high and low level of the square wave signals are related to circuit parameters;
s2: calculating positive and negative level time, thereby determining cycle time;
s3: calculating the square wave duty ratio;
s4: calculating a direct current component;
s5: judging whether the direct current system has insulation faults according to the square wave duty ratio and the direct current component, wherein the insulation faults exist when the square wave duty ratio is not 50% or the direct current component is not 0, and the insulation faults do not exist when the duty ratio is 50% and the direct current component is 0.
Preferably, the positive and negative level time in the step S2 is calculated as follows:
wherein t is 1 Is positive in time, t 2 Time of negative level, L 1 Inductance value at high level, L 2 At a negative level, the inductance value, R L Is the resistance value of the inductor, R 1 In an oscillating circuitResistance value of resistor R1, R 2 Is the resistance value of a resistor R2 in the oscillating circuit, R 3 Is the resistance of the resistor R3 in the oscillating circuit.
Preferably, the cycle time in the step S2 is a sum of a positive level time t1 and a negative level time t 2.
Preferably, the duty cycle calculation formula of the step S3 is as follows:
wherein D is duty cycle, t 1 Is positive in time, t 2 Is a negative level time.
Preferably, the dc component calculation formula in step S4 is as follows:
wherein A is 0 Is a direct current component, T is a square wave period, T 1 For positive and negative level continuous time difference, um is positive amplitude of square wave after oscillation, -Um is negative amplitude of square wave after oscillation, and k is period number.
The beneficial effects of the invention are as follows:
through the set current transformer iron core, the lead, the measuring coil, the oscillating circuit and the measuring circuit, a current transformer structure and a circuit model are built, a current detection method based on pulse width change is provided, the characteristics that the inductance current cannot be suddenly changed are utilized, the voltages of the positive and negative input ends of the comparator are compared with each other, square wave signals of positive and negative levels are output, the time, the period and the amplitude of the high and low levels of the square wave signals are related to circuit parameters, and the square wave duty ratio and the direct current are obtained through an algorithm according to the difference between the positive and negative level times output by the oscillating circuit. The problem of the insufficient precision of current direct current transformer has been solved to the current insufficient precision of having solved high resistance earth leakage current and has not obviously led to the problem of being difficult to detect, has characteristics such as high integration, interference killing feature are strong, the accuracy is high. Therefore, the invention can play the role of early warning, avoid the ground fault from being continuously worsened, and play an important role in the safe operation of the direct current system.
Drawings
FIG. 1 is a schematic block diagram of an insulation fault monitoring circuit based on the pulse width variation principle;
FIG. 2 is a diagram of an oscillating circuit;
FIG. 3 is a schematic diagram of an inductance measurement circuit;
fig. 4 is a schematic diagram of a dc signal measurement circuit.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are some, but not all embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
It should be understood that the terms "comprises" and "comprising," when used in this specification and the appended claims, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
It is also to be understood that the terminology used in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in this specification and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.
It should be further understood that the term "and/or" as used in the present specification and the appended claims refers to any and all possible combinations of one or more of the associated listed items, and includes such combinations.
Embodiments of the present invention are set forth in connection with fig. 1-4 to further illustrate the technical solution of the present invention.
Fig. 1 shows a schematic block diagram of an insulation fault monitoring circuit based on a pulse width variation principle, which is provided by an embodiment of the invention, and as shown in fig. 1, the insulation fault monitoring circuit comprises a current transformer iron core, a wire, a measuring coil, an oscillating circuit and a measuring circuit; the measuring coil and the lead are wound on the current transformer iron core; the wire is connected with the oscillating circuit, and the measuring coil is respectively connected with the oscillating circuit and the measuring circuit; the measuring circuit is connected with the oscillating circuit; the measuring graph circuit comprises an inductance measuring circuit and a direct current signal measuring circuit, wherein the direct current signal measuring circuit is used for filtering alternating current signals to obtain direct current signals and outputting square waves, and the inductance measuring circuit is used for calculating positive and negative level time. The inductance measuring circuit comprises a venturi bridge sine wave oscillator, a voltage follower and an inductance-voltage conversion circuit, and the direct current signal measuring circuit consists of a filter circuit, an amplifying circuit and a zeroing circuit.
The measuring principle is that the inductance of the iron core is affected by the environmental magnetic field, and the inductance value is different during charging and discharging, so that the duty ratio of the square wave output by the oscillating circuit formed by the iron core is different. When the inductance is magnetized repeatedly, the inductance value is affected by current, magnetic flux, cross-sectional area of the iron core and turns, and the inductance value is different. By utilizing the characteristic that the inductive current cannot be suddenly changed, the voltages of the positive and negative input ends of the comparator are compared with each other to output positive and negative square wave signals, and the time, period and amplitude of the high and low level of the square wave signals are related to circuit parameters. Positive and negative level times can be calculated from the oscillating circuit of fig. 2 and equation (1); the positive and negative level time can be used for obtaining the cycle time T=t1+t2, and the positive level time is divided by the cycle time according to the calculation formula (2) to obtain the square wave duty ratio. The following are expressions of the formula (1) and the formula (2):
wherein t is 1 Is positive in time, t 2 Time of negative level, L 1 Inductance value at high level, L 2 At a negative level, the inductance value, R L Is the resistance value of the inductor, R 1 Is the resistance value of a resistor R1 in the oscillating circuit, R 2 Is the resistance value of a resistor R2 in the oscillating circuit, R 3 Is the resistance of the resistor R3 in the oscillating circuit.
Wherein D is duty cycle, t 1 Is positive in time, t 2 Is a negative level time.
In an ideal state, when the direct current system has no insulation fault, the positive and negative level time of the square wave is consistent, and the positive and negative direct current amounts in Fourier decomposition of the square wave are mutually counteracted, namely, no direct current component exists, and the direct current component is 0; when the DC system has insulation faults, the balance of the original positive and negative currents is broken, leakage current exists, inductance values are different due to the fact that the inductance is charged and discharged, therefore, the time of positive and negative levels of the square wave output by the oscillating circuit is inconsistent, the duty ratio is not changed to be 50%, the positive and negative direct currents in Fourier decomposition are not mutually counteracted, the direct current component is not 0, and whether the DC feeder branch has insulation faults is accurately judged. The calculation formula of the direct current component is shown as formula (3), and the calculation formula of formula (3) is as follows:
wherein A is 0 Is a direct current component, T is a square wave period, T 1 For positive and negative level continuous time difference, um is positive amplitude of square wave after oscillation, -Um is negative amplitude of square wave after oscillation, and k is period number.
Fig. 2 shows a circuit diagram of an oscillating circuit, which includes a resistor R1, a resistor R2, a resistor R3, a comparator, a capacitor C1, and an inductance L, as shown in fig. 2; the inductor L is an inductor with a core, and the capacitor C1 is a filter capacitor for filtering alternating current; the resistor R1 is connected with the comparator and the coil, the inductor L is connected with the other coil, the resistor R1 is further connected with the comparator and the resistor R2, the resistor R2 is further connected with the resistor R3 and the capacitor C1, and the capacitor C1 is further connected with the resistor R3 and the inductor L. As can be seen from fig. 2, L is a cored inductor, and C1 is a filter capacitor for filtering ac current. The upper and lower limit threshold of the circuit is + -U0 x R2/(R1+R2). Assuming that U0 is positive voltage at the beginning, the inductor L is charged positively, the current is gradually increased, the voltage at the negative input end of the comparison circuit is smaller than the upper limit threshold value, the output is kept at a positive level, the output level is changed to be negative voltage until the absolute value of the partial pressure on R4 is equal to the comparison threshold value, the output polarity is suddenly changed to be negative at the moment, the direction and the magnitude of the inductor current cannot be suddenly changed, a gradual decreasing process is carried out until the direction is changed to continue charging, when the absolute value of the voltage at the negative input end of the comparator is equal to the comparison threshold value again, the output is changed again, one cycle is completed, and the circuit can output square wave signals of positive and negative levels in an infinite cycle.
Fig. 3 shows a schematic diagram of an inductance measurement circuit, which, as shown in fig. 3, consists of a venturi bridge sine wave oscillator, a voltage follower, and an inductance-voltage conversion circuit. Wherein R1, C1, R2 and C2 form a frequency-selecting network, R1=R2 and C1=C2, then the oscillation frequency w=1/R1×C1, a sinusoidal voltage signal Um is output by a sinusoidal wave oscillator of a Venturi bridge, and is converted into an inductance-voltage conversion circuit through a voltage follower 1:1 to obtain Vo. Since R, w and Um are known, the inductance Lx can be calculated according to the formula (4), and the formula (4) is as follows:
fig. 4 shows a schematic diagram of a dc signal measurement circuit, which, as shown in fig. 4, consists of a filter circuit, an amplifying circuit and a zeroing circuit. The filter circuit is used for filtering alternating current components output by the oscillating circuit so as to output direct current, R1, R2, R3, C1 and C3 form a first-order filter circuit for filtering higher harmonic waves, then the higher harmonic waves pass through a second-order filter circuit (a first-order low-pass filter circuit), the cut-off frequency is 1Hz, and the signal is subjected to two-order filtering to obtain ideal direct current. After the filtering is finished, the output voltage can reflect the duty ratio change of the oscillating circuit within a certain range, but the change is very tiny, so that the amplification is needed, the duty ratio change is more obvious, and the processing is facilitated. And amplifying R6/R7+1 according to the voltage output by the filter circuit, and then entering a zeroing circuit. When the current transformer does not measure current, the output voltage of the current transformer is zeroed, wherein a voltage source and a sliding rheostat are arranged in the current transformer, and Uw is the voltage obtained by changing the output of the sliding rheostat. The zero setting circuit adds the output voltage of the Uw and the output voltage of the amplifying circuit, the output voltage is changed to be 0V when the current is not measured by changing the output of the Uw, the output voltage is changed according to a certain proportion, and finally the output voltage Uo1= -R10/R8 Ui-R10/R11 Uw is output.
The embodiment also provides an insulation fault monitoring method based on the pulse width variation principle, which is applied to the insulation fault monitoring circuit based on the pulse width variation principle, and comprises the following steps:
s1: by utilizing the characteristic that the inductance current cannot be suddenly changed, the voltages of the positive and negative input ends of the comparator are compared with each other to output positive and negative square wave signals, and the time, period and amplitude of the high and low level of the square wave signals are related to circuit parameters;
s2: calculating positive and negative level time, thereby determining cycle time; the positive and negative level time is calculated as follows:
wherein t is 1 Is positive in time, t 2 Time of negative level, L 1 Inductance value at high level, L 2 At a negative level, the inductance value, R L Is the resistance value of the inductor, R 1 Is the resistance value of a resistor R1 in the oscillating circuit, R 2 Is the resistance value of a resistor R2 in the oscillating circuit, R 3 Is the resistance of the resistor R3 in the oscillating circuit.
The cycle time is the sum of a positive level time t1 and a negative level time t 2.
S3: calculating the square wave duty ratio; the duty cycle calculation formula is as follows:
wherein D is duty cycle, t 1 Is positive in time, t 2 Is a negative level time.
S4: calculating a direct current component; the dc component calculation formula is as follows:
wherein A is 0 Is a direct current component, T is a square wave period, T 1 For positive and negative level continuous time difference, um is positive amplitude of square wave after oscillation, -Um is negative amplitude of square wave after oscillation, and k is period number.
S5: judging whether the direct current system has insulation faults according to the square wave duty ratio and the direct current component, wherein the insulation faults exist when the square wave duty ratio is not 50% or the direct current component is not 0, and the insulation faults do not exist when the duty ratio is 50% and the direct current component is 0.
In summary, in this embodiment, through the set current transformer core, the wire, the measurement coil, the oscillation circuit and the measurement circuit, the current transformer structure and the circuit model are built, and the current detection method based on pulse width variation is provided, by using the characteristic that the inductance current cannot be suddenly changed, the positive and negative input voltages of the comparator are compared with each other, square wave signals of positive and negative levels are output, the time, the period and the amplitude of the high and low levels of the square wave signals are related to circuit parameters, and the square wave duty ratio and the direct current are obtained through an algorithm according to the difference between the positive and negative levels of the time output by the oscillation circuit. The problem of the insufficient precision of current direct current transformer has been solved to the current insufficient precision of having solved high resistance earth leakage current and has not obviously led to the problem of being difficult to detect, has characteristics such as high integration, interference killing feature are strong, the accuracy is high. Therefore, the invention can play the role of early warning, avoid the continuous deterioration of the ground fault, play an important role in the safe operation of the direct current system and solve the problems in the background technology.
The above embodiments are only for illustrating the technical solution of the present invention, and not for limiting the same; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some or all of the technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the invention, and are intended to be included within the scope of the appended claims and description.
Claims (9)
1. The insulation fault monitoring circuit based on the pulse width change principle is characterized by comprising a current transformer iron core, a wire, a measuring coil, an oscillating circuit and a measuring circuit; the measuring coil and the lead are wound on the current transformer iron core; the wire is connected with the oscillating circuit, and the measuring coil is respectively connected with the oscillating circuit and the measuring circuit; the measuring circuit is connected with the oscillating circuit; the measuring graph circuit comprises an inductance measuring circuit and a direct current signal measuring circuit, wherein the direct current signal measuring circuit is used for filtering alternating current signals to obtain direct current signals and outputting square waves, and the inductance measuring circuit is used for calculating positive and negative level time.
2. An insulation fault monitoring circuit based on the pulse width variation principle according to claim 1, wherein the oscillating circuit comprises a resistor R1, a resistor R2, a resistor R3, a comparator, a capacitor C1 and an inductance L; the inductor L is an inductor with a core, and the capacitor C1 is a filter capacitor for filtering alternating current; the resistor R1 is connected with the comparator and the coil, the inductor L is connected with the other coil, the resistor R1 is further connected with the comparator and the resistor R2, the resistor R2 is further connected with the resistor R3 and the capacitor C1, and the capacitor C1 is further connected with the resistor R3 and the inductor L.
3. An insulation fault monitoring circuit based on the principle of pulse width variation according to claim 1, wherein the inductance measurement circuit comprises a venturi bridge sine wave oscillator, a voltage follower and an inductance-voltage conversion circuit.
4. The insulation fault monitoring circuit based on the pulse width variation principle according to claim 1, wherein the direct current signal measuring circuit is composed of a filter circuit, an amplifying circuit and a zeroing circuit.
5. An insulation fault monitoring method based on a pulse width variation principle is applied to the insulation fault monitoring circuit based on the pulse width variation principle as claimed in any one of claims 1 to 4, and is characterized by comprising the following steps:
s1: by utilizing the characteristic that the inductance current cannot be suddenly changed, the voltages of the positive and negative input ends of the comparator are compared with each other to output positive and negative square wave signals, and the time, period and amplitude of the high and low level of the square wave signals are related to circuit parameters;
s2: calculating positive and negative level time, thereby determining cycle time;
s3: calculating the square wave duty ratio;
s4: calculating a direct current component;
s5: judging whether the direct current system has insulation faults according to the square wave duty ratio and the direct current component, wherein the insulation faults exist when the square wave duty ratio is not 50% or the direct current component is not 0, and the insulation faults do not exist when the duty ratio is 50% and the direct current component is 0.
6. The insulation fault monitoring method based on the pulse width variation principle according to claim 5, wherein the positive and negative level time in the step S2 is calculated as follows:
wherein t is 1 Is positively chargedFlat time, t 2 Time of negative level, L 1 Inductance value at high level, L 2 At a negative level, the inductance value, R L Is the resistance value of the inductor, R 1 Is the resistance value of a resistor R1 in the oscillating circuit, R 2 Is the resistance value of a resistor R2 in the oscillating circuit, R 3 Is the resistance of the resistor R3 in the oscillating circuit.
7. The insulation fault monitoring method according to claim 6, wherein the cycle time in the step S2 is a sum of a positive level time t1 and a negative level time t 2.
8. The insulation fault monitoring method based on the pulse width variation principle according to claim 5, wherein the duty cycle calculation formula of the step S3 is as follows:
wherein D is duty cycle, t 1 Is positive in time, t 2 Is a negative level time.
9. The insulation fault monitoring method based on the pulse width variation principle according to claim 5, wherein the dc component calculation formula of the step S4 is as follows:
wherein A is 0 Is a direct current component, T is a square wave period, T 1 For positive and negative level continuous time difference, um is positive amplitude of square wave after oscillation, -Um is negative amplitude of square wave after oscillation, and k is period number.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202310247824.8A CN116540030A (en) | 2023-03-15 | 2023-03-15 | Insulation fault monitoring circuit and method based on pulse width change principle |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202310247824.8A CN116540030A (en) | 2023-03-15 | 2023-03-15 | Insulation fault monitoring circuit and method based on pulse width change principle |
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| Publication Number | Publication Date |
|---|---|
| CN116540030A true CN116540030A (en) | 2023-08-04 |
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| Application Number | Title | Priority Date | Filing Date |
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| CN202310247824.8A Withdrawn CN116540030A (en) | 2023-03-15 | 2023-03-15 | Insulation fault monitoring circuit and method based on pulse width change principle |
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| CN (1) | CN116540030A (en) |
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- 2023-03-15 CN CN202310247824.8A patent/CN116540030A/en not_active Withdrawn
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Application publication date: 20230804 |