Insulation resistance and capacitance measuring circuit and method based on monopulse double-edge analysis

Abstract

The invention discloses an insulation resistance and capacitance measuring circuit and method based on monopulse double-edge analysis, and relates to the related field of the electrical insulation online monitoring technology, and the circuit comprises a detected object and an insulation detection circuit. The insulation detection circuit comprises a controlled pulse voltage source, a coupling resistance network, a current sensor, a switch control module, a signal modulation circuit and a processor. The measurement method implemented based on the circuit comprises the following steps: injecting a common-mode voltage pulse into a transmission line of the power transmission system by adopting a pulse transmitter; pulse current response is collected in real time, a current oscillogram is drawn, and a three-point sampling method is introduced to record a current value for insulation impedance parameter calculation; according to a load condition, a double-edge verification method is applied based on a pulse current attenuation characteristic, and insulation impedance parameters including a resistive component and a capacitive component are independently calculated by analyzing a pulse current rising edge and a pulse current falling edge. According to the invention, non-intrusive synchronous monitoring of resistive and capacitive components of line-to-ground impedance is realized, and the detection precision is improved.

Description

Technical Field

[0001] The present application relates to the field of electrical insulation online monitoring technology, and in particular to an insulation resistance and capacitance measurement circuit and method based on single-pulse double-edge analysis. Background Art

[0002] Insulation resistance and capacitance measurement are important links in the maintenance and operation management of electrical equipment. They are widely used in electric vehicle charging systems, photovoltaic power generation, energy storage equipment, and AC and DC power transmission scenarios. Insulation resistance refers to the ratio between the voltage applied between two electrodes in the insulation structure of the power transmission system and the leakage current flowing through the pair of electrodes. It is an important parameter for measuring the insulation performance of electrical equipment; capacitors are components that store electrical energy, and their capacitance determines the energy storage capacity of the circuit.

[0003] By regularly measuring insulation resistance, problems such as aging, moisture, and damage to insulating materials can be discovered in advance, and corresponding measures can be taken in a timely manner to address these problems, thereby achieving equipment failure prediction and health management, thereby avoiding short circuits, leakages, and other faults in electrical equipment; by measuring the capacitance parameters of capacitors, the quality of capacitors can be evaluated, and problems such as dielectric aging and internal short circuits in capacitors can be determined, and timely replacement can be made to ensure circuit reliability.

[0004] The traditional measurement method uses the unbalanced bridge method. By controlling the switching of the balanced bridge and the unbalanced bridge in the detection circuit, the voltage detection results and leakage current detection results corresponding to each output branch are obtained, and the insulation impedance is calculated based on the detection results. This method requires switching switches to form an asymmetric grounding impedance and establishes a binary equation to solve the resistive component of the ground impedance. It cannot measure the capacitive component and is only applicable to DC isolation systems. It cannot be expanded to AC scenarios. The switch is switched multiple times and the response speed is slow. Summary of the Invention

[0005] In response to the technical problems of the above-mentioned prior art, the present application provides an insulation resistance and capacitance measurement circuit and method based on single-pulse double-edge analysis. By introducing a single pulse and combining the current attenuation characteristics of the rising and falling edges of the pulse, non-invasive synchronous monitoring of the line-to-ground impedance, including resistive and capacitive components, is achieved. It is compatible with AC and DC systems and achieves millisecond-level response.

[0006] The present application provides an insulation resistance and capacitance measurement circuit based on single pulse double edge analysis, which consists of a detected object and an insulation detection circuit. The detected object is the resistive component of the power transmission line to ground impedance, the first resistor R p and the second resistor R n , capacitive component first capacitor C p and the second capacitor C n; The insulation detection circuit includes: a controlled pulse voltage source, a coupling resistor network, a current sensor, a switch control module, a signal modulation circuit and a processor; the object to be detected and the insulation detection circuit form a series relationship, and the processor in the insulation detection circuit divides the branches into branches that are respectively connected in series with the controlled pulse voltage source, the coupling resistor network, the current sensor, the switch control module and the signal modulation circuit, and the branches form a parallel relationship.

[0007] The detected object also includes a power supply voltage V pn , first switch K12, second switch K34 and load resistor R L By controlling the different states of the two switches, multi-scenario expansion is achieved:

[0008] When the first switch K12 and the second switch K34 are both turned off, the power supply voltage V pn and the load resistor R L The branch is disconnected, and the detection circuit is connected to the resistive and capacitive components of the impedance to ground to detect the pure line impedance, including the first resistor R p , the second resistor R n , the first capacitor C p and the second capacitor C n ;

[0009] When the first switch K12 is closed and the second switch K34 is open, the power supply voltage V pn The branch is connected, the load resistance R L The branch is disconnected, the detection circuit is connected to the power supply voltage V pn , the resistive and capacitive components of the ground impedance are connected to achieve the power supply voltage V pn , total insulation resistance R z and total insulation capacitance C z The total insulation resistance R z is the first resistor R p and the second resistor R n The parallel value of the total insulation capacitance C z is the first capacitor C p and the second capacitor C n The parallel value of

[0010] When the first switch K12 is open and the second switch K34 is closed, the power supply voltage V pn The branch is disconnected, the load resistance R L The branch is connected, the detection circuit and the load resistor R L , the resistive and capacitive components of the ground impedance are connected to achieve the load terminal voltage and the total insulation resistance R z and total insulation capacitance C z Joint detection.

[0011] The controlled pulse voltage source is controlled by a processor to inject common mode voltage into the power transmission line. The amplitude of the common mode voltage pulse V1 is 10-100V, the pulse width and amplitude are adjustable, and the injection point is located between the positive and negative busbars and the protective ground PE.

[0012] The coupling resistor network includes a first coupling resistor R1 and a second coupling resistor R2, which isolate the detected object from the insulation detection circuit, limit the current of the detection circuit, and protect the detection circuit from damage;

[0013] The switch control module includes a first control switch S1 and a second control switch S2, which control the on and off of the insulation detection circuit;

[0014] The first current sensor CS1 and the second current sensor CS2 are used to detect the current value in the loop, providing real-time data for subsequent drawing of the current waveform to analyze the rising and falling edges of the current;

[0015] The signal modulation circuit includes three AFE modules to realize current / voltage conversion, filtering and amplification. The AFE1 module is located between the current sensor and the processor, the AFE2 is located between the first coupling resistor R1 and the processor branch, and the AFE3 is located between the second coupling resistor R2 and the processor branch.

[0016] The processor is used to receive measurement data from the current sensor and the AFE module, calculate the resistive component and the capacitive component of the power transmission line-to-ground impedance based on a three-point sampling method and a double-edge test method, and send a warning signal.

[0017] Based on the above insulation resistance and capacitance measurement circuit, the present application provides an insulation resistance and capacitance measurement method based on single pulse double edge analysis, the method comprising:

[0018] (1) A pulse transmitter is used to inject common-mode voltage pulses into the transmission line of the power transmission system, which acts on the positive and negative busbars through the coupling resistor;

[0019] (2) Real-time acquisition of pulse current response, drawing of current waveform, introduction of three-point sampling method, recording of current values ​​at three moments, and measurement of insulation resistance parameters;

[0020] (3) According to the load conditions, the dual-edge verification method is applied based on the pulse current attenuation characteristics. The insulation impedance parameters, including the resistive component and the capacitive component, are calculated independently by analyzing the rising and falling edges of the pulse current.

[0021] The present invention discloses the following technical effects:

[0022] The present invention proposes an insulation resistance and capacitance measurement circuit and method based on single-pulse double-edge analysis. By constructing an insulation detection circuit, introducing a common-mode voltage pulse, and based on a three-point sampling method and a single pulse double-edge verification method, the insulation impedance and parasitic capacitance of the power transmission line are measured simultaneously, overcoming the limitation of the traditional measurement method that can only measure resistive impedance, improving the system safety assessment dimension, and providing data support for fault prediction and health management of the power system. In addition, the common-mode pulse injection mechanism proposed in the present invention is compatible with DC and AC power systems, expanding the application scenarios of the measurement method; the insulation detection circuit proposed in the present invention adopts a non-invasive design and can achieve millisecond-level response without interrupting power supply; a double-edge redundant verification method is introduced to independently calculate the resistance and capacitance parameters by analyzing the rising and falling edges of a single pulse, thereby improving measurement accuracy; in order to reduce the computing power requirements of the microcontroller unit, a three-point sampling method is used instead of exponential fitting to improve measurement efficiency. The present invention sets a dual-switch mechanism, which flexibly controls the detection range of the circuit by controlling different combinations of switch states, thereby realizing switching detection of the line end, power end, and load end. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings of the embodiments of the present invention are briefly introduced below. Flowcharts are used in this application to illustrate the operations performed by the system according to the embodiments of the present application. It should be understood that the preceding or following operations are not necessarily performed in precise order. Instead, various steps may be processed in reverse order or simultaneously as needed. Furthermore, other operations may be added to these processes, or one or more operations may be removed from these processes.

[0024] Figure 1 Schematic diagram of the insulation resistance and capacitance measurement circuit based on single pulse double edge analysis provided in an embodiment of the present application.

[0025] Figure 2 Flowchart of the insulation resistance and capacitance measurement method based on single pulse double edge analysis provided in an embodiment of the present application.

[0026] Figure 3 Schematic diagram of pulse signal injection for the insulation resistance and capacitance measurement circuit based on single-pulse double-edge analysis provided in an embodiment of the present application.

[0027] Figure 4 The first capacitor C is provided in the embodiment of the present application when the system is lightly loaded. p With the first resistor R p Schematic diagram of the current loop.

[0028] Figure 5 The pulse voltage V provided in the embodiment of the present application s With the first pulse current I p Schematic diagram of the rising edge waveform of (t).

[0029] Reference symbol: red line is pulse voltage V s Waveform, the green line is the first pulse current I p (t) Waveform.

[0030] Figure 6 The first resistor R when the system is overloaded provided in the embodiment of the present application p , the second resistor R n , the first capacitor C p and the second capacitor C n Schematic diagram of a circuit that is forced into parallel connection.

[0031] Figure 7 Schematic diagram of the pulse current falling edge model provided in an embodiment of the present application.

[0032] Figure 8 The first pulse current I provided in the embodiment of the present application p (t) Current waveform at the falling edge.

[0033] Figure 9 A schematic diagram illustrating the effect of differential mode current on pulse current sampling provided in an embodiment of the present application. DETAILED DESCRIPTION

[0034] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below.

[0035] In order to make the purpose, technical solutions and advantages of this application clearer, the application will be further described in detail below with reference to the accompanying drawings. The described embodiments should not be regarded as limiting this application. All other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0036] In the following description, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product, or server that includes a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or modules that are not explicitly listed or are inherent to these processes, methods, products, or devices. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs. The terms used herein are for the purpose of describing the embodiments of this application only.

[0037] Example 1: This application embodiment provides an insulation resistance and capacitance measurement circuit and method based on single pulse double edge analysis. The detailed structure of the circuit is as follows: Figure 1 As shown, it includes a detected object and an insulation detection circuit.

[0038] The object to be detected is the resistive component of the impedance of the power transmission line to the ground, the first resistor R p and the second resistor R n , capacitive component first capacitor C p and the second capacitor C n The insulation detection circuit includes: a controlled pulse voltage source V1, a first coupling resistor R1 and a second coupling resistor R2, a first current sensor CS1 and a second current sensor CS2, a first control switch S1 and a second control switch S2, a signal modulation circuit AFE and a processor.

[0039] Based on the above insulation resistance and capacitance measurement circuit, the present application provides an insulation resistance and capacitance measurement method based on single pulse double edge analysis, such as Figure 2 As shown, the method includes:

[0040] Step S10: injecting common-mode voltage pulses into the power transmission line using a pulse transmitter, and applying the pulses to the positive and negative busbars via coupling resistors.

[0041] In this embodiment, the pulse signal injection method is as follows: Figure 3 As shown:

[0042] Inject a common mode voltage pulse V1 into the power transmission system, close the first control switch K1 and the second control switch K2, and the first pulse current I p With the second pulse current I n Through coupling resistor R c Acting on the power supply terminal V op and V on , and then pass through the first resistor R p With the second resistor R n Return to pulse V1; common mode voltage pulse injection avoids interference with the power supply circuit, ensuring the power supply voltage V pn Stable, non-invasive measurement; coupling resistance R c The injected common-mode voltage pulse is distributed to the positive and negative bus bars to ensure that the pulse signal acts evenly on the bus bars.

[0043] Step S20 collects the pulse current response in real time, draws a current waveform diagram, introduces a three-point sampling method, and records the current values ​​at three moments for measuring the insulation resistance parameters.

[0044] In this embodiment, a three-point sampling method is used to achieve engineering perfection. In actual engineering, the voltage oscillates at the initial time t0, and the first pulse current I at the starting time is measured. p(t0) is difficult; at the same time, microcontroller units are generally used as calculation units in engineering applications, and fitting time constants is difficult.

[0045] Three-point sampling method, i.e. recording t1, t2 and t ∞ The first pulse current I p (t1), I p (t2) and I p (∞), let t ∞ >t2>t1>0, the time constant τ is obtained by recording the current value, and the derivation process is as follows:

[0046] For any time t, I p (t) all satisfy the following formula:

[0047]

[0048] Let A=I p (t0)-I p (∞), its physical meaning is the total attenuation amplitude of the first pulse current; I p (t0)=V S / R c , where V S Indicates the amplitude of the common mode pulse voltage V1, I p (∞) After waiting for a long enough time, we can directly measure it, so A is a known quantity, and the above formula can be simplified to:

[0049]

[0050] For time t1 and t2 respectively:

[0051]

[0052] The attenuation amplitudes ΔI(t1) and ΔI(t2) at time t1 and t2 are expressed as:

[0053]

[0054] Dividing the above two equations we get:

[0055]

[0056] Taking the natural logarithm of the above formula:

[0057]

[0058] Therefore, the time constant τ is expressed as:

[0059]

[0060] Based on the physical meaning of the above formula, it is only necessary to measure the instantaneous first pulse current I at time t1 and t2 respectively. p (t1) and I p (t2), measure the steady-state current I of the first pulse current p (∞), the time constant τ can be calculated for subsequent calculation of resistance and capacitance without the need for complex function fitting, which reduces the difficulty of engineering application. The above method is also applicable to the second pulse current I n (t) Calculation of the time constant τ.

[0061] Step S30 , according to the load condition, a double-edge verification method is applied based on the pulse current attenuation characteristics, and the insulation impedance parameters, including the resistive component and the capacitive component, are independently calculated by analyzing the rising edge and the falling edge of the pulse current.

[0062] In this embodiment, the rising edge of the pulse current is analyzed first:

[0063] When the power transmission system is unloaded or lightly loaded, that is, the load resistance R L >>R p ||R n , R p |R n Represents the first resistor R p With the second resistor R n In parallel, the first resistor R p With the second resistor R n Through the load resistor R L The parallel circuit impedance is large, and the first pulse current I p For example, the circuit Figure 4 As shown, the circuit includes a pulse voltage source V1, the voltage value of which is V s ; Coupling resistor R c , the first resistor R p , the first capacitor C p and voltage V cp , at this time, the first pulse current I can be observed p The waveform of the first resistor R is analyzed. p With the first capacitor C p , V s Waveform and I p (t) Current waveform Figure 5 As shown:

[0064] Starting from time t0, I p According to the time constant τ, the exponential trend increases from I p (t0) decays to I p (∞), select t1, t2 and t ∞ The first resistance R is calculated using the three-point sampling method. p With the first capacitor Cp :

[0065] Known coupling resistance R c and voltage V s , from I p (t) Read the current value I from the current waveform p (t1), I p (t2) and I p (∞), in the steady state t ∞ At this moment, the capacitor is equivalent to an open circuit. At this time, the current no longer changes and is in the horizontal part. It is measured long enough after the pulse ends. According to I p (∞) Calculate the total resistance R eq :

[0066]

[0067] From this, the first resistance R can be solved p :

[0068]

[0069] According to the current value I p (t1), I p (t2) and I p (∞), combined with the calculated first resistance R p , and the known coupling resistance R c , further calculation to obtain the first capacitance C p ; Coupling resistor R c and the first resistor R p Parallel pair C p Discharge, the time constant τ is expressed as:

[0070]

[0071] Substituting the time constant calculated in step S20 into the equation, we can obtain:

[0072]

[0073] After finishing, we can get:

[0074]

[0075] Substitute ΔI(t1)=I p (t1)-I p (∞), ΔI(t2)=I p (t2)-I p (∞) we can get:

[0076]

[0077] Similarly, the three-point sampling method is used to measure the second pulse current I n (t) At t1, t2 and t ∞ Current value at the moment I n (t1), I n (t2) and I n (∞), combined with the known quantities, the second resistance R n With the second capacitor C n :

[0078]

[0079]

[0080] When the power transmission system is heavily loaded or the internal resistance of the power source is very small, that is, the load resistance R L <<R p ||R n When R p and R n By R L Forced parallel connection, such as Figure 6 As shown, R p and R n 、C p and C n A parallel relationship is automatically formed, and the total loop current I can be observed at this time c (t), the total insulation resistance R z and total insulation capacitance C z , where R z =R p ||R n 、C z =C p ||C n .

[0081] When the power transmission system is under heavy load, the total current analysis method is used to detect the total loop current after injecting common mode pulses: I c (t) = I p (t)+I n (t), at this time the coupling resistance is also in parallel, so the coupling resistance is to I c (t) Apply the three-point sampling method to measure the current value I c (t1), I c (t2) and I c (∞), directly calculate the total insulation resistance R z and total insulation capacitance C z :

[0082]

[0083] To improve measurement accuracy, after analyzing the rising edge of the pulse current, we analyze the falling edge of the pulse current to achieve redundancy testing, which is divided into light load and heavy load conditions:

[0084] When the power transmission system is unloaded or lightly loaded, that is, the load resistance R L >>R p ||R n , the pulse current falling edge model is as follows Figure 7 As shown, the pulse source is at t′ 0- At this moment, the voltage is V s Reduced to 0V, V s Equivalent to a short circuit, the coupling resistance R c With the first resistor R p The first capacitor C is connected in parallel p Discharge, discharge current curve is as follows Figure 8 As shown, the first pulse steady-state current before the jump The first pulse steady-state current after the jump I p (∞)=0.

[0085] When the pulse voltage is from V s When it jumps to 0V, the first capacitor C p Through the first resistor R p and coupling resistor R c Discharge, first pulse current I p (t) Satisfy:

[0086]

[0087] Among them, the first pulse current at the instant of transition The first resistance R is calculated by the same three-point sampling method. p and the first capacitor C p :

[0088] Select t′ before the falling edge 0- Measure the first pulse current I at all times p (t′ 0- ), t′ 0- Then select t'1 and t'2, and t'2>t'1>0, and measure the first pulse current value I p (t′1) and I p (t′2);

[0089] According to the known V s and R c , solve for the first resistor R p :

[0090]

[0091] Further calculate the time constant τ:

[0092]

[0093] According to the time constant τ, the first capacitance C is calculated p :

[0094]

[0095] Similarly, the three-point sampling method is used to measure the second pulse current I n (t) at the falling edge t′ 0- , the current value I at time t′1 and t′2 p (t′ 0- ), I n (t′1) and I n (t′2), combined with the known quantities, the second resistance R n With the second capacitor C n :

[0096]

[0097] When the power transmission system is heavily loaded or the internal resistance of the power source is very small, that is, the load resistance R L <<R p ||R n When R p and R n By R L Forced parallel connection, using the total current analysis method, injecting common mode pulses, and detecting the total loop current I c (t) At this time, the coupling resistors are in parallel relationship. to I c (t) Apply the three-point sampling method and select the falling edge time t′ 0- , t′1 and t′2, measure the current value I c (t′ 0- ), I c (t′1) and I c (t′2), directly calculate the total insulation resistance R z and total insulation capacitance C z :

[0098]

[0099] Measuring the impedance component during the falling edge of the pulse current avoids the instantaneous oscillation when the power is turned on, which is beneficial to improving the signal-to-noise ratio; combining the results of the rising and falling edges of the pulse current for cross-validation can reduce measurement errors.

[0100] In actual circuits, Figure 9 As shown, due to the two coupling resistors R c The access will be in R cA differential mode current I is introduced d , the calculation formula is:

[0101]

[0102] For a steady-state system, I d It is also steady-state; I d The presence of the first pulse current I p and the second pulse current I n Sampling, I d Direction and I n Same as I p On the contrary, considering the influence of differential mode current on the three-point sampling method, the calculation formulas of the resistive and capacitive components of impedance are revised:

[0103] Rising edge stage:

[0104]

[0105] Falling edge phase:

[0106]

[0107] For the total insulation resistance R z and total insulation capacitance C z , because I c =I p +I n is the vector sum, and the summation process eliminates I d The influence of , the formula remains unchanged.

[0108] Example 2: This application embodiment provides an insulation resistance and capacitance measurement circuit and method based on single pulse double edge analysis, taking an electric vehicle charging pile as an application example, using Figure 1 The detection circuit shown, combined with the measurement process described in Example 1, measures the total insulation resistance and capacitive reactance in the charging pile:

[0109] According to the national standard GB / T 18487.1-201, the insulation impedance requirements of charging piles are shown in Table 1.

[0110] Table 1 Charging pile insulation impedance requirements specified in national standard GB / T 18487.1-201

[0111] state Total insulation resistance requirements (1000V system) Normal charging >500kΩ Interval alarm 100kΩ-500kΩ Forced shutdown ≤100kΩ

[0112] In this embodiment, the pulse power supply voltage V s =50V, coupling resistance R′ c =R1||R2=100kΩ, and measure the total loop current I at t1, t2, and t3 respectively. c(t), the measured data are shown in Table 2.

[0113] Table 2 Measurement data of charging piles in Example 2

[0114] time <![CDATA[t1=5.1ms]]> <![CDATA[t2=30.3ms]]> <![CDATA[t3 = 1s (steady state)]]> <![CDATA[I c (t)]]> 427.5μA 223μA 99.6μA

[0115] According to the measured data, calculate the total insulation resistance R z and total insulation capacitance C z :

[0116]

[0117]

[0118] The total insulation resistance R is obtained by calculating z Comparison with national standards indicates that the charging pile's power transmission system is currently in the interval warning phase, with the processor in the detection circuit sending a warning signal. The following error analysis of the measured data is performed, and the error between the actual and measured values ​​is shown in Table 3.

[0119] Table 3 Error analysis of charging pile measurement data in Example 2

[0120]

[0121] Through error analysis, it can be obtained that at the steady-state moment t3, the pulse current I c (t3) and total insulation resistance R z There is a linear relationship, R z The measurement error can be easily controlled within ±2%. z When I c (t) is exponentially related to time t. A slight time deviation in measurement will lead to a large systematic error. By optimizing the time deviation during measurement, the error can be controlled within ±5%.

[0122] The three-point sampling algorithm and single pulse double-edge verification method proposed in the present invention can simultaneously measure the insulation impedance and parasitic capacitance of the line, and can achieve an impedance error of ±2% and a capacitive reactance error of ±5%, which has strong practical value.

[0123] The above specific embodiments do not constitute a limitation to the scope of protection of this application. It should be understood by those skilled in the art that various modifications, combinations and substitutions can be made according to design requirements and other factors. Any modifications, equivalent replacements and improvements made within the spirit and principles of this application should be included in the scope of protection of this application. In some cases, the actions or steps recorded in this application can be performed in an order different from that in the embodiments and can still achieve the desired results. In addition, the processes depicted in the accompanying drawings do not necessarily require the specific order or continuous order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

Claims

1. The insulation resistance and capacitance measurement circuit based on single pulse double edge analysis is characterized by: The circuit includes a detected object and an insulation detection circuit; the detected object is a first resistor R p and the second resistor R n , capacitive component first capacitor C p and the second capacitor C n ; The insulation detection circuit includes: a controlled pulse voltage source, a coupling resistor network, a current sensor, a switch control module, a signal modulation circuit and a processor; the object to be detected and the insulation detection circuit form a series relationship, and the processor in the insulation detection circuit divides the branches into branches that are respectively connected in series with the controlled pulse voltage source, the coupling resistor network, the current sensor, the switch control module and the signal modulation circuit, and the branches form a parallel relationship.

2. The insulation resistance and capacitance measurement circuit based on single pulse double edge analysis according to claim 1, characterized in that: The detected object also includes a power supply voltage V pn , first switch K12, second switch K34 and load resistor R L , power supply voltage V pn , load resistance R L The resistive component of the impedance to ground and the capacitive component of the impedance to ground are connected in parallel; the first switch K12 and the second switch K34 respectively control the power supply voltage V pn and the load resistor R L The opening and closing of the branch circuit can be expanded to multiple scenarios by controlling the different states of the two switches: When the first switch K12 and the second switch K34 are both turned off, the power supply voltage V pn and the load resistor R L The branch is disconnected, and the detection circuit is connected to the resistive and capacitive components of the impedance to ground to detect the pure line impedance, including the first resistor R p , the second resistor R n , the first capacitor C p and the second capacitor C n ; When the first switch K12 is closed and the second switch K34 is open, the power supply voltage V pn The branch is connected, the load resistance R L The branch is disconnected, the detection circuit is connected to the power supply voltage V pn , the resistive and capacitive components of the ground impedance are connected to achieve the power supply voltage V pn , total insulation resistance R z and total insulation capacitance C z The total insulation resistance R z is the first resistor R p and the second resistor R n The parallel value of the total insulation capacitance C z is the first capacitor C p and the second capacitor C n The parallel value of When the first switch K12 is open and the second switch K34 is closed, the power supply voltage V pn The branch is disconnected, the load resistance R L The branch is connected, the detection circuit and the load resistor R L , the resistive and capacitive components of the ground impedance are connected to achieve the load terminal voltage and the total insulation resistance R z and total insulation capacitance C z Joint detection.

3. The insulation resistance and capacitance measurement circuit based on single pulse double edge analysis according to claim 1, characterized in that: The controlled pulse voltage source is controlled by a processor to inject common mode voltage into the power transmission line. The amplitude of the common mode voltage pulse V1 is 10-100V, the pulse width and amplitude are adjustable, and the injection point is located between the positive and negative busbars and the protective ground PE.

4. The insulation resistance and capacitance measurement circuit based on single pulse double edge analysis according to claim 1, characterized in that: The coupling resistor network includes a first coupling resistor R1 and a second coupling resistor R2, which isolate the detected object from the insulation detection circuit, limit the current of the detection circuit, and protect the detection circuit from damage; The switch control module includes a first control switch S1 and a second control switch S2, which control the on and off of the insulation detection circuit; The current sensor includes a first current sensor CS1 and a second current sensor CS2, which are used to detect the current value in the loop and provide real-time data for subsequent drawing of the current waveform to analyze the rising and falling edges of the current; The signal modulation circuit includes three AFE modules to realize current / voltage conversion, filtering and amplification. The AFE1 module is located between the current sensor and the processor, the AFE2 is located between the first coupling resistor R1 and the processor branch, and the AFE3 is located between the second coupling resistor R2 and the processor branch. The processor is used to receive measurement data from the current sensor and the AFE module, calculate the resistive component and the capacitive component of the power transmission line-to-ground impedance based on a three-point sampling method and a double-edge test method, and send a warning signal.

5. The insulation resistance and capacitance measurement method based on single pulse double edge analysis is characterized in that: The method is implemented by the insulation resistance and capacitance measurement circuit based on single pulse double edge analysis according to claims 1 to 4, comprising: (1) A pulse transmitter is used to inject common-mode voltage pulses into the transmission line of the power transmission system, which acts on the positive and negative busbars through the coupling resistor; (2) Real-time acquisition of pulse current response, drawing of current waveform, introduction of three-point sampling method, recording of current values ​​at three moments, and measurement of insulation resistance parameters; (3) According to the load conditions, the dual-edge verification method is applied based on the pulse current attenuation characteristics. The insulation impedance parameters, including the resistive component and the capacitive component, are calculated independently by analyzing the rising and falling edges of the pulse current.

6. The insulation resistance and capacitance measurement method based on single pulse double edge analysis according to claim 5, characterized in that: In step (2), the three-point sampling method is used to calculate the time constant: Record t1, t2 and t ∞ The first pulse current I p (t1), I p (t2) and I p (∞), let t ∞ >t2>t1>0, the time constant is obtained by recording the current value, and the time constant τ is expressed as: Where, ΔI(t1)=I p (t1)-I p (∞), ΔI(t2)=I p (t2)-I p (∞), I p (t0) = V S / R c , V S is the voltage value of the common mode pulse voltage, R c is the coupling resistor.

7. The insulation resistance and capacitance measurement method based on single pulse double edge analysis according to claim 5, characterized in that: In step (3), when the power transmission system is unloaded or lightly loaded, the insulation resistance parameters are calculated by analyzing the rising edge of the pulse current based on the three-point sampling method: The coupling resistance R is known c and common mode pulse voltage V s , from the first pulse current I p (t) Read the current value I in the waveform p (t1), I p (t2) and steady-state current I p (∞), according to I p (∞) Calculate the total resistance R eq : Therefore, the first resistance R p : According to the current value I p (t1), I p (t2) and I p (∞), combined with the calculated first resistance R p , and the known coupling resistance R c , further calculation to obtain the first capacitance C p : Coupling resistor R c and the first resistor R p The first capacitor C is connected in parallel p Discharge, the time constant τ is expressed as: Substituting the time constant τ calculated in step (2) into the formula, we can obtain: Similarly, the three-point sampling method is used to measure the second pulse current I n (t) At t1, t2 and t ∞ Current value at the moment I n (t1), I n (t2) and I n (∞), combined with the known quantities, solve for the second resistance R n With the second capacitor C n :

8. The insulation resistance and capacitance measurement method based on single pulse double edge analysis according to claim 5, characterized in that: In step (3), when the power transmission system is under heavy load, the load resistance R L < <R p ||R n When R p and R n By R L Forced parallel connection, analysis of the rising edge of the pulse current: Using the total current analysis method, after injecting the common mode pulse, the total loop current I is detected c (t): I c (t) = I p (t)+I n (t), I p (t) and I n (t) represent the first pulse current and the second pulse current respectively. At this time, the coupling resistance is also in a parallel relationship, so the coupling resistance is to I c (t) Apply the three-point sampling method to measure the total loop current I c (t) At t1, t2 and t ∞ Current value at the moment I c (t1), I c (t2) and I c (∞), directly calculate the total insulation resistance R z and total insulation capacitance C z : Among them, V S is the voltage value of the common mode pulse voltage.

9. The insulation resistance and capacitance measurement method based on single pulse double edge analysis according to claim 5, characterized in that: In step (3), when the power transmission system is unloaded or lightly loaded, the falling edge of the pulse current is analyzed based on the three-point sampling method, and the insulation resistance parameters are calculated again to verify the measurement data: Select t′ before the falling edge 0- Measure the first pulse current I at all times p (t′ 0- ), t′ 0- Then select the time t′1 and t′2, and t′2>t′1>0, and measure the first pulse current I p (t′1) and I p (t′2); According to the known common-mode pulse voltage V s and coupling resistor R c , solve for the first resistor R p and the first capacitor C p : Similarly, the three-point sampling method is used to measure the second pulse current I n (t) at the falling edge t′ 0- , the current value I at time t′1 and t′2 p (t′ 0- ), I n (t′1) and I n (t′2), combined with the known quantities, the second resistance R n With the second capacitor C n :

10. The insulation resistance and capacitance measurement method based on single pulse double edge analysis according to claim 5, characterized in that: In step (3), when the power transmission system is overloaded or the internal resistance of the power supply is very small, the total current analysis method is used to analyze the falling edge of the pulse current: After injecting the common mode pulse, the total loop current I is detected c (t), at this time the coupling resistors are in parallel relationship. to I c (t) Apply the three-point sampling method and select the falling edge time t′ 0- , the current value I at t′1 and t′2 c (t′ 0- ), I c (t′1) and I c (t′2), directly calculate the total insulation resistance R z and total insulation capacitance C z : Among them, V S is the voltage value of the common-mode pulse voltage; the impedance component is measured at the falling edge of the pulse current to avoid the instantaneous oscillation when the power is turned on; the results of the rising and falling edges of the pulse current are combined for cross-verification to reduce measurement errors.

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