Porcelain insulator zero measuring device and high-voltage loop small current and distributed voltage zero measuring method

Abstract

The invention discloses a porcelain insulator zero measuring device and a high-voltage loop small current and distributed voltage zero measuring method, and the porcelain insulator zero measuring device comprises a low-voltage pulse generator which is used for converting a received voltage signal into a voltage pulse signal with a set frequency; the boosting transformer is used for converting the voltage pulse signal sent by the low-voltage pulse generator into a voltage signal I; the voltage doubling circuit is used for converting the voltage signal I output by the boosting transformer into a voltage signal II; the detection circuit is used for converting the voltage signal II output by the voltage doubling circuit into a detection signal; and the discharge end POUT + and the discharge end POUT-are connected with the output end of the detection circuit and used for being lapped on steel caps at the two ends of the porcelain insulator. According to the invention, the insulator is not damaged in the measurement process, and the defects of the insulator can be comprehensively detected.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of porcelain insulator detection, and particularly relates to a porcelain insulator zero measurement device and a high-voltage loop small current and distributed voltage zero measurement method. BACKGROUND

[0002] Due to the influence of factory quality and running environment, the internal micro-crack defects of porcelain insulators may continuously increase to cause deterioration in different degrees. When the defects increase to a certain degree, the withstand voltage of the insulator will decrease, and the standard specified value is 45-50KV. When the applied voltage exceeds the withstand level of the insulator itself, breakdown discharge will occur in the insulator.

[0003] The insulator may also exhibit resistance characteristics when there are internal defects; the insulator may also exhibit resistance characteristics or surface discharge phenomena when there are external attached dirty substances.

[0004] The detection methods of the traditional portable defect insulator detection equipment include high-voltage breakdown method and shake table method. The high-voltage breakdown method is to apply a standard pulse voltage (50kV or more) to the insulator, and then measure whether the insulator can withstand the voltage within 500-1000ms. If the voltage amplitude on the insulator is low or the voltage waveform rapidly decreases, it indicates that the insulator has insulation defects; if the voltage decreases by less than the set range within the set time, it indicates that the insulator is in good insulation. The shake table method is to measure the loop current under the application of 2500-5000V DC voltage to the insulator, so as to calculate the resistance value of the insulator.

[0005] The advantage of the high-voltage breakdown method is that when the withstand voltage of the insulator is less than the standard or the resistance is less than the specified value, the defect can be measured; the disadvantage is that this pressurizing method is further destructive to insulators with different defect degrees, and is not completely suitable for live-line detection. If there are many insulators with light or moderate deterioration in the porcelain insulator string of the running line, since the micro-cracks do not form a through channel, the porcelain insulator still retains part of the insulation resistance, so that the insulator string can still be operated. However, after the high-voltage breakdown method is used for measurement, the number of deteriorated pieces in the string may further increase, resulting in a number of insulator pieces lower than the minimum insulator piece number for safe operation, and causing flashover failure of the insulator string.

[0006] The advantage of the shake table method is that the insulation resistance can be safely measured; the disadvantage is that because the measurement voltage is too low, some high-tonnage or lightly deteriorated insulators may not exhibit low resistance characteristics under 5000V voltage, and thus the insulator defects cannot be comprehensively detected, resulting in zero value missed detection.

[0007] The standard method of the zero value detection of the on-line insulator still has a distribution voltage method, specifically, the actual working voltage value of each piece of the on-line insulator string is measured, and whether the insulator distribution voltage meets the standard requirement is judged to determine the deterioration (the distribution voltage exceeds 50% of the standard reference value and is not lower than the adjacent normal insulator), the distribution voltage of the zero value insulator is low, so whether the insulator is in the zero value state is judged according to the height of the distribution voltage. The disadvantage of this method is that: if several deteriorated porcelain insulator pieces in the middle part of the long porcelain insulator string share the voltage originally lower, when one or several insulator pieces are slightly or moderately deteriorated, the voltage distribution of the adjacent insulator is often not significantly different, and the missed detection is easy to occur. At the same time, the traditional distribution voltage method is difficult to measure the porcelain insulator of the ultra-high voltage line. SUMMARY

[0008] In order to solve the problems in the prior art, the present application provides a porcelain insulator zero measurement device and a high-voltage loop small current and distribution voltage zero measurement method, which can ensure that the insulator is not damaged during measurement and can comprehensively detect the defects of the insulator.

[0009] To achieve the above object, the technical scheme adopted by the present application is: In a first aspect, a porcelain insulator zero measurement device is provided, comprising: a low-voltage pulse generator for converting a received voltage signal into a voltage pulse signal of a set frequency; a step-up transformer for converting the voltage pulse signal output by the low-voltage pulse generator into a voltage signal one; a voltage doubling circuit for converting the voltage signal one output by the step-up transformer into a voltage signal two, wherein the voltage signal two is an integer multiple of the voltage signal one; a detection circuit for converting the voltage signal two output by the voltage doubling circuit into a detection signal; and a discharge end POUT+ and a discharge end POUT- connected to the output end of the detection circuit and used for lapping on the steel caps at both ends of the porcelain insulator.

[0010] Further, the step-up transformer is an audio step-up transformer.

[0011] Further, the voltage doubling circuit comprises a plurality of voltage doubling units connected in series, each voltage doubling unit comprising a capacitor and a diode, and the negative electrode of the diode is connected to one end of the capacitor; wherein the positive electrode of the diode in the front-stage voltage doubling unit is connected to the other end of the capacitor in the rear-stage voltage doubling unit, and the negative electrode of the diode in the front-stage voltage doubling unit is connected to the positive electrode of the diode in the rear-stage voltage doubling unit; the other end of the capacitor in the first-stage voltage doubling unit is connected to the output point H0 of the step-up transformer, and the positive electrode of the diode in the first-stage voltage doubling unit is connected to the output point L0 of the step-up transformer.

[0012] Further, a preamplifier circuit is further included, which is used for outputting a corresponding voltage signal to the low-voltage pulse generator according to a received set input signal.

[0013] Further, the detection circuit comprises a filter circuit, the filter circuit comprises a high-voltage resistor U22 and a high-voltage resistor U23, one end of the high-voltage resistor U22 and one end of the high-voltage resistor U23 are connected to the output end of the voltage doubler circuit respectively; the other end of the high-voltage resistor U22 and the other end of the high-voltage resistor U23 are connected to one end of a capacitor C3 and one end of a capacitor C4 respectively, and the other end of the capacitor C3 is connected to the other end of the capacitor C4.

[0014] Further, the detection circuit further comprises a sampling resistor U18 and a sampling resistor U46, one end of the sampling resistor U18 is connected to one end of the capacitor C3, the other end of the sampling resistor U18 is grounded and connected to the discharge end POUT- through the sampling resistor U46, the high-voltage resistor U38 and the high-voltage resistor U37; the other end of the sampling resistor U18 is also connected to the discharge end POUT+ through the high-voltage resistor U34, the high-voltage resistor U39, the high-voltage resistor U11 and the high-voltage resistor U12; a diode U40, a diode U41, a diode U42, a diode U43, a diode U44 and a diode U45 are connected in series, the negative electrode of the diode U40 is connected to the common end of the high-voltage resistor U11 and the high-voltage resistor U39, the positive electrode of the diode U45 is connected to one end of the capacitor C3, and the positive electrode of the diode U42 is connected to one end of the capacitor C4.

[0015] Further, the detection circuit further comprises an operational amplifier chip U47, a pin IN1- of the operational amplifier chip U47 is connected to one end of a resistor R1, one end of a resistor R2 and the positive electrode of a diode D1, the other end of the resistor R1 is connected to the common end of the sampling resistor U46 and the high-voltage resistor U38, the other end of the resistor R2 is connected to a pin OUT1 of the operational amplifier chip U47, and the negative electrode of the diode D1 is grounded; a pin IN2- of the operational amplifier chip U47 is connected to the positive electrode of a diode D2, one end of a resistor R3 and one end of a resistor R4, the negative electrode of the diode D2 is grounded, the other end of the resistor R3 is connected to one end of the capacitor C3, and the other end of the resistor R4 is connected to a pin OUT2 of the operational amplifier chip U47; the pin OUT1 of the operational amplifier chip U47 is connected to an output terminal ADC123-IN11 of the detection circuit, and the pin OUT2 of the operational amplifier chip U47 is connected to an output terminal ADC123-IN12 of the detection circuit.

[0016] In the second aspect, a method for measuring zero current of a high-voltage loop of a porcelain insulator is provided, which is based on the porcelain insulator zero current measuring device in the first aspect, and comprises the following steps: setting a voltage signal of an input low-voltage pulse generator, the voltage signal forms a high-voltage loop small current acting on a porcelain insulator to be measured through the porcelain insulator zero current measuring device in the first aspect; collecting a high-voltage loop small current value flowing through the porcelain insulator to be measured within a set time, and then obtaining an insulation resistance of the porcelain insulator to be measured; and determining a state of the porcelain insulator to be measured according to the insulation resistance and a set insulation resistance criterion.

[0017] Further, the insulation resistance criterion I includes: if the insulation resistance of the porcelain insulator under test is in the normal threshold interval, the porcelain insulator under test is a normal porcelain insulator; if the insulation resistance of the porcelain insulator under test is in the defect threshold interval, the porcelain insulator under test is a defective inferior porcelain insulator; and if the insulation resistance of the porcelain insulator under test is in the zero value threshold interval, the porcelain insulator under test is a zero value porcelain insulator.

[0018] Further, the voltage signals input to the low voltage pulse generator are set in ascending order, and for each input voltage signal, a corresponding insulation resistance of the porcelain insulator under test is obtained; when the insulation resistance of the porcelain insulator under test is less than or equal to the set insulation threshold at the current voltage signal, it is determined that the current porcelain insulator has a zero value phenomenon at the current voltage signal, and the input voltage signal is no longer increased for the current porcelain insulator.

[0019] In a third aspect, a porcelain insulator distributed voltage on-line zero measurement method is provided, which is based on the porcelain insulator high voltage loop small current zero measurement method of the second aspect, and includes: disconnecting the voltage doubling circuit, so that the outputs of the discharge terminals POUT+ and POUT- connected to the steel caps on both ends of the porcelain insulator are zero, and the distributed voltage on the porcelain insulator is input to the detection circuit through the discharge terminals POUT+ and POUT-; reading the voltage value detected by the detection circuit and correcting it to obtain the actual voltage value on the current porcelain insulator; sequentially detecting each porcelain insulator on the porcelain insulator string and comparing adjacent porcelain insulators, and identifying the zero value porcelain insulator according to the set porcelain insulator zero value criterion.

[0020] Further, the porcelain insulator zero value criterion comprises: (1) if the distribution voltage of the current porcelain insulator is less than 50% of the distribution voltage of the adjacent porcelain insulator, the current porcelain insulator is a zero value porcelain insulator; (2) if the distribution voltage of the current porcelain insulator is less than 50% of the standard distribution voltage, the current porcelain insulator is a zero value porcelain insulator; (3) if the distribution voltage peak value of the current porcelain insulator is less than a set peak voltage: (A) the insulation resistance of the current porcelain insulator under the first set voltage signal and the second set voltage signal is measured by using the porcelain insulator high voltage loop small current zero measurement method; (B) the state of the current porcelain insulator is judged according to the set insulation resistance criterion two based on the insulation resistance of the current porcelain insulator; (4) if the distribution voltage peak value of the current porcelain insulator is greater than the set peak voltage: (a) the insulation resistance of the current porcelain insulator under the third set voltage signal and the fourth set voltage signal is measured by using the porcelain insulator high voltage loop small current zero measurement method; wherein the third set voltage signal is the superimposed voltage of the distribution voltage of the current porcelain insulator and the voltage loaded on the current porcelain insulator, and does not exceed the set upper limit voltage one; the fourth set voltage signal is the superimposed voltage of the distribution voltage of the current porcelain insulator and the voltage loaded on the current porcelain insulator, and does not exceed the set upper limit voltage two; (b) the state of the current porcelain insulator is judged according to the set insulation resistance criterion two based on the insulation resistance of the current porcelain insulator.

[0021] Further, the insulation resistance criterion two comprises: if the insulation resistance measured twice is located in the set normal threshold interval, the current porcelain insulator is judged as a normal porcelain insulator, if the insulation resistance measured once is located in the suspected low value threshold interval, the current porcelain insulator is judged as a suspected low value porcelain insulator, if the insulation resistance measured once is located in the low value threshold interval, the current porcelain insulator is judged as a low value porcelain insulator, if the insulation resistance measured once is located in the suspected zero value threshold interval, the current porcelain insulator is judged as a suspected zero value porcelain insulator, and if the insulation resistance measured once is located in the zero value threshold interval, the current porcelain insulator is judged as a zero value porcelain insulator.

[0022] Compared with the prior art, the present application has the following beneficial effects: the low voltage pulse generator for converting the received voltage signal into a voltage pulse signal of a set frequency; the step-up transformer for converting the voltage pulse signal output by the low voltage pulse generator into a voltage signal one; the voltage doubling circuit for converting the voltage signal two output by the voltage doubling circuit into a detection signal; the distribution voltage measurement is combined with the high voltage loop small current method, which can retain the respective advantages of the above high voltage breakdown method, the oscillometer method and the distribution voltage method, and avoid their respective shortcomings, so as to ensure that the insulator is not damaged during the measurement process, and the defects of the insulator can be comprehensively detected. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 This is a circuit principle block diagram of a porcelain insulator zero detection device provided by an embodiment of the present invention; Figure 2 1 is a schematic diagram of the circuit principle of a boost transformer in an embodiment of the present invention; Figure 3 1 is a schematic diagram of the circuit principle of the voltage doubling circuit in an embodiment of the present invention; Figure 4 1 is a schematic diagram of the circuit principle of the detection circuit in an embodiment of the present invention; Figure 5 is the discharge curve of a normal insulator; Figure 6 It is the discharge curve graph collected when the probe is suspended; Figure 7 This is the discharge curve collected when a 1G high-voltage resistor is connected in parallel to a normal insulator; Figure 8 is the discharge curve of the zero-value insulator; Figure 9 1 is a schematic diagram of the circuit principle of the front-end circuit in an embodiment of the present invention; Figure 10 It is the waveform diagram of the operating insulator distributed voltage and high voltage output. DETAILED DESCRIPTION

[0024] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention.

[0025] Example 1 like Figure 1 As shown, a porcelain insulator zero detection device includes: a low-voltage pulse generator for converting a received voltage signal into a voltage pulse signal of a set frequency; a step-up transformer for converting the voltage pulse signal emitted by the low-voltage pulse generator into voltage signal one; a voltage doubling circuit for converting voltage signal one output by the step-up transformer into voltage signal two, wherein voltage signal two is an integer multiple of voltage signal one; a detection circuit for converting voltage signal two output by the voltage doubling circuit into a detection signal; and a discharge terminal POUT+ and a discharge terminal POUT- connected to the output end of the detection circuit and configured to overlap the steel caps at both ends of the porcelain insulator.

[0026] In the present invention, the low-voltage pulse generator is a 10KHz low-voltage pulse generator, and the step-up transformer is an audio frequency step-up transformer. Figure 2As shown, the application adopts push-pull structure to drive a conventional audio step-up transformer, and the secondary voltage of the transformer can reach 6KV or above. The step-up drive in the practical circuit of the application adopts 10KHZ frequency, and the transformer step-up ratio is 200, so when the voltage signal of the input low-voltage pulse generator is VCC24V=30v, the output terminal HO-LO of the step-up transformer is ±6KV.

[0027] Due to the electrical isolation effect of the transformer, the output voltage and input voltage level of the transformer are isolated, so the high-voltage step-up part and the input part of the transformer are electrically isolated, that is, and the main control part is electrically isolated. After the high-voltage part and the main control part are electrically isolated, the huge level change in the high-voltage step-up process is avoided to interfere with the main control circuit; at the same time, the detection circuit is in the high-voltage loop, so it needs to be powered by an isolation power transformer, and at the same time, the signals obtained by the detection circuit are sent to the main control circuit through optical communication reception and signal processing, and the communication unit.

[0028] As shown in Figure 2 The emitter of the triode Q17 (S9014) is grounded, the base is connected to the terminal TIM5_CH1 (for receiving the voltage pulse signal output by the low-voltage pulse generator) through the resistor R42 (1kΩ), and the collector is connected to the power supply VCC12V through the resistor R33 (10kΩ); the collector of the triode Q17 is also connected to the pin IN of the isolated gate driver U9 (IRS2104STRPBF) and one end of the resistor R44 (1kΩ); the other end of the resistor R44 is connected to the base of the triode Q18 (S9014), the emitter of the triode Q18 is grounded, and the collector is connected to the power supply VCC12V through the resistor R43 (10kΩ); the collector of the triode Q18 is also connected to the pin IN of the isolated gate driver U7 (IRS2104STRPBF).

[0029] The pin VCC of the isolated gate driver U9 is connected to the anode of diode D5 (SS14L), the power supply VCC 12V, one end of capacitor C35 (10uF), and one end of resistor R30 (10kΩ); the pin COM of the isolated gate driver U9 is grounded, the other end of capacitor C35 is grounded, and the other end of resistor R30 is connected to the pin SD# of the isolated gate driver U9; the cathode of diode D5 is connected to the pin VB of the isolated gate driver U9 and one end of capacitor C36 (10uF), the pin HO of the isolated gate driver U9 is connected to one end of resistor R31 (30Ω), the pin LO is connected to one end of resistor R32 (30Ω), the pin VS of the isolated gate driver U9 is connected to the other end of capacitor C36, the source of field effect transistor Q5 (20N06D), the drain of field effect transistor Q6 (20N06D), the anode of diode D6 (SMF30A), the cathode of diode D7 (SMF30A), and the input end one of transformer U10; the other end of resistor R31 is connected to the gate of field effect transistor Q5, the other end of resistor R32 is connected to the gate of field effect transistor Q6, the drain of field effect transistor Q5 is connected to the power supply VCC 24V and the cathode of diode D6, and the source of field effect transistor Q6 is grounded, and the anode of diode D7 is grounded.

[0030] The pin VCC of the isolated gate driver U7 is connected to the anode of diode D8 (SS14L), the power supply VCC 12V, one end of capacitor C37 (10uF), and one end of resistor R34 (10kΩ); the pin COM of the isolated gate driver U9 is grounded, the other end of capacitor C37 is grounded, and the other end of resistor R34 is connected to the pin SD# of the isolated gate driver U7; the cathode of diode D8 is connected to the pin VB of the isolated gate driver U7 and one end of capacitor C38 (10uF), the pin HO of the isolated gate driver U9 is connected to one end of resistor R35 (30Ω), the pin LO is connected to one end of resistor R37 (30Ω), the pin VS of the isolated gate driver U9 is connected to the other end of capacitor C38, the source of field effect transistor Q7 (20N06D), the drain of field effect transistor Q9 (20N06D), the anode of diode D9 (SMF30A), the cathode of diode D10 (SMF30A), and the input end two of transformer U10; the other end of resistor R35 is connected to the gate of field effect transistor Q9, the other end of resistor R37 is connected to the gate of field effect transistor Q9, the drain of field effect transistor Q7 is connected to the power supply VCC 24V and the cathode of diode D9, the source of field effect transistor Q9 is grounded, and the anode of diode D10 is grounded.

[0031] The output end HO-LO (for outputting voltage signal one) of transformer U10 is ±6KV.

[0032] The voltage doubling circuit comprises a plurality of voltage doubling units connected in series, each of the voltage doubling units comprising a capacitor and a diode, and the negative electrode of the diode is connected to one end of the capacitor; wherein the positive electrode of the diode in the front-stage voltage doubling unit is connected to the other end of the capacitor in the rear-stage voltage doubling unit, and the negative electrode of the diode in the front-stage voltage doubling unit is connected to the positive electrode of the diode in the rear-stage voltage doubling unit; the other end of the capacitor in the first-stage voltage doubling unit is connected to the output point HO of the step-up transformer, and the positive electrode of the diode in the first-stage voltage doubling unit is connected to the output point LO of the step-up transformer.

[0033] As shown in Figure 3 The capacitor C5 (10nF) and the diode U24 (2CL77) form the first-stage voltage doubling unit, the capacitor C10 (10nF) and the diode U25 (2CL77) form the second-stage voltage doubling unit, and so on, and there are totally 10 voltage doubling units, wherein the capacitors C6-C9 and the capacitors C11-C14 are all the same, and the capacitance value of each of the capacitors is 10nF; the diodes U26-U33 are all the same, and the model of each of the diodes is 2CL77. When the input is 6KV direct current, the voltage between the output ends P_0K and P_60K (for outputting voltage signal two) is 60KV.

[0034] The present application utilizes the alternating characteristics of the output of the transformer, and realizes multi-stage step-up through the circuit network composed of diodes and capacitors, and realizes the final output of direct current of up to 60KV or above. The 10-step voltage doubling circuit adopted by the present application uses 10 high-voltage silicon stacks (i.e. the diodes U24-U33) and 10 high-voltage capacitors (the capacitors C5-C14).

[0035] The high-voltage output end after voltage doubling is P-60K / P-0K, and in order to reduce the 10KHz high-frequency component in the high-voltage output, a symmetrical RC filter network composed of a high-voltage resistor U22 (2MΩ), a high-voltage resistor U23 (2MΩ) and capacitors C3 (10nF) and C4 (10nF) is added. The two ends of the capacitors C3 and C4 are the final direct current high-voltage ends.

[0036] As shown in Figure 4 The filter circuit comprises the high-voltage resistor U22 and the high-voltage resistor U23, one end of the high-voltage resistor U22 and one end of the high-voltage resistor U23 are respectively connected to the output end of the voltage doubling circuit; the other end of the high-voltage resistor U22 and the other end of the high-voltage resistor U23 are respectively connected to one end of the capacitor C3 and one end of the capacitor C4, and the other end of the capacitor C3 is connected to the other end of the capacitor C4.

[0037] One end of the sampling resistor U18 (14KΩ) is connected to one end of the capacitor C3, and the other end of the sampling resistor U18 is grounded and connected to the discharge end POUT- through the sampling resistor U46 (14KΩ), the high-voltage resistor U38 (100MΩ) and the high-voltage resistor U37 (100MΩ).

[0038] The other end of the sampling resistor U18 is also connected to the discharge end POUT+ through a high-voltage resistor U34 (1GΩ), a high-voltage resistor U39 (1GΩ), a high-voltage resistor U11 (100MΩ), and a high-voltage resistor U12 (100MΩ).

[0039] A diode U40 (2CL77), a diode U41 (2CL77), a diode U42 (2CL77), a diode U43 (2CL77), a diode U44 (2CL77), and a diode U45 (2CL77) are connected in series, and the negative electrode of the diode U40 is connected to the common end of the high-voltage resistor U11 and the high-voltage resistor U39, the positive electrode of the diode U45 is connected to one end of the capacitor C3, and the positive electrode of the diode U42 is connected to one end of the capacitor C4. In the present application, the diode U40, the diode U41, the diode U42, the diode U43, the diode U44, and the diode U45 are all high-voltage silicon stacks.

[0040] The pin IN1 of the operational amplifier chip U47 (LM358BIDR) is connected to one end of a resistor R1 (2MΩ), one end of a resistor R2 (2MΩ), and the positive electrode of a diode D1 (1N4148WT), the other end of the resistor R1 is connected to the common end of a sampling resistor U46 and a high-voltage resistor U38, the other end of the resistor R2 (2MΩ) is connected to the pin OUT1 of the operational amplifier chip U47, and the negative electrode of the diode D1 is grounded.

[0041] The pin IN2 of the operational amplifier chip U47 is connected to the positive electrode of a diode D2 (1N4148WT), one end of a resistor R3 (2MΩ), and one end of a resistor R4 (2MΩ), the negative electrode of the diode D2 is grounded, one end of the resistor R3 is connected to one end of the capacitor C3, and the other end of the resistor R4 is connected to the pin OUT2 of the operational amplifier chip U47; the pin OUT1 of the operational amplifier chip U47 is connected to the output terminal ADC123-IN11 of the detection circuit, and the pin OUT2 of the operational amplifier chip U47 is connected to the output terminal ADC123-IN12 of the detection circuit.

[0042] The external measurement output end points of the present application are POUT- and POUT+, which are connected to the DC high-voltage end after being connected in series with a 200MΩ high-voltage resistor; a total of 400MΩ of resistance is connected in series in the measurement loop, limiting the discharge current when the insulator zero-value breakdown occurs, and avoiding further damage to the defective insulator during the measurement process to the greatest extent. The two 14kΩ resistors U46 and U18 in the circuit are signal sampling resistors, which have a resistance value of less than one ten-thousandth of the total resistance of 400MΩ of U37, U38, U11, and U12, so the existence of these two resistors can be ignored when calculating the discharge current of the high-voltage loop.

[0043] The discharge terminal POUT+ and the discharge terminal POUT- are connected to the insulator to be measured through the metal push pin. Generally, the electrical characteristics of the insulator are equivalent to a capacitor C (10-15 pf) in parallel with a resistor R. A good insulator has a resistance R close to infinity. An insulator with a resistance of 2 GΩ or more is considered to be good, an insulator with a resistance of 500 MΩ or less is considered to be a zero-value insulator, and an insulator with a resistance less than 2 GΩ and greater than 500 MΩ is considered to be a defective poor-quality insulator.

[0044] In the present application, the 14KΩ resistors U18 and U46 are sampling resistors for the high-voltage loop small-current zero measurement method and the distributed voltage on-line zero measurement method, respectively. GND on the diagram is the power supply reference zero point of the detection circuit. The detection circuit converts the voltage changes on the sampling resistors U18 and U46 into the voltage outputs ADC123-IN12 and ADC123-IN11 of the operational amplifier through a double operational amplifier, respectively. When the current flowing through the sampling resistors U18 and U46 is 0, the output of the operational amplifier is 3.3V. When the current reaches 150μA, the output is 0.3V. The greater the current, the lower the voltage, until the current reaches 165μA, the output is 0V, and the operational amplifier reaches saturation. Therefore, the maximum detection current is 165μA.

[0045] When detecting the withstand voltage of the insulator, the high-voltage circuit outputs a specified high voltage (generally between 20KV and 60KV) according to the instructions of the system. The capacitor C3 and C4 can reach the specified DC high voltage (U) within 40ms. This high voltage first passes through the resistors U39 and U34 (1GΩ) with a total resistance of 2GΩ, and then passes through the 14KΩ sampling resistor U18 to form an internal loop, generating a loop current of U / 2G. At the same time, this high voltage also passes through the resistors U11 and U12, is connected in series to the insulator (C and R are connected in parallel) from POUT+, and then passes through POUT- to the resistors U37 and U38 and the sampling resistors U46 and U18 to form an external loop. The output voltage ADC123-IN12 of the operational amplifier is equal to the sum of the currents of the two loops multiplied by the 14KΩ resistor. If the high-voltage circuit fails to generate high voltage U, neither the internal loop nor the external loop will generate current, and the control circuit can immediately determine that there is a high-voltage fault and stop the invalid detection. Therefore, the present application can ensure the effectiveness of high-voltage detection. When the high voltage U is normally generated, the current of the internal loop is known: U / 2G ohm, and the part exceeding the internal loop current is the current of the external loop.

[0046] The current on the detection resistor U18 includes the current of the internal loop, which is known: U / 2G ohms, and the current of the external loop U / (R+U11+U12+U37+U38)=U / (R+400MΩ); the total current is (U / 2G+U / (R+400MΩ)). This current is amplified after entering the operational amplifier and is converted into a voltage signal ADC123-IN12. The current conversion efficiency of the operational amplifier is set as K, and then the resistance R=U / ((K×(3.3-ADC123-IN12)-U / 2G))-400MΩ. In the case where the value of K is determined, the equivalent resistance R value of the insulator can be directly calculated according to the value of ADC123-IN12. For the convenience of illustration, the software system is processed as follows.

[0047] (1) For a normal insulator, the output corresponding to AD123-IN12 is as follows: when a 60KV high voltage U is applied for 500ms, and AD123-IN12 is sampled at 1KHZ. The ADC of the single-chip microcomputer is 12 bits, and the original sampling value is 0-4095 corresponding to 0-3.3V of the operational amplifier; under the 60KV voltage, the current of the internal loop is 60KV / 2G=30μA, and the voltage change on the 14K ohm sampling resistor is 30μA×14KΩ resistor=420MV. In order to conveniently reflect the current of the external loop, the sampling data is transformed by the single-chip microcomputer software: 0-2.88V voltage corresponds to 0-255 data output.

[0048] When the current of the external loop is 0, the sampling voltage corresponding to the ADC is 3.3V-420MV=2.88V, and the sampling value is 255, as shown in the following formula: Figure 5 The ADC sampling output under the measurement of the normal insulator is stably at the value 239, the voltage on the sampling resistor is (239 / 255)×2.88=2.7v, the current on the sampling resistor is (3.3v-2.7v) / 14k=43μA, which indicates that the current of the external loop is 43-30=13μA, and the voltage drop on the 400MΩ resistor connected in series in the external loop is 13μA×400M=5200V, so the voltage at the two ends of the insulator is stably at 60KV-5.2KV=54.8KV, and the insulator resistance is calculated as 54.8KV / 13μA=4.2G ohms.

[0049] (2) When the probe is not connected to the insulator, the ADC sampling value output is stable at 231, corresponding to the voltage on the sampling resistor (231 / 256) * 2.88v = 2.61V, the current on the sampling resistor = (3.3v-2.61v) / 14k = 49μA; then the external loop current = 49μA-30μA = 19μA, the voltage on the external loop series resistor 400M = 19μA*400M = 7.6KV, the withstand voltage of the air on both sides of the probe = 60KV-7.6KV = 52.4KV, if converted into insulation resistance, the insulation resistance = 52.4KV / 19μA = 2.7G ohms.

[0050] As shown in Figure 6 , the R of the insulator is almost infinite, which has no effect on the loop current, and the loop charging time constant of the capacitor C is 400M*15PF = 6mS, and the high-voltage circuit also needs 40ms-100ms of time, so the above curve is generated, in the normal insulator measurement curve, the downward and then upward pulse is the process of charging the capacitor C to voltage U from 0 to the specified value U, and the loop current is displayed; there is no such capacitor charging process when the probe is suspended. Although the resistance results measured by both are greater than 2G ohms (measured value 220), the resistance of the normal insulator (measured value 239) is still greater than that of the suspended probe (measured value 231), which also shows that the isolation of the insulator porcelain disc increases the creepage distance, and the air insulation of the two probes in the suspended state is poor.

[0051] (3) A good insulator is connected in parallel with a 1G high-voltage resistor, and the sampling curve obtained is shown in Figure 7 .

[0052] The ADC sampling value is 201, corresponding to the voltage on the sampling resistor = (201 / 256) * 2.88v = 2.27v, corresponding to the current on the sampling resistor = (3.3v-2.27v) / 14k = 74μA; thus the external loop current = 74-30 = 44μA, the voltage on the external loop series resistor 400M = 44μA*400M ohms = 17.6kv, then the withstand voltage on the insulator = 60KV-17.6KV = 42.4KV, if calculated as insulation resistance, the insulation resistance = 42.6KV / 44μA = 0.97G ohms.

[0053] Because there is a 1G resistor in the high-voltage loop, the loop current increases when charging the capacitor C, and finally stabilizes at a relatively large loop current; the equivalent resistance is about 1G ohms.

[0054] (4) Actual measurement of a known zero-value insulator.

[0055] ADC sampling value is 155, corresponding voltage on sampling resistance = (155 / 256) * 2.88v = 1.38v, corresponding current on sampling resistance = (3.3v-1.38v) / 14k = 137uA; thus, the external loop current = 137-30 = 107uA, the voltage drop on the 400M resistance in series in the external loop = 107uA * 400M ohms = 42.8kv, so the withstand voltage on the insulator = 60KV-42.8KV = 17.2KV, if calculated as insulation resistance, insulation resistance = 17.2KV / 107uA = 160M ohms.

[0056] This zero value insulator maintains a relatively large current under high voltage, in the 200ms-500ms time period, the equivalent resistance in the external loop is lower than the 500M ohm resistance defined in the application, and it is determined as a zero value insulator, as shown in the figure. Figure 8

[0057] The application also includes a preamplifier circuit, which is part of the main control circuit, for outputting corresponding voltage signals to the low voltage pulse generator according to the received setting input signals.

[0058] The application controls the voltage of the preamplifier low voltage circuit VCC24V, and due to the fixed relationship between voltage boosting and voltage doubling, the voltage output of the high voltage generator is accurately controlled. Figure 9 As shown in the figure, by controlling A0, A1, A2 of the analog switch U3 (CD4051BM / TR) in the application, the feedback resistance network of the boost circuit LM3478 is changed, and the voltage of VCC24V is controlled to 5V, 10V, 15V, 20V, 22.5V, 25V, 27.5V, 30V respectively; the corresponding high voltage output is divided into 8 gears (10KV, 20KV, 30KV, 40KV, 45KV, 50KV, 55KV, 60KV).

[0059] ​The power supply VCC24V is connected to the one end of resistors R15 (1.88kΩ), R11 (2.06kΩ), R10 (2.28kΩ), R9 (2.55kΩ), R8 (2.89kΩ), R7 (3.94kΩ), R6 (6.2kΩ), R5 (14.5kΩ) through resistor R16 (43kΩ), and the other ends of resistors R15, R11, R10, R9, R8, R7, R6, R5 are connected to pins Y7, Y6, Y5, Y4, Y3, Y2, Y1, Y0 of analog switch U3 (CD4051BM / TR) respectively. The power supply VCC24V is connected to pin FB of power supply chip U5 (LM3478MAX / NOPB) through resistor R16. The pin Z, pin E#, pin VEE, pin VSS of analog switch U3 are grounded. The pin VDD of analog switch U3 is connected to power supply VCC12V6 and one end of capacitor C24 (100nF), and the other end of capacitor C24 is grounded.

[0060] The anode of diode D11 (SS56F) and one end of capacitor C23 (100nF) are grounded; the cathode of diode D11 is connected to one end of power inductor L1 (10μH), the other end of capacitor C23, and the drain of field effect transistor U4 (20P10); the other end of power inductor L1 is connected to the drain of field effect transistor Q3 (NCE6080K) and the anode of diode D3 (SS56F); the gate of field effect transistor U4 is connected to one end of resistor R17 (30kΩ) and the drain of field effect transistor Q2 (AO3400); the source and gate of field effect transistor Q2 are connected to pin DR of power supply chip U5 and the gate of field effect transistor Q3; the other end of resistor R17 is connected to the source of field effect transistor U4, power supply VCC12V6, one end of capacitor C25 (100μF), one end of capacitor C26 (100μF), one end of capacitor C27 (100μF), one end of capacitor C28 (100μF), and pin VIN of power supply chip U5; the other ends of capacitor C25, capacitor C26, capacitor C27, and capacitor C28 are grounded.

[0061] Pin ISEN of power supply chip U5 is connected to one end of capacitor C22 (10pF) and one end of resistor R12 (100Ω), the other end of capacitor C22 is grounded, and the other end of resistor R12 is connected to one end of high-voltage resistor U6 (20mΩ) and the source of field effect transistor Q3, the other end of high-voltage resistor U6 is grounded; the cathode of diode D3 is connected to one end of capacitor C15 (100μF), one end of capacitor C16 (100μF), one end of capacitor C21 (100μF), one end of capacitor C17 (100μF), one end of capacitor C18 (100nF), and power supply VCC24V; the other ends of capacitor C15, capacitor C16, capacitor C21, capacitor C17, and capacitor C18 are grounded.

[0062] The pin COMP of the power chip U5 is connected to one end of the capacitor C19 (10nF) and one end of the capacitor C20 (220nF), the other end of the capacitor C19 is grounded, and the other end of the capacitor C20 is grounded through the resistor R13 (1.05kΩ). The pin AGND of the power chip U5 is grounded. The pin FA / SD of the power chip U5 is grounded through the resistor R14 (82kΩ). The pin PGND of the power chip U5 is grounded.

[0063] The insulator is measured by using voltage steps from small to large, and once the insulator has a zero value phenomenon, the applied voltage is no longer increased to avoid further expansion of the defect insulator caused by the excessively high applied voltage.

[0064] Embodiment two Based on the porcelain insulator zero measurement device described in embodiment one, the embodiment provides a high-voltage loop small current zero measurement method for porcelain insulators, comprising: Setting a voltage signal of an input low-voltage pulse generator, the voltage signal forms a high-voltage loop small current acting on the porcelain insulator to be measured through the porcelain insulator zero measurement device described in embodiment one; Collecting the high-voltage loop small current value flowing through the porcelain insulator to be measured within a set time, and then obtaining the insulation resistance of the porcelain insulator to be measured; According to the set insulation resistance criterion one, the state of the porcelain insulator to be measured is determined according to the insulation resistance.

[0065] The insulation resistance criterion one comprises: If the insulation resistance Rx of the porcelain insulator to be measured is located in the normal threshold interval (Rx>2GΩ), the porcelain insulator to be measured is a normal porcelain insulator; If the insulation resistance Rx of the porcelain insulator to be measured is located in the defect threshold interval (500MΩ<Rx<2GΩ), the porcelain insulator to be measured is a defective inferior porcelain insulator; If the insulation resistance Rx of the porcelain insulator to be measured is located in the zero value threshold interval (Rx<500MΩ), the porcelain insulator to be measured is a zero value porcelain insulator.

[0066] The high-voltage loop small current method for measuring the zero value of the insulator of the present application is different from the traditional insulator withstand voltage method for measuring zero. A pulse high voltage is applied to the insulator, and then the change of the voltage on the insulator is detected: (1) The normal insulator can reach the specified voltage and slowly reduce the voltage after the pulse high voltage disappears; (2) The inferior insulator can basically reach the specified voltage, but the voltage is quickly reduced after the pulse high voltage disappears; (3) Zero value insulator cannot reach the specified voltage, and the voltage decreases quickly after the pulse high voltage disappears.

[0067] The problems of the traditional method are: (1) whether the specified voltage can be added on the insulator depends not only on the performance of the insulator, but also on the power (internal resistance) of the pulse high voltage generator, so the performance consistency of the high voltage pulse generator has a higher requirement; (2) when the high voltage pulse transient is added to the insulator, a large current discharge may occur when the zero value insulator or the poor contact of the measuring probe is encountered, even if the good insulator, the pulse voltage transient applied to the insulator capacitor will also produce a large current, and the electromagnetic interference generated by the large current is easy to affect other circuits; (3) when the poor quality insulator cannot bear the specified high voltage, the sudden application of high voltage may cause the insulator to be directly physically broken and completely damaged, which will not cause adverse consequences to the insulator not installed on the line, but it is very dangerous to use in on-line measurement: for example, there are many poor quality insulators on a insulator string, but due to the design margin, these poor quality insulators can still bear the voltage to make the line work normally, but if the pulse high voltage is directly applied to such insulators during measurement, the measured poor quality insulator may be directly broken down to become zero value, and after multiple poor quality insulators become zero value, the bearing voltage of other insulators will inevitably rise, and in the worst case, the insulator cannot bear the voltage and short circuit! The high voltage loop small current method of the application is different from the traditional voltage withstand measurement zero method.

[0068] The high voltage generated in the application is a controllable continuous direct current high voltage, which is applied to the insulator through a 400M ohm resistor, and the current is limited to a maximum of 150uA (150uA when the applied voltage is 60KV, and the limited current decreases proportionally when the applied voltage decreases); through the detection of the loop current, it is determined whether the insulator rises to the specified high voltage; during the measurement, no more attention is paid to the transient change of the voltage on the insulator, only the last loop current of the insulator within 200ms-500ms after the high voltage is applied is determined; according to the last loop current and the corresponding applied voltage, the equivalent resistance of the insulator under the given high voltage can be calibrated in the form of resistance.

[0069] During detection, the voltage signal of the input low voltage pulse generator is set in the order from small to large, and an insulating resistance of the porcelain insulator to be measured is obtained corresponding to each input voltage signal; when the insulating resistance of the porcelain insulator to be measured is less than or equal to the set insulating threshold under the current voltage signal, it is determined that the current porcelain insulator appears zero value phenomenon under the current voltage signal, and the input voltage signal is not increased for the current porcelain insulator, so as to avoid that the high applied voltage causes the defective insulator to further expand the defect.

[0070] Example three The porcelain insulator distribution voltage on-line measurement zero method comprises the following steps: The voltage value detected by the detection circuit is read and corrected to obtain the actual voltage value on the porcelain insulator. The voltage value detected by the detection circuit is read and corrected to obtain the actual voltage value on the porcelain insulator. The voltage value detected by the detection circuit is read and corrected to obtain the actual voltage value on the porcelain insulator.

[0071] When the distribution voltage is detected, the high-voltage boosting circuit stops working, and the P-60K / P-0K output is 0; when the POUT+ / POUT- is connected to the steel cap of the insulator, the distribution voltage on the insulator is applied to the two points. When the distribution voltage is in the negative half cycle, the POUT+ is a negative voltage, the POUT- is a positive voltage, the high-voltage silicon stacks U40, U41, U42, U43, U44 and U45 are turned on, the equivalent resistance of the POUT+ / POUT- path is 400M ohms (two 14K resistors are ignored), at this time, the output of the first operational amplifier remains 3.3V unchanged. Because the connecting resistance is relatively small, there is a relatively large difference between the measured distribution voltage and the actual distribution voltage, so the operational amplifier in the measurement circuit maintains the 3.3V output, and the system does not adopt the negative half cycle distribution voltage; when the distribution voltage is in the positive half cycle, the POUT+ is a positive voltage, the POUT- is a negative voltage, the high-voltage silicon stacks U40, U41, U42, U43, U44 and U45 are turned off, the equivalent resistance of the POUT+ / POUT- path is 2400M ohms (two 14K resistors are ignored), at this time, the output of the first operational amplifier decreases with the increase of the distribution voltage; the equivalent capacitance of a normal insulator is 10-15PF, and according to 10PF, the AC impedance under 50HZ is 1 / WC=300M ohms. The connecting resistance of 2400M ohms in the application reduces the original insulator connecting impedance from 300M to 267M, so the measured distribution voltage is 89% (267 / 300) of the actual distribution voltage, and the measured distribution voltage can be corrected by adding an 11% connecting error to make the detected distribution voltage closer to the actual value.

[0072] The present application integrates insulator voltage distribution measurement and high-voltage small current loop measurement into one device. When measuring power outage, the distribution voltage measurement is not started, only high-voltage measurement is performed; when measuring under power, the distribution voltage on the insulator is measured first, and then the appropriate high-voltage gear is determined for high-voltage withstand voltage measurement according to the existing distribution voltage on the insulator, so as to avoid the total amount of the distribution voltage superimposed on the high-voltage measurement exceeding the withstand voltage limit of the insulator.

[0073] The porcelain insulator distribution voltage on-line measurement zero method and zero value and low value judgment principle are as follows: (1) The probe is overlapped on both ends of the measured porcelain insulator, the distribution voltage measurement is started, and the obtained sampling data is transmitted to the main MCU. The normal distribution voltage is a 50Hz near-sine wave, but due to the relationship of the circuit structure, the system impedance in one half of the 50Hz cycle is 2.4G, and the system impedance in the other half cycle is 400M. Considering that the larger the impedance is, the more accurate the data obtained is, so only the half cycle pattern corresponding to the 2.4G impedance is used, and the distribution voltage value of the insulator is determined according to the peak value in the pattern.

[0074] (2) Corresponding to the physical arrangement of the porcelain insulator, the distribution voltage values of a string of porcelain insulators are compared with each other. The insulator whose distribution voltage value is obviously less than 50% of the adjacent value is the insulator working in zero value state; the insulator whose distribution voltage value is obviously lower than 50% of the standard distribution voltage is also determined as a zero value insulator. The insulator with very low distribution voltage must have zero value problem, but the insulator with very high distribution voltage may also have zero value or low value problem, because the equivalent AC impedance of the insulator capacitor is about 400M ohms, and the poor quality insulator with 1000M or so resistance value will also share a larger distribution voltage in the circuit.

[0075] (3) For the insulator with distribution voltage (peak value) less than 15KV, (A) first, 30KV (first set voltage signal) high voltage is applied for high-voltage loop current measurement, when the high-voltage loop current corresponding impedance is greater than 2G, 50KV (second set voltage signal) high voltage is applied for high-voltage loop current measurement, and then the high-voltage loop current corresponding impedance is judged. When the second corresponding impedance is greater than 2G, it is judged as a normal insulator; when the impedance measured at the specified high voltage is between 1.5G and 2G, it is judged as a suspected low value insulator; when the impedance measured at the specified high voltage is between 1.5G and 1G, it is judged as a low value; when the impedance measured at the specified high voltage is between 1G and 0.5G, it is judged as a suspected zero value; when the impedance measured at the specified high voltage is less than 500M, it is judged as a zero value.

[0076] (4) For the insulator with distribution voltage greater than 15KV, how much value of the applied high voltage needs to be estimated; the first applied high voltage (the third set voltage signal) plus the distribution voltage value is not greater than 40KV (the set upper limit voltage one), and the second applied high voltage (the fourth set voltage signal) plus the distribution voltage value is not greater than 60KV (the set upper limit voltage two); the judgment basis is the same as above.

[0077] (5) Figure 10 is the data measured in the actual online running line, Figure 10 the green curve in is the distribution voltage measurement data.

[0078] The distribution voltage (AD123-IN11, sampled at 2khz) only shows the value in half of the 50HZ cycle, and the peak voltage of the measured distribution voltage is 20KV; therefore, the high voltage U is selected as 40KV for measurement, and in the high voltage measurement curve (AD123-IN12, sampled at 1KHZ) (red curve) the influence of the superimposed distribution voltage can be seen, and at the same time, the equivalent resistance of this insulator under high voltage is above 2G ohms, so it is determined to be a normal insulator.

[0079] In summary, the zero value criterion of the porcelain insulator includes: (1) If the distribution voltage of the current porcelain insulator is less than 50% of the distribution voltage of the adjacent porcelain insulator, the current porcelain insulator is a zero value porcelain insulator; (2) If the distribution voltage of the current porcelain insulator is less than 50% of the standard distribution voltage, the current porcelain insulator is a zero value porcelain insulator; (3) If the peak value of the distribution voltage of the current porcelain insulator is less than the set peak voltage: (A) the porcelain insulator zero measurement method described in embodiment two is used to measure the insulation resistance of the current porcelain insulator under the first set voltage signal and the second set voltage signal respectively; (B) based on the insulation resistance of the current porcelain insulator, the state of the current porcelain insulator is judged according to the set insulation resistance criterion two; (4) If the peak value of the distribution voltage of the current porcelain insulator is greater than the set peak voltage: (a) the porcelain insulator zero measurement method described in embodiment two is used to measure the insulation resistance of the current porcelain insulator under the third set voltage signal and the fourth set voltage signal respectively; wherein the third set voltage signal is the superimposed voltage of the distribution voltage of the current porcelain insulator and the voltage loaded on the current porcelain insulator, and does not exceed the set upper limit voltage one; the fourth set voltage signal is the superimposed voltage of the distribution voltage of the current porcelain insulator and the voltage loaded on the current porcelain insulator, and does not exceed the set upper limit voltage two; (b) based on the insulation resistance of the current porcelain insulator, the state of the current porcelain insulator is judged according to the set insulation resistance criterion two.

[0080] The insulation resistance criterion two includes: If the measured insulation resistance is in the normal threshold interval (Rx>2GΩ) twice, the porcelain insulator is judged as normal porcelain insulator, If the measured insulation resistance is in the suspected low value threshold interval (1.5GΩ If the measured insulation resistance is in the low value threshold interval (1GΩ If the measured insulation resistance is in the suspected zero value threshold interval (0.5GΩ If the measured insulation resistance is in the zero value threshold interval (Rx<500MΩ), the porcelain insulator is judged as zero value porcelain insulator.

[0081] The insulator voltage distribution measurement and high voltage small current loop measurement are integrated into one device, and when the power-off measurement is performed, the distribution voltage measurement is not started, and only the high voltage measurement is performed. When the zero value measurement is performed on the on-line running insulator, the distribution voltage of the measured insulator is measured first, and then according to the existing distribution voltage on the porcelain insulator, the appropriate high voltage gear is determined to perform the high voltage loop small current measurement, so that the total amount of the distribution voltage superimposed with the high voltage measurement does not exceed the withstand voltage limit of the insulator. The superimposed distribution voltage and high voltage is close to 60KV but does not exceed 60KV, so that the possible zero value defect of the insulator can be measured, and the overvoltage and overcurrent damage to the insulator in the measurement process can be ensured.

[0082] The above is only the preferred embodiment of the present application, and it should be pointed out that for ordinary skilled in the art, without departing from the technical principles of the present application, a number of improvements and modifications can be made, and these improvements and modifications should be considered as the protection scope of the present application.

Claims

1. A porcelain insulator zero detection device, characterized in that: include: A low-voltage pulse generator for converting a received voltage signal into a voltage pulse signal of a set frequency; A step-up transformer for converting the voltage pulse signal emitted by the low-voltage pulse generator into a voltage signal; a voltage doubling circuit for converting a voltage signal 1 output by a step-up transformer into a voltage signal 2, wherein the voltage signal 2 is an integer multiple of the voltage signal 1; A detection circuit for converting the voltage signal output by the voltage multiplier circuit into a detection signal; It is connected to the output end of the detection circuit and is used to connect the discharge end POUT+ and the discharge end POUT- on the steel caps at both ends of the porcelain insulator.

2. The porcelain insulator zero detection device according to claim 1, characterized in that: The step-up transformer is an audio step-up transformer.

3. The porcelain insulator zero detection device according to claim 1, characterized in that: The voltage multiplier circuit includes a plurality of voltage multiplier units connected in series, each of the voltage multiplier units includes a capacitor and a diode, and the cathode of the diode is connected to one end of the capacitor; The positive electrode of the diode in the front-stage voltage multiplier unit is connected to the other end of the capacitor in the rear-stage voltage multiplier unit, and the negative electrode of the diode in the front-stage voltage multiplier unit is connected to the positive electrode of the diode in the rear-stage voltage multiplier unit. The other end of the capacitor in the first-stage voltage doubling unit is connected to the output point HO of the boost transformer, and the anode of the diode in the first-stage voltage doubling unit is connected to the output point LO of the boost transformer.

4. The porcelain insulator zero detection device according to claim 1, characterized in that: It also includes a front-end circuit, which is used to output a corresponding voltage signal to the low-voltage pulse generator according to the received setting input signal.

5. The porcelain insulator zero detection device according to claim 4, characterized in that: The detection circuit includes a filtering circuit, which includes a high-voltage resistor U22 and a high-voltage resistor U23. One end of the high-voltage resistor U22 and one end of the high-voltage resistor U23 are respectively connected to the output end of the voltage doubler circuit; the other end of the high-voltage resistor U22 and the other end of the high-voltage resistor U23 are respectively connected to one end of the capacitor C3 and one end of the capacitor C4, and the other end of the capacitor C3 is connected to the other end of the capacitor C4.

6. The porcelain insulator zero detection device according to claim 5, characterized in that: The detection circuit also includes a sampling resistor U18 and a sampling resistor U46. One end of the sampling resistor U18 is connected to one end of the capacitor C3, and the other end of the sampling resistor U18 is grounded and connected to the discharge terminal POUT- through the sampling resistor U46, the high-voltage resistor U38 and the high-voltage resistor U37; The other end of the sampling resistor U18 is also connected to the discharge terminal POUT+ through the high-voltage resistor U34, the high-voltage resistor U39, the high-voltage resistor U11 and the high-voltage resistor U12; Diode U40, diode U41, diode U42, diode U43, diode U44 and diode U45 are connected in series in sequence, and the cathode of diode U40 is connected to the common end of high-voltage resistor U11 and high-voltage resistor U39, the anode of diode U45 is connected to one end of capacitor C3, and the anode of diode U42 is connected to one end of capacitor C4.

7. The porcelain insulator zero detection device according to claim 6, characterized in that: The detection circuit also includes an operational amplifier chip U47, wherein a pin IN1 of the operational amplifier chip U47 is connected to one end of a resistor R1, one end of a resistor R2, and the positive electrode of a diode D1, the other end of the resistor R1 is connected to the common end of a sampling resistor U46 and a high-voltage resistor U38, the other end of the resistor R2 is connected to a pin OUT1 of the operational amplifier chip U47, and the negative electrode of the diode D1 is grounded; Pin IN2- of the op amp chip U47 is connected to the positive electrode of the diode D2, one end of the resistor R3 and one end of the resistor R4, the negative electrode of the diode D2 is grounded, the other end of the resistor R3 is connected to one end of the capacitor C3, and the other end of the resistor R4 is connected to the pin OUT2 of the op amp chip U47; the pin OUT1 of the op amp chip U47 is connected to the output terminal ADC123-IN11 of the detection circuit, and the pin OUT2 of the op amp chip U47 is connected to the output terminal ADC123-IN12 of the detection circuit.

8. A method for measuring zero current of a high-voltage circuit of a porcelain insulator, characterized in that: The method is based on the porcelain insulator zero detection device according to any one of claims 4 to 7, and comprises: A voltage signal is set as an input to a low-voltage pulse generator, and the voltage signal is passed through the porcelain insulator zero detection device according to any one of claims 4 to 7 to form a low-voltage loop current acting on the porcelain insulator to be tested; Collect the low current value of the high-voltage circuit flowing through the porcelain insulator to be tested within the set time, and then obtain the insulation resistance of the porcelain insulator to be tested; According to the set insulation resistance criterion 1, the state of the porcelain insulator to be tested is determined according to the insulation resistance.

9. The method for measuring zero current of a high-voltage circuit of a porcelain insulator according to claim 8, characterized in that: Insulation resistance criterion 1, including: If the insulation resistance of the porcelain insulator to be tested is within the normal threshold range, the porcelain insulator to be tested is a normal porcelain insulator; If the insulation resistance of the porcelain insulator to be tested is within the defect threshold range, the porcelain insulator to be tested is a defective and inferior porcelain insulator; If the insulation resistance of the porcelain insulator to be tested is within the zero-value threshold range, the porcelain insulator to be tested is a zero-value porcelain insulator.

10. The method for measuring zero current of a high-voltage circuit of a porcelain insulator according to claim 8, characterized in that: The voltage signal of the input low-voltage pulse generator is set in order from small to large. Each input voltage signal corresponds to an insulation resistance of the porcelain insulator to be tested. When the insulation resistance of the porcelain insulator to be tested is less than or equal to the set insulation threshold under the current voltage signal, it is determined that the current porcelain insulator has a zero value phenomenon under the current voltage signal, and the input voltage signal for the current porcelain insulator is no longer increased.

11. A method for online zero measurement of distributed voltage on porcelain insulators, characterized in that: The method is based on the method for measuring zero current of a high-voltage circuit of a porcelain insulator according to any one of claims 8 to 10, and comprises: Disconnect the voltage multiplier circuit to make the output of the discharge terminal POUT+ and the discharge terminal POUT- connected to the steel caps at both ends of the porcelain insulator zero, and the distributed voltage on the porcelain insulator is input into the detection circuit through the discharge terminal POUT+ and the discharge terminal POUT-; Read the voltage value detected by the detection circuit and make corrections to obtain the actual voltage value on the current porcelain insulator; Each porcelain insulator on the porcelain insulator string is detected in turn, and adjacent comparison is performed, and the zero-value porcelain insulator is identified according to the set porcelain insulator zero-value criterion.

12. The method for online zero measurement of distributed voltage of porcelain insulators according to claim 11, characterized in that: The zero value criteria for porcelain insulators include: (1) If the distributed voltage of the current porcelain insulator is less than 50% of the distributed voltage of the adjacent porcelain insulator, the current porcelain insulator is a zero-value porcelain insulator; (2) If the current distributed voltage of the porcelain insulator is lower than 50% of the standard distributed voltage, the current porcelain insulator is a zero-value porcelain insulator; (3) If the peak value of the current distributed voltage of the porcelain insulator is less than the set peak voltage: (A) using the porcelain insulator high-voltage circuit small current zero measurement method, respectively measure the insulation resistance of the current porcelain insulator under the first set voltage signal and the second set voltage signal; (B) based on the insulation resistance of the current porcelain insulator, determine the state of the current porcelain insulator according to the set insulation resistance criterion 2; (4) If the peak value of the current distributed voltage of the porcelain insulator is greater than the set peak voltage: (a) the porcelain insulator high-voltage circuit small current zero measurement method is used to measure the insulation resistance of the current porcelain insulator under the third set voltage signal and the fourth set voltage signal respectively; wherein the third set voltage signal is the superimposed voltage of the current distributed voltage of the porcelain insulator and the voltage loaded on the current porcelain insulator, and does not exceed the set upper limit voltage 1; the fourth set voltage signal is the superimposed voltage of the current distributed voltage of the porcelain insulator and the voltage loaded on the current porcelain insulator, and does not exceed the set upper limit voltage 2; (b) based on the insulation resistance of the current porcelain insulator, the state of the current porcelain insulator is judged according to the set insulation resistance criterion 2.

13. The method for online zero measurement of distributed voltage of porcelain insulators according to claim 12, characterized in that: Insulation resistance criterion 2, including: If the insulation resistance measured twice is both within the set normal threshold range, the current porcelain insulator is judged to be normal. If the insulation resistance measured at any time is within the suspected low value threshold range, the current porcelain insulator is judged to be a suspected low value porcelain insulator. If the insulation resistance measured at any time is within the low value threshold range, the current porcelain insulator is judged to be a low value porcelain insulator. If the insulation resistance measured at any time is within the suspected zero value threshold range, the current porcelain insulator is judged to be a suspected zero value porcelain insulator. If the insulation resistance measured at any time is within the zero-value threshold interval, the current porcelain insulator is determined to be a zero-value porcelain insulator.

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