Energy harvesting circuit, SF6 gas density relay and energy harvesting circuit and method for high-voltage primary equipment

Abstract

This invention discloses an energy harvesting circuit for converting a microampere-level current source into a low-voltage milliampere-level energy source. It includes at least two parallel-connected step-down current multiplier units, a trigger circuit, and a charging capacitor C1. Each step-down current multiplier unit includes a series-connected charging isolation diode D3, a parallel-connected discharge positive isolation diode D4, a parallel-connected discharge negative isolation diode D5, and an energy storage capacitor C2. The trigger circuit includes a voltage triggering device D2 and a unidirectional thyristor or field-effect transistor Q1. This invention also discloses an energy harvesting circuit and method for high-voltage primary equipment. This invention directly harvests microampere-level energy from the DC220V power supply of the alarm contact of the SF6 gas density relay or the leakage current of the high-voltage primary equipment through the energy harvesting circuit, eliminating the need for laying separate power cables for the SF6 density relay or the high-voltage primary equipment.

Description

Technical Field

[0001] This invention relates to the field of energy harvesting technology, and in particular to an energy harvesting circuit, an SF6 gas density relay, and an energy harvesting circuit and method for high-voltage primary equipment. Background Technology

[0002] Traditional SF6 density relays indicate the SF6 gas pressure at 20°C using a pointer method (in engineering, the pressure at 20°C represents the SF6 gas density), and output contact-based information in conjunction with set alarm and interlock values. Currently, there is an SF6 density relay with remote transmission capabilities available both domestically and internationally. This requires an independent power supply, typically DC 24V. Implementing this type of equipment necessitates on-site trenching and laying of numerous power cables, power supplies, and power terminal boxes, resulting in a large workload, difficult maintenance, and significant safety risks, especially for older substation facilities.

[0003] Furthermore, traditional surge arresters are monitored using mechanical discharge counters. These counters use mechanical pointer ammeters to indicate the surge arrester's leakage current on-site, and the mechanical counters display the cumulative number of surge arrester discharge events. This requires staff to periodically record and analyze the data. Currently, there are portable testing instruments available both domestically and internationally capable of online measurement of surge arrester leakage current. However, this still requires staff to carry the instrument to the site periodically for testing and manual data analysis. There are also online monitoring devices available to replace mechanical discharge counters. These devices can monitor surge arrester leakage current and discharge events online and transmit data remotely. However, these devices are bulky and require the laying of independent power and communication cables. This necessitates extensive cable laying in trenches during project implementation, making the project complex and maintenance difficult. For older substations, this poses a significant safety risk. Summary of the Invention

[0004] To address the problems existing in the prior art, the purpose of this invention is to provide an energy harvesting circuit, an SF6 gas density relay, and an energy harvesting circuit and method for high-voltage primary equipment. This invention can eliminate the need for laying independent power cables.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: an energy harvesting circuit for converting a microampere-level current source into a low-voltage milliampere-level energy source, comprising at least two parallel-connected step-down current multiplier units, a trigger circuit, and a charging capacitor C1. Each step-down current multiplier unit includes a series-connected charging isolation diode D3, a parallel-connected positive discharge isolation diode D4, a parallel-connected negative discharge isolation diode D5, and an energy storage capacitor C2. The trigger circuit includes a voltage triggering device D2 and a unidirectional thyristor or field-effect transistor Q1. The positive output terminal of the microampere-level current source is connected to the anode of the series-connected charging isolation diode D3 of the first-stage step-down current multiplier unit. The cathode of the series-connected charging isolation diode D3 is connected to one end of the energy storage capacitor C2. The other end of the energy storage capacitor C2 is connected to the anode of the series-connected charging isolation diode D3 of the next-stage step-down current multiplier unit. The energy storage capacitor C2 of the last-stage step-down current multiplier unit is connected to the negative output terminal of the microampere-level current source. The parallel-connected positive discharge isolation diode of each stage... The anode of isolation diode D4 is connected to the cathode of series charging isolation diode D3. The cathode of each stage of parallel discharge positive isolation diode D4 is connected to the unidirectional thyristor or field-effect transistor Q1. The unidirectional thyristor or field-effect transistor Q1 is connected to one end of the charging capacitor C1 through resistor R2. The cathode of each stage of parallel discharge negative isolation diode D5 is connected to the output terminal of the energy storage capacitor C2. The anode of each stage of parallel discharge negative isolation diode D5 is connected to the other end of the charging capacitor C1. One end of voltage trigger device D2 is connected to the anode of series charging isolation diode D3 of the first stage buck current multiplier unit. The other end of voltage trigger device D2 is connected to the unidirectional thyristor or field-effect transistor Q1 through resistor R3. This is used to control the conduction and cutoff of the unidirectional thyristor or field-effect transistor Q1, so that the buck current multiplier unit charges and stores energy in the charging capacitor C1 through the unidirectional thyristor or field-effect transistor Q1 and resistor R2, thereby obtaining a low-voltage milliampere constant current source.

[0006] As a further improvement of the present invention, the energy harvesting circuit also includes a voltage comparator U1 and a DC / DC converter U2. The charging capacitor C1 is connected to the DC / DC converter U2. The voltage comparator U1 controls the enable terminal of the DC / DC converter U2 to turn on the power supply adjustment and output a low-voltage milliampere level energy with a stable supply voltage according to the voltage of the charging capacitor C1.

[0007] As a further improvement of the present invention, the charging capacitor C1 is a Faraday capacitor or a lithium-ion capacitor.

[0008] As a further improvement of the present invention, the voltage triggering device D2 is a voltage triggering diode.

[0009] The present invention also provides an SF6 gas density relay energy acquisition circuit for converting a high-voltage constant voltage source into a low-voltage milliampere level energy source. The circuit includes the energy acquisition circuit described above, and also includes a current limiting circuit, which is disposed between the anodes of the series charging isolation diode D3 of the first-stage step-down current multiplier unit.

[0010] As a further improvement of the present invention, the SF6 gas density relay energy acquisition circuit further includes a bridge rectifier D1, which is disposed between the high voltage constant voltage source and the current limiting circuit, or between the current limiting circuit and the step-down current multiplier unit, for realizing the positive and negative polarity matching of the power supply.

[0011] As a further improvement of the present invention, the current limiting circuit is a series constant current source I1 or a current limiting resistor.

[0012] This invention also provides a method for obtaining energy from an SF6 gas density relay. The method employs the SF6 gas density relay energy acquisition circuit described above. The SF6 gas density relay energy acquisition circuit and the alarm contact of the SF6 gas density relay are connected in parallel and then connected to the secondary power system circuit. The SF6 gas density relay energy acquisition circuit converts the high-voltage constant voltage source obtained from the secondary power system circuit into low-voltage milliampere-level energy and then supplies power to each circuit module of the electronic circuit section of the SF6 gas density relay.

[0013] The present invention also provides an energy acquisition circuit for high-voltage primary equipment, used to convert an AC current source into low-voltage milliampere-level energy, including the energy acquisition circuit as described above, and also including a bridge rectifier D7, wherein the bridge rectifier D7 is disposed between the AC current source and the step-down current multiplier unit, and is used to rectify the AC leakage current of the high-voltage primary equipment into a DC current source through D7.

[0014] As a further improvement of the present invention, a protection circuit is also included, which includes a zinc oxide resistor RV1, a wire-wound resistor R1, and a voltage-type trigger diode D6. The zinc oxide resistor RV1 is connected in series in the leakage current grounding circuit of the high-voltage primary equipment. One end of the zinc oxide resistor RV1 is connected to one of the input terminals of the bridge rectifier D7 via the wire-wound resistor R1, and the other end of the zinc oxide resistor RV1 is connected to the other input terminal of the bridge rectifier D7. The voltage-type trigger diode D6 is connected in parallel between the two input terminals of the bridge rectifier D7.

[0015] As a further improvement of the present invention, the high-voltage primary equipment is a surge arrester or a capacitor-type equipment.

[0016] The present invention also provides a method for obtaining energy from high-voltage primary equipment. The method uses the high-voltage primary equipment energy acquisition circuit described above, and connects the high-voltage primary equipment energy acquisition circuit in series to the high-voltage primary equipment leakage current grounding circuit. The high-voltage primary equipment energy acquisition circuit acquires the leakage current of the monitored high-voltage primary equipment with current source characteristics, converts it into low-voltage milliampere-level energy, and then supplies power to the circuit module.

[0017] The beneficial effects of this invention are:

[0018] This invention obtains microampere-level energy directly from the DC220V power supply of the alarm contact of the SF6 gas density relay or the leakage current of the high-voltage primary equipment through an energy acquisition circuit, eliminating the need to lay separate power cables for the SF6 density relay or the high-voltage primary equipment. Attached Figure Description

[0019] Figure 1 This is a schematic diagram illustrating the engineering application of the SF6 gas density relay contacts in Example 1.

[0020] Figure 2 This is a schematic diagram of the circuit structure of Embodiment 1 of the present invention;

[0021] Figure 3 This is a schematic diagram of the circuit structure of Embodiment 2 of the present invention. Detailed Implementation

[0022] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0023] Example 1

[0024] like Figure 2As shown, an energy harvesting circuit for converting a microampere-level current source into a low-voltage milliampere-level energy source includes at least two parallel-connected step-down current multiplier units, a trigger circuit, and a charging capacitor C1. Each step-down current multiplier unit includes a series charging isolation diode D3, a parallel discharge positive isolation diode D4, a parallel discharge negative isolation diode D5, and an energy storage capacitor C2. The trigger circuit includes a voltage triggering device D2 and a unidirectional thyristor or field-effect transistor Q1. The positive output terminal of the microampere-level current source is connected to the anode of the series charging isolation diode D3 of the first-stage step-down current multiplier unit. The cathode of the series charging isolation diode D3 is connected to one end of the energy storage capacitor C2, and the other end of the energy storage capacitor C2 is connected to the anode of the series charging isolation diode D3 of the next-stage step-down current multiplier unit. The energy storage capacitor C2 of the last-stage step-down current multiplier unit is connected to the negative output terminal of the microampere-level current source. The anode of each parallel discharge positive isolation diode D4 is connected to the negative output terminal of the microampere-level current source. The cathode of the series charging isolation diode D3 is connected to the cathode of the parallel discharge positive isolation diode D4, and the cathode of the parallel discharge positive isolation diode D4 is connected to the unidirectional thyristor or field-effect transistor Q1. The unidirectional thyristor or field-effect transistor Q1 is connected to one end of the charging capacitor C1 through resistor R2. The cathode of the parallel discharge negative isolation diode D5 is connected to the output terminal of the energy storage capacitor C2, and the anode of the parallel discharge negative isolation diode D5 is connected to the other end of the charging capacitor C1. One end of the voltage trigger device D2 is connected to the anode of the series charging isolation diode D3 of the first-stage buck current multiplier unit, and the other end of the voltage trigger device D2 is connected to the unidirectional thyristor or field-effect transistor Q1 through resistor R3. This is used to control the conduction and cutoff of the unidirectional thyristor or field-effect transistor Q1, so that the buck current multiplier unit charges and stores energy in the charging capacitor C1 through the unidirectional thyristor or field-effect transistor Q1 and resistor R2, thereby obtaining a low-voltage milliampere constant current source.

[0025] In this embodiment, the energy harvesting circuit further includes a voltage comparator U1 and a DC / DC converter U2. The charging capacitor C1 is connected to the DC / DC converter U2. The voltage comparator U1 controls the enable terminal of the DC / DC converter U2 to turn on the power supply adjustment and output a stable low-voltage milliampere energy according to the voltage of the charging capacitor C1.

[0026] In this embodiment, the charging capacitor C1 is a Faraday capacitor or a lithium-ion capacitor.

[0027] In this embodiment, the voltage triggering device D2 is a voltage triggering diode.

[0028] This embodiment also provides an SF6 gas density relay energy acquisition circuit for converting a high-voltage constant voltage source into a low-voltage milliampere level energy source. It includes the energy acquisition circuit described above, and also includes a current limiting circuit, which is located between the anodes of the series charging isolation diode D3 of the first-stage step-down current multiplier unit.

[0029] In this embodiment, the SF6 gas density relay energy acquisition circuit further includes a bridge rectifier D1, which is located between the high-voltage constant voltage source and the current limiting circuit, or between the current limiting circuit and the step-down current multiplier unit, to achieve positive and negative polarity matching of the power supply.

[0030] In this embodiment, the current limiting circuit is a series constant current source I1 or a current limiting resistor.

[0031] This embodiment also provides a method for obtaining energy from an SF6 gas density relay. The method uses the SF6 gas density relay energy acquisition circuit described above. The SF6 gas density relay energy acquisition circuit and the alarm contact of the SF6 gas density relay are connected in parallel and then connected to the power secondary system circuit. The SF6 gas density relay energy acquisition circuit converts the high-voltage constant voltage source obtained from the power secondary system circuit into low-voltage milliampere-level energy and then supplies power to each circuit module of the electronic circuit section of the SF6 gas density relay.

[0032] The following is a further explanation of the principle of the SF6 gas density relay in the energy harvesting circuit of this embodiment:

[0033] like Figure 1 As shown, in practical engineering applications, the alarm and interlocking contacts of the SF6 gas density relay are connected to the intermediate relay or monitoring and control device via a DC220V power supply to transmit pressure status information. The alarm contact of the SF6 density relay MK1 and the coil of the 1ZJ intermediate relay are connected in series to a DC220V power supply. When the SF6 gas is at its normal pressure, the alarm contact is in an open circuit state. At this time, the 1ZJ intermediate relay control coil is not energized, and the intermediate relay is not energized. The voltage across the alarm contact is equal to the DC220V voltage. When SF6 gas leakage causes the pressure to drop to the set alarm value, the alarm contact closes, the 1ZJ intermediate relay control coil is energized, and the intermediate relay is energized, transmitting a low SF6 gas pressure alarm message. The voltage across the alarm contact is approximately equal to DC0V, and the driving current of the intermediate relay control coil is in the range of several milliamps. The alarm contact of the SF6 density relay MK2 and the input of the monitoring and control device are connected in series to a DC220V power supply. Its operation is the same as the aforementioned intermediate relay, and the driving current of the monitoring and control device input is in the range of several milliamps.

[0034] The SF6 gas density relay is designed to draw microampere-level energy directly from the DC220V power supply at the alarm contacts, eliminating the need for a separate power cable. For example... Figure 2 As shown, the series-type constant current source I1 converts a DC 220V voltage source into a microamp-level current source. The series-type constant current source I1 can also be a simple current-limiting resistor. In the circuit, the series-type constant current source I1 can be connected in series before or after the bridge rectifier D1. In engineering applications, the alarm contacts of the SF6 density relay do not distinguish between positive and negative poles. The purpose of the bridge rectifier D1 is to achieve automatic polarity matching. The series-type constant current source I1 and the bridge rectifier D1 are connected in series to the DC 220V voltage source. After matching the power supply polarity, the output voltage is a constant microamp-level current of up to 220V.

[0035] A constant microampere current charges multiple buck current multiplier units in series. Each buck current multiplier unit consists of diodes and capacitors, including a series charging isolation diode D3, a parallel discharge positive isolation diode D4, a parallel discharge negative isolation diode D5, and an energy storage capacitor C2. The energy storage capacitor C2 stores primary energy. The multi-stage buck current multiplier units charge the energy storage capacitor C2 through the series charging isolation diode D3. After charging, the energy storage capacitor C2 is connected in parallel to supply power to the subsequent circuit through the parallel discharge positive isolation diode D4 and the parallel discharge negative isolation diode D5. This achieves high-voltage charging with microampere current and low-voltage power supply with milliampere current.

[0036] The voltage-triggered device D2, when the series-connected buck current multiplier units are charged to the trigger voltage value of the voltage-triggered device, turns on. This, through resistor R3, controls the conduction of the unidirectional thyristor or MOSFET Q1. After Q1 turns on, multiple buck current multiplier units are connected in parallel, charging and storing energy in the charging capacitor C1 of the supercapacitor or lithium-ion capacitor through Q1 and resistor R2. The circuit can adjust the current multiplication ratio and output voltage value by adjusting the number of series-connected buck current multiplier units and the trigger voltage value of the voltage-triggered device D2.

[0037] When the SF6 density relay is first connected to the system, the voltage of the charging capacitor C1 is initially low and insufficient to support operation. Voltage comparator U1 identifies the voltage of charging capacitor C1. When the voltage of charging capacitor C1 reaches a certain threshold, voltage comparator U1 controls the EN enable terminal of DC / DC converter U2 to turn on the power regulation output. Buck-Boost automatic step-up / step-down DC / DC converter U2 regulates the output to a constant voltage, which supplies power to the entire digital circuit. Under normal circumstances, the SF6 pressure is at its rated value, the alarm contact is open, and the energy acquisition circuit operates normally. At this time, a microamp-level current flows through the intermediate relay, but it is far below its operating threshold current and is therefore unaffected. When the SF6 pressure falls below the set alarm value, the alarm contact closes, and the intermediate relay activates. At this time, the energy acquisition circuit cannot operate normally, and the circuit continues to operate relying on the energy stored in charging capacitor C1.

[0038] Example 2

[0039] like Figure 3As shown, an energy harvesting circuit for converting a microampere-level current source into a low-voltage milliampere-level energy source includes at least two parallel-connected step-down current multiplier units, a trigger circuit, and a charging capacitor C1. Each step-down current multiplier unit includes a series charging isolation diode D3, a parallel discharge positive isolation diode D4, a parallel discharge negative isolation diode D5, and an energy storage capacitor C2. The trigger circuit includes a voltage triggering device D2 and a unidirectional thyristor or field-effect transistor Q1. The positive output terminal of the microampere-level current source is connected to the anode of the series charging isolation diode D3 of the first-stage step-down current multiplier unit. The cathode of the series charging isolation diode D3 is connected to one end of the energy storage capacitor C2, and the other end of the energy storage capacitor C2 is connected to the anode of the series charging isolation diode D3 of the next-stage step-down current multiplier unit. The energy storage capacitor C2 of the last-stage step-down current multiplier unit is connected to the negative output terminal of the microampere-level current source. The anode of each parallel discharge positive isolation diode D4 is connected to the negative output terminal of the microampere-level current source. The cathode of the series charging isolation diode D3 is connected to the cathode of the parallel discharge positive isolation diode D4, and the cathode of the parallel discharge positive isolation diode D4 is connected to the unidirectional thyristor or field-effect transistor Q1. The unidirectional thyristor or field-effect transistor Q1 is connected to one end of the charging capacitor C1 through resistor R2. The cathode of the parallel discharge negative isolation diode D5 is connected to the output terminal of the energy storage capacitor C2, and the anode of the parallel discharge negative isolation diode D5 is connected to the other end of the charging capacitor C1. One end of the voltage trigger device D2 is connected to the anode of the series charging isolation diode D3 of the first-stage buck current multiplier unit, and the other end of the voltage trigger device D2 is connected to the unidirectional thyristor or field-effect transistor Q1 through resistor R3. This is used to control the conduction and cutoff of the unidirectional thyristor or field-effect transistor Q1, so that the buck current multiplier unit charges and stores energy in the charging capacitor C1 through the unidirectional thyristor or field-effect transistor Q1 and resistor R2, thereby obtaining a low-voltage milliampere constant current source.

[0040] In this embodiment, the energy harvesting circuit further includes a voltage comparator U1 and a DC / DC converter U2. The charging capacitor C1 is connected to the DC / DC converter U2. The voltage comparator U1 controls the enable terminal of the DC / DC converter U2 to turn on the power supply adjustment and output a stable low-voltage milliampere energy according to the voltage of the charging capacitor C1.

[0041] In this embodiment, the charging capacitor C1 is a Faraday capacitor or a lithium-ion capacitor.

[0042] In this embodiment, the voltage triggering device D2 is a voltage triggering diode.

[0043] This embodiment also provides a high-voltage primary equipment energy acquisition circuit for converting an AC current source into a low-voltage milliampere level energy source. It includes the energy acquisition circuit described above, and also includes a bridge rectifier D7. The bridge rectifier D7 is located between the AC current source and the step-down current multiplier unit, and is used to rectify the AC leakage current of the high-voltage primary equipment into a DC current source through D7.

[0044] In this embodiment, a protection circuit is also included. The protection circuit includes a zinc oxide resistor RV1, a wire-wound resistor R1, and a voltage-type trigger diode D6. The zinc oxide resistor RV1 is connected in series in the leakage current grounding circuit of the high-voltage primary equipment. One end of the zinc oxide resistor RV1 is connected to one of the input terminals of the bridge rectifier D7 via the wire-wound resistor R1, and the other end of the zinc oxide resistor RV1 is connected to the other input terminal of the bridge rectifier D7. The voltage-type trigger diode D6 is connected in parallel between the two input terminals of the bridge rectifier D7.

[0045] In this embodiment, the high-voltage primary equipment is a surge arrester or a capacitor-type device.

[0046] This embodiment also provides a method for obtaining energy from high-voltage primary equipment. The method uses the high-voltage primary equipment energy acquisition circuit described above. The high-voltage primary equipment energy acquisition circuit is connected in series to the high-voltage primary equipment leakage current grounding circuit. The high-voltage primary equipment energy acquisition circuit acquires the leakage current of the monitored high-voltage primary equipment with current source characteristics, converts it into low-voltage milliampere-level energy, and then supplies power to the circuit module.

[0047] The following explanation uses a surge arrester as an example to further illustrate the principle of the high-voltage primary equipment in the energy harvesting circuit of this embodiment:

[0048] For example Figure 3 As shown, the surge arrester with constant current source characteristics has leakage current flowing into the circuit from port 1 and out from port 2. The zinc oxide resistor RV1 provides protection during surge arrester discharge. Normally, it is in a high-impedance state, and the surge arrester's leakage current does not flow through RV1. When the surge arrester discharges, the zinc oxide resistor RV1 conducts, and the current flows through RV1, thus protecting the downstream circuit. The wire-wound resistor R1 has both resistive and inductive characteristics. Normally, the surge arrester's leakage current flowing through the wire-wound resistor R1 generates a very small terminal voltage that does not affect the circuit operation. When the surge arrester discharges, the inductive characteristic of the wire-wound resistor prevents the current from increasing, while the resistive characteristic of the wire-wound resistor generates a higher terminal voltage, further protecting the downstream circuit. The voltage-type trigger diode D6 is normally in a high-impedance cutoff state. When the surge arrester discharges, the remaining voltage energy after protection by the wire-wound resistor causes the voltage-type trigger diode D6 to conduct, releasing energy and protecting the downstream circuit. The decoupling filter capacitor C1 performs decoupling filtering to purify ripple interference.

[0049] The AC leakage current of the surge arrester is rectified into a DC constant current source by D7, and then converted into a low-voltage milliampere level energy by the energy acquisition circuit, which then powers the circuit module, such as the circuit module of the monitoring device of the high-voltage primary equipment. The working principle of its energy acquisition circuit is the same as that of Example 1.

[0050] The embodiments described above are merely illustrative of specific implementations of the present invention, and while the descriptions are detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. An energy harvesting circuit, characterized by, The application relates to a micro-ampere current source conversion into a low-voltage milli-ampere energy source, which comprises at least two stages of voltage-reducing current-multiplying units arranged in parallel, a trigger circuit and a charging capacitor C1, wherein each stage of the voltage-reducing current-multiplying units comprises a series charging isolation diode D3, a parallel discharging positive isolation diode D4, a parallel discharging negative isolation diode D5 and an energy storage capacitor C2, the trigger circuit comprises a voltage trigger device D2 and a unidirectional thyristor or a field effect tube Q1; the positive output end of the micro-ampere current source is connected with the anode of the series charging isolation diode D3 of the first stage of voltage-reducing current-multiplying units, the cathode of the series charging isolation diode D3 is connected with one end of the energy storage capacitor C2, the other end of the energy storage capacitor C2 is connected with the anode of the series charging isolation diode D3 of the next stage of voltage-reducing current-multiplying units, the energy storage capacitor C2 of the last stage of voltage-reducing current-multiplying units is connected with the negative output end of the micro-ampere current source, the anode of the parallel discharging positive isolation diode D4 of each stage is connected with the cathode of the series charging isolation diode D3, the cathode of the parallel discharging positive isolation diode D4 of each stage is connected with the unidirectional thyristor or the field effect tube Q1, the unidirectional thyristor or the field effect tube Q1 is connected with one end of the charging capacitor C1 through a resistor R2, the cathode of the parallel discharging negative isolation diode D5 of each stage is connected with the output end of the energy storage capacitor C2, and the anode of the parallel discharging negative isolation diode D5 of each stage is connected with the other end of the charging capacitor C1; one end of the voltage trigger device D2 is connected with the anode of the series charging isolation diode D3 of the first stage of voltage-reducing current-multiplying units, and the other end of the voltage trigger device D2 is connected with the unidirectional thyristor or the field effect tube Q1 through a resistor R3, so as to control the conduction and cut-off of the unidirectional thyristor or the field effect tube Q1, thereby enabling the voltage-reducing current-multiplying units to charge the charging capacitor C1 through the unidirectional thyristor or the field effect tube Q1 and the resistor R2, so as to obtain a low-voltage milli-ampere constant current source; the energy acquisition circuit further comprises a voltage comparator U1 and a DC / DC converter U2, the charging capacitor C1 is connected with the DC / DC converter U2, and the voltage comparator U1 controls the enabling end of the DC / DC converter U2 to open the power adjustment and output a low-voltage milli-ampere energy source with a stable power supply voltage according to the voltage of the charging capacitor C1.

2. The energy harvesting circuit of claim 1, wherein, The charging capacitor C1 is a Faraday capacitor or a lithium ion capacitor.

3. The energy harvesting circuit of claim 1, wherein, The voltage trigger device D2 is a voltage trigger diode.

4. A SF6 gas density relay energy acquisition circuit, characterized by, The application relates to a high-voltage constant voltage source conversion into a low-voltage milli-ampere energy source, which comprises the energy acquisition circuit according to any one of claims 1-3 and a current limiting circuit, and the current limiting circuit is arranged between the anodes of the series charging isolation diodes D3 of the first stage of voltage-reducing current-multiplying units.

5. The SF6 gas density relay energy harvesting circuit of claim 4, wherein, The SF6 gas density relay energy acquisition circuit further comprises a bridge rectifier D1, which is arranged between the high-voltage constant voltage source and the current limiting circuit or between the current limiting circuit and the voltage-reducing current-multiplying units, so as to realize the positive and negative polarity matching of the power supply.

6. The SF6 gas density relay energy harvesting circuit according to claim 4 or 5, characterized in that, The current limiting circuit is a series constant current source I1 or a current limiting resistor.

7. A method for obtaining energy for an SF6 gas density relay, characterized by, The SF6 gas density relay energy acquisition circuit according to any one of claims 4-6 is connected in parallel with the alarm contact of the SF6 gas density relay and then connected into a power secondary system loop, and the SF6 gas density relay energy acquisition circuit converts a high-voltage constant voltage source acquired from the power secondary system loop into a low-voltage milliampere-level energy to supply power to each circuit module of the SF6 gas density relay electronic circuit part.

8. A high voltage primary equipment energy acquisition circuit, characterized by The energy acquisition circuit according to any one of claims 1-3 is used to convert an alternating current source into a low-voltage milliampere-level energy, and further comprises a bridge rectifier D7 arranged between the alternating current source and the voltage-reducing current-multiplying unit and used to rectify the alternating leakage current of the high-voltage primary equipment into a direct current source through the bridge rectifier D7.

9. The high voltage primary equipment energy harvesting circuit of claim 8, wherein, Further comprising a protection circuit comprising a zinc oxide resistor RV1, a wire-wound resistor R1 and a voltage-type trigger diode D6, the zinc oxide resistor RV1 is connected in series in a leakage current grounding loop of the high-voltage primary equipment, one end of the zinc oxide resistor RV1 is connected to one input end of the bridge rectifier D7 through the wire-wound resistor R1, the other end of the zinc oxide resistor RV1 is connected to the other input end of the bridge rectifier D7, and the voltage-type trigger diode D6 is connected in parallel between the two input ends of the bridge rectifier D7.

10. The high voltage primary equipment energy harvesting circuit of claim 8 or 9, wherein, The high-voltage primary equipment is a lightning arrester or a capacitor-type equipment.

11. A method for energy acquisition of high voltage primary equipment, characterized by, The high-voltage primary equipment energy acquisition circuit according to any one of claims 8-10 is connected in series into a leakage current grounding loop of the high-voltage primary equipment, and the high-voltage primary equipment energy acquisition circuit acquires the leakage current with current source characteristics of the monitored high-voltage primary equipment, converts the leakage current into a low-voltage milliampere-level energy to supply power to circuit modules.

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