Energy acquisition circuit and energy acquisition method for SF6 gas density relay

Abstract

The application discloses an energy acquisition circuit for transforming a high-voltage constant voltage source into a low-voltage milliampere energy source, comprising a power management chip U1, a high-frequency transformer T1 and an energy storage capacitor C5, wherein the high-frequency transformer T1 comprises a primary winding and a feedback winding on the input side and a secondary winding on the output side; the application also discloses an energy acquisition method of an SF6 gas density relay, wherein the energy acquisition circuit is connected in parallel with alarm contacts of the SF6 gas density relay and then connected into a power secondary system loop, and the energy acquisition circuit transforms a high-voltage constant voltage source acquired from the power secondary system loop into a low-voltage milliampere energy source to supply power to each circuit module of an electronic circuit part of the SF6 gas density relay; and the application directly acquires a microampere energy source from the alarm contacts DC220V power supply through the energy acquisition circuit, thereby eliminating the need to lay an independent power cable.

Description

Technical Field

[0001] The present invention relates to the technical field of gas density relays, and in particular to an energy acquisition circuit and an energy acquisition method of an SF6 gas density relay. Background Art

[0002] Traditional SF6 density relays use a pointer to indicate the SF6 gas pressure value at 20°C (the pressure value at 20°C is used in engineering projects to represent SF6 gas density), and output contact-type information in combination with set alarm and lockout values. Currently, there is a type of SF6 density relay with remote transmission capabilities, which requires an independent operating power supply, typically a 24V DC power supply. This equipment requires on-site trenching and laying of a large number of power cables, power supplies, and power terminal boxes during project implementation. This is a heavy workload and difficult to maintain later, especially posing safety risks for older substation facilities. Summary of the Invention

[0003] In order to solve the problems existing in the prior art, the purpose of the present invention is to provide an energy acquisition circuit and an energy acquisition method for an SF6 gas density relay. The present invention obtains microampere-level energy directly from the alarm contact DC220V power supply through the energy acquisition circuit, eliminating the need to lay an independent power cable.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is: an energy acquisition circuit for converting a high-voltage constant-voltage source into a low-voltage milliampere-level energy source, including a power management chip U1, a high-frequency transformer T1 and an energy storage capacitor C5. The SOURCE pin of the power management chip U1 is grounded through a resistor R2. The high-frequency transformer T1 includes a primary winding and a feedback winding on the input side and a secondary winding on the output side. One end of the primary winding is connected to the positive output end of the high-voltage constant-voltage source, and the other end of the primary winding is connected to the DRAIN pin of the power management chip U1. One end of the feedback winding is connected to the BIAS pin of the power management chip U1, and the other end of the feedback winding is grounded. Grounded resistors R4 and R5 are also connected in parallel at both ends of the feedback winding, and the resistors R4 and R5 are arranged in series. The common end of the resistors R4 and R5 is connected to the FB pin of the power management chip U1. The two ends of the secondary winding are connected to the two ends of the energy storage capacitor C5 for charging and storing energy in the energy storage capacitor C5, thereby obtaining low-voltage milliampere-level energy.

[0005] As a further improvement of the present invention, the energy acquisition circuit further includes a bridge rectifier D1 , which is provided between the high voltage constant voltage source and the primary winding of the high frequency transformer T1 .

[0006] As a further improvement of the present invention, the energy acquisition circuit further includes a decoupling capacitor C1 , one end of the decoupling capacitor C1 is connected to the input end of the primary winding of the high-frequency transformer, and the other end of the decoupling capacitor C1 is grounded.

[0007] As a further improvement of the present invention, the energy acquisition circuit also includes a freewheeling filter circuit, which includes a freewheeling diode D5 and a filter capacitor C4. The filter capacitor C4 is arranged in parallel with the secondary winding of the high-frequency transformer T1, and the freewheeling diode D5 is arranged in series between the output end of the secondary winding of the high-frequency transformer T1 and the filter capacitor C4. The anode of the freewheeling diode D5 is connected to the output end of the secondary winding of the high-frequency transformer T1, and the cathode of the freewheeling diode D5 is connected to the filter capacitor C4.

[0008] As a further improvement of the present invention, the energy acquisition circuit also includes a voltage comparator U2 and a DC / DC converter U3. The energy storage capacitor C5 is connected to the DC / DC converter U3. The voltage comparator U2 controls the enable end of the DC / DC converter U3 to start power adjustment and output a low-voltage milliampere energy with a stable supply voltage according to the voltage of the energy storage capacitor C5.

[0009] As a further improvement of the present invention, a diode D3 and a diode D4 are further provided in parallel at both ends of the primary winding of the high-frequency transformer T1, the anode of the diode D3 is connected to one end of the primary winding, the cathode of the diode D3 is connected to the cathode of the diode D4, and the anode of the diode D4 is connected to the other end of the primary winding.

[0010] As a further improvement of the present invention, a rectifier and filter circuit is further provided between the feedback winding of the high-frequency transformer T1 and the BIAS pin of the power management chip U1. The rectifier and filter circuit includes a rectifier diode D2, a resistor R3 and a filter capacitor C3. The anode of the rectifier diode D2 is connected to the feedback winding, the cathode of the rectifier diode D2 is connected to one end of the resistor R3, the other end of the resistor R3 is connected to the BIAS pin, one end of the filter capacitor C3 is connected to the common end of the resistor R3 and the BIAS pin, and the other end of the filter capacitor C3 is grounded.

[0011] As a further improvement of the present invention, the VCC pin of the power management chip U1 is grounded through the filter capacitor C2, the IREG pin is grounded through the resistor R1, and the EN pin and the GND pin are both grounded.

[0012] As a further improvement of the present invention, the model of the power management chip U1 is LT8315.

[0013] The present invention also provides an energy acquisition method for an SF6 gas density relay, which uses the energy acquisition circuit as described above, connects the energy acquisition circuit and the alarm contact of the SF6 gas density relay in parallel and then connects them to the power secondary system loop. The energy acquisition circuit converts the high-voltage constant voltage source obtained from the power secondary system loop into a low-voltage milliampere-level energy and then supplies power to each circuit module of the electronic circuit part of the SF6 gas density relay.

[0014] The beneficial effects of the present invention are:

[0015] The present invention obtains microampere-level energy directly from the DC220V power supply of the alarm contact through the energy acquisition circuit, eliminating the need to lay an independent power cable for the SF6 density relay. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is the schematic diagram of the SF6 gas density relay contact engineering application;

[0017] Figure 2 Schematic diagram of the circuit structure of an embodiment of the present invention. DETAILED DESCRIPTION

[0018] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0019] Example

[0020] like Figure 2 As shown, an energy acquisition circuit is used to convert a high-voltage constant-voltage source into a low-voltage milliampere-level energy source, including a power management chip U1, a high-frequency transformer T1 and an energy storage capacitor C5. The SOURCE pin of the power management chip U1 is grounded through a resistor R2. The high-frequency transformer T1 includes a primary winding and a feedback winding on the input side and a secondary winding on the output side. One end of the primary winding is connected to the positive output end of the high-voltage constant-voltage source, and the other end of the primary winding is connected to the DRAIN pin of the power management chip U1. One end of the feedback winding is connected to the BIAS pin of the power management chip U1, and the other end of the feedback winding is grounded. Grounded resistors R4 and R5 are also connected in parallel at both ends of the feedback winding, and the resistors R4 and R5 are arranged in series. The common end of the resistors R4 and R5 is connected to the FB pin of the power management chip U1. The two ends of the secondary winding are connected to the two ends of the energy storage capacitor C5, which is used to charge and store energy in the energy storage capacitor C5, thereby obtaining low-voltage milliampere-level energy.

[0021] In this embodiment, the energy acquisition circuit further includes a bridge rectifier D1 , which is provided between the high voltage constant voltage source and the primary winding of the high frequency transformer T1 .

[0022] In this embodiment, the energy harvesting circuit further includes a decoupling capacitor C1 , one end of the decoupling capacitor C1 is connected to the input end of the primary winding of the high-frequency transformer, and the other end of the decoupling capacitor C1 is grounded.

[0023] In this embodiment, the energy acquisition circuit also includes a freewheeling filter circuit, which includes a freewheeling diode D5 and a filter capacitor C4. The filter capacitor C4 is arranged in parallel with the secondary winding of the high-frequency transformer T1, and the freewheeling diode D5 is arranged in series between the output end of the secondary winding of the high-frequency transformer T1 and the filter capacitor C4. The anode of the freewheeling diode D5 is connected to the output end of the secondary winding of the high-frequency transformer T1, and the cathode of the freewheeling diode D5 is connected to the filter capacitor C4.

[0024] In this embodiment, the energy acquisition circuit also includes a voltage comparator U2 and a DC / DC converter U3. The energy storage capacitor C5 is connected to the DC / DC converter U3. The voltage comparator U2 controls the enable end of the DC / DC converter U3 to start power adjustment and output a low-voltage milliampere energy with a stable supply voltage according to the voltage of the energy storage capacitor C5.

[0025] In this embodiment, a diode D3 and a diode D4 are further provided in parallel at both ends of the primary winding of the high-frequency transformer T1, the anode of the diode D3 is connected to one end of the primary winding, the cathode of the diode D3 is connected to the cathode of the diode D4, and the anode of the diode D4 is connected to the other end of the primary winding.

[0026] In this embodiment, a rectifier and filter circuit is further provided between the feedback winding of the high-frequency transformer T1 and the BIAS pin of the power management chip U1. The rectifier and filter circuit includes a rectifier diode D2, a resistor R3 and a filter capacitor C3. The anode of the rectifier diode D2 is connected to the feedback winding, the cathode of the rectifier diode D2 is connected to one end of the resistor R3, the other end of the resistor R3 is connected to the BIAS pin, one end of the filter capacitor C3 is connected to the common end of the resistor R3 and the BIAS pin, and the other end of the filter capacitor C3 is grounded.

[0027] In this embodiment, the VCC pin of the power management chip U1 is grounded via a filter capacitor C2 , the IREG pin is grounded via a resistor R1 , and both the EN pin and the GND pin are grounded.

[0028] In this embodiment, the model of the power management chip U1 is LT8315; the pins of LT8315 are defined as follows:

[0029] VCC pin: internal power supply pin, provides connection to external filter capacitor C2 for decoupling and filtering of power supply;

[0030] IREG pin: output current adjustment pin, the output current is adjusted by programming through the external resistor R1 to ground;

[0031] EN pin: power enable pin, grounded to turn on the power supply;

[0032] GND pin: ground pin;

[0033] SOURCE pin: Switch tube current detection pin, which is connected to ground through an external resistor R2 to measure the current of the switch tube;

[0034] DRAIN pin: switch tube output drive pin, connected to the primary winding of high-frequency transformer T1;

[0035] FB pin: voltage feedback pin, output voltage is adjusted by programming through external resistors R4 and R5;

[0036] BIAS pin: power supply pin.

[0037] This embodiment also provides an energy acquisition method for an SF6 gas density relay, which uses the energy acquisition circuit as described in the claim above, connects the energy acquisition circuit and the alarm contact of the SF6 gas density relay in parallel, and then connects them to the power secondary system loop. The energy acquisition circuit converts the high-voltage constant voltage source obtained from the power secondary system loop into a low-voltage milliampere-level energy and then supplies power to each circuit module of the electronic circuit part of the SF6 gas density relay.

[0038] The principle of the SF6 gas density relay including the energy acquisition circuit of this embodiment is further explained below:

[0039] like Figure 1 As shown in the figure, in actual engineering applications, the alarm and locking contacts of the SF6 gas density relay are connected to an intermediate relay or measurement 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 the DC220V power supply. When the SF6 gas pressure is at normal values, the alarm contact is open. 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 the SF6 gas leaks and the pressure drops to the set alarm value, the alarm contact closes, the 1ZJ intermediate relay control coil is energized, and the intermediate relay is energized, transmitting the low SF6 gas pressure alarm. The voltage across the alarm contact is approximately DC0V, and the intermediate relay control coil drives the pull-in current of several milliamperes. The alarm contact of the SF6 density relay MK2 and the measurement and control device are connected in series to the DC220V power supply. Its operation is similar to the aforementioned intermediate relay, and the measurement and control device input drive current is several milliamperes.

[0040] The energy acquisition circuit and alarm contacts are connected in parallel to the power secondary system circuit. In engineering applications, the alarm contacts of SF6 density relays do not distinguish between positive and negative poles. The bridge rectifier D1 is designed to automatically match the positive and negative polarity of the power supply. The energy acquisition circuit mainly consists of an ultra-low static power consumption isolated DC / DC switching power supply and a storage capacitor. Figure 2 As shown, an ultra-low static power consumption isolated DC / DC switching power supply is composed of a decoupling capacitor C1, a filter capacitor C2, a resistor R1, a power management chip U1, a resistor R2, a resistor R3, a filter capacitor C3, a rectifier diode D2, a resistor R4, a resistor R5, a diode D3, a diode D4, a high-frequency transformer T1, a freewheeling diode D5, and a filter capacitor C4. The energy acquisition circuit is connected in parallel to the alarm contact. To avoid false alarm operation, the core of its design is that the current obtained by the power supply at one time is in the microampere level. Ordinary power supplies cannot meet the design requirements.

[0041] The power management chip U1 in this implementation is the LT8315, a micropower, high-voltage flyback converter with an integrated 630V / 300mA switch. Regulation does not require an opto-isolator. The device samples the output voltage from the isolated flyback waveform appearing across the transformer's tertiary winding to reduce overall circuit power consumption. Quasi-resonant boundary mode operation improves load regulation, reduces transformer size, and maintains high efficiency. Output regulation provides both constant current and constant voltage regulation. Decoupling capacitor C1 provides decoupling for the power supply and eliminates power switching noise; high-frequency transformer T1 is designed with three windings: primary winding, secondary winding, and feedback winding; diode D3 and diode D4 are the primary winding of high-frequency transformer T1 to eliminate reverse induced electromotive force and protect the output MOSFET of power management chip U1 from damage; currently conventional switching power supplies use linear optocouplers to provide feedback control loops from the output voltage. This design makes it difficult to achieve low static current of the power supply. The feedback winding of high-frequency transformer T1 is used to provide feedback voltage. The feedback voltage is adjusted through resistors R4 and R5 and then sent to the FB pin of power management chip U1. Power management chip U1 dynamically adjusts the voltage error amplifier inside power management chip U1 according to the feedback voltage of FB pin to determine the output voltage of the power supply. At the same time, the feedback voltage is rectified by rectifier diode D2, filtered by resistor R3 and filter capacitor C3, and then provided to the working voltage of power management chip U1. This design makes the static current of the power supply The current is as low as a few microamperes; the primary winding current of the power supply flows through the DRAIN pin of the power management chip U1, and forms a voltage on the resistor R2 through the SOURCE pin of the power management chip U1. The power management chip U1 measures the voltage and primary current by detecting the voltage on the SOURCE pin. A constant current source is internally connected to the IREG pin of the power management chip U1, forming a voltage programmed according to the value of the resistor R1 on the resistor R1. This voltage and the voltage formed on the resistor R2 by the aforementioned primary winding current of the power supply are simultaneously sent to the error amplifier. The error amplifier outputs an error control signal according to the programmed configuration to achieve constant current regulation of the output current. The power supply output of this design has voltage regulation and constant current characteristics, that is, when any size load is added to the secondary side of the power supply, its output current is always constant at the set value; the secondary winding of the high-frequency transformer T1 is freewheeling through the freewheeling diode D5 and filtered by the filter capacitor C4 to output a DC5V voltage. When the secondary side of the power supply is designed to obtain milliampere current, the power supply consumes microampere current at the primary side. Energy storage capacitor C5, a farad or lithium-ion capacitor, is used to store energy. After initial energy storage is complete, voltage comparator U2 detects the voltage of capacitor C5 and controls the EN enable terminal of DC / DC converter U3 to enable power regulation. Buck-Boost DC / DC converter U3 regulates the output voltage to a constant voltage, which supplies power to the entire digital circuit.

[0042] Under normal circumstances, the SF6 pressure is at the rated value, the alarm contact is open, and the energy acquisition circuit works normally. At this time, a microampere current flows through the intermediate relay, but it is far lower than its action threshold current and is therefore not affected. When the SF6 pressure is lower than the set alarm value, the alarm contact closes and the intermediate relay is activated. At this time, the energy acquisition circuit cannot work normally, and the circuit continues to work by relying on the energy stored in the energy storage capacitor C5.

[0043] The above-described embodiments merely represent specific implementations of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, and all such variations and improvements fall within the scope of protection of the present invention.

Claims

1. A method for obtaining energy from an SF6 gas density relay, characterized in that: An energy acquisition circuit is used to convert a high-voltage constant-voltage source into a low-voltage milliampere-level energy source, including a power management chip U1, a high-frequency transformer T1, and an energy storage capacitor C5. The SOURCE pin of the power management chip U1 is grounded through a resistor R2. The high-frequency transformer T1 includes a primary winding and a feedback winding on the input side and a secondary winding on the output side. One end of the primary winding is connected to the positive output end of the high-voltage constant-voltage source, and the other end of the primary winding is connected to the DRAIN pin of the power management chip U1. One end of the feedback winding is connected to the BIAS pin of the power management chip U1, and the other end of the feedback winding is grounded. Grounded resistors R4 and R5 are also connected in parallel at both ends of the feedback winding, and the resistors R4 and R5 are arranged in series. The common end of the resistors R4 and R5 is connected to the FB pin of the power management chip U1. The two ends of the secondary winding are connected to the two ends of the energy storage capacitor C5 for charging and storing energy in the energy storage capacitor C5, thereby obtaining low-voltage milliampere-level energy. The energy acquisition circuit also includes a voltage comparator U2 and a DC / DC converter U3. The energy storage capacitor C5 is connected to the DC / DC converter U3. The voltage comparator U2 controls the enable terminal of the DC / DC converter U3 to start power adjustment and output a low-voltage milliampere energy with a stable supply voltage according to the voltage of the energy storage capacitor C5. The energy acquisition method includes: The 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 loop. The energy acquisition circuit converts the high-voltage constant voltage source obtained from the power secondary system loop into a low-voltage milliampere-level energy and then supplies power to each circuit module of the electronic circuit part of the SF6 gas density relay.

2. The energy acquisition method of the SF6 gas density relay according to claim 1, characterized in that: The energy acquisition circuit further includes a bridge rectifier D1 , which is provided between the high voltage constant voltage source and the primary winding of the high frequency transformer T1 .

3. The energy acquisition method of the SF6 gas density relay according to claim 1 or 2, characterized in that: The energy acquisition circuit further includes a decoupling capacitor C1 , one end of the decoupling capacitor C1 is connected to the input end of the primary winding of the high-frequency transformer, and the other end of the decoupling capacitor C1 is grounded.

4. The energy acquisition method of the SF6 gas density relay according to claim 3, characterized in that: The energy acquisition circuit also includes a freewheeling filter circuit, which includes a freewheeling diode D5 and a filter capacitor C4. The filter capacitor C4 is arranged in parallel with the secondary winding of the high-frequency transformer T1, and the freewheeling diode D5 is arranged in series between the output end of the secondary winding of the high-frequency transformer T1 and the filter capacitor C4. The anode of the freewheeling diode D5 is connected to the output end of the secondary winding of the high-frequency transformer T1, and the cathode of the freewheeling diode D5 is connected to the filter capacitor C4.

5. The energy acquisition method of the SF6 gas density relay according to claim 1, characterized in that: A diode D3 and a diode D4 are further provided in parallel at both ends of the primary winding of the high-frequency transformer T1. The anode of the diode D3 is connected to one end of the primary winding, the cathode of the diode D3 is connected to the cathode of the diode D4, and the anode of the diode D4 is connected to the other end of the primary winding.

6. The energy acquisition method of the SF6 gas density relay according to claim 1 or 5, characterized in that: A rectifier and filter circuit is also provided between the feedback winding of the high-frequency transformer T1 and the BIAS pin of the power management chip U1. The rectifier and filter circuit includes a rectifier diode D2, a resistor R3 and a filter capacitor C3. The anode of the rectifier diode D2 is connected to the feedback winding, the cathode of the rectifier diode D2 is connected to one end of the resistor R3, the other end of the resistor R3 is connected to the BIAS pin, one end of the filter capacitor C3 is connected to the common end of the resistor R3 and the BIAS pin, and the other end of the filter capacitor C3 is grounded.

7. The energy acquisition method of the SF6 gas density relay according to claim 1, characterized in that: The VCC pin of the power management chip U1 is grounded through a filter capacitor C2, the IREG pin is grounded through a resistor R1, and the EN pin and the GND pin are both grounded.

8. The energy acquisition method of the SF6 gas density relay according to claim 1 or 7, characterized in that: The model of the power management chip U1 is LT8315.

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