A current limiting detuning device based on flow-sensitive material

Abstract

The invention discloses a current limiting harmonic elimination device based on flow-sensitive materials, which belongs to the field of current limiting harmonic elimination devices, and includes a power grid, a voltage transformer, a current limiting harmonic elimination device, a trap filter and a measuring instrument connected in sequence; the current limiting harmonic elimination device includes harmonic elimination resistors Ra, Rb, Rc, Rn and a ventilation and heat dissipation shell for integrating the harmonic elimination resistors Ra, Rb, Rc and Rn, wherein the harmonic elimination resistors Ra, Rb and Rc are respectively connected in series to the primary winding of the voltage transformer in the A, B and C three-phase circuits, and the harmonic elimination resistor Rn is connected in series between the primary neutral point of the voltage transformer and the ground; the inlet terminals of the harmonic elimination resistors Ra, Rb and Rc are respectively connected to the primary outlet terminals of the corresponding voltage transformer PT. The invention can quickly and timely discharge the heat generated by the harmonic elimination resistors through the ventilation and heat dissipation shell, and the current limiting harmonic elimination device of the present application can solve the problem of ferromagnetic resonance relative to ground overvoltage and phase-to-phase overvoltage surge current, and effectively avoid the occurrence of PT cabinet burning and fuse blowing accidents.

Description

Technical Field

[0001] The invention relates to a current limiting detuning device, in particular to a current limiting detuning device based on a flow-sensitive material. Background Art

[0002] In a neutral point ungrounded system or a low-current grounded system, when an unloaded busbar is closed, single-phase arc grounding disappears, or the system load changes drastically, the nonlinear core of the electromagnetic voltage transformer may become saturated, causing the excitation current of the winding to increase rapidly. In severe cases, the excitation current may reach more than 100 times the rated excitation current, causing the high-voltage fuse of the voltage transformer to blow, and forming a special single-phase or three-phase resonant circuit with the ground capacitance of the line and equipment, resulting in continuous and high-amplitude overvoltage on the equipment in the circuit.

[0003] There are several measures to suppress overvoltage of electromagnetic voltage transformer in neutral point non-effective grounding system:

[0004] 1. Change system parameters:

[0005] 1) Use a PT with a high saturation point. A common solution is to use a PT with a high inflection point or a capacitive voltage transformer in a 10kV system.

[0006] 2) The neutral point is grounded through the arc suppression coil, which is equivalent to connecting an inductor element with an inductance value much smaller than its excitation inductance in parallel with the PT, thereby completely breaking the parameter matching relationship and making it less likely for ferromagnetic resonance to occur;

[0007] 3) 4PT wiring method, the core is to add a zero-sequence voltage transformer to the primary neutral point of the single-phase PT. In this way, when a single-phase grounding fault occurs, the zero-sequence voltage transformer bears the phase voltage, while the main PT is still under the positive-sequence symmetrical voltage. The transformer core will not enter the saturation zone, thereby suppressing the occurrence of ferromagnetic resonance.

[0008] 2. Increase system damping:

[0009] 1) The open delta winding of the PT is connected to a damping resistor, which is equivalent to connecting a resistor in parallel to the high-voltage winding of the PT. Once the system has ferromagnetic resonance, the role of the inductance will be small, and the resonance energy will be released through the resistor. The smaller the connected resistance, the smaller the impact of the nonlinear inductance on the circuit, and the better it can suppress the occurrence of resonance;

[0010] 2) The neutral point of the PT primary winding is connected to a detuning resistor, referred to as primary detuning. A nonlinear resistor detuning damping device (i.e., current limiting detuning device) is installed between the neutral point of the PT primary winding and the ground to achieve the effect of suppressing resonance.

[0011] Among them, the current limiting harmonic elimination device is the most widely used. However, since the harmonic elimination resistor generates heat in the process of suppressing resonance, if the heat cannot be quickly discharged, the harmonic elimination resistor will be burned, thereby increasing the operating cost. The existing current limiting harmonic elimination device does not pay enough attention to heat dissipation, and the heat dissipation is not timely or fast enough. In addition, although the existing current limiting harmonic elimination device plays a role in limiting the resonant overvoltage, it has never been fundamentally solved, and the PT cabinet burnout and fuse blowing accidents still occur continuously. Therefore, those skilled in the art provide a current limiting harmonic elimination device based on flow-sensitive materials to solve the problems raised in the above background technology. Summary of the invention

[0012] The purpose of the present invention is to provide a current limiting harmonic elimination device based on flow-sensitive materials. Through the ventilation and heat dissipation shell, the heat generated by the harmonic elimination resistor can be quickly and timely discharged. The current limiting harmonic elimination device of the present application can solve the problem of relative overvoltage caused by ferromagnetic resonance and the problem of phase-to-phase overvoltage surge, effectively avoiding the occurrence of PT cabinet burning and fuse blowing accidents, so as to solve the problems raised in the above-mentioned background technology.

[0013] To achieve the above object, the present invention provides the following technical solutions:

[0014] A current limiting harmonic elimination device based on flow-sensitive materials comprises a power grid, a voltage transformer, a current limiting harmonic elimination device, a trap filter and a measuring instrument connected in sequence; the current limiting harmonic elimination device comprises harmonic elimination resistors Ra, Rb, Rc, Rn and a ventilation and heat dissipation shell for integrating the harmonic elimination resistors Ra, Rb, Rc and Rn, wherein the harmonic elimination resistors Ra, Rb and Rc are respectively connected in series to the primary winding of the voltage transformer in the A, B and C three-phase circuits, and the harmonic elimination resistor Rn is connected in series between the primary neutral point of the voltage transformer and the ground; the inlet terminals of the harmonic elimination resistors Ra, Rb and Rc are respectively connected to the primary outlet terminals of the corresponding voltage transformer PT, and the outlet terminals of the harmonic elimination resistors Ra, Rb and Rc are connected to the earth terminal, and the primary inlet terminal of the voltage transformer PT is connected to the power grid.

[0015] The heat generated by the detuning resistor can be quickly and timely discharged through the ventilation and heat dissipation shell, and the current limiting detuning device of the present application can solve the problem of relative overvoltage caused by ferromagnetic resonance and the problem of phase-to-phase overvoltage surge, effectively avoiding the occurrence of PT cabinet burning and fuse blowing accidents.

[0016] As a further solution of the present invention: current transformers CTa, CTb, CTc are respectively connected in series in the circuit between the outgoing terminals of the detuning resistors Ra, Rb, Rc and the ground terminal.

[0017] As a further solution of the present invention: a current transformer CTn is connected in series in the circuit between the detuning resistor Rn and the ground.

[0018] The current transformer is connected in series with the detuning resistor to collect the operating current of the detuning resistor in real time. During normal operation, the current signal of the current transformer is small, which is the rated current of the voltage transformer. When a system failure occurs, due to the current limiting characteristics of the detuning resistor, the current signal of the current transformer changes from large to small in a short time. If the current signal of the current transformer is always large, it means that the detuning resistor is faulty and needs to be replaced in time.

[0019] As a further solution of the present invention: the detuning resistors Ra, Rb, Rc, and Rn are made of flow-sensitive materials.

[0020] As a further solution of the present invention: the detuning resistors Ra, Rb, Rc, and Rn are made of current-limiting materials with positive temperature characteristics.

[0021] The present application utilizes the current-limiting characteristics of current-sensitive materials. When ferromagnetic resonance occurs, the resistance suddenly increases to destroy the conditions for its occurrence. After the system fault disappears, it quickly returns to the initial state without affecting the characteristics of the voltage transformer.

[0022] As a further solution of the present invention: the ventilation and heat dissipation shell specifically includes: a base, the detuning resistor Rn is fixed inside the base, and the top surface of the base is fixedly connected with three parallel vertical shells, a placement cavity is opened inside the vertical shell, and the upper and lower ends of the placement cavity are opened with card slots, a quartz sand sleeve is clamped between two of the card slots, the detuning resistors Ra, Rb, and Rc are respectively fixed inside the three quartz sand sleeves, a wiring electrode is fixedly connected to the top of the vertical shell, an air-blowing shell is fixedly connected between two adjacent vertical shells, an inner cavity is opened inside the air-blowing shell, and a partition is fixedly connected inside the inner cavity, and the partition separates the inner cavity. The cavity is separated into an air chamber and a power chamber, and a push block is provided inside the power chamber, a limiting mechanism is provided at the top of the push block, and a supporting mechanism is provided below the push block, a driving mechanism is provided on one side of the push block to drive the push block forward, and the other side of the push block is fixedly connected with an optical axis, one end of the optical axis passes through a partition and is fixedly connected with a piston, and the piston can move back and forth inside the air chamber, a spring column is sleeved on the outside of the optical axis, and both ends of the spring column are fixedly connected to the partition and the push block respectively, through holes are provided on both sides of one end of the air chamber, and the two through holes are respectively connected to the placement chambers on both sides of the air chamber shell, and a plurality of slots connected to the placement chamber are provided on the top of the outer side surface of the vertical shell.

[0023] The detuning resistor generates heat when in use. At this time, the driving mechanism operates to push the push block forward, thereby driving the optical axis forward. The piston follows the advance and pushes the air in the inflation chamber from the through hole into the placement chamber, while the quartz sand sleeve absorbs the heat generated by the detuning resistor. The air entering the placement chamber is quickly discharged from the vertical shell through the slots. The fast-flowing air quickly takes away the heat on the quartz sand sleeve.

[0024] As a further solution of the present invention: the driving mechanism specifically includes: a motor fixed on the inner wall of one side of the power chamber, the motor output end is fixedly connected with a rotating shaft, and one end of the rotating shaft is movably embedded in the inner wall of the other side of the power chamber, a turntable body is fixedly connected to the outer side surface of the rotating shaft, and three evenly distributed rotating arms are fixedly connected to the outer side surface of the turntable body, one end of the rotating arm is movably connected to a driving wheel, and a step is provided on a side of the push block close to the driving mechanism, and when the rotating arm rotates, it drives the driving wheel to hit the step of the push block to push the push block forward.

[0025] The operation of the motor drives the shaft to rotate, and then drives the turntable body and the rotating arm to rotate, and the driving wheel on the rotating arm hits the step of the push block to push the push block forward, and then drives the piston forward, and the air is quickly discharged through the slot to form "exhalation". At this time, the spring column is compressed. After the driving wheel is separated from the step of the push block, the spring column releases its elastic potential energy to restore the push block to its original position, and then drives the piston backward. At this time, the outside air enters the placement chamber and the inflation chamber through the slot, and then the air refluxes to form "inhalation". As the driving wheel on the next rotating arm hits the step of the push block, the push block moves forward again, driving the piston to move forward again, and then completes the "exhalation" again. In this way, the heat absorbed by the quartz sand sleeve can be quickly and timely discharged by repeating the cycle.

[0026] As a further solution of the present invention: the limiting mechanism specifically includes: a limiting bar fixed at the middle position of the top end of the push block, and the limiting bar is movably stuck in a limiting groove opened at the top end of the inner wall of the power cavity.

[0027] When the push block moves forward or backward, the limit bar moves forward or backward in the limit groove to ensure the stability of the push block.

[0028] As a further solution of the present invention: the supporting mechanism specifically includes: multiple groups of horizontally parallel supporting rollers, the number of supporting rollers in each group is several, and the supporting rollers are in contact with the bottom end surface of the push block, and each group of supporting rollers has a shaft rod running through the inside and movably connected thereto, and the two ends of the shaft rod are respectively embedded in the inner walls on both sides of the power cavity.

[0029] When the push block moves forward or backward, the support roller provides support for the push block, and the support roller rotates during the movement of the push block to reduce friction resistance.

[0030] As a further solution of the present invention: the transfer function of the notch filter is

[0031]

[0032] Set the notch frequency ω n=60hz, notch depth ξ2 / ξ1=1 / 1000, notch bandwidth (frequency difference when attenuated to -3db)=10hz, S is the Laplace operator, then a notch filter that filters out 60hz power frequency can be designed through bilinear transformation;

[0033] After calculation, the transfer function of the notch filter is:

[0034]

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] 1. The detuning resistor is connected in series between the primary winding of the voltage transformer and the primary neutral point of the voltage transformer and the ground, which destroys the conditions for the occurrence of ferromagnetic resonance at the high-voltage end and eliminates the occurrence of ferromagnetic resonance more quickly and effectively.

[0037] 2. The "3+1 series-parallel connection method" can solve both the ferromagnetic resonance relative to ground overvoltage problem and the phase-to-phase overvoltage surge problem.

[0038] 3. The "3+1 series-parallel connection method" is adopted to ensure that the initial resistance of the series detuning resistor at the high-voltage end is small enough to reduce the influence of the detuning resistor on the characteristics of the voltage transformer during normal operation, and also ensure that the resistance of the detuning resistor relative to the ground and between phases is large enough in the fault state to quickly limit the current and ensure that the voltage transformer is not saturated and resonant.

[0039] 4. Utilizing the current-limiting characteristics of current-sensitive materials, when ferromagnetic resonance occurs, the resistance suddenly increases to destroy the conditions for its occurrence. After the system fault disappears, it quickly returns to the initial state without affecting the characteristics of the voltage transformer.

[0040] 5. The heat generated by the detuning resistor can be quickly and timely discharged through the set ventilation and heat dissipation shell. Specifically, the detuning resistor generates heat when in use. At this time, the driving mechanism runs to push the push block forward, thereby driving the optical axis forward. The piston follows the forward movement and pushes the air in the inflation chamber from the through hole into the placement chamber, while the quartz sand sleeve absorbs the heat generated by the detuning resistor. The air entering the placement chamber is quickly discharged from the vertical shell through the slots. The fast-flowing air quickly takes away the heat on the quartz sand sleeve.

[0041] 6. Through the set driving mechanism, when in use, the motor runs to drive the rotating shaft to rotate, and then drives the turntable body and the rotating arm to rotate, and the driving wheel on the rotating arm hits the step of the push block to push the push block forward, and then drives the piston forward, and the air is quickly discharged through the slot to form "exhalation". At this time, the spring column is compressed. After the driving wheel is separated from the step of the push block, the spring column releases its elastic potential energy to restore the push block to its original position, and then drives the piston to retreat. At this time, the outside air enters the placement chamber and the inflation chamber through the slot, and then the air refluxes to form "inhalation". As the driving wheel on the next rotating arm hits the step of the push block, the push block moves forward again, driving the piston to move forward again, and then completes the "exhalation" again. In this way, the heat absorbed by the quartz sand sleeve can be quickly and timely discharged by the reciprocating cycle.

[0042] 7. Through the setting of the limit mechanism, when the push block moves forward or backward, the limit bar moves forward or backward in the limit groove to ensure the stability of the push block movement.

[0043] 8. Through the support mechanism, when the push block moves forward or backward, the support roller provides support for the push block, and the support roller rotates during the movement of the push block to reduce friction resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 A schematic diagram of the circuit connection structure of a current limiting and detuning device based on a current-sensitive material;

[0045] Figure 2 It is a structural block diagram of a current limiting detuning device based on flow-sensitive materials;

[0046] Figure 3 It is a schematic diagram of the structure of a ventilation and heat dissipation housing in a current limiting and harmonic elimination device based on flow-sensitive materials;

[0047] Figure 4 An internal view of an air-blowing housing in a current-limiting detuning device based on a flow-sensitive material;

[0048] Figure 5 A current limiting detuning device based on flow-sensitive materials Figure 3 A magnified view of middle;

[0049] Figure 6 A structural view of a limiting mechanism and a supporting mechanism in a current limiting detuning device based on a flow-sensitive material;

[0050] Figure 7 This is a schematic diagram of the structure of a driving mechanism in a current limiting detuning device based on flow-sensitive materials.

[0051] In the figure: 1. base; 2. vertical shell; 3. placement cavity; 4. card slot; 5. quartz sand sleeve; 6. wiring electrode; 7. air-blowing shell; 8. inner cavity; 9. partition; 10. push block; 11. driving mechanism; 1101. motor; 1102. rotating shaft; 1103. turntable body; 1104. rotating arm; 1105. driving wheel; 12. optical axis; 13. piston; 14. spring column; 15. through hole; 16. supporting roller; 17. shaft; 18. limit strip; 19. limit groove. DETAILED DESCRIPTION

[0052] In order to better understand the above technical solution, the above technical solution will be described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0053] See also Figures 1 to 7 In an embodiment of the present invention, a current limiting harmonic elimination device based on a flow-sensitive material comprises a power grid, a voltage transformer, a current limiting harmonic elimination device, a trap filter and a measuring instrument connected in sequence; the current limiting harmonic elimination device comprises harmonic elimination resistors Ra, Rb, Rc, Rn and a ventilation and heat dissipation shell for integrating the harmonic elimination resistors Ra, Rb, Rc, Rn, wherein the harmonic elimination resistors Ra, Rb, Rc are respectively connected in series with the primary winding of the voltage transformer in the three-phase circuits A, B, and C, and the harmonic elimination resistor Rn is connected in series between the primary neutral point of the voltage transformer and the ground; the inlet terminals of the harmonic elimination resistors Ra, Rb, and Rc are respectively connected to the primary outlet terminals of the corresponding voltage transformer PT, and the outlet terminals of the harmonic elimination resistors Ra, Rb, and Rc are connected to the earth terminal, and the primary inlet terminal of the voltage transformer PT is connected to the power grid. Under normal operation, the detuning resistors Ra, Rb, Rc, and Rn present low resistance and do not affect the characteristics of the voltage transformer (voltage error, phase error). When a system fault occurs and a surge current or overvoltage occurs relative to the ground (for example, phase A to the ground), the resistance values ​​of Ra and Rn increase sharply, suppressing the current, making the voltage transformer unsaturated, destroying the resonance condition, and achieving the effect of detuning. When the system fault disappears, the resistance values ​​of Ra and Rn quickly return to the initial state and do not affect the normal operation of the voltage transformer. When a phase-to-phase (for example, phase A and phase B) fault occurs, the voltage transformer will be detuned. During surge current, the resistance values ​​of Ra and Rb increase sharply, suppressing the current, making the voltage transformer unsaturated, destroying the resonance condition, and achieving the effect of detuning; when the system fault disappears, the resistance values ​​of Ra and Rb quickly return to the initial state, without affecting the normal operation of the voltage transformer. In addition, the heat generated by the detuning resistor can be quickly and timely discharged through the set ventilation and heat dissipation shell, and the current limiting detuning device of the present application can solve the problem of relative overvoltage due to ferromagnetic resonance and the problem of phase-to-phase overvoltage surge current, effectively avoiding the occurrence of PT cabinet burning and fuse blowing accidents.

[0054] In this embodiment: the circuit between the outlet terminals of the detuning resistors Ra, Rb, Rc and the earth terminal is connected in series with current transformers CTa, CTb, CTc, respectively. The circuit between the detuning resistor Rn and the ground is connected in series with a current transformer CTn. The current transformer is connected in series with the detuning resistor to collect the operating current of the detuning resistor in real time; during normal operation, the current signal of the current transformer is small, which is the rated current of the voltage transformer; when a system failure occurs, due to the current limiting characteristics of the detuning resistor, the current signal of the current transformer changes from large to small in a short time. If the current signal of the current transformer is always relatively large, it means that the detuning resistor is faulty and needs to be replaced in time. Among them, the current transformers CTa, CTb, CTc are respectively fixed below the detuning resistors Ra, Rb, Rc and inside the quartz sand sleeve 5, while the current transformer CTn is fixed on one side of the detuning resistor Rn and inside the base 1.

[0055] In this embodiment: the detuning resistors Ra, Rb, Rc, and Rn are made of flow-sensitive materials. Furthermore, the detuning resistors Ra, Rb, Rc, and Rn are made of current-limiting materials with positive temperature characteristics. The present application utilizes the current-limiting characteristics of flow-sensitive materials, and when ferromagnetic resonance occurs, the resistance suddenly increases to destroy the conditions for its occurrence. After the system fault disappears, it quickly returns to the initial state without affecting the characteristics of the voltage transformer.

[0056] In this embodiment, the current transformer is a high-precision current transformer. In order to understand the operating state of the detuning resistor, the detuning resistor is connected in series with the high-precision current transformer to collect the operating current of the detuning resistor.

[0057] In this embodiment: the ventilation and heat dissipation shell specifically includes: a base 1, a detuning resistor Rn is fixed inside the base 1, and three parallel vertical shells 2 are fixedly connected to the top surface of the base 1, a placement cavity 3 is opened inside the vertical shell 2, and a card slot 4 is opened at both upper and lower ends of the placement cavity 3, a quartz sand sleeve 5 is clamped between the two card slots 4, the detuning resistors Ra, Rb, and Rc are respectively fixed inside the three quartz sand sleeves 5, a wiring electrode 6 is fixedly connected to the top of the vertical shell 2 for connecting a voltage transformer, an air-blowing shell 7 is fixedly connected between two adjacent vertical shells 2, an inner cavity 8 is opened inside the air-blowing shell 7, and a partition 9 is fixedly connected inside the inner cavity 8, and the partition 9 separates the inner cavity 8 into an air-blowing cavity and a dynamic cavity. A force chamber, and a push block 10 is provided inside the power chamber, a limit mechanism is provided at the top of the push block 10, and a supporting mechanism is provided below the push block 10, a driving mechanism 11 is provided on one side of the push block 10 to drive the push block 10 forward, and an optical axis 12 is fixedly connected to the other side of the push block 10, one end of the optical axis 12 passes through the partition 9 and is fixedly connected to a piston 13, and the piston 13 can move back and forth inside the air chamber, a spring column 14 is sleeved on the outside of the optical axis 12, and the two ends of the spring column 14 are respectively fixedly connected to the partition 9 and the push block 10, through holes 15 are opened on both sides of one end of the air chamber, and the two through holes 15 are respectively connected to the placement chambers 3 on both sides of the air chamber shell 7, and a plurality of slots connected to the placement chamber 3 are opened on the top of the outer side of the vertical shell 2. The detuning resistor generates heat when in use. At this time, the driving mechanism 11 runs to push the push block 10 forward, thereby driving the optical axis 12 forward, and the piston 13 follows and pushes the air in the inflation chamber from the through hole 15 into the placement chamber 3, while the quartz sand sleeve 5 absorbs the heat generated by the detuning resistor. The air entering the placement chamber 3 is quickly discharged from the vertical shell 2 through the slots, and the fast-flowing air quickly takes away the heat on the quartz sand sleeve 5.

[0058] In this embodiment: the driving mechanism 11 specifically includes: a motor 1101 fixed on the inner wall of one side of the power chamber, the output end of the motor 1101 is fixedly connected with a rotating shaft 1102, and one end of the rotating shaft 1102 is movably embedded in the inner wall of the other side of the power chamber, a turntable body 1103 is fixedly connected to the outer surface of the rotating shaft 1102, and three evenly distributed rotating arms 1104 are fixedly connected to the outer surface of the turntable body 1103, one end of the rotating arm 1104 is movably connected with a driving wheel 1105, and a step is provided on one side of the push block 10 close to the driving mechanism 11, and when the rotating arm 1104 rotates, it drives the driving wheel 1105 to hit the step of the push block 10 to push the push block 10 forward. The operation of motor 1101 drives the rotating shaft 1102 to rotate, thereby driving the turntable body 1103 and the rotating arm 1104 to rotate, and the driving wheel 1105 on the rotating arm 1104 hits the step of the pushing block 10 to push the pushing block 10 forward, thereby driving the piston 13 forward, and the air is quickly discharged through the slot to form "exhalation". At this time, the spring column 14 is compressed. After the driving wheel 1105 is separated from the step of the pushing block 10, the spring column 14 releases its elastic potential energy to restore the pushing block 10 to its original position, thereby driving the piston 13 to retreat. At this time, the outside air enters the placement chamber 3 and the inflation chamber through the slot, thereby causing the air to reflux to form "inhalation". As the driving wheel 1105 on the next rotating arm 1104 hits the step of the pushing block 10, the pushing block 10 moves forward again, driving the piston 13 to move forward again, thereby completing the "exhalation" again. In this way, the heat absorbed by the quartz sand sleeve 5 can be quickly and timely discharged by repeating the cycle.

[0059] In this embodiment, the limiting mechanism specifically includes: a limiting strip 18 fixed at the middle position of the top of the push block 10, and the limiting strip 18 is movable in a limiting groove 19 provided at the top of the inner wall of the power chamber. When the push block 10 moves forward or backward, the limiting strip 18 moves forward or backward in the limiting groove 19 to ensure the stability of the movement of the push block 10.

[0060] In this embodiment, the support mechanism specifically includes: multiple groups of horizontally parallel support rollers 16, each group of support rollers 16 has a plurality of support rollers 16, and the support rollers 16 are in contact with the bottom end surface of the push block 10, and each group of support rollers 16 is connected with a shaft 17 through which they are movably connected, and the two ends of the shaft 17 are respectively embedded in the inner walls of the two sides of the power chamber. When the push block 10 moves forward or backward, the support rollers 16 provide support for the push block 10, and the support rollers 16 rotate during the movement of the push block 10 to reduce friction resistance.

[0061] In this embodiment: the transfer function of the notch filter is:

[0062]

[0063] Set the notch frequency ω n=60hz, notch depth ξ2 / ξ1=1 / 1000, notch bandwidth (frequency difference when attenuated to -3db)=10hz, S is the Laplace operator, then a notch filter that filters out 60hz power frequency can be designed through bilinear transformation;

[0064] After calculation, the transfer function of the notch filter is:

[0065]

[0066] The working principle of the present invention is: under normal operating conditions, the detuning resistors Ra, Rb, Rc, and Rn present low resistance and do not affect the characteristics of the voltage transformer (voltage error, phase error); when a system fault occurs and a surge current or overvoltage is generated relative to the ground (for example, phase A to the ground), the resistance values ​​of Ra and Rn increase sharply, suppressing the current, making the voltage transformer unsaturated, destroying the resonance condition, and achieving the effect of detuning; when the system fault disappears, the resistance values ​​of Ra and Rn quickly return to the initial state, and do not affect the normal operation of the voltage transformer; when a surge current is generated between phases (for example, phase A and phase B), the resistance values ​​of Ra and Rb increase sharply, suppressing the current, making the voltage transformer unsaturated, destroying the resonance condition, and achieving the effect of detuning; when the system fault disappears, the resistance values ​​of Ra and Rb quickly return to the initial state, and do not affect the normal operation of the voltage transformer. When the voltage transformer is operating normally, it transforms the voltage of the power grid and supplies power to the measuring instrument. The measuring instrument (such as a voltmeter) is used to measure the voltage of the line, and the notch filter filters out the 60hz power frequency interference to improve the accuracy of the measuring instrument. It should be noted that in order to better filter out the 60hz power frequency, this application uses a notch filter to achieve this technical purpose. The notch filter transfer function is:

[0067]

[0068] Set the notch frequency ω n =60hz, notch depth ξ2 / ξ1=1 / 1000, notch bandwidth (frequency difference when attenuated to -3db)=10hz, S is the Laplace operator, then a notch filter can be designed through bilinear transformation.

[0069] After calculation, the transfer function of the notch filter is:

[0070]

[0071] In addition, the detuning resistor generates heat when in use. At this time, the driving mechanism 11 operates to push the push block 10 forward, thereby driving the optical axis 12 forward, and the piston 13 follows and pushes the air in the air chamber from the through hole 15 into the placement chamber 3, and the quartz sand sleeve 5 absorbs the heat generated by the detuning resistor, and the air entering the placement chamber 3 is quickly discharged from the vertical shell 2 through the slots, and these fast-flowing air quickly takes away the heat on the quartz sand sleeve 5. The specific operation process of the driving mechanism 11 is as follows: the motor 1101 operates to drive the rotating shaft 1102 to rotate, thereby driving the turntable body 1103 and the rotating arm 1104 to rotate, and the driving wheel 1105 on the rotating arm 1104 hits the step of the push block 10 to push the push block 10. The push block 10 moves forward, and then drives the piston 13 forward, and the air is quickly discharged through the slot to form "exhalation". At this time, the spring column 14 is compressed. After the driving wheel 1105 separates from the step of the push block 10, the spring column 14 releases the elastic potential energy to restore the push block 10 to its original position, and then drives the piston 13 to retreat. At this time, the outside air enters the placement chamber 3 and the inflation chamber through the slot, and then the air refluxes to form "inhalation". As the driving wheel 1105 on the next rotating arm 1104 hits the step of the push block 10, the push block 10 moves forward again and drives the piston 13 to move forward again, and then completes "exhalation" again. In this way, the heat absorbed by the quartz sand sleeve 5 can be quickly and timely discharged in a reciprocating manner. In the process of the push block 10 moving forward or backward, the limit bar 18 follows the forward or backward movement in the limit slot 19 to ensure the stability of the movement of the push block 10. At the same time, the support roller 16 provides support for the push block 10, and the support roller 16 rotates during the movement of the push block 10 to reduce friction resistance.

[0072] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

[0073] What is described above is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A current limiting detuning device based on flow-sensitive materials, characterized in that: It includes a power grid, a voltage transformer, a current limiting harmonic elimination device, a notch filter and a measuring instrument connected in sequence; The current limiting harmonic elimination device includes harmonic elimination resistors Ra, Rb, Rc, Rn and a ventilation and heat dissipation housing for integrating the harmonic elimination resistors Ra, Rb, Rc, Rn, wherein the harmonic elimination resistors Ra, Rb, Rc are respectively connected in series with the primary winding of the voltage transformer in the three-phase circuits A, B, and C, and the harmonic elimination resistor Rn is connected in series between the primary neutral point of the voltage transformer and the ground; the inlet terminals of the harmonic elimination resistors Ra, Rb, and Rc are respectively connected to the primary outlet terminals of the corresponding voltage transformer PT, and the outlet terminals of the harmonic elimination resistors Ra, Rb, and Rc are connected to the earth terminal, and the primary inlet terminal of the voltage transformer PT is connected to the power grid; A current transformer CTn is connected in series in the circuit between the detuning resistor Rn and the ground; The ventilation and heat dissipation shell specifically includes: a base, the detuning resistor Rn is fixed inside the base, and the top surface of the base is fixedly connected with three parallel vertical shells, a placement cavity is opened inside the vertical shell, and the upper and lower ends of the placement cavity are opened with card slots, a quartz sand sleeve is clamped between two of the card slots, the detuning resistors Ra, Rb, and Rc are respectively fixed inside the three quartz sand sleeves, a wiring electrode is fixedly connected to the top of the vertical shell, an air-blowing shell is fixedly connected between two adjacent vertical shells, an inner cavity is opened inside the air-blowing shell, and a partition is fixedly connected inside the inner cavity, and the partition separates the inner cavity into an air-blowing shell and an air-blowing shell. cavity and a power cavity, and a push block is provided inside the power cavity, a limiting mechanism is provided at the top of the push block, and a supporting mechanism is provided under the push block, a driving mechanism is provided on one side of the push block to drive the push block forward, and an optical axis is fixedly connected to the other side of the push block, one end of the optical axis passes through the partition and is fixedly connected to a piston, and the piston can move back and forth inside the air-inflating cavity, a spring column is sleeved on the outside of the optical axis, and the two ends of the spring column are respectively fixedly connected to the partition and the push block, through holes are provided on both sides of one end of the air-inflating cavity, and the two through holes are respectively communicated with the placement cavities on both sides of the air-inflating shell body, and a plurality of slots connected with the placement cavities are provided on the top of the outer side surface of the vertical shell body; The driving mechanism specifically includes: a motor fixed on the inner wall of one side of the power chamber, the output end of the motor is fixedly connected to a rotating shaft, and one end of the rotating shaft is movably embedded in the inner wall of the other side of the power chamber, a turntable body is fixedly connected to the outer side of the rotating shaft, and three evenly distributed rotating arms are fixedly connected to the outer side of the turntable body, one end of the rotating arm is movably connected to a driving wheel, and a step is provided on a side of the push block close to the driving mechanism, and when the rotating arm rotates, it drives the driving wheel to hit the step of the push block to push the push block forward.

2. A current limiting harmonic elimination device based on flow-sensitive materials according to claim 1, characterized in that: Current transformers CTa, CTb, CTc are respectively connected in series in the circuit between the outgoing terminals of the detuning resistors Ra, Rb, Rc and the ground terminal.

3. The current limiting harmonic elimination device based on flow-sensitive material according to claim 1, characterized in that: The detuning resistors Ra, Rb, Rc and Rn are made of flow-sensitive materials.

4. The current limiting harmonic elimination device based on flow-sensitive material according to claim 3 is characterized in that: The detuning resistors Ra, Rb, Rc and Rn are made of current-limiting materials with positive temperature characteristics.

5. The current limiting and harmonic elimination device based on flow-sensitive materials according to claim 1, characterized in that: The limiting mechanism specifically includes: a limiting bar fixed at the middle position of the top end of the push block, and the limiting bar is movably clamped in a limiting groove opened at the top end of the inner wall of the power cavity.

6. The current limiting harmonic elimination device based on flow-sensitive material according to claim 1, characterized in that: The support mechanism specifically includes: multiple groups of horizontally parallel support rollers, each group of the support rollers has a plurality of support rollers, and the support rollers are in contact with the bottom end surface of the push block, and each group of the support rollers has a shaft rod running through the inside and movably connected thereto, and the two ends of the shaft rod are respectively embedded in the inner walls on both sides of the power cavity.

7. The current limiting harmonic elimination device based on flow-sensitive material according to claim 1, characterized in that: The transfer function of the notch filter is Set the notch frequency ω n =60hz, notch depth ξ2 / ξ1=1 / 1000, notch bandwidth (frequency difference when attenuated to -3db)=10hz, S is the Laplace operator, then a notch filter that filters out 60hz power frequency can be designed through bilinear transformation; After calculation, the transfer function of the notch filter is:

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