CN117406130A - AC/DC leakage current detection device based on fluxgate principle - Google Patents
AC/DC leakage current detection device based on fluxgate principle Download PDFInfo
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- 239000000523 sample Substances 0.000 claims abstract description 10
- 230000004907 flux Effects 0.000 claims description 65
- 238000004804 winding Methods 0.000 claims description 21
- 238000005070 sampling Methods 0.000 claims description 12
- 230000005284 excitation Effects 0.000 claims description 10
- 230000035699 permeability Effects 0.000 claims description 8
- 230000000694 effects Effects 0.000 claims description 6
- 239000002707 nanocrystalline material Substances 0.000 claims description 3
- 230000000149 penetrating effect Effects 0.000 abstract 1
- 238000005457 optimization Methods 0.000 description 9
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- 230000008569 process Effects 0.000 description 4
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- 238000013461 design Methods 0.000 description 2
- 230000005674 electromagnetic induction Effects 0.000 description 2
- 230000004044 response Effects 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- 238000011282 treatment Methods 0.000 description 2
- 238000000137 annealing Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
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- 230000003137 locomotive effect Effects 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
- G01R31/52—Testing for short-circuits, leakage current or ground faults
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
- G01R19/175—Indicating the instants of passage of current or voltage through a given value, e.g. passage through zero
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R33/00—Arrangements or instruments for measuring magnetic variables
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Abstract
The invention relates to the technical field of current detection, and discloses an alternating current/direct current leakage current detection device based on a fluxgate principle, which comprises a fluxgate probe composed of a first magnetic core T1, a second magnetic core T2 and a third magnetic core T3 which are arranged side by side, wherein current Ip to be detected sequentially penetrates through the third magnetic core T3, the second magnetic core T2 and the first magnetic core T1 through wires so as to be connected with the fluxgate probe, the first magnetic core T1 is provided with a direct current zero-flux detection circuit, the second magnetic core T2 is provided with an excitation-flux compensation circuit, the third magnetic core T3 is provided with an alternating current zero-flux detection circuit, the direct current zero-flux detection circuit is used for detecting whether exciting current generated by the current to be detected penetrating through the third magnetic core T3, the second magnetic core T2 and the first magnetic core T1 is balanced, and the output end of the direct current zero-flux detection circuit is connected with the excitation-flux compensation circuit. The invention can realize pure direct current linear detection under strong interference.
Description
Technical Field
The invention relates to the technical field of current detection, in particular to an alternating current-direct current leakage current detection device and method based on a fluxgate principle.
Background
On a motor train, a direct current insulation system on a train carriage needs to be monitored in real time to prevent electric leakage. The leakage current sensor is used for monitoring whether the positive bus and the negative bus of each carriage of the vehicle are balanced through the DC110V line current vector sum of the leakage current sensor, and outputting corresponding voltage signals to the conditioning module, and when the leakage exceeds a pre-alarm threshold value, alarm signals are sent out, so that the safety of vehicle equipment and personal electricity is ensured.
At present, most of direct current leakage current sensors in the market are designed based on a magnetic modulation principle, and whether the direct current leakage current sensors are sensors based on an open-loop or closed-loop magnetic modulation principle, the direct current leakage current sensors are based on a single-loop fluxgate effect, and the response frequency of a system is low due to the low scanning voltage frequency of a fluxgate detector, so that the principle is only suitable for direct current (or low frequency) leakage detection. The dual-magnetic-ring universal AC/DC leakage current sensor is designed based on an AC/DC independent detection mode, and the test precision of DC leakage current is affected when AC exists in the system. The two direct current leakage current sensor principles have the condition of inaccurate leakage measurement under the strong interference environment.
When the harmonic content of the AC20KV network voltage network current of the motor train unit is higher, the harmonic content of the leakage current of the DC110 is higher due to conduction interference; when the trailer inverter or the charger works, the generated common-mode interference signal (the frequency can reach several KHz) generates resonance in a frequency band when the vehicle is positioned in certain specific sections, so that the common-mode current in the DC110V line of the vehicle is amplified, and the direct-current leakage current sensor is caused to alarm by mistake.
Disclosure of Invention
In order to solve the above problems, the present invention provides a fluxgate leakage current sensor based on zero magnetic flux detection. The core idea is based on zero-flux coil compensation, so that the sensor works in a zero-flux state, and false alarm caused by conduction interference DC110 leakage current is avoided.
The invention is realized by the following technical scheme:
the utility model provides an alternating current-direct current leakage current detection device based on fluxgate principle, its characterized in that includes by the annular first magnetic core T1 that sets up side by side, fluxgate probe that third magnetic core T3 constitutes, wait to detect electric current Ip through the wire pass through in proper order third magnetic core T3 and first magnetic core T1 thereby insert fluxgate probe, first magnetic core T1 has set up direct current zero magnetic flux detection circuit, third magnetic core T3 has set up alternating current zero magnetic flux detection circuit, direct current zero magnetic flux detection circuit and alternating current zero magnetic flux detection circuit are used for detecting and pass third magnetic core T3 and first magnetic core T1 wait to detect the exciting current that the electric current produced and balance, just the sampling end of direct current zero magnetic flux detection circuit and the sampling end of alternating current zero magnetic flux detection circuit are connected through the input with the proportional-integrator respectively, the output of proportional-integrator is connected with power amplifier, power amplifier's output passes through secondary winding C, load resistance RL ground in proper order, secondary winding C is commonly winded between third magnetic core T3 and first magnetic core T1.
As optimization, the first input end of the direct current zero magnetic flux detection circuit is connected with a low-pass filter, the first input end of the direct current zero magnetic flux detection circuit is a sampling end of the direct current zero magnetic flux detection circuit, the low-pass filter is used for collecting exciting current of the first input end of the direct current zero magnetic flux detection circuit, the output end of the low-pass filter is connected with the output end of the alternating current zero magnetic flux detection circuit through a subtracter and the input end of a proportional-integral device, and the output end of the alternating current zero magnetic flux detection circuit is the sampling end of the alternating current zero magnetic flux detection circuit.
As optimization, the transformer also comprises a second magnetic core T2 which is arranged between the first magnetic core T1 and the third magnetic core T3 in parallel, wherein an excitation magnetic flux compensation circuit is arranged on the second magnetic core T2, the output end of the direct current zero magnetic flux detection circuit is connected with the excitation magnetic flux compensation circuit, the excitation magnetic flux compensation circuit is used for inhibiting modulation ripples induced by excitation magnetic flux generated by excitation current in the first magnetic core T1 in a lead wire and a secondary winding C of the current Ip to be detected due to a transformer effect, and the secondary winding on one side between the three magnetic cores T3 and the first magnetic core T1 passes through the second magnetic core T2.
As an optimization, the direct current zero magnetic flux detection circuit comprises an operational amplifier A1, a first resistor R1, a second resistor R2, a third resistor R3 and a square wave driving coil S, wherein the square wave driving coil S is wound on the first magnetic core T1, a first end of the square wave driving coil S is grounded through the third resistor R3, the first end of the square wave driving coil S is also connected with a negative input end of the operational amplifier A1 and a low-pass filter, a second end of the square wave driving coil S is connected with a positive input end of the operational amplifier A1 in series through the second resistor R2, and one end, commonly connected with the positive input end of the operational amplifier A1 and the second resistor R2, is grounded through the first resistor R1 in series.
As an optimization, the excitation magnetic flux compensation circuit comprises a fourth resistor R4, a unit gain inverter A2 and an intermediate coil S ', wherein the intermediate coil S' is wound on the second magnetic core T2, one end of the intermediate coil S 'is grounded through being connected with the fourth resistor R4 in series, the other end of the intermediate coil S' is connected with the output end of the unit gain inverter A2, and the input end of the unit gain inverter A2 is connected with the output end of the operational amplifier A1.
As an optimization, the alternating current zero magnetic flux detection circuit is an alternating current coil W wound on the third magnetic core T3, one end of the alternating current coil W is grounded, and the other end of the alternating current coil W is connected with the other input end of the subtracter.
As an optimization, the shapes of the first magnetic core T1, the second magnetic core T2 and the third magnetic core T3 may be square, oval or round.
As an optimization, the magnetic permeability of the first magnetic core T1, the second magnetic core T2 and the third magnetic core T3 is not less than 200000.
As an optimization, the first magnetic core T1, the second magnetic core T2, and the third magnetic core T3 are all saturable inductors.
As an optimization, the materials of the first magnetic core T1, the second magnetic core T2 and the third magnetic core T3 are nanocrystalline materials.
Compared with the prior art, the invention has the following advantages and beneficial effects:
in the invention, the current I is input P The magnetic flux gate probe is connected through the lead penetration, the probe formed by multiple rings converts the input complex signal into alternating current and direct current signal magnetic flux and sends the alternating current and direct current signal magnetic flux to the zero magnetic flux detector (the direct current zero magnetic flux detection circuit and the alternating current zero magnetic flux detection circuit), the zero magnetic flux detector detects whether the closed loop magnetic flux is zero or not in real time, if not, the zero magnetic flux detector generates a driving signal so as to generate a compensation current in the secondary winding C, the magnitude of the compensation current is proportional to the magnitude of the input current, the waveform is consistent, the process is completed in extremely short time, the magnetic circuit is ensured to work in a zero magnetic flux state, the detection of complex waveforms such as alternating current and direct current is truly realized through sampling the voltage on the load resistor, and the alternating current and direct current detection mode overcomes the defect that the traditional modulation and demodulation mode cannot detect high-frequency alternating current is truly realized; the sampling voltage is amplified and then filtered by a multi-order low-pass filter or digital filter, and the high-frequency interference signal is filtered, so that the pure direct current linear detection under the strong interference can be realized.
Drawings
In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the drawings that are needed in the examples will be briefly described below, it being understood that the following drawings only illustrate some examples of the present invention and therefore should not be considered as limiting the scope, and that other related drawings may be obtained from these drawings without inventive effort for a person skilled in the art. In the drawings:
fig. 1 is a schematic structural diagram of an ac/dc leakage current detection device based on the fluxgate principle according to the present invention.
Detailed Description
For the purpose of making apparent the objects, technical solutions and advantages of the present invention, the present invention will be further described in detail with reference to the following examples and the accompanying drawings, wherein the exemplary embodiments of the present invention and the descriptions thereof are for illustrating the present invention only and are not to be construed as limiting the present invention.
An ac/dc leakage current detection device based on fluxgate principle in embodiment 1 includes a fluxgate probe composed of a first magnetic core T1, a second magnetic core T2, and a third magnetic core T3 which are arranged side by side, a current Ip to be detected sequentially passes through the third magnetic core T3, the second magnetic core T2, and the first magnetic core T1, thereby accessing the fluxgate probe, dc zero flux detection circuits are commonly arranged on the first magnetic core T1 and the second magnetic core T2, ac zero flux detection circuits are arranged on the third magnetic core T3, an exciting magnetic flux compensation circuit is arranged on the second magnetic core T2, an ac zero flux detection circuit is arranged on the third magnetic core T3, the ac zero flux detection circuit is an ac coil W wound on the third magnetic core T3, one end of the ac coil W is grounded, the other end of the ac coil W is connected with another input end of the subtracter, the dc zero flux detection circuits are used for detecting the ac zero flux that passes through the third magnetic core T3, the second magnetic core T2, and the ac zero flux compensation circuit is used for suppressing the effect of the ac zero flux in the ac magnetic core T1, and the ac zero flux compensation circuit is used for suppressing the ac zero flux compensation circuit.
In this embodiment, a low-pass filter is connected to the first input end of the dc zero-flux detection circuit, the low-pass filter is configured to collect ac excitation current of the first input end of the dc zero-flux detection circuit, the output end of the low-pass filter and the output end of the ac zero-flux detection circuit are connected to the input end of the proportional-integrator through a subtractor, the input end of the proportional-integrator sequentially passes through a secondary winding C and a load resistor RL and is grounded through a power amplifier, the secondary winding C is wound between a third magnetic core T3 and a first magnetic core T1, and one secondary winding between the third magnetic core T3 and the first magnetic core T1 passes through a second magnetic core T2.
More specifically, the dc zero magnetic flux detection circuit includes an operational amplifier A1, a first resistor R1, a second resistor R2, a third resistor R3, and a square wave driving coil S, where the square wave driving coil S is wound on the first magnetic core T1, and a first end of the square wave driving coil S is grounded through the third resistor R3, and the first end of the square wave driving coil S is further connected to a negative input end of the operational amplifier A1 and a low-pass filter, a second end of the square wave driving coil S is connected to a positive input end of the operational amplifier A1 through a series connection with the second resistor R2, and an end, connected together, of the positive input end of the operational amplifier A1 and the second resistor R2 is grounded through a series connection with the first resistor R1.
The direct current zero magnetic flux detection circuit is essentially a hysteresis comparator type RL square wave oscillation circuit, the operational amplifier A1 works in a voltage comparator state, and the first resistor R1 and the third resistor R3 set the turning point voltage of the comparator. Because of the use of symmetrical dual power supplies, the signal output by the operational amplifier A1 is a bipolar square wave that is symmetrical in both positive and negative directions. The square wave drives the coil S to form a magnetic flux gate effect, and the purpose of detecting whether the direct current is stable or not is achieved by detecting the exciting current change on the third resistor R3. The circuit has simple structure, can reduce the design and debugging difficulty, saves time and raw materials, and realizes low cost.
The exciting magnetic flux compensation circuit comprises a fourth resistor R4, a unit gain inverter A2 and a middle coil S ', wherein the middle coil is subjected to magnetic core parameter screening and matching, winding process parameters are set to be consistent with parameters of a square wave driving coil S, the middle coil S' is wound on the second magnetic core T2, one end of the middle coil S 'is grounded through being connected with the fourth resistor R4 in series, the fourth resistor R4 is an exciting current sampling resistor, the other end of the middle coil S' is connected with the output end of the unit gain inverter A2, and the input end of the unit gain inverter A2 is connected with the output end of the operational amplifier A1.
The fluxgate sensing element is intentionally designed as a "saturable inductor", the inductance value of which, like any inductor, depends on the permeability of the magnetic core. When the magnetic flux density is high, the magnetic core is saturated, the magnetic permeability is low, and the inductance is low. At low magnetic flux densities, the inductance is large. It is wound by toroidal core (different applications may use cores of different shapes such as square, oval etc.). In order to improve the sensitivity, the magnetic cores T1, T2 and T3 are made of nanocrystalline materials with extremely high initial magnetic permeability, and the initial magnetic permeability reaches over 200000 (maximum 600000) after special treatments such as high-temperature annealing and constant magnetic treatment. The design of the "saturable inductor" is purposeful. Any changed external field (magnetic field generated by input current) can influence the saturation level of the magnetic field, and change the magnetic permeability of the magnetic core, so that the inductance value of the magnetic field is changed, the average value of exciting current is influenced, and the detection purpose is achieved. The saturation inductor is designed fully, the change is obvious, and the optimal effect can be achieved by a certain winding (the number of turns of the coil, the size of the magnetic core is determined by the field application condition) and setting exciting current (by testing the magnetic permeability curve setting of the magnetic core).
The proportional-integrator PI, the power amplifier PA, the secondary winding C and the load resistor RL form a closed loop, the secondary winding C is wound on three magnetic cores T1, T2 and T3 which are stacked back to back (see FIG. 1, the secondary winding C is wound on the three magnetic cores), wherein the compensation current flowing through the secondary winding is used for counteracting the magnetic field (I P N P ＝I c N c The ampere turns are balanced, and the magnetic fields generated by the currents are equal in size and opposite in direction, so that zero magnetic flux detection is realized.
The voltage on the load RL can reflect the primary current Ip, the voltage tracks the input current signal in real time, and a direct current leakage current analog signal is needed in actual field detection, so that the alternating current signal which is interfered is needed to be filtered after the tracking signal is amplified at the sampling end, and meanwhile, the requirement of response time is considered to be less than 350ms, and the use requirement of a locomotive can be met by adopting a 6-order Butterworth low-pass filter (also can be realized by adopting a digital filter).
The specific process of DC detection is as follows:
when the detected current Ip is dc, the faraday electromagnetic induction law is not established, and thus the ac zero-flux detection circuit does not operate (corresponds to a short circuit), and at this time, as is known from the closed-loop fluxgate basic principle, the square wave drives the excitation in the coil SThe average value of the magnetic current iex is zero, i.e. the output signal Vdc after the low-pass filter is zero, and because the ac zero-flux detection circuit is not operated under the condition, the induced voltage Vac on the ac coil W is zero, and the system error signal Ve is zero, i.e. the system is in an ampere-turn balance state, I is present at this time P N P ＝I c N c (I P To input current, N P For the number of turns of the input coil (the input coil is the wire of the detected current, normally 1 or a plurality of turns), I c To compensate for current, N c To compensate for the number of coil turns (i.e., the number of turns of secondary winding C)). However, the flux imbalance due to any cause will result in a non-zero average value of the excitation current iex of the dc zero flux detection circuit, i.e. the system error signal will not be zero, which will drive the power amplifier PA output compensation current as the error signal of the proportional-integrator PI until the system reaches the ampere-turn balance again (I P N P ＝I c N c Ampere-turn balance).
The specific process for carrying out the alternating current detection is as follows:
the ac coil W is wound around the third magnetic core T3 to form a detection winding of the magnetic integrator, and at the same time, serves as an ac zero-magnetic-flux detection circuit. When the detected current Ip is ac, the dc zero-flux detection circuit is not operated due to the limitation of the excited current frequency and the cut-off frequency of the high pass filter (V DC Circuit part, corresponding to a short circuit), the detection device can be regarded as a zero-flux active ac current transformer, the operation principle of which is similar to the closed loop formed by the dc zero-flux detection circuit, the same being that the high open loop gain of the proportional-integrator PI enables the system to be always in a zero-flux state within a certain frequency range, except that the ac error signal Vac is obtained by the ac flux detection winding W according to faraday's law of electromagnetic induction.
The foregoing description of the embodiments has been provided for the purpose of illustrating the general principles of the invention, and is not meant to limit the scope of the invention, but to limit the invention to the particular embodiments, and any modifications, equivalents, improvements, etc. that fall within the spirit and principles of the invention are intended to be included within the scope of the invention.
Claims (10)
1. The utility model provides an alternating current-direct current leakage current detection device based on fluxgate principle, its characterized in that includes by the annular first magnetic core T1 that sets up side by side, fluxgate probe that third magnetic core T3 constitutes, wait to detect electric current Ip through the wire pass through in proper order third magnetic core T3 and first magnetic core T1 thereby insert fluxgate probe, first magnetic core T1 has set up direct current zero magnetic flux detection circuit, third magnetic core T3 has set up alternating current zero magnetic flux detection circuit, direct current zero magnetic flux detection circuit and alternating current zero magnetic flux detection circuit are used for detecting and pass third magnetic core T3 and first magnetic core T1 wait to detect the exciting current that the electric current produced and balance, just the sampling end of direct current zero magnetic flux detection circuit and the sampling end of alternating current zero magnetic flux detection circuit are connected through the input with the proportional-integrator respectively, the output of proportional-integrator is connected with power amplifier, power amplifier's output passes through secondary winding C, load resistance RL ground in proper order, secondary winding C is commonly winded between third magnetic core T3 and first magnetic core T1.
2. The ac/dc leakage current detection device based on the fluxgate principle according to claim 1, wherein the first input end of the dc zero-flux detection circuit is connected with a low-pass filter, the first input end of the dc zero-flux detection circuit is a sampling end of the dc zero-flux detection circuit, the low-pass filter is used for collecting exciting current of the first input end of the dc zero-flux detection circuit, the output end of the low-pass filter is connected with the output end of the ac zero-flux detection circuit through a subtractor and the input end of a proportional-integral, and the output end of the ac zero-flux detection circuit is the sampling end of the ac zero-flux detection circuit.
3. The ac/dc leakage current detection device based on the fluxgate principle according to claim 2, further comprising a second magnetic core T2 disposed between the first magnetic core T1 and the third magnetic core T3 in parallel, wherein an exciting magnetic flux compensation circuit is disposed on the second magnetic core T2, an output end of the dc zero magnetic flux detection circuit is connected to the exciting magnetic flux compensation circuit, and the exciting magnetic flux compensation circuit is configured to suppress a modulation ripple induced in the wire of the current Ip to be detected and the secondary winding C by the transformer effect by exciting magnetic flux generated by exciting current in the first magnetic core T1, and one of the secondary windings between the three magnetic cores T3 and the first magnetic core T1 passes through the second magnetic core T2.
4. The ac/dc leakage current detection device based on the fluxgate principle according to claim 3, wherein the dc zero-flux detection circuit comprises an operational amplifier A1, a first resistor R1, a second resistor R2, a third resistor R3, and a square wave driving coil S, wherein the square wave driving coil S is wound on the first magnetic core T1, a first end of the square wave driving coil S is grounded through the third resistor R3, and the first end of the square wave driving coil S is further connected with a negative input end of the operational amplifier A1 and a low-pass filter, a second end of the square wave driving coil S is connected with a positive input end of the operational amplifier A1 through series connection of the second resistor R2, and an end, which is commonly connected with the positive input end of the operational amplifier A1 and the second resistor R2, is grounded through series connection of the first resistor R1.
5. The ac/dc leakage current detection apparatus according to claim 4, wherein said excitation magnetic flux compensation circuit comprises a fourth resistor R4, a unity gain inverter A2, and an intermediate coil S ′ The intermediate coil S ′ Wound around the second core T2 and the intermediate coil S ′ One end of the intermediate coil S is grounded through the fourth resistor R4 connected in series ′ The other end of the single-gain inverter A2 is connected with the output end of the single-gain inverter A2, and the input end of the single-gain inverter A2 is connected with the output end of the operational amplifier A1.
6. The ac/dc leakage current detection apparatus according to claim 1, wherein the ac zero-flux detection circuit is an ac coil W wound around the third magnetic core T3, one end of the ac coil W is grounded, and the other end of the ac coil W is connected to the other input end of the subtractor.
7. The ac/dc leakage current detection device according to claim 3, wherein the first, second and third magnetic cores T1, T2, T3 may have a square, oval or round shape.
8. The ac/dc leakage current detection apparatus according to claim 3, wherein the magnetic permeability of the first magnetic core T1, the second magnetic core T2, and the third magnetic core T3 is not less than 200000.
9. The ac/dc leakage current detection apparatus according to claim 3, wherein the first magnetic core T1, the second magnetic core T2, and the third magnetic core T3 are all saturable inductors.
10. The ac/dc leakage current detection apparatus according to claim 3, wherein the first magnetic core T1, the second magnetic core T2, and the third magnetic core T3 are made of nanocrystalline materials.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202311245162.7A CN117406130A (en) | 2023-09-25 | 2023-09-25 | AC/DC leakage current detection device based on fluxgate principle |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202311245162.7A CN117406130A (en) | 2023-09-25 | 2023-09-25 | AC/DC leakage current detection device based on fluxgate principle |
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| CN117406130A true CN117406130A (en) | 2024-01-16 |
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| CN202311245162.7A Pending CN117406130A (en) | 2023-09-25 | 2023-09-25 | AC/DC leakage current detection device based on fluxgate principle |
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