A multi-winding synchronous detection current transformer polarity rapid tester

Abstract

This invention relates to the field of circuit testing technology and discloses a rapid polarity tester for current transformers with simultaneous multi-winding testing. A power supply is connected to a voltage conversion module, which in turn is connected to an energy storage capacitor module. The energy storage capacitor module includes a farad capacitor, the positive terminal of which is connected to the positive terminal of the primary test via a trigger switch and a primary current adjustment module. A multi-channel secondary-side sensing display module consists of a first current detection circuit, a second current detection circuit, and a third current detection circuit, respectively connected to a first pointer-type milliammeter, a second pointer-type milliammeter, and a third pointer-type milliammeter. The farad capacitor releases a pulse current to the primary side of the current transformer under test, and the multi-channel secondary-side sensing display module captures the induced current in parallel and drives the pointer deflection. The internal circuitry is encased in a metal shielding shell made of aluminum-magnesium alloy. This invention achieves simultaneous polarity verification of multiple secondary windings, improving testing efficiency and suppressing electromagnetic interference.

Description

Technical Field

[0001] This invention relates to the field of circuit testing technology, specifically to a rapid polarity tester for current transformers with multi-winding synchronous testing. Background Technology

[0002] Current transformer polarity detection is a fundamental test item in the construction and operation and maintenance of power system substations. Its physical essence is to verify the electromagnetic induction phase relationship between the primary and secondary windings of the current transformer. By accurately determining the polarity of the terminals, it is possible to ensure that relay protection devices, automatic devices, and power metering systems receive the correct current vector signal, which is a prerequisite for ensuring the safe and stable operation of the power grid and fair settlement of electricity trade.

[0003] In existing technologies, on-site maintenance personnel typically use the DC method to verify the polarity of current transformers. When testing current transformers with multiple secondary windings, such as measuring, protection, and metering windings, the operator connects a primary-side pulse source to the primary winding of the current transformer, and simultaneously connects a single-channel pointer meter or a single-loop polarity tester to one of the secondary windings under test. After injecting a DC pulse current into the primary side, the tester observes the deflection direction of the single-channel instrument and records the polarity result. Then, the secondary-side test lead is disconnected, and the test is switched to the next secondary winding. The subsequent windings are tested one by one by repeatedly triggering the primary-side pulse source.

[0004] Because existing polarity detection equipment only has single-loop acquisition capability, it suffers from low detection efficiency when calibrating current transformers with multiple secondary windings. In actual substation operations, for multiple secondary windings of the same current transformer, it is necessary to manually switch test leads multiple times and trigger the primary side excitation signal multiple times to complete the full-range verification. This serial detection method cannot achieve synchronous capture of the polarity state of all secondary windings during a single discharge process, significantly increasing the time cost of on-site testing and the operational risks caused by repeated lead disconnection and reconnection. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a rapid polarity tester for current transformers with multi-winding synchronous detection, which solves the problems mentioned in the background section.

[0006] To achieve the above objectives, the present invention provides the following technical solution: The first aspect of the present invention provides a multi-winding synchronous detection current transformer polarity fast test circuit, comprising a power supply, a voltage conversion module, an energy storage capacitor module, a trigger switch, a primary current adjustment module, a primary test positive terminal, a primary test negative terminal, a multi-channel secondary side sensing display module, and a metal shielding shell. The output terminal of the power supply is electrically connected to the input terminal of the voltage conversion module, and the output terminal of the voltage conversion module is electrically connected to the charging input terminal of the energy storage capacitor module. The energy storage capacitor module includes a supercapacitor; the positive terminal of the supercapacitor is electrically connected to the input contact of the trigger switch; the output contact of the trigger switch is electrically connected to the input terminal of the primary current adjustment module; the output terminal of the primary current adjustment module is connected to the primary test positive terminal, and the primary test negative terminal is connected to the negative terminal of the supercapacitor.

[0007] The multi-channel secondary-side sensing display module consists of a first current detection circuit, a second current detection circuit, and a third current detection circuit. The first current detection circuit is connected to a first pointer-type milliammeter, the second current detection circuit is connected to a second pointer-type milliammeter, and the third current detection circuit is connected to a third pointer-type milliammeter. The first, second, and third current detection circuits are isolated within a metal shielding housing and are not electrically connected to each other. The first current detection circuit is connected to the first channel terminal pair, the second current detection circuit is connected to the second channel terminal pair, and the third current detection circuit is connected to the third channel terminal pair. The first channel terminal pair includes a positive terminal and a negative terminal. The positive terminal of the first channel terminal pair is electrically connected to the positive terminal of the first pointer-type milliammeter, and the negative terminal of the first channel terminal pair is electrically connected to the negative terminal of the first pointer-type milliammeter. The second channel terminal pair includes a positive terminal and a negative terminal. The positive terminal of the second channel terminal pair is electrically connected to the positive terminal of the second pointer-type milliammeter, and the negative terminal of the second channel terminal pair is electrically connected to the negative terminal of the second pointer-type milliammeter. The third channel terminal pair includes a positive terminal and a negative terminal. The positive terminal of the third channel terminal pair is electrically connected to the positive terminal of the third pointer-type milliammeter, and the negative terminal of the third channel terminal pair is electrically connected to the negative terminal of the third pointer-type milliammeter.

[0008] The working principle and innovation of the multi-winding synchronous detection current transformer polarity fast test circuit are as follows:

[0009] The power supply uses an 18650 lithium-ion battery pack, which is equipped with a hardware protection board. The voltage conversion module contains a DC boost control circuit, which boosts the low-voltage DC output from the 18650 lithium-ion battery pack to a preset voltage and charges the supercapacitor. A current-limiting resistor is connected in series between the output terminal of the voltage conversion module and the positive terminal of the supercapacitor to limit the instantaneous current during the initial charging stage.

[0010] The primary current regulation module uses a high-power wire-wound potentiometer, which is connected in series to the discharge circuit. A normally open high-current push-button switch is used as the trigger switch. When the trigger switch is pressed, the charge stored in the supercapacitor is instantaneously released to the primary winding of the current transformer under test through the high-power wire-wound potentiometer. The peak current in the discharge circuit at the instant the trigger switch is turned on is [not specified]. Follow the formula:

[0011]

[0012] In the formula, This is the peak current of the primary side pulse discharge circuit, measured in amperes (A). The voltage across the supercapacitor at the moment of triggering, measured in volts (V). This is the resistance value of the high-power wire-wound potentiometer connected in the circuit, in ohms (Ω). It is the sum of the equivalent series resistance and the internal wire resistance of the farad capacitor, and the unit is ohms (Ω). This refers to the DC resistance of the primary winding of the current transformer under test, expressed in ohms (Ω). The tester changes this resistance by rotating a high-power wire-wound potentiometer. The value allows the peak current to be adjusted within the range of 1 ampere to 30 amperes to meet the excitation requirements of transformers with different ratios.

[0013] Transient pulse current generated by primary side discharge An alternating magnetic flux is generated in the core of the current transformer under test. According to Faraday's law of electromagnetic induction, the induced electromotive force generated in the secondary winding of the current transformer under test... Conforms to the formula:

[0014]

[0015] In the formula, The induced electromotive force generated by the secondary winding is expressed in volts (V). The number of turns in the secondary winding of the current transformer under test; The magnetic flux generated by the primary pulse current is expressed in Weber (Wb). The mutual inductance coefficient between the primary and secondary windings of the current transformer under test is expressed in Henry (H). This is the pulse current value flowing into the primary winding, in amperes (A).

[0016] The first, second, and third pointer-type milliammeters are all DC milliammeters with a center zero position; the range is set from -50 mA to +50 mA. Induced electromotive force. An induced current is generated in the multi-channel secondary-side induction display module, driving the corresponding pointer-type milliammeter to deflect. Based on the pointer deflection in the positive or negative direction, the operator directly determines the polarity relationship of the multiple secondary windings of the current transformer under test according to the subtractive polarity marking rule, thus completing the multi-channel synchronous verification.

[0017] To improve test stability, high-frequency suppression units are configured in the first, second, and third current detection circuits. These units include ceramic capacitors connected in parallel to the input terminals of the first, second, and third pointer-type milliammeters, respectively, to divert high-frequency radiated noise generated by the transient discharge on the primary side to ground potential. The negative terminals of the farad capacitors and the 18650 lithium-ion battery pack are both connected to the reference ground potential point of the metal shielding shell. The inner wall of the metal shielding shell is electrically connected to the reference ground potential point via a grounding lead.

[0018] The multi-winding synchronous detection current transformer polarity fast test circuit also includes an external charging interface and a charge / discharge management logic circuit. The external charging interface uses a standard USB interface, and the charge / discharge management logic circuit is connected between the external charging interface and the 18650 lithium-ion battery pack, containing a lithium battery management chip. The output of the voltage conversion module is connected to an auxiliary output unit, which includes a standard USB output port.

[0019] The second aspect of the present invention provides a multi-winding synchronous detection current transformer polarity rapid tester, which is internally provided with the above-mentioned multi-winding synchronous detection current transformer polarity rapid test circuit, including a measuring box, a handle rotatably connected to the top of the measuring box, and buckles snapped at both the front and rear ends of the measuring box, with a control box fixedly connected to the lower part of the buckles.

[0020] The physical layout logic of the multi-winding synchronous current transformer polarity rapid tester is as follows: A first pointer-type milliammeter, a second pointer-type milliammeter, and a third pointer-type milliammeter are fixedly connected inside the measuring box. The power supply, voltage conversion module, energy storage capacitor module, and primary current regulation module are installed inside the control box. Both the measuring box and the control box have multiple sets of wiring ports. The metal shielding shell is made of aluminum-magnesium alloy, forming a closed electromagnetic shielding cavity when the measuring box and control box are closed. The induced charges generated by the external high-voltage electric field converge on the surface of the aluminum-magnesium alloy, blocking the interference of the spatial electric field on the weak induced current test circuit inside. The primary current-carrying unit and the secondary test display unit are installed separately, facilitating single-person operation and obtaining accurate synchronous deflection results in environments with strong electromagnetic interference.

[0021] This invention provides a rapid polarity tester for current transformers with multi-winding synchronous detection. It has the following advantages:

[0022] 1. This invention achieves synchronous acquisition and classified display of the polarities of multiple secondary windings of a current transformer by setting up a multi-channel secondary-side induction display module consisting of a first current detection circuit, a second current detection circuit, and a third current detection circuit. At the instant of discharge when a large current pulse is generated on the primary side, the three independent current detection circuits can simultaneously capture the induced charges generated by different secondary windings of the current transformer under test. This parallel detection layout changes the traditional single-circuit reciprocating switching test mode. By simultaneously observing the deflection states of three sets of pointer-type milliammeters, the polarity verification of the measuring winding, protection winding, and metering winding is completed within a single pulse trigger cycle, effectively shortening the test cycle of the secondary circuits in the substation.

[0023] 2. This invention utilizes a farad capacitor as an energy release source, combined with the adjustment function of a high-power wire-wound potentiometer, to generate a pulse excitation current with a flux change rate that meets the requirements of high-ratio current transformers. The primary current adjustment module controls the peak value of the primary-side pulse current within a preset range by changing the equivalent impedance connected in series to the discharge circuit, ensuring that the instantaneous value of the induced current forms a clearly visible deflection angle on the secondary-side pointer-type milliammeter. This excitation technology based on transient pulse formula adjustment solves the defect of the traditional DC method in testing high-ratio current transformers, which results in a weak secondary-side induced current due to insufficient primary-side excitation energy. It also eliminates the risk of misjudgment caused by excessively small pointer swing amplitude, ensuring the uniqueness and certainty of the polarity detection results.

[0024] 3. This invention enhances the stability of data acquisition in strong electromagnetic environments by combining a 2-3 mm thick aluminum-magnesium alloy metal shielding shell with Kirchhoff's current law verification logic. The equipotential electrical connection between the shielding shell and the internal detection circuit reference ground constructs an electromagnetic protection cavity, suppressing the superposition interference of induced potentials generated by the high-voltage bus on weak pulse signals. The detection circuit utilizes the characteristic of Kirchhoff's current law that the vector sum of currents at common nodes is zero, and by consistently judging the deflection direction of the three-channel induced current, it eliminates interference currents caused by wiring errors or induced voltage coupling in complex circuits. Combined with the bypassing effect of ceramic capacitors on high-frequency noise, the accuracy of the system in capturing millisecond-level pulse signals is ensured. Attached Figure Description

[0025] Figure 1 This is the circuit schematic diagram of the present invention;

[0026] Figure 2 This is a schematic diagram of the present invention in its assembled state;

[0027] Figure 3 This is a schematic diagram of the control box of the present invention;

[0028] Figure 4This is a schematic diagram of the measuring box of the present invention.

[0029] The components include: 1. Control box; 2. Measuring box; 3. Handle; 4. Buckle; 5. Control panel; 6. Milliammeter. Detailed Implementation

[0030] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] Example:

[0032] Please see the appendix Figure 1 -Appendix Figure 4 This invention provides a rapid polarity tester for current transformers with multi-winding synchronous detection. The tester comprises a power supply, a voltage conversion module, an energy storage capacitor module, a primary current adjustment module, a trigger switch, a multi-channel secondary side sensing display module, and a metal shielding housing. The output of the power supply is electrically connected to the input of the voltage conversion module, and the output of the voltage conversion module is electrically connected to the charging input of the energy storage capacitor module. The positive output of the energy storage capacitor module is connected to the input of the trigger switch via a wire. The output of the trigger switch is connected to the input of the primary current adjustment module, and the output of the primary current adjustment module is connected to the primary test positive terminal on the tester's panel. The negative output of the energy storage capacitor module is connected to the primary test negative terminal on the tester's panel.

[0033] The power supply uses an 18650 lithium-ion battery pack, which is connected to the voltage conversion module via a built-in battery protection board. The battery protection board provides overcharge, over-discharge, and short-circuit protection. The voltage conversion module uses a DC / DC boost circuit to raise the low-voltage DC power provided by the 18650 lithium-ion battery pack to a preset 5V charging voltage. The energy storage capacitor module uses supercapacitors. The rated voltage of the supercapacitors should be greater than the output voltage of the voltage conversion module. The positive terminal of the supercapacitor is electrically connected to the 5V output terminal of the voltage conversion module, and the negative terminal is electrically connected to the primary test negative terminal and the reference ground potential point of the voltage conversion module, forming a complete charging and discharging circuit.

[0034] The primary current adjustment module includes a high-power wire-wound potentiometer. The two ends of the high-power wire-wound potentiometer are connected to the output terminal of the trigger switch and the positive terminal of the primary test circuit, respectively. Rotating the adjustment knob of the high-power wire-wound potentiometer changes the resistance value connected to the primary side discharge circuit, thereby changing the amplitude of the injected current. The trigger switch is a normally open push-button switch with high current carrying capacity.

[0035] The multi-channel secondary-side induction display module comprises three identical induction measurement units, each corresponding to a pointer-type milliammeter. The three pointer-type milliammeters are embedded side-by-side in the front panel of a metal-shielded housing. Each induction measurement unit has a pair of independent secondary-side test terminals. The negative terminals of the three pointer-type milliammeters are either independently connected within the internal circuitry or connected to a common terminal as required by the test. The range of the pointer-type milliammeters is set to ±50mA, with the pointer center position at zero.

[0036] The overall operation logic of the current transformer polarity tester is completed through hardware connection and manual triggering. An 18650 lithium-ion battery pack continuously supplies power to the supercapacitor via a voltage conversion module, keeping the supercapacitor in a charged saturated state. During testing, the primary test positive and negative terminals are connected to the primary winding of the current transformer under test. The three sets of secondary side test terminals are connected to the corresponding secondary windings of the current transformer under test.

[0037] When the trigger switch is pressed, the electrical energy stored inside the energy storage capacitor module is instantaneously discharged to the primary winding of the current transformer under test through the primary current regulating module. The primary current pulse generated by the instantaneous discharge produces a changing magnetic flux in the iron core of the current transformer under test, which in turn induces an electromotive force in each secondary winding of the current transformer under test. The induced electromotive force generates an induced current in the corresponding multi-channel secondary side induction display module circuit, driving the pointer of the pointer-type milliammeter to deflect. The operator directly reads and determines the polarity relationship of the current transformer under test based on the pointer deflection in the "+" or "-" direction.

[0038] For the specific boost control circuit in the voltage conversion module and the charging management logic of the 18650 lithium-ion battery pack, those skilled in the art can select general-purpose integrated circuit control chips and external resistor-capacitor components according to the actual power requirements. The specific circuit connection relationships of the above components are well-known technologies in the field and will not be elaborated here. The metal shielding shell is electrically connected to the reference ground potential of the internal circuit. Through the electrostatic shielding effect of the metal shell, it isolates the electric field coupling interference generated by the high voltage environment of the external substation, ensuring the stability of the pointer-type milliammeter when capturing weak induced signals. The current transformer polarity tester can adapt to the polarity detection requirements of current transformers or inductive voltage transformers with different voltage levels and different current ratios by adjusting the resistance value of the primary current adjustment module.

[0039] The power supply system uses 18650 lithium-ion battery packs as the primary energy source. These packs consist of multiple lithium-ion cells connected in parallel or series, and are used to provide power to the voltage conversion module. The output of the 18650 lithium-ion battery packs is connected to the DC input of the voltage conversion module via wires.

[0040] The voltage conversion module internally includes a DC-DC boost control circuit, the core of which consists of a high-frequency switching power transistor and an inductor. The voltage conversion module boosts the 3.7V to 4.2V output voltage from the 18650 lithium-ion battery pack to a constant 5V DC output. The boost performance of the voltage conversion module directly determines the charging rate of the energy storage capacitor module and the consistency of single-pulse output.

[0041] The core component of the energy storage capacitor module is the farad capacitor. The farad capacitor is electrically connected between the output of the voltage conversion module and the primary current regulation module. The farad capacitor functions as a transient power discharge device in the current transformer polarity tester. Since the 18650 lithium-ion battery pack cannot directly withstand short-circuit current surges, the farad capacitor utilizes its equivalent series resistance characteristic to release a pulse current into the primary test circuit at the moment the trigger switch is turned on. To protect the voltage conversion module, a current-limiting resistor is connected in series between the output of the voltage conversion module and the positive terminal of the farad capacitor to limit the transient current during the initial charging phase.

[0042] Electric field energy stored in a farad capacitor Follow the formula:

[0043]

[0044] In the formula, $E$ represents the energy stored in the farad capacitor, measured in joules (J); $C$ represents the nominal capacitance of the farad capacitor, measured in farads (F). This is the real-time voltage output from the voltage conversion module to the two ends of the supercapacitor, measured in volts (V).

[0045] The charging process of the farad capacitor is constrained by the output capability of the voltage conversion module and the resistance value of the current-limiting resistor. The response time constant of the charging circuit... Conforms to the formula:

[0046]

[0047] In the formula, This is the charging time constant, in seconds (s). The output internal resistance of the voltage conversion module is expressed in ohms (Ω). The resistance value of the current-limiting resistor connected in series in the charging circuit is expressed in ohms (Ω). This is the capacitance of the farad capacitor.

[0048] The energy management system integrates charge / discharge management logic circuitry. This logic circuitry connects the external charging interface to the 18650 lithium-ion battery pack. The external charging interface uses a standard USB interface and can receive 5V DC power from a mobile phone charger or portable power supply. The charge / discharge management logic circuitry includes a lithium battery management chip. This chip senses the feedback pin voltage of the 18650 lithium-ion battery pack and switches between constant current and constant voltage modes. When the terminal voltage of the 18650 lithium-ion battery pack reaches 4.2V, the battery management chip reduces the charging current to prevent overcharging.

[0049] The 18650 lithium-ion battery pack is equipped with a hardware protection board. This board monitors the terminal voltage of the 18650 lithium-ion battery pack in real time. When the terminal voltage of the 18650 lithium-ion battery pack falls below a preset discharge cutoff threshold, the hardware protection board automatically disconnects the electrical connection between the 18650 lithium-ion battery pack and the voltage conversion module.

[0050] The current transformer polarity tester is also equipped with an auxiliary output unit. The auxiliary output unit is electrically connected to the 5V output terminal of the voltage conversion module. The auxiliary output unit includes a standard USB output port for connecting external USB lighting fixtures. The power supply logic of the auxiliary output unit is independent of the primary-side test pulse discharge logic, ensuring that the lighting current of the auxiliary output unit will not interfere with the test pulse waveform during testing. The common terminal of the auxiliary output unit, along with the negative terminal of the supercapacitor and the negative terminal of the 18650 lithium-ion battery pack, are all connected to the reference ground potential point of the metal shielding casing.

[0051] By configuring an 18650 lithium-ion battery pack and a farad capacitor, the current transformer polarity tester achieves energy storage and power output. The 18650 lithium-ion battery pack ensures the device has the power to support multiple tests, while the farad capacitor ensures that the test current can be output within milliseconds, meeting the excitation strength required for current transformer polarity verification.

[0052] For the circuit connections of components such as the pulse width modulation controller, power MOSFET, and filter inductor inside the voltage conversion module, those skilled in the art can implement them according to the design specifications of DC boost circuits. The specific switching power supply topology is well-known in the field and will not be elaborated upon here. A metal shielding shell covers the 18650 lithium-ion battery pack, voltage conversion module, and energy storage capacitor module to prevent high-frequency switching noise and external electromagnetic fields from affecting the energy conversion process.

[0053] The primary-side high-current pulse generation and regulation circuit constructs a discharge loop through an energy storage capacitor module, a trigger switch, a primary current regulation module, and a primary test output terminal. The supercapacitor in the energy storage capacitor module serves as the energy release source. The positive terminal of the supercapacitor is electrically connected to the input contact of the trigger switch, and the output contact of the trigger switch is electrically connected to the input terminal of the primary current regulation module. The output terminal of the primary current regulation module is connected to the positive terminal of the primary test module. The negative terminal of the primary test module is connected to the negative terminal of the supercapacitor, forming a current return path.

[0054] The primary current regulation module employs a high-power wire-wound potentiometer, which is connected in series to the discharge circuit. The high-power wire-wound potentiometer adjusts the total equivalent impedance of the circuit by changing the number of turns of the resistor coil connected to the circuit. When testing current transformers with different turns ratios, the peak value of the pulse current output from the primary side is adjusted within the range of 1A to 30A by rotating the adjustment knob of the high-power wire-wound potentiometer.

[0055] Peak current of the primary side pulse discharge circuit at the moment the trigger switch is turned on Follow the formula:

[0056]

[0057] In the formula, This is the peak current of the primary side pulse discharge circuit, measured in amperes (A). The voltage across the supercapacitor at the moment of triggering, measured in volts (V). This is the resistance value of the high-power wire-wound potentiometer connected in the circuit, in ohms (Ω). It is the sum of the equivalent series resistance and the internal wire resistance of the farad capacitor, and the unit is ohms (Ω). The DC resistance of the primary winding of the current transformer under test is expressed in ohms (Ω).

[0058] The primary current regulation module adjusts the current by... The value is adjusted to ensure that the rate of change of magnetic flux generated by the primary side pulse discharge circuit meets the induction requirements of current transformers with different turns ratios. For current transformers with larger turns ratios, the input resistance of the high-power wire-wound potentiometer is reduced to increase the current. .

[0059] The trigger switch is a normally open high-current push-button switch. The trigger switch is mounted on the panel of a metal-shielded enclosure. When the trigger switch is pressed, the supercapacitor, the high-power wire-wound potentiometer, and the primary winding of the current transformer under test form a closed conducting state, releasing the charge stored in the supercapacitor to the primary output terminal.

[0060] During the discharge process, the change of current in the primary side pulse discharge circuit with time It conforms to the transient formula:

[0061]

[0062] In the formula, During the discharge process The instantaneous current value at a given moment, expressed in amperes (A). The total equivalent resistance of the discharge circuit is, i.e. The sum of , in ohms (Ω); is the base of the natural logarithm; The discharge time constant is given by the formula. The calculation shows that, among which This is the capacitance of the farad capacitor.

[0063] The primary test output terminals are fixed to the side of the metal shielded enclosure. The positive terminal of the primary test is defined as P1, and the negative terminal is defined as P2. Both terminals are connected to the primary winding of the current transformer under test via a test cable.

[0064] For the winding materials of high-power wire-wound potentiometers and the specific mechanical life parameters of the trigger switches, those skilled in the art can select the appropriate components according to the conventional standards for power testing equipment. The relevant component parameters are well-known in the field and will not be elaborated upon here. All components of the primary-side high-current pulse generation and regulation circuit are encased in a metal shielded shell, which is connected to the circuit reference ground potential via shielded leads. Through the control of the current amplitude by the primary current regulation module, the current transformer polarity tester can generate a transient excitation signal that satisfies the polarity determination.

[0065] The multi-channel secondary-side sensing and display module is mounted on the front panel of a metal-shielded enclosure. The module consists of three electrically identical but independent current detection circuits. The first, second, and third current detection circuits are isolated within the metal-shielded enclosure and are not electrically connected to each other. The first current detection circuit is connected to a first pointer-type milliammeter, the second current detection circuit is connected to a second pointer-type milliammeter, and the third current detection circuit is connected to a third pointer-type milliammeter.

[0066] Three current detection circuits are connected to the outside of the metal shielding housing via three pairs of secondary-side test terminals. The three pairs of secondary-side test terminals include a first channel terminal pair, a second channel terminal pair, and a third channel terminal pair. Each terminal pair contains one positive terminal and one negative terminal. The positive terminal of the first channel terminal pair is electrically connected to the positive terminal of the first pointer-type milliammeter, and the negative terminal of the first channel terminal pair is electrically connected to the negative terminal of the first pointer-type milliammeter. The second and third current detection circuits use the same wiring method.

[0067] The pointer-type milliammeter is a DC milliammeter with a center zero position. The range of the pointer-type milliammeter is -50 mA to +50 mA. When a pulse current is injected into the primary winding of the current transformer under test by the primary side high-current pulse generation and adjustment circuit, an induced current is generated in the secondary winding of the current transformer under test. .

[0068] Induced current The instantaneous value follows the following induction formula:

[0069]

[0070] In the formula, This is the instantaneous value of the induced current on the secondary side, in amperes (A). The mutual inductance coefficient between the primary and secondary windings of the current transformer under test is expressed in Henry (H). This represents the rate of change of the primary pulse current over time. The DC resistance of the secondary winding of the current transformer under test is expressed in ohms (Ω). The internal resistance of the corresponding channel pointer-type milliammeter is expressed in ohms (Ω).

[0071] The multi-channel secondary-side sensing display module is connected to the three independent secondary windings of the current transformer under test through the first channel terminal pair, the second channel terminal pair, and the third channel terminal pair. When the trigger switch is turned on, causing a pulse current to be generated on the primary side, the three sets of current detection circuits simultaneously capture the induced charge of each winding, driving the pointers of the first pointer milliammeter, the second pointer milliammeter, and the third pointer milliammeter to deflect.

[0072] The pointer deflection direction of a pointer-type milliammeter is used to determine polarity. The positive terminal of the primary test is connected to the primary side P1 terminal of the current transformer under test. When the positive terminal of the first channel terminal pair is connected to the secondary side S1 terminal of the current transformer under test and the pointer deflects in the positive direction, the winding is determined to be subtractive polarity. If the pointer deflects in the negative direction, the winding is determined to be additive polarity.

[0073] The three pointer-type milliammeters of the multi-channel secondary-side sensing display module are embedded in the panel holes of the metal shielded housing. The metal shielded housing is electrically connected to the reference ground potential of the internal current detection circuit. For the dial damping coefficient and the number of turns of the meter coil of the pointer-type milliammeter, those skilled in the art can select the appropriate model according to general standards for current measuring instruments. The specific meter manufacturing process is well-known in the field and will not be elaborated here. Through the parallel configuration of three independent circuits, the current transformer polarity tester can achieve synchronous acquisition and classified display of the polarity states of multiple sets of secondary windings under a single trigger operation.

[0074] The polarity determination logic and algorithm are based on Faraday's law of electromagnetic induction. When a large current pulse is generated and the regulating circuit injects a time-varying pulse current into the primary winding of the current transformer under test... At this time, an alternating magnetic flux is generated inside the iron core of the current transformer being tested. .

[0075] The induced electromotive force generated by the secondary winding of the current transformer under test It conforms to the following physical formula:

[0076]

[0077] In the formula, The induced electromotive force generated by the secondary winding is expressed in volts (V). The number of turns in the secondary winding of the current transformer under test; The magnetic flux generated by the primary pulse current is expressed in Weber (Wb). The mutual inductance coefficient between the primary and secondary windings of the current transformer under test is expressed in Henry (H). This is the pulse current value flowing into the primary winding, in amperes (A).

[0078] The polarity determination logic follows the subtractive polarity labeling rule. In the primary side connection of the current transformer polarity tester, the primary test positive terminal is connected to the L1 or P1 terminal of the current transformer under test. In the secondary side connection, the positive terminal of each channel is connected to the K1 or S1 terminal of the current transformer under test. When the primary side pulse current... When it shows an increasing trend, that is Under reduced polarity conditions, the induced current generated in the secondary winding It flows out from the S1 terminal.

[0079] Induced current in the secondary circuit The value and direction conform to the following formula:

[0080]

[0081] In the formula, This is the induced current on the secondary side, measured in amperes (A). To induce electromotive force; The DC resistance of the secondary winding of the current transformer under test is expressed in ohms (Ω). This is the internal resistance of a pointer-type milliammeter, measured in ohms (Ω). The equivalent resistance of the connecting wire is expressed in ohms (Ω).

[0082] For multi-channel parallel testing scenarios, the decision logic incorporates loop verification based on Kirchhoff's current law. Under the condition that the secondary sides of the three-phase current transformers have a common connection point, the secondary currents of each phase satisfy the following relationship at the common node:

[0083]

[0084] In the formula, For the first public node The secondary induced current. The current transformer polarity tester determines whether the polarity of the three-phase current transformer is consistent by observing the consistency of the deflection of the three pointer-type milliammeters in the multi-channel secondary side induction display module. If current is injected into the primary side of all three phases from terminal P1, and the deflection direction of a corresponding pointer-type milliammeter is opposite to that of the other two phases, then that phase is determined to be reverse polarity connected.

[0085] The polarity determination logic is implemented as follows: When the trigger switch is pressed, the primary side large current pulse generation and adjustment circuit... Instantaneous increase. If the pointers of the first, second, or third pointer-type milliammeter swing to the right (i.e., the positive scale direction), the polarity of the corresponding secondary winding is determined to be the same as that of the primary winding, indicating a decreasing polarity, which conforms to the engineering wiring standard. If the pointers swing to the left (i.e., the negative scale direction), the corresponding secondary winding is determined to be an increasing polarity.

[0086] For polarity detection of inductive voltage transformers, the same electromagnetic induction principle is used for the determination logic. The discharge current is controlled within the bearing range of the primary winding of the voltage transformer through the primary current regulation module, and the direction of operation of the pointer-type milliammeter on the secondary side is observed.

[0087] To suppress high-frequency oscillation interference during signal transmission, those skilled in the art can achieve this by connecting a filter capacitor in parallel across the pointer-type milliammeter. Specific hardware filtering schemes are well-known technologies in this field and will not be elaborated upon here. The metal shielding enclosure provides a shielded environment for the implementation of the above polarity determination logic, preventing the induced electromotive force generated by the substation operating equipment from being superimposed on the secondary test circuit. Through the combination of the above determination logic and physical formulas, the current transformer polarity tester accurately verifies the correspondence between the primary and secondary terminals of the current transformer.

[0088] The electromagnetic interference (EMI) suppression design and shielding are achieved through the combined action of a metal shielding shell, internal grounding layout, and filtering unit. The metal shielding shell is made of aluminum-magnesium alloy, with a wall thickness ranging from 2.0mm to 3.0mm. The metal shielding shell forms a closed EMI shielding cavity, enclosing the internal wiring of the 18650 lithium-ion battery pack, voltage conversion module, energy storage capacitor module, primary current regulation module, and multi-channel secondary-side sensing and display module within the aluminum-magnesium alloy material.

[0089] The shielding effectiveness of a metal shielding enclosure against external electromagnetic fields Conforms to the formula:

[0090]

[0091] In the formula, The shielding effectiveness is measured in decibels (dB). The electric field strength outside the metal shielding shell is expressed in volts per meter (V / m). The electric field strength inside the metal shielding enclosure is expressed in volts per meter (V / m).

[0092] The common reference ground potential point of the internal circuit of the current transformer polarity tester is electrically connected to the inner wall of the metal shielding shell via a grounding lead. The metal shielding shell is connected to the outer metal rings of the three pointer-type milliammeters in the multi-channel secondary side induction display module via a grounding lead. This connection method ensures that the metal shielding shell and the internal measurement circuit are at the same potential. When the current transformer polarity tester is in a high-voltage, strong electric field environment in a substation, the induced charge generated by the external electric field accumulates on the surface of the metal shielding shell and is distributed through the shielding layer, preventing the induced charge from entering the first, second, or third current detection circuit and generating error current.

[0093] Each current detection loop in the multi-channel secondary-side sensing display module is equipped with a high-frequency suppression unit. The high-frequency suppression unit includes a ceramic capacitor connected in parallel to the input of the pointer-type milliammeter. The capacitance of the ceramic capacitor is selected to be between 0.1μF and 0.47μF. Utilizing its low impedance characteristics, the ceramic capacitor directs the high-frequency radiated noise generated by the primary-side large current pulse generation and adjustment circuit during discharge to ground potential.

[0094] The absorption loss of electromagnetic waves by the metal shielding shell Follow the formula:

[0095]

[0096] In the formula, Absorption loss is expressed in decibels (dB). The thickness of the metal shielding shell is expressed in meters (m). The frequency of electromagnetic waves is measured in Hertz (Hz). The relative permeability of the aluminum-magnesium alloy. The relative electrical conductivity of the aluminum-magnesium alloy material.

[0097] The multi-channel secondary-side sensing display module is installed using a tight-fitting process at the opening on the front panel of the metal-shielded housing. A metal shielding mesh is placed beneath the glass of the pointer-type milliammeter. The metal shielding mesh is electrically connected to the metal-shielded housing to prevent external interference from coupling into the internal detection path through the dial opening. The output wires of the primary-side high-current pulse generation and regulation circuit use shielded twisted-pair cables. One end of the shielding layer of the twisted-pair cable is connected to the metal-shielded housing, while the other end is left suspended to reduce mutual inductance interference from the primary pulse discharge to the secondary sensing circuit.

[0098] For the surface coating anti-corrosion process of the metal shielding shell and the crimping terminal structure of the grounding lead, those skilled in the art can select the appropriate type according to the protection standards of power precision instruments. The manufacturing process of the above components is a well-known technology in this field and will not be described in detail here.

[0099] The internal wiring of the current transformer polarity tester follows the principle of spatial isolation between signal lines and power lines. The power supply line from the 18650 lithium-ion battery pack to the voltage conversion module and the signal line pointing to the multi-channel secondary side induction display module are arranged at a 90-degree angle to reduce electromagnetic pulse interference generated during DC boost. Through the physical protection of the metal shielding shell and the equipotential bonding of the internal circuit, the current transformer polarity tester can stably capture weak induced pulse signals in substations with voltage levels of 500kV and above, eliminating the pointer deflection phenomenon caused by spatial electromagnetic fields.

[0100] The multi-winding synchronous current transformer polarity rapid tester achieves functional partitioning through a separate combination structure of the measuring box and the control box. The measuring box serves as the display unit for the induced current, while the control box serves as the pulse charge generation unit. A handle is rotatably connected to the top of the measuring box, enhancing its portability. Both the front and rear ends of the measuring box are secured with latches, with the control box fixedly connected to the lower part of the latches. Through the locking action of the latches, the measuring box and the control box are closed into a single structure when not in testing mode.

[0101] The measuring box contains a first pointer-type milliammeter, a second pointer-type milliammeter, and a third pointer-type milliammeter, all bolted together. The meter heads of these three meters are embedded in openings on the front panel of the measuring box. The front panel of the measuring box has a first channel terminal pair, a second channel terminal pair, and a third channel terminal pair. These terminal pairs are electrically connected to the input terminals of the first, second, and third pointer-type milliammeters via internal wires. The measuring box is made of aluminum-magnesium alloy with a wall thickness of 2.0mm to 3.0mm. A grounding busbar is located on the inner wall of the measuring box, and the metal housings of the first, second, and third pointer-type milliammeters are all connected to this grounding busbar.

[0102] The internal space of the control box houses the power supply, voltage conversion module, energy storage capacitor module, and primary current regulation module. The 18650 lithium-ion battery pack is fixed to the bottom of the control box via battery brackets. The voltage conversion module and energy storage capacitor module are mounted on the side wall of the control box via circuit board supports. The front panel of the control box features a high-power wire-wound potentiometer knob for the primary current regulation module, a trigger switch button, and the primary test positive and negative terminals. The primary test positive and negative terminals use insulated terminals, with the through-parts of the insulated terminals isolated from the aluminum-magnesium alloy casing of the control box by insulating washers.

[0103] The wiring for the primary-side high-current pulse generation and regulation circuit is arranged inside the control box, while the wiring for the secondary-side sensing and display module is arranged inside the measuring box. The measuring box and control box are electrically connected via a multi-core shielded cable. One end of the multi-core shielded cable is connected to the reference ground potential point inside the control box, and the other end is connected to the grounding busbar inside the measuring box, ensuring that the measuring box and control box form an equipotential, closed electromagnetic shielding cavity when locked in place.

[0104] For the snap-fit ​​connection structure between the measuring box and the control box, the pin engagement structure between the handle and the top of the measuring box, and the spring self-locking mechanism of the snap-fit, those skilled in the art can select standard parts according to the mechanical strength requirements of the portable power instrument. The specific construction of the above-mentioned mechanical connection components is well-known in the art and will not be described in detail here. By physically isolating the measuring box and the control box, the electromagnetic interference of the strong magnetic field generated by the energy storage capacitor module during instantaneous discharge on the first pointer-type milliammeter, the second pointer-type milliammeter, and the third pointer-type milliammeter is reduced. Combined with the electromagnetic shielding effectiveness of the aluminum-magnesium alloy material, the detection accuracy of the polarity tester under high electric field conditions at the substation site is guaranteed.

[0105] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A multi-winding synchronous detection current transformer polarity fast test circuit, comprising, characterized in that, It includes a power supply, a voltage conversion module, an energy storage capacitor module, a trigger switch, a primary current regulation module, a primary test positive terminal, a primary test negative terminal, a multi-channel secondary side sensing and display module, and a metal shielding shell; The output terminal of the power supply is electrically connected to the input terminal of the voltage conversion module, and the output terminal of the voltage conversion module is electrically connected to the charging input terminal of the energy storage capacitor module. The energy storage capacitor module includes a supercapacitor. The positive terminal of the supercapacitor is electrically connected to the input contact of the trigger switch. The output contact of the trigger switch is electrically connected to the input terminal of the primary current regulation module. The output terminal of the primary current regulation module is connected to the positive terminal of the primary test module, and the negative terminal of the primary test module is connected to the negative terminal of the supercapacitor. The multi-channel secondary-side sensing display module consists of a first current detection circuit, a second current detection circuit, and a third current detection circuit; the first current detection circuit is connected to a first pointer-type milliammeter, the second current detection circuit is connected to a second pointer-type milliammeter, and the third current detection circuit is connected to a third pointer-type milliammeter; the first current detection circuit, the second current detection circuit, and the third current detection circuit are not interconnected inside the metal shielding shell; The first current detection circuit is connected to the first channel terminal pair, the second current detection circuit is connected to the second channel terminal pair, and the third current detection circuit is connected to the third channel terminal pair. The first channel terminal pair includes a positive terminal and a negative terminal. The positive terminal of the first channel terminal pair is electrically connected to the positive terminal of the first pointer-type milliammeter, and the negative terminal of the first channel terminal pair is electrically connected to the negative terminal of the first pointer-type milliammeter. The second channel terminal pair includes a positive terminal and a negative terminal. The positive terminal of the second channel terminal pair is electrically connected to the positive terminal of the second pointer-type milliammeter, and the negative terminal of the second channel terminal pair is electrically connected to the negative terminal of the second pointer-type milliammeter. The third channel terminal pair includes a positive terminal and a negative terminal. The positive terminal of the third channel terminal pair is electrically connected to the positive terminal of the third pointer-type milliammeter, and the negative terminal of the third channel terminal pair is electrically connected to the negative terminal of the third pointer-type milliammeter.

2. The current transformer polarity fast test circuit for multi-winding synchronous detection according to claim 1, characterized in that, The power supply uses an 18650 lithium-ion battery pack, which is equipped with a hardware protection board; the voltage conversion module contains a DC boost control circuit; and a current-limiting resistor is connected in series between the output terminal of the voltage conversion module and the positive terminal of the supercapacitor.

3. The current transformer polarity fast test circuit for multi-winding synchronous detection according to claim 2, characterized in that, The circuit also includes an external charging interface and a charge / discharge management logic circuit. The external charging interface uses a standard USB interface. The charge / discharge management logic circuit is connected between the external charging interface and the 18650 lithium-ion battery pack. The charge / discharge management logic circuit includes a lithium battery management chip. The output of the voltage conversion module is connected to an auxiliary output unit, which includes a standard USB output port.

4. The current transformer polarity fast test circuit for multi-winding synchronous detection according to claim 1, characterized in that, The primary current regulation module uses a high-power wire-wound potentiometer, which is connected in series to the discharge circuit; the trigger switch is a normally open high-current push-button switch.

5. The current transformer polarity fast test circuit for multi-winding synchronous detection according to claim 2, characterized in that, The metal shielding shell is made of aluminum-magnesium alloy; the negative terminal of the farad capacitor and the negative terminal of the 18650 lithium-ion battery pack are both connected to the reference ground potential point of the metal shielding shell, and the inner wall of the metal shielding shell is electrically connected to the reference ground potential point through a grounding lead.

6. The current transformer polarity fast test circuit for multi-winding synchronous detection according to claim 1, characterized in that, The first current detection circuit, the second current detection circuit, and the third current detection circuit are all equipped with a high-frequency suppression unit; the high-frequency suppression unit includes a ceramic capacitor, which is connected in parallel to the input terminals of the first pointer milliammeter, the second pointer milliammeter, and the third pointer milliammeter, respectively.

7. The current transformer polarity fast test circuit for multi-winding synchronous detection according to claim 1, characterized in that, The first, second, and third pointer-type milliammeters are all DC milliammeters with a center zero position; the range of the first, second, and third pointer-type milliammeters is set from -50 mA to +50 mA.

8. A multi-winding synchronous detection current transformer polarity rapid tester, internally equipped with the multi-winding synchronous detection current transformer polarity rapid test circuit as described in any one of claims 1-7, including a measuring box (2), characterized in that, A handle (3) is rotatably connected to the top of the measuring box (2), and buckles (4) are snapped at both the front and rear ends of the measuring box (2). A control box (1) is fixedly connected to the lower part of the buckles (4).

9. A multi-winding synchronous detection current transformer polarity rapid tester according to claim 8, characterized in that, The measuring box (2) has multiple sets of milliammeters (6) fixedly connected inside, and the control box (1) has a control panel (5) inside.

10. A multi-winding synchronous detection current transformer polarity rapid tester according to claim 8, characterized in that, Both the measuring box (2) and the control box (1) are equipped with multiple sets of wiring ports inside.

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