CN212321729U - Current transformer secondary circuit contact resistance live detection device - Google Patents
Current transformer secondary circuit contact resistance live detection device Download PDFInfo
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- CN212321729U CN212321729U CN202021003016.5U CN202021003016U CN212321729U CN 212321729 U CN212321729 U CN 212321729U CN 202021003016 U CN202021003016 U CN 202021003016U CN 212321729 U CN212321729 U CN 212321729U
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Abstract
The utility model belongs to the technical field of the contact resistance test, especially a current transformer secondary circuit contact resistance live detection device. The electric part is arranged in the shell and comprises a detection wiring module, a power supply module, a voltage-controlled current source module, a current signal detection and conditioning module, a voltage signal detection and conditioning module, an LC alternating current path module, a loop protection module, a CPU control module, a display/operation module and a direction switching module; the CPU control module is connected with the display/operation module, the voltage-controlled current source module, the current signal detection and conditioning module, the voltage signal detection and conditioning module, the direction switching module and the loop protection module; the voltage-controlled current source module is connected with the LC alternating current path module through the direction switching module, and the LC alternating current path module is connected with the loop protection module; the detection wiring module is connected with the loop protection module, the voltage signal detection conditioning module and the detected junction box loop.
Description
Technical Field
The utility model belongs to the technical field of the contact resistance test, especially a current transformer secondary circuit contact resistance live detection device is applicable to power production under the various environment, especially detects the reliable measuring equipment who requires highly to the power supply.
Background
With the covering application of the electric energy acquisition system, a large number of electric energy metering faults are discovered and processed, wherein the current imbalance phenomenon accounts for a large proportion. At present, the suspected faults can be treated only by power failure detection, and the normal production and life of power consumers are seriously influenced. According to the analysis of the prior detection condition: loose wiring and oxidation of contacts are the most significant failure factors. Meanwhile, due to the fact that wiring is not firm, a circuit is unbalanced due to oxidation of a contact, and faults are eliminated unintentionally due to the fact that related screws are disassembled and screwed again in the conventional power failure detection process, and therefore the fault judgment is difficult. Because the current transformer operating regulations stipulate that open circuit is not allowed, few researches are currently conducted on testing the live contact resistance of the transformer. If the contact resistance of the current secondary circuit can be tested under the condition of normal power utilization, and the comparison between the test values of different phases can judge whether the current imbalance is caused by the contact resistance or the normal phase deviation load. The power failure times can be reduced, the electric quantity loss is reduced, and the potential safety hazard of power failure operation is avoided.
SUMMERY OF THE UTILITY MODEL
The utility model aims at the above-mentioned weak point provide an electrified detection device of current transformer secondary circuit contact resistance, and the device can play a role when not having the contact failure in the measurement judgement current secondary circuit under the situation of not having a power failure, especially adapts to the unbalanced test demand of electric current of examination electric energy collection system discovery.
The utility model discloses an adopt following technical scheme to realize:
a current transformer secondary circuit contact resistance live detection device is composed of a shell and an electrical part, wherein the electrical part is arranged in the shell and comprises a detection wiring module, a power supply module, a voltage-controlled current source module, a current signal detection conditioning module, a voltage signal detection conditioning module, an LC alternating current path module, a circuit protection module, a CPU control module, a display/operation module and a direction switching module;
the CPU control module is respectively connected with the display/operation module, the voltage-controlled current source module, the current signal detection and conditioning module, the voltage signal detection and conditioning module, the direction switching module and the loop protection module; the power supply module is respectively connected with the voltage-controlled current source module, the current signal detection and conditioning module, the voltage signal detection and conditioning module and the CPU control module and provides working electric energy for the connected modules; the voltage-controlled current source module is connected with the LC alternating current path module through the direction switching module, and the LC alternating current path module is connected with the loop protection module in parallel; the detection wiring module is connected with the loop protection module, the voltage signal detection conditioning module and the detected junction box loop;
the detection wiring module consists of a current output line and a voltage signal line, wherein the current output line consists of two lines with the sectional area larger than 2mm2The soft copper wire of form, voltage signal line comprises the shielded paired line of area, and current output line draws forth from return circuit protection module, and voltage signal line draws forth from voltage signal detection conditioning module through direction switching module, uses when needs the utility model discloses the device is done the test, can test on receiving the current wiring hole of measurement terminal box respectively with current output line and voltage signal line.
The CPU control module adopts a commercially available ARM single chip microcomputer as a core, outputs 0-2.5V analog voltage signals transmitted by the voltage-controlled current source module, outputs 0-10A current by the corresponding voltage-controlled current source, and sets the voltage-controlled current source output as follows in the measurement process and sequence: +5A, -4A, +3A, -2A, +1A, -0.5A, +0.2A, 0A, each value measurement time is 2S, so as to verify the contact resistance difference under different currents and realize the demagnetization effect; and collecting digital signals transmitted by the current signal detection and conditioning module and the voltage signal detection and conditioning module, and calculating the resistance value of a secondary loop of the current transformer so as to judge the state of the loop.
The power module is connected with the storage battery connected with the charging module, so that the utility model provides the working electric energy of the device without an external power supply.
Be equipped with switch on the casing, switch links to each other with power module, is used for control the utility model discloses the work of device with stop.
The power module converts the DC power supply sent by the external power adapter or the 24V voltage sent by the internal storage battery into stabilized DC + 24V, + -12V, + -5V +3.3V power supply voltage to be used by other connected modules, the power module can automatically select the internal storage battery as the power supply when no external adaptive power supply exists, and automatically switch the external power supply to supply power when the power adapter is connected, and charge the storage battery.
And the voltage-controlled current source module is used for converting the analog voltage signal sent by the CPU control module into a current signal and amplifying the current by using the current amplifying circuit of the voltage-controlled current source module, thereby realizing the external output of the exciting current.
The current signal detection and conditioning module converts the excitation current output by the voltage-controlled current source module into a voltage signal by using the sampling resistor, conditions the voltage signal by using a current detection chip in the current signal detection and conditioning module, and converts the voltage signal into a digital signal which can be identified by a singlechip of the CPU control module by using an analog-to-digital conversion chip.
The voltage signal detection and conditioning module converts a voltage signal formed by exciting current in a secondary circuit of the current transformer into a digital signal which can be identified by a singlechip of the CPU control module by an analog-to-digital conversion chip after operational amplification conditioning and power frequency filtering.
The LC alternating current path module utilizes a capacitor-inductor series resonance principle, the power frequency impedance is zero when LC resonance occurs, and meanwhile, the capacitor has the characteristic of isolating direct current, so that a power frequency bypass is provided for a secondary circuit of the current transformer, the safety of the secondary circuit is ensured, direct current excitation can only flow from the secondary circuit, and accurate current excitation response is formed.
The circuit protection module is formed by connecting a normally closed relay with the current capacity larger than 10A and a transient suppression diode in parallel, provides an auxiliary bypass path for a secondary circuit with a current transformer and provides an energy leakage path for an LC resonance circuit of the LC alternating current path module; the transient suppression diode is used for preventing the overvoltage of the loop from damaging the measuring device.
The display/operation module consists of a liquid crystal screen and an operation button; the liquid crystal screen is arranged on the shell and is used for displaying the control output, the current detection signal, the voltage detection signal, the relay action state, the secondary circuit state of the current transformer and other information of the device; the operation button provides the operation interaction of the device for the user; the operating button is connected with the CPU control module through a lead; the operation buttons include a confirmation key, a return key, an up key, a down key, a left key, and a right key.
The direction switching module is realized by a double-throw relay through wiring, a forward current test mode is adopted when the CPU controls a low level signal, and a reverse excitation current test mode is adopted when the CPU controls a high level signal, so that the positive and negative (+/-) alternative test of the tested loop is realized.
The utility model discloses the advantage of device includes: the secondary circuit of the current transformer in a charged no-load state is put into an LC alternating current path module to ensure that the secondary side of the current transformer is not opened, and then a controllable direct current excitation is applied to the secondary circuit in a stepping mode; the direct current voltage of the loop is measured, the loop contact resistance is detected by using the ohm law, and then the contact state of the secondary loop is judged through the direct current resistance value. The utility model discloses a design of going on under the electrified condition of side is once special to current transformer, need not the power consumer and have a power failure and can detect current transformer secondary circuit, can generally be applicable to power production under the various environment, especially detect the measuring equipment that the reliable requirement of power supply is high.
Drawings
The present invention will be further explained with reference to the accompanying drawings:
FIG. 1 is a schematic diagram of the structure of the device of the present invention;
FIG. 2 is a schematic diagram of the electrical components of the present invention;
FIG. 3 is a schematic view of the connection mode between the device and the device to be detected when the device of the present invention is in use;
FIG. 4 is a schematic diagram of the voltage signal detecting and conditioning module of the present invention;
fig. 5 is a schematic diagram of the voltage-controlled current source module according to the present invention;
fig. 6 is a schematic diagram of the current signal detecting and conditioning module of the present invention;
fig. 7 is a schematic diagram of the LC ac path module according to the present invention;
fig. 8 is a schematic diagram of the circuit protection module according to the present invention;
fig. 9 is a working schematic diagram of the CPU control module of the present invention;
fig. 10 is a schematic diagram of the operation of the direction switching module of the present invention;
fig. 11 is a schematic diagram of the operation of the power module of the present invention;
fig. 12 is a timing diagram of the excitation current test according to the present invention.
In the figure: 1. the device comprises a shell, 2, a touch display screen, 3, an operation button, 4 and a power switch.
Detailed Description
The present invention will be described in detail with reference to the accompanying drawings 1 to 12 and specific embodiments.
Referring to the attached drawings 1 and 2, the utility model relates to a current transformer secondary circuit contact resistance live detection device comprises casing 1 and electric part, and electric part sets up on the circuit board in casing 1, electric part is including detecting wiring module, power module, voltage-controlled current source module, current signal and taking care of detection module, voltage signal and taking care of detection module, LC interchange route module, return circuit protection module, CPU control module, demonstration/operation module and direction switching module.
The CPU control module is respectively connected with the voltage-controlled current source module, the current signal detection and conditioning module, the voltage signal detection and conditioning module, the direction switching module 1, the direction switching module 2, the protection module and the display/operation module. The voltage-controlled current source module is connected with the direction switching module 1 through a protection fuse and a sampling resistor R9. The current signal detection and conditioning module is connected with the CPU control module after detecting voltage signals at two ends of the sampling resistor R9, the voltage signal detection and conditioning module is connected with the direction switching module 1 and the CPU control module, and the LC alternating current path module is connected with the test cable L2 after being connected with the protection module in parallel. The test cable L1 and the test cable L2 are connected to the device body and the junction box of the circuit under test, respectively.
The CPU control module is used as a control core and outputs controllable direct current exciting current to a tested loop by controlling the voltage-controlled current source module, the current signal detection and conditioning module synchronously detects the exciting current through the sampling resistor R9 and feeds back the exciting current to the CPU control module, the voltage signal detection and conditioning module detects the response voltage of the exciting current in the tested loop through the detection loop, and the CPU control module can calculate the resistance value of the tested loop through the response voltage and the exciting current and draw an exciting response curve.
Because the voltage-controlled current source module can only output unidirectional excitation current, the voltage signal detection conditioning module is only designed aiming at positive voltage, in order to achieve the purpose of testing the electrified excitation current in the negative direction, the voltage signal detection conditioning module and the test cable L1 are connected in series with a direction switching module 1, a direction switching module 2 is connected in series between the voltage-controlled current source module and the LC alternating current path module, and the two direction switching modules have the same principle; the CPU control module outputs high level signals to two modules (a direction switching module 1 and a direction switching module 2) at the same time, and the high level signals correspond to the negative excitation current testing direction; when low level signals are output simultaneously, the testing direction of the positive exciting current is corresponded to, and therefore the alternating testing effect of the positive exciting current and the negative exciting current is achieved.
The display/operation module adopts a commercially available 5-inch touch display screen 2, the display/operation module and the CPU control module are matched to display the tested voltage and current parameters, display the test process and display the measurement judgment result, and meanwhile, the touch display screen 2 is utilized to convey the operation of a user to the CPU control module to achieve the effect of control interaction. In order to control conveniently, the display/operation module also adopts an operation button 3, and the operation button 3 is connected with the CPU control module through a lead; operating button 3 includes power key, last key, lower key, left key, right key, enter key and returns the key, and the power key is opened and is closed the utility model discloses the device, last key, lower key, left key, right key are used for the adjustment to select the function menu position, and enter key is used for confirming the menu function of selecting, returns the key and is used for returning higher level's menu.
Referring to fig. 3, in the detection connection module of the present invention, L1 and L2 are test cables, test cable L1 is a current output cable, S1 and S2 are end contacts of test cable L1, test cable L2 is a voltage signal acquisition cable, S3 and S4 are end contacts of test cable L2, end contact S1 of test cable L1 and end contact S3 of test cable L2 are connected to an input position of the connection box at the same time, end contact S2 of test cable L1 and end contact S4 of test cable L2 are connected to an output position of the connection box at the same time; the test cable L1 and the test cable L2 are subjected to branching measurement, so that the situation that a current transformer and an electric energy meter are detected after being disassembled from a junction box is avoided, the tightness degree of an original wiring screw is not damaged, the contact condition of a loop is reflected most accurately, and the situation that the current transformer loop is detected due to the fact that the resistance of a test wire of the test cable L1 divides voltage signals.
Referring to fig. 4, the utility model discloses a voltage signal detects and conditions module, the test cable L2 shown in fig. 3 will be measured the voltage signal transmission of return circuit and put AD629 to the accurate fortune in fig. 4, accurate fortune is put AD629 and has the characteristics of measuring differential signal under the high common mode voltage, through accurate fortune put AD629 can furthest reduce the common mode interference of outside test loop, carry out once isolation to the outside return circuit simultaneously, accurate fortune is put AD629 and is measured the return circuit response voltage signal with the difference voltage signal promptly and pass through the power frequency band elimination filter that becomes by resistance R1, resistance R2, resistance R3, electric capacity C1, electric capacity C2, electric capacity C3 and fortune are put OP1 and fortune are put OP2 in fig. 4, further filter the power frequency interference that obtains in the voltage signal; the power frequency band elimination filter filters power frequency interference in the voltage signals transmitted by the precision operational amplifier AD629 and then transmits the voltage signals to the sampling module, the analog voltage signals are converted into 16-bit digital signals which can be processed by the CPU control module, and the digital voltage signals are transmitted to the CPU control module for processing. The values of the resistor R1 and the resistor R2 are 318.4 kOmega, the values of the capacitor C1 and the capacitor C2 are 0.01uF, the value of the resistor R3 is 159.2 kOmega, and the value of the capacitor C3 is 0.02 uF; the resistor R4 is a potentiometer and is used for adjusting the quality of the power frequency band-stop filter; the operational amplifiers OP1 and OP2 are operational amplifiers, generally, a high-gain and low-bias OP77 operational amplifier is selected; the sampling module adopts a high-precision 16-bit AD7606 model digital-to-analog conversion chip.
Referring to fig. 5, the voltage-controlled current source module is used for converting a voltage of 0-2.5V sent by a single chip microcomputer of the CPU control module into a current of 0-10A for output, the voltage-controlled current source module adopts an operational amplifier OP3 as a front-end operational amplifier, and a field effect transistor IRF530 is connected in series behind an operational amplifier OP 3; the positive phase input end of the operational amplifier OP3 is connected in series with a resistor R5 and a capacitor C5 in sequence and then grounded; the drain (D pole) of the field effect transistor IRF530 is grounded through a resistor R6, and the resistor R6 is a sampling resistor; the source electrode (S pole) end of the field effect transistor IRF530 is connected with a capacitor C4 and a resistor R7 in series; the operational amplifier OP3 adopts OP77 model low load regulation rate high gain low offset operational amplifier, utilizes the sampling resistor R6 to convert the voltage analog signal transmitted by the CPU control module into current signal, and utilizes the field effect transistor IRF530 as current expanding loop to increase the current output power and output the current. Wherein, the resistor R5 is a 470 omega common metal film resistor; the resistor R6 is a sampling resistor with a resistance value of 3 omega formed by connecting 4 precise metal film resistors with the precision of 12 omega and the temperature drift coefficient of 0.1% and the temperature drift coefficient of 25ppm in parallel, the field effect transistor IRF530 adopts a chip with the model of IRF530 as a current expansion element, the resistor R7 adopts a metal film resistor with the resistance value of 3 omega and the power of 2W, and the capacitor C5 is a 0.1uF capacitor.
Referring to fig. 6, the current signal detecting and conditioning module adopts a current detecting chip, a VCC terminal of the current detecting chip is grounded through a capacitor C6, and an OUT terminal of the current detecting chip is connected in series with an operational amplifier OP 4; a detection end A and a detection end B which are connected with two ends of the sampling resistor R9 in the picture 2 are respectively led out from the current detection chip; the current signal detection and conditioning module detects the excitation current by measuring the voltage signals generated at two ends of the sampling resistor R9 when the excitation current flows through the sampling resistor R9 in fig. 2. The sampling resistor R9 in fig. 2 uses a low temperature coefficient manganin sampling resistor with a typical value of 10m omega. The voltage signals at the two ends of the manganin sampling resistor have the characteristics of potential suspension and small potential difference. The current signal detection and conditioning module selects a special current detection chip MAX4173T/F/H type chip, and is matched with a following circuit consisting of an operational amplifier OP4 to convert and condition a suspended excitation current signal into a voltage signal which can be measured, send the voltage signal to a digital-to-analog conversion sampling chip and then convert the voltage signal into a digital current signal which can be processed by a CPU control module.
Referring to fig. 7, the LC ac path module includes an LC resonant circuit at 50Hz power frequency, which is composed of an inductor L8 and a capacitor C7, and a filter capacitor C9 and a filter capacitor C8 are connected in parallel to the LC resonant circuit; the LC resonance circuit only provides a passage for power frequency and high frequency, and has an isolation effect on excitation current and direct current voltage. Wherein, the inductance L1 takes the value of 0.001H, and the capacitance C1 takes the value of 0.01014F; the LC alternating current path module provides a power frequency path for an external tested loop, particularly a current transformer, and the open-circuit state of the current transformer is avoided when the tested loop is untied. The capacitor C9 and the capacitor C8 are BP capacitors of 1uF and 0.01uF respectively, and provide high-frequency and secondary high-frequency paths for the loop.
Referring to fig. 8, the circuit protection module is composed of a transistor Q1, a relay and a TVS, wherein the input end of the transistor Q1 is connected with the control signal of the CPU control module, the emitter of the transistor Q1 is connected with the resistor R8 and the coil of the relay, and the contact of the relay is connected in parallel with the TVS. The circuit protection module is used for preventing overvoltage from occurring in the test circuit and is connected with TVS in parallel at two ends of the current output terminal; normally closed relay passes through the triode drive, is the closure state under the normal conditions, will the utility model discloses the device inserts when being surveyed the return circuit, has guaranteed that current transformer is in the closure state, opens triode output high level drive relay through CPU control module at the test stage, and the LC power frequency resonance circuit of figure 7 this moment still can provide the interchange passageway for external current transformer, avoids current transformer open circuit state, after the test, CPU control module output low level, and the relay is closed, ensures that the outside is surveyed current transformer and is in the short-circuit condition.
Referring to fig. 9, a CPU control module as a control core outputs a controllable dc excitation current to a measured loop by controlling a voltage-controlled current source module, a current signal conditioning and detecting module synchronously detects the magnitude of the excitation current through a sampling resistor and feeds the detected excitation current back to the CPU control module, a voltage signal conditioning and detecting module detects the response voltage of the excitation current in the measured loop through the detection loop, and the CPU control module can calculate the contact resistance value of the measured loop through the response voltage and the excitation current and draw a loop excitation response curve. The CPU control module controls the action of the relay of the protection module by outputting a control signal to the protection module, so that the protection control is enhanced. The CPU control module outputs control signals to the direction switching module 1 and the direction switching module 2 to realize the positive and negative direction switching of the exciting current of the tested loop.
The CPU control module adopts an ARM chip model STM32F407, has low power consumption and high calculation performance, is provided with a GPIO interface, can drive the relay of the protection module to open and close, can drive the relay of the direction switching module to open and close, can read the voltage signal and the current signal transmitted by the voltage signal conditioning module and the current signal conditioning detection module, and can calculate the contact resistance of a tested loop. The CPU control module is provided with an analog-to-digital conversion interface which can output a direct current control voltage signal to the voltage-controlled current source module so as to output a controllable current to the tested loop. Typical values and orders are set as: +5A, -4A, +3A, -2A, +1A, -0.5A, +0.2A, 0A, so as to verify the contact resistance difference under different currents and realize the demagnetization effect.
Referring to fig. 10, the direction switching module includes two double-throw relays, a transistor Q2 and a resistor R18, a relay coil is connected to an emitter of the transistor Q2, a terminal J11 of the relay JDQ1 is connected to a terminal J23 of the relay JDQ2, and a terminal J13 of the relay JDQ1 is connected to a terminal J21 of the relay JDQ2, and the direction switching module switches contact positions by driving the double-throw relays to be turned on and off by using the transistor, and then can realize a forward current excitation test mode when a low level signal is sent from the CPU control module according to a connection mode shown in fig. 10. When the CPU control module sends a high level signal, the test mode is a reverse current excitation test mode.
Referring to fig. 11, the power module includes a storage battery, a DC/DC ± 12V DC power module, a DC/DC5V DC power module, a voltage regulator (AMS 1117 chip) and a transistor Q13, the power adapter 24V input is connected to the storage battery via a diode D11 and a triode Q13, the storage battery is connected to DC/DC ± 12V and DC/DC5V via a power switch, DC/DC5V is converted into a 3.3V voltage via the AMS1117 chip to supply power to the CPU control module, and the power switch is disposed on the housing. The power module can automatically select the commercial power or the storage battery as the power supply of the device of the utility model, and output the power of + 24V, + 12V, +5V, +3.3V to each module stably. The power adapter selects a commercial AC 220-DC 24V power adapter, a triode Q13 and a diode D11 form a power selection circuit, when the commercial power is available, Q13 is conducted, the storage battery is charged and supplies power to the device, when the commercial power is not available, Q13 is closed, the storage battery supplies power to the device, and the power module adopts a commercial DC/DC +/-12V, DC/DC5V chip and an AMS1117 chip to convert the power supply voltage of each module and supply power.
Referring to the attached figure 12, an excitation current test time sequence relation diagram is shown, a CPU control module outputs a voltage analog signal of 0-2.5V, a voltage-controlled current source module is used for outputting excitation current of 0-10A, a direction switching module is used for exciting current of-10A-plus-10A, and specifically, the excitation current time sequence test shown in the figure 12 is adopted.
The utility model discloses the concrete test method of device, including following step:
(1) testing the wiring;
connecting one end of a test cable L1 to a device voltage detection terminal, connecting an S1 contact at the other end of the test cable L1 to an A terminal position (a CT side vacant terminal) of an electric energy meter junction box lead-in wire, and connecting an S2 contact of the test cable L1 to a b terminal position (an electric energy meter side vacant terminal) of an electric energy meter junction box lead-out wire; connecting one end of a test cable L2 to a device current output terminal, connecting an S3 joint at the other end of the test cable L2 to an A terminal position (a CT side vacant terminal) of an electric energy meter junction box lead-in wire, and connecting an S4 joint at the other end of the test cable L2 to a b terminal position (an electric energy meter side vacant terminal) of an electric energy meter junction box lead-out wire;
(2) the power switch is turned on to enable the device to start working, the CPU control module controls the relay of the protection module to be closed by default, the poking piece of the tested junction box is poked to the idle connection position, namely, the short circuit state is not generated, and at the moment, the current transformer is still in the short circuit state through the closing of the relay;
(3) the CPU control module controls the relay of the protection module to be disconnected, the LC alternating current access module is in a resonance state at the moment, the tested current transformer is still in a short-circuit state for power frequency, and the tested current transformer is in an open-circuit state for direct current.
(4) The CPU control module controls the voltage-controlled current to output the excitation current 5A for 2 seconds, the current signal detection and conditioning module tests that the output current 5A is consistent with a set value, the voltage signal detection and conditioning module tests a response voltage signal of a tested loop under the excitation current of +/-5A and sends the response voltage signal to the CPU control module for calculation, and the CPU control module calculates the contact resistance when the +/-5A is excited;
(5) the CPU control module controls to output 4A excitation current and controls a direction switching loop to realize the contact resistance test and record of the-4A excitation current;
(6) sequentially adjusting the CPU control module to control the excitation current and adjusting the direction switching circuit, and testing the contact resistance corresponding to the +5A, -4A, +3A, -2A, +1A, -0.5A, +0.2A and 0A excitation current; the corresponding time sequences of the excitation currents +5A, -4A, +3A, -2A, +1A, -0.5A, +0.2A and 0A are 0-2 s, 2-4 s, 4-6 s, 6-8 s, 8-10 s, 10-12 s, 12-14 s and 14-16 s respectively;
(7) the CPU control module controls the relay of the protection loop to be closed, and displays the contact resistance, the measurement time sequence and the excitation current magnitude curve of the tested loop so as to judge the state of the tested loop.
(8) And after the power switch is turned off, the terminal box shifting sheet is recovered, and the test wiring is removed, so that the test is completed.
The utility model discloses constitute by two sets of test wires, utilize the terminal box wiring, furthest reduces to being surveyed the return circuit and changes, and test cable L1 and L2' S S1 and S3, S2 and S4 are connected at binding post play, avoid the current output cable to being surveyed the return circuit influence. Power module can judge automatically and select to use commercial power or battery to do the utility model discloses the power supply provides power supply simultaneously for the device charges for the battery when inserting the commercial power, utilizes the battery to do when no commercial power the utility model discloses the device supplies power. The voltage signal conditioning and detecting module utilizes a differential operational amplifier to avoid common-mode interference, utilizes a double-T power frequency band elimination filter circuit to filter power frequency interference, and converts the power frequency interference into a digital signal which can be processed by a CPU through a high-precision digital-to-analog converter. Typical values and orders for the excitation pattern are set as: +5A, -4A, +3A, -2A, +1A, -0.5A, +0.2A, 0A, so as to verify the contact resistance difference under different currents and realize the demagnetization effect. The voltage-controlled current source module is characterized in that a voltage-controlled current composed of a high-precision operational amplifier and a Moss tube is utilized, and a voltage signal output by a CPU can be converted into a current to excite a tested loop. The current signal detection module utilizes a special current detection chip and a sampling resistor to form a current detection loop which can measure the potential suspension characteristic. The CPU control module outputs different torrent currents by controlling the voltage-controlled current source, collects the response voltage and the real output current value of the tested loop, and calculates the contact resistance of the tested loop under different excitation currents (typical values +5A, -4A, +3A, -2A, +1A, -0.5A, + 0.2A) by using the ohm law so as to judge the contact condition of the secondary loop of the current transformer. And comparing the different phase test values to judge whether the three-phase current imbalance reason is caused by contact resistance or normal phase deflection load. The LC alternating current path module utilizes an LC resonance principle to form a series power frequency resonance circuit with LC to provide a power frequency circuit for a tested circuit, and the current transformer is ensured to be in a non-open-circuit low-resistance state. Its characteristic of return circuit protection module utilizes TVS to carry out overvoltage protection to the binding post, prevents that the overvoltage in the return circuit is right the utility model discloses components and parts damage, utilize CPU control relay's break-make simultaneously, for being surveyed return circuit current transformer provides the short circuit route, reduce the risk of opening a way. Meanwhile, after the test is finished, the resonance circuit provides an energy discharge channel by conducting the relay.
The utility model discloses testing arrangement discovers through the in-service use, and the wiring is simple, and the test is accurate, because need not the power consumer and have a power failure and can detect current transformer secondary circuit, therefore convenient to use can generally be applicable to power production under the various environment, especially detects to the reliable measuring equipment that requires height of power supply.
Claims (7)
1. The utility model provides a current transformer secondary circuit contact resistance live detection device which characterized in that: the electric part is arranged in the shell and comprises a detection wiring module, a power supply module, a voltage-controlled current source module, a current signal detection and conditioning module, a voltage signal detection and conditioning module, an LC alternating current path module, a loop protection module, a CPU control module, a display/operation module and a direction switching module;
the CPU control module is respectively connected with the display/operation module, the voltage-controlled current source module, the current signal detection and conditioning module, the voltage signal detection and conditioning module, the direction switching module and the loop protection module; the power supply module is respectively connected with the voltage-controlled current source module, the current signal detection and conditioning module, the voltage signal detection and conditioning module and the CPU control module and provides working electric energy for the connected modules; the voltage-controlled current source module is connected with the LC alternating current path module through the direction switching module, and the LC alternating current path module is connected with the loop protection module in parallel; the detection wiring module is connected with the loop protection module, the voltage signal detection conditioning module and the detected junction box loop;
the voltage-controlled current source module is used for converting the analog voltage signal sent by the CPU control module into a current signal and amplifying the current by using the current amplifying circuit of the voltage-controlled current source module, so that the external output of the exciting current is realized;
a protection fuse, a sampling resistor and a diode are connected in series between the voltage-controlled current source module and the LC alternating current path module, the current signal detection and conditioning module converts the excitation current output by the voltage-controlled current source module into a voltage signal by using the sampling resistor, conditions the voltage signal by using a current detection chip in the current signal detection and conditioning module, and converts the voltage signal into a digital signal which can be identified by a singlechip of the CPU control module by using an analog-to-digital conversion chip;
the voltage signal detection and conditioning module is used for converting a voltage signal formed by exciting current in a secondary circuit of the current transformer into a digital signal which can be identified by a singlechip of the CPU control module by an analog-to-digital conversion chip after operational amplification conditioning and power frequency filtering;
the LC alternating current path module utilizes a capacitor-inductor series resonance principle, the power frequency impedance is zero when LC resonance occurs, and meanwhile, the capacitor has the characteristic of isolating direct current, so that a power frequency bypass is provided for a secondary circuit of the current transformer, the safety of the secondary circuit is ensured, direct current excitation can only flow from the secondary circuit, and accurate current excitation response is formed;
the circuit protection module is formed by connecting a normally closed relay with the current capacity larger than 10A and a transient suppression diode in parallel, provides an auxiliary bypass path for a secondary circuit with a current transformer and provides an energy leakage path for an LC resonance circuit of the LC alternating current path module.
2. The apparatus for detecting the electrification of the contact resistance of the secondary circuit of the current transformer according to claim 1, wherein: the detection wiring module consists of a current output line and a voltage signal line, wherein the current output line consists of two lines with the sectional area larger than 2mm2The voltage signal line is led out from the circuit protection module, and the voltage signal line is led out from the voltage signal detection conditioning module through the direction switching module.
3. The apparatus for detecting the electrification of the contact resistance of the secondary circuit of the current transformer according to claim 1, wherein: the CPU control module adopts an ARM single chip microcomputer as a core, outputs 0-2.5V analog voltage signals transmitted by the voltage-controlled current source module, outputs 0-10A current by the corresponding voltage-controlled current source, and sets the voltage-controlled current source output to be in the measuring process and in the order: +5A, -4A, +3A, -2A, +1A, -0.5A, +0.2A, 0A, each value measurement time is 2S, so as to verify the contact resistance difference under different currents and realize the demagnetization effect; and collecting digital signals transmitted by the current signal detection and conditioning module and the voltage signal detection and conditioning module, and calculating the resistance value of a secondary loop of the current transformer so as to judge the state of the loop.
4. The apparatus for detecting the electrification of the contact resistance of the secondary circuit of the current transformer according to claim 1, wherein: and the power module is connected with a storage battery connected with the charging module.
5. The apparatus for detecting the electrification of the contact resistance of the secondary circuit of the current transformer according to claim 1, wherein: the power module converts the DC power supply sent by the external power adapter or the 24V voltage sent by the internal storage battery into stabilized DC + 24V, + -12V, + -5V +3.3V power supply voltage to be used by other connected modules, the power module can automatically select the internal storage battery as the power supply when no external adaptive power supply exists, and automatically switch the external power supply to supply power when the power adapter is connected, and charge the storage battery.
6. The apparatus for detecting the electrification of the contact resistance of the secondary circuit of the current transformer according to claim 1, wherein: and the shell is provided with a power switch which is connected with the power module and used for controlling the work and stop of the device.
7. The apparatus for detecting the electrification of the contact resistance of the secondary circuit of the current transformer according to claim 1, wherein: the display/operation module consists of a liquid crystal screen and an operation button; the liquid crystal screen is arranged on the shell; the operating button is connected with the CPU control module through a lead; the operation buttons include a confirmation key, a return key, an up key, a down key, a left key, and a right key.
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| CN202021003016.5U CN212321729U (en) | 2020-06-04 | 2020-06-04 | Current transformer secondary circuit contact resistance live detection device |
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| CN202021003016.5U CN212321729U (en) | 2020-06-04 | 2020-06-04 | Current transformer secondary circuit contact resistance live detection device |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111487466A (en) * | 2020-06-04 | 2020-08-04 | 国网江苏省电力有限公司宿迁供电分公司 | Electrified detection device for direct current resistance of secondary circuit of current transformer |
| CN111487469A (en) * | 2020-06-04 | 2020-08-04 | 国网江苏省电力有限公司宿迁供电分公司 | Current transformer secondary circuit contact resistance live detection device |
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2020
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111487466A (en) * | 2020-06-04 | 2020-08-04 | 国网江苏省电力有限公司宿迁供电分公司 | Electrified detection device for direct current resistance of secondary circuit of current transformer |
| CN111487469A (en) * | 2020-06-04 | 2020-08-04 | 国网江苏省电力有限公司宿迁供电分公司 | Current transformer secondary circuit contact resistance live detection device |
| CN111487469B (en) * | 2020-06-04 | 2024-06-04 | 国网江苏省电力有限公司宿迁供电分公司 | Electrified detection device for contact resistance of secondary circuit of current transformer |
| CN111487466B (en) * | 2020-06-04 | 2024-06-07 | 国网江苏省电力有限公司宿迁供电分公司 | Electrified detection device for direct-current resistor of secondary loop of current transformer |
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