CN219574243U - High-resistance fault loop resistance precision measurement circuit for railway signal cable - Google Patents
High-resistance fault loop resistance precision measurement circuit for railway signal cable Download PDFInfo
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- CN219574243U CN219574243U CN202320279294.0U CN202320279294U CN219574243U CN 219574243 U CN219574243 U CN 219574243U CN 202320279294 U CN202320279294 U CN 202320279294U CN 219574243 U CN219574243 U CN 219574243U
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y04—INFORMATION OR COMMUNICATION TECHNOLOGIES HAVING AN IMPACT ON OTHER TECHNOLOGY AREAS
- Y04S—SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS
- Y04S10/00—Systems supporting electrical power generation, transmission or distribution
- Y04S10/50—Systems or methods supporting the power network operation or management, involving a certain degree of interaction with the load-side end user applications
- Y04S10/52—Outage or fault management, e.g. fault detection or location
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Abstract
The utility model relates to a railway signal cable high-resistance fault loop resistance precise measurement circuit which comprises a first cable wiring terminal, a second cable wiring terminal, an AD converter, a controller, a reference resistor and an operational amplifier, wherein the first cable wiring terminal and the second cable wiring terminal are respectively connected with two ends of a tested cable, the first cable wiring terminal and the second cable wiring terminal are connected with the input end of the AD converter, the second cable wiring terminal is grounded through the reference resistor, the reference voltage end of the reference resistor is connected with the reference voltage end of the AD converter and the inverting input end of the operational amplifier, the output end of the AD converter is connected with the input end of the controller, and the output end of the operational amplifier is connected with the first cable wiring terminal. According to calculation, the equivalent loop resistance of the tested cable is only related to the reference resistance, so that the detection precision can be improved.
Description
Technical Field
The utility model relates to a high-resistance fault loop resistance precise measurement circuit for a railway signal cable.
Background
Railway signal cables require periodic measurements of loop resistance to ensure that the condition of the cable is good. The prior art is that the staff measures the ring resistance of cable with the universal meter, however, the precision of universal meter is limited, can cause certain detection error when the universal meter is operated by the manual work moreover. Most importantly, the existing measurement mode involves relatively many electrical parameters of other devices, and if errors exist in the electrical parameters of the other devices, the detection accuracy of the cable loop resistance is affected.
Disclosure of Invention
The utility model provides a railway signal cable high-resistance fault loop resistance precise measurement circuit which is used for solving the technical problem that the precision of the existing cable loop resistance detection mode is not high.
A railway signal cable high-resistance fault loop resistance precision measurement circuit comprises:
the first cable connecting terminal and the second cable connecting terminal are used for connecting two ends of a tested cable respectively;
an AD converter;
a controller;
a reference resistor; and
an operational amplifier;
the first cable binding post and the second cable binding post are connected the input of AD converter, the second cable binding post passes through reference resistance ground connection, reference voltage end of reference resistance connects the reference voltage end of AD converter with operational amplifier's inverting input, the output of AD converter is connected the input of controller, operational amplifier's output is connected first cable binding post.
In one embodiment, the railway signal cable high-resistance fault loop resistance precision measurement circuit further comprises a DA converter, wherein the output end of the controller is connected with the input end of the DA converter, and the output end of the DA converter is connected with the non-inverting input end of the operational amplifier.
In one embodiment, the railway signal cable high-resistance fault loop resistance precision measurement circuit further comprises a man-machine interface, and the interaction end of the controller is connected with the man-machine interface.
In one embodiment, the railway signal cable high-resistance fault loop resistance precision measurement circuit further comprises a temperature sensor for detecting the ambient temperature at the tested cable, and the output end of the temperature sensor is connected with the input end of the controller.
The technical effects of the utility model include: based on each component and circuit connection relation of the railway signal cable high-resistance fault loop resistance precise measurement circuit provided by the utility model, the calculation shows that the equivalent loop resistance of the measured cable is only related to the resistance value of the reference resistor, and the electrical parameters of other related devices are fewer, so that the railway signal cable high-resistance fault loop resistance precise measurement circuit can improve the detection precision and avoid detection interference caused by other factors.
Drawings
FIG. 1 is a circuit diagram of a railway signal cable high resistance fault loop resistance precision measurement circuit;
fig. 2 is a schematic diagram of a circuit for detecting a high-resistance fault loop resistance precision measurement of a railway signal cable.
Detailed Description
As shown in fig. 1, the present embodiment provides a railway signal cable high-resistance fault loop resistance precision measurement circuit, which includes a first cable connection terminal P1, a second cable connection terminal P2, an AD converter U1, a controller M1, a reference resistor Rref and an operational amplifier U2.
The first cable connection terminal P1 and the second cable connection terminal P2 are used for respectively connecting two ends of a tested cable, in particular a railway signal cable. As a specific embodiment, since it is necessary to apply a current to the cable under test, for ease of understanding, it is set that the cable under test has a current input end and a current output end, and the first cable connection terminal P1 is connected to the current input end of the cable under test, and the second cable connection terminal P2 is connected to the current output end of the cable under test. The AD converter U1 is a conventional conversion device that converts an analog signal into a digital signal. The controller M1 is a conventional control chip such as a Microprocessor (MCU). The reference resistor Rref is used for providing a reference resistance value, and the resistance value is determined according to actual needs. The operational amplifier U2 may be a conventional operational amplifier device, and in this embodiment, the operational amplifier U2 is a precision operational amplifier.
The first cable connection terminal P1 and the second cable connection terminal P2 are connected to input terminals of the AD converter U1, i.e., analog signal input terminals (AIN 0 and AIN1 terminals). The second cable connection terminal P2 is grounded through a reference resistor Rref, a reference voltage end of the reference resistor Rref, that is, a non-grounded end is connected with a reference voltage end (Vref end) of the AD converter U1 and an inverting input end of the operational amplifier U2, an output end of the AD converter U1 is connected with an input end of the controller M1, and an output end of the operational amplifier U2 is connected with the first cable connection terminal P1.
As a specific embodiment, the railway signal cable high-resistance fault loop resistance precision measurement circuit further comprises a DA converter U3, wherein the DA converter U3 is a conversion device for converting a conventional digital signal into an analog signal. The output end of the controller M1 is connected with the input end of the DA converter U3, and the output end of the DA converter U3 is connected with the non-inverting input end of the operational amplifier U2.
As a specific implementation mode, the railway signal cable high-resistance fault loop resistance precision measurement circuit further comprises a human-computer interface U4, such as a touch screen or a combination of a display screen and a keyboard, and the interactive end of the controller M1 is connected with the human-computer interface U4 to realize data display and data input.
As a specific implementation mode, the railway signal cable high-resistance fault loop resistance precision measurement circuit further comprises a temperature sensor U5, wherein the temperature sensor U5 is used for detecting the ambient temperature of a measured cable, the distance between the temperature sensor U5 and the measured cable is relatively short, the reliability of a temperature detection result is improved, and more preferably, the temperature sensor U5 can be fixed on the surface of the measured cable. The output end of the temperature sensor U5 is connected with the input end of the controller M1.
The detection process of the equivalent loop resistance of the cable under test is described with reference to fig. 2.
In fig. 2, rx represents an equivalent loop resistance of a cable to be measured, R0 represents an equivalent resistance of a stylus or a lead, vref represents a reference voltage (i.e., a voltage of a reference resistor Rref), vi represents an AD acquisition voltage, vx represents a terminal voltage of the cable to be measured, vda represents an output voltage of the DA converter U3, I1 represents an excitation current, I2 represents a load current, and I3 represents a reference current.
The cable under test is connected to the measurement circuit in fig. 1. The test principle and procedure of the cable loop resistance are deduced below.
(1) Excitation current generation:
the exciting current mainly comprises a constant current source circuit consisting of an operational amplifier U2, a reference resistor Rref, a DA converter U3 and an equivalent loop resistance Rx of a tested cable, and an adjustable current source is provided for the test circuit. The DA converter U3 outputs the voltage Vda to the non-inverting input terminal of the operational amplifier U2, and the voltage Vref across the reference resistor Rref is inputted to the inverting input terminal of the operational amplifier U2. The operational amplifier U2 is an in-phase amplifier, and according to the characteristics of the operational amplifier, the output voltage Vda of the DA converter U3 is equal to the voltage of the reference resistor Rref:
Vda＝Vref
(2) Current path:
the non-inverting and inverting inputs of the operational amplifier U2 and the differential input of the AD converter U1 are both high impedance inputs, and no current flows. The excitation current I1, the load current I2 in the cable under test and the current I3 in the reference resistor Rref are therefore all equal:
I1＝I2＝I3
(3) Reference voltage of AD converter U1:
the reference voltage of the AD converter U1 is the voltage value at two ends of the reference resistor Rref, and the ohm law indicates that the reference voltage Vref of the AD converter U1 is equal to the excitation current Ix multiplied by the resistance value of the reference resistor Rref:
Vref＝I3×Rref
(4) AD acquisition voltage:
the resolution of the AD converter U1 is 16 bits, let the discretized data of the AD conversion be D, and according to the principle of AD sampling, the AD acquires the voltage:
(5) Measured cable terminal voltage:
the measured cable terminal voltage Vx is equal to the resistance of the equivalent loop resistance Rx of the cable multiplied by the current flowing I2 according to ohm's law:
Vx＝I2×Rx
(6) Relation between AD acquisition voltage and cable terminal voltage:
since the input channel of the AD converter U1 is a high impedance input, no current flows, so the current flowing through the equivalent resistor R0 of the stylus or lead is zero, and the AD pickup voltage Vi is equal to the terminal voltage Vx of the cable:
Vi＝Vx
(7) Solving a system of equations according to the above relation:
solving the equation set can be:
(8) Conclusion reached in (7)Wherein Rref is a precise resistor with a fixed resistance value, D is discretized data acquired by AD of the AD converter U1, and the equivalent loop resistance Rx of the tested cable can be calculated.
(9) Test error analysis:
from the formulaIt can be seen that, through the carefully designed precise measurement circuit, the loop resistance of the cable to be measured is irrelevant to the reference voltage of the AD converter U1, the accuracy of the excitation current I1, the accuracy of the DA converter U3, the factors such as the stylus or the lead resistor R0, and the like, and is only relevant to the resistance value of the reference resistor Rref, so that the test accuracy can be significantly improved. If the accuracy of the resistance value of the reference resistor Rref is 0.01%, the test accuracy of the cable loop resistance is also 0.01%, and the length error of the cable with the length of 10km is only 1 meter.
After the cable loop resistance is obtained, the cable length can be calculated. Effect of ambient temperature on calculated cable length: the loop resistance Rx of the cable is measured, the resistance per unit length of the railway signal cable at 20 ℃ is generally 22.5 omega/km, and the formula can be usedThe length of the cable (in meters) was calculated. It appears that the measurement of the loop resistance Rx of the cable can be counted as long as it is sufficiently accurateThe relatively accurate cable length is calculated, but the influence of the ambient temperature on the calculated cable length is ignored, the temperature coefficient of the signal cable is equal to 4000ppm, and the measurement error is very large when the ambient temperature changes greatly, so that the influence of the ambient temperature at the measured cable needs to be considered. Therefore, the temperature sensor U4 is added in the test circuit to measure the ambient temperature of the tested cable, and the corresponding loop resistance value at the ambient temperature (such as 20 ℃) can be obtained according to the temperature coefficient of the signal cable, so that the more accurate cable length can be calculated.
Therefore, by means of precise circuit design, influences of factors such as reference voltage, exciting current, meter pen or lead resistor R0, system internal resistance and the like are eliminated, and more accurate cable loop resistance values can be measured. And the ring resistance value corresponding to the ambient temperature is calculated through the temperature coefficient, so that the influence of the ambient temperature on the test result is eliminated, and the calculated cable length is more accurate.
Claims (4)
1. A railway signal cable high-resistance fault loop resistance precision measurement circuit is characterized by comprising:
the first cable connecting terminal and the second cable connecting terminal are used for connecting two ends of a tested cable respectively;
an AD converter;
a controller;
a reference resistor; and
an operational amplifier;
the first cable binding post and the second cable binding post are connected the input of AD converter, the second cable binding post passes through reference resistance ground connection, reference voltage end of reference resistance connects the reference voltage end of AD converter with operational amplifier's inverting input, the output of AD converter is connected the input of controller, operational amplifier's output is connected first cable binding post.
2. The precise measurement circuit for high-resistance fault loop resistance of railway signal cable according to claim 1, wherein the precise measurement circuit for high-resistance fault loop resistance of railway signal cable further comprises a DA converter, an output end of the controller is connected to an input end of the DA converter, and an output end of the DA converter is connected to a non-inverting input end of the operational amplifier.
3. The railway signal cable high-resistance fault loop resistance precision measurement circuit according to claim 1, further comprising a human-machine interface, wherein the interaction end of the controller is connected with the human-machine interface.
4. The precise measurement circuit for high-resistance fault loop resistance of railway signal cable according to claim 1, wherein the precise measurement circuit for high-resistance fault loop resistance of railway signal cable further comprises a temperature sensor for detecting the ambient temperature of the tested cable, and an output end of the temperature sensor is connected with an input end of the controller.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202320279294.0U CN219574243U (en) | 2023-02-21 | 2023-02-21 | High-resistance fault loop resistance precision measurement circuit for railway signal cable |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202320279294.0U CN219574243U (en) | 2023-02-21 | 2023-02-21 | High-resistance fault loop resistance precision measurement circuit for railway signal cable |
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| Publication Number | Publication Date |
|---|---|
| CN219574243U true CN219574243U (en) | 2023-08-22 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202320279294.0U Active CN219574243U (en) | 2023-02-21 | 2023-02-21 | High-resistance fault loop resistance precision measurement circuit for railway signal cable |
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2023
- 2023-02-21 CN CN202320279294.0U patent/CN219574243U/en active Active
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