System, method and equipment for measuring alternating current resistance of cable

Abstract

The embodiment of the invention provides a cable alternating current resistance measuring system, method and equipment. The system comprises a power supply unit, a zero-phase closing switch unit, a transition loop unit, a to-be-measured cable and a cable measurement loop unit, and the zero-phase closing switch unit is connected with the transition loop unit and the cable measurement loop unit and used for controlling connection or disconnection between the transition loop unit or the cable measurement loop unit and the power supply unit. The power supply unit is connected with the zero-phase closing switch unit and is used for supplying power to the transition loop unit or the cable measurement loop unit, and the transition loop unit is connected with the zero-phase closing switch unit and is used for stably transitioning closing overvoltage generated by the power supply unit to preset voltage; and the cable measurement loop unit is connected with the zero-phase closing switch and the cable to be measured and is used for determining the alternating-current resistance of the cable to be measured. According to the technical scheme, the influence of switching-on overvoltage in a loop can be avoided, and the alternating-current resistance of the to-be-tested cable can be accurately obtained.

Description

Technical Field

[0001] This application relates to the field of power testing technology, and in particular to a system, method and device for measuring the AC resistance of a cable. Background Technology

[0002] Large-section cables, as key components in power transmission systems, are widely used in high-voltage transmission, industrial power distribution, rail transportation, and new energy grid connection. Due to their large cross-sectional area, the AC resistance of the cable directly affects the system's transmission efficiency, energy consumption, and equipment lifespan. In engineering practice, the AC resistance of the cable needs to be determined through experimental measurement to evaluate its current carrying capacity, thermal stability, and electrical performance.

[0003] Currently, the measurement of AC resistance of cables mainly relies on calorimetry and electrical methods. Calorimetry calculates AC resistance by measuring the heat generated when the cable is energized and combining this with the principle of heat transfer; electrical methods are based on Ohm's law and calculate AC resistance by directly measuring the voltage and current signals of the cable.

[0004] However, traditional measurement methods are prone to transient overvoltages and harmonic interference at the moment of closing the circuit breaker, which can damage the measuring equipment or distort the measurement data, resulting in poor accuracy of AC resistance testing. Summary of the Invention

[0005] This application provides a system, method, and device for measuring the AC resistance of cables, in order to improve the accuracy of AC resistance testing of cables.

[0006] In a first aspect, embodiments of this application provide a cable AC resistance measurement system, comprising: a power supply unit, a zero-phase closing switch unit, a transition circuit unit, a cable under test, and a cable measurement circuit unit;

[0007] The zero-phase closing switch unit is connected to the transition circuit unit and the cable measurement circuit unit respectively, and is used to control the connection or disconnection between the transition circuit unit and the power supply unit, and to control the connection or disconnection between the cable measurement circuit unit and the power supply unit.

[0008] The power supply unit is connected to the zero-phase closing switch unit and is used to supply power to the transition circuit unit when the zero-phase closing switch controls the transition circuit unit to connect with the power supply unit, or to supply power to the cable measurement circuit unit when the zero-phase closing switch controls the cable measurement circuit unit to connect with the power supply unit.

[0009] The transition circuit unit is connected to the zero-phase closing switch and is used to smoothly transition the closing overvoltage generated by the power supply unit to a preset voltage when the zero-phase closing switch controls the transition circuit unit to connect with the power supply unit.

[0010] The cable measurement circuit unit is connected to the zero-phase closing switch and the cable under test, respectively, and is used to determine the AC resistance of the cable under test when the zero-phase closing switch controls the transition circuit unit to disconnect from the power supply unit according to the preset voltage, and controls the cable measurement circuit unit to connect to the power supply unit.

[0011] In one or more embodiments, the zero-phase closing switch unit further includes: a voltage sensor, a phase resolution unit, and an execution unit;

[0012] The voltage sensor is connected to the power supply unit and is used to collect the first voltage data of the power supply unit in real time.

[0013] The phase resolution unit is connected to the voltage sensor and is used to determine the voltage phase of the first voltage data;

[0014] The execution unit is connected to the transition circuit unit and the cable measurement circuit unit respectively, and is used to control the on / off state of the transition circuit unit and the cable measurement circuit unit according to the voltage phase.

[0015] In one or more embodiments, the transition circuit unit further includes: a current-limiting resistor and a filter capacitor;

[0016] The current-limiting resistor is used to control the current amplitude of the transition circuit unit to be less than a first preset threshold.

[0017] The filter capacitor is used to filter out high-frequency harmonics in the voltage data of the transition circuit unit.

[0018] In one or more embodiments, the transition loop unit further includes: a parameter adjustment unit;

[0019] The parameter adjustment unit is used to adjust the first parameter of the current-limiting resistor and the second parameter of the filter capacitor.

[0020] In one or more embodiments, the cable measurement circuit unit further includes: a cable fixing unit, a current transformer, and a data acquisition and processing unit;

[0021] The cable fixing unit is connected to the cable under test and is used to fix the cable under test.

[0022] The current transformer is connected to the cable under test and is used to control the current data of the cable under test.

[0023] The data acquisition and processing unit is connected to the current transformer and the cable under test, respectively, and is used to acquire and process the voltage and current data of the cable under test.

[0024] In one or more embodiments, the data acquisition and processing unit further includes: a first digital signal processor, a second digital signal processor, and a data processing unit;

[0025] The first digital signal processor is connected to the current transformer and is used to collect the first current data of the cable under test.

[0026] The second digital signal processor is connected to the cable under test and is used to acquire the second voltage data of the cable under test;

[0027] The data processing unit is connected to the first digital signal processor and the second digital signal processor, and is used to perform conversion processing on the first current data and the second voltage data.

[0028] Secondly, embodiments of this application provide a method for measuring the AC resistance of a cable, applied to a cable measurement circuit unit in the cable AC resistance measurement system described in the first aspect, the method comprising:

[0029] Acquire the first current data and the second voltage data of the cable under test;

[0030] The first current data is adjusted until it equals the current carrying capacity of the cable under test, and at least one second current data and at least one corresponding third voltage data of the cable under test are determined.

[0031] The AC resistance data of the cable under test is determined based on the at least one second current data and the corresponding at least one third voltage data.

[0032] In one or more embodiments, determining the AC resistance data of the cable under test based on the at least one second current data and the corresponding at least one third voltage data includes:

[0033] Based on the at least one second current data and the corresponding at least one third voltage data, at least one first AC resistance data of the cable under test is determined;

[0034] The AC resistance data of the cable under test are determined by summing and averaging all the first AC resistance data.

[0035] In one or more embodiments, the method further includes:

[0036] The first current data and the second voltage data are converted to obtain the first current waveform data and the second voltage waveform data.

[0037] The first current waveform data and the second voltage waveform data are visualized.

[0038] Thirdly, embodiments of this application provide a cable AC resistance measuring device, which is applied to a cable measuring circuit unit in the cable AC resistance measuring system described in the first aspect, the device comprising:

[0039] The acquisition module is used to acquire the first current data and the second voltage data of the cable under test.

[0040] The processing module is used to adjust the first current data until the first current data is equal to the current carrying value of the cable under test, and to determine at least one second current data and at least one corresponding third voltage data of the cable under test.

[0041] The determination module is used to determine the AC resistance data of the cable under test based on the at least one second current data and the corresponding at least one third voltage data.

[0042] In one or more embodiments, the determining module is specifically used for:

[0043] Based on the at least one second current data and the corresponding at least one third voltage data, at least one first AC resistance data of the cable under test is determined;

[0044] The AC resistance data of the cable under test are determined by summing and averaging all the first AC resistance data.

[0045] In one or more embodiments, the processing module is further configured to:

[0046] The first current data and the second voltage data are converted to obtain the first current waveform data and the second voltage waveform data.

[0047] The first current waveform data and the second voltage waveform data are visualized.

[0048] Fourthly, embodiments of this application provide an electronic device, the electronic device comprising: the above-described cable AC resistance measurement system;

[0049] Or / and, the electronic device includes: a cable measurement loop unit in the cable AC resistance measurement system, the cable measurement loop unit being used to perform the method described above.

[0050] This application provides a system, method, and apparatus for measuring the AC resistance of a cable. The system includes: a power supply unit, a zero-phase closing switch unit, a transition circuit unit, a cable under test, and a cable measurement circuit unit. The zero-phase closing switch unit is connected to both the transition circuit unit and the cable measurement circuit unit, and is used to control the connection or disconnection between the transition circuit unit or the cable measurement circuit unit and the power supply unit. The power supply unit is connected to the zero-phase closing switch unit to supply power to the transition circuit unit or the cable measurement circuit unit. The transition circuit unit is connected to the zero-phase closing switch unit to smoothly transition the closing overvoltage generated by the power supply unit to a preset voltage. The cable measurement circuit unit is connected to both the zero-phase closing switch unit and the cable under test, and is used to determine the AC resistance of the cable under test. The technical solution of this application can avoid the influence of closing overvoltage in the circuit and accurately obtain the AC resistance of the cable under test. Attached Figure Description

[0051] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0052] Figure 1 Schematic diagram of the structure of the cable AC resistance measurement system provided in the embodiments of this application Figure 1 ;

[0053] Figure 2 Schematic diagram of the structure of the cable AC resistance measurement system provided in the embodiments of this application Figure 2 ;

[0054] Figure 3 Schematic diagram of the structure of the cable AC resistance measurement system provided in the embodiments of this application Figure 3 ;

[0055] Figure 4 Schematic diagram of the structure of the cable AC resistance measurement system provided in the embodiments of this application Figure 4 ;

[0056] Figure 5 Schematic diagram of the structure of the cable AC resistance measurement system provided in the embodiments of this application Figure 5 ;

[0057] Figure 6 Schematic diagram of the structure of the cable AC resistance measurement system provided in the embodiments of this application Figure 6 ;

[0058] Figure 7 A schematic flowchart illustrating the method for measuring the AC resistance of a cable provided in an embodiment of this application;

[0059] Figure 8A schematic diagram of the structure of the cable AC resistance measuring device provided in the embodiments of this application;

[0060] Figure 9 This is a schematic diagram of the structure of an electronic device provided in an embodiment of this application.

[0061] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0062] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0063] Before introducing the embodiments of this application, the terms involved in the embodiments of this application will be explained first:

[0064] Overvoltage during closing: refers to a pulse voltage exceeding the effective value of the voltage generated when the transformer secondary side is closed;

[0065] Zero phase: refers to the zero-crossing moment of a sinusoidal current or voltage waveform;

[0066] AC resistance of a cable: refers to the active resistance of a cable that transmits AC power. Its value is greater than that of DC resistance and requires correction through calculation and estimation as well as actual experimental measurement.

[0067] Next, the application background of the embodiments of this application will be explained:

[0068] Large-section cables, as key components in power transmission systems, are widely used in high-voltage transmission, industrial power distribution, rail transportation, and new energy grid connection. Due to their large cross-sectional area, the AC resistance of the cable directly affects the system's transmission efficiency, energy consumption, and equipment lifespan. In engineering practice, the AC resistance of the cable needs to be determined through experimental measurement to evaluate its current carrying capacity, thermal stability, and electrical performance.

[0069] Currently, the measurement of AC resistance of cables mainly relies on calorimetry and electrical methods. Calorimetry calculates AC resistance by measuring the heat generated when the cable is energized and combining this with the principle of heat transfer; electrical methods are based on Ohm's law and calculate AC resistance by directly measuring the voltage and current signals of the cable.

[0070] During the measurement of AC resistance of cables, the traditional closing method can interfere with the measurement signal. One issue is the generation of transient harmonics. When the voltage is at a non-zero crossing point, especially near the voltage peak, closing the switch on a capacitive or nonlinear load circuit can excite the circuit's inherent oscillations. These oscillations typically have frequencies much higher than the power frequency, potentially reaching thousands of hertz, and include high-order harmonic components. Therefore, during experimental measurements, the transient harmonics generated at the moment of closing the switch are superimposed on the inherent harmonics of the power grid, causing severe distortion of the measurement results.

[0071] On the other hand, it generates inrush current, which is a huge decaying current. For measurement personnel, this makes the testing work difficult because the huge inrush current may trigger the protection circuit device, making it impossible to carry out subsequent normal load tests; it will also affect the stable power measurement value.

[0072] However, traditional measurement methods are prone to transient overvoltages and harmonic interference at the moment of closing the circuit breaker, which can damage the measuring equipment or distort the measurement data, resulting in poor accuracy of AC resistance testing.

[0073] The cable AC resistance measurement system provided in this application aims to solve the aforementioned technical problems of the prior art. The technical concept of this application is as follows: Due to the small AC resistance of large-section cables, the cable test circuit is equivalent to an unloaded circuit during the closing circuit, generating closing overvoltage. Traditional testing methods may cause damage to cable testing equipment and distortion in cable AC resistance measurement due to closing overvoltage, inrush current, and harmonic interference. Therefore, this application considers stabilizing the closing overvoltage in the circuit before measuring the AC resistance of the cable under test. In the technical solution of this application, a transition circuit unit is set up to achieve a smooth voltage transition. Furthermore, a zero-phase closing switch unit is set up to monitor the voltage phase. After the voltage stabilizes at a preset voltage, the transition circuit unit is disconnected from the power supply unit, and the cable measurement circuit unit is connected to the power supply unit, ensuring that closing is completed near the voltage zero-crossing point, suppressing transient inrush current and harmonic interference, and thus accurately measuring the AC resistance of the cable under test.

[0074] The technical solution of this application and how the technical solution of this application solves the above-mentioned technical problems are described in detail below with specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments. The embodiments of this application will now be described with reference to the accompanying drawings.

[0075] Figure 1 Schematic diagram of the structure of the cable AC resistance measurement system provided in the embodiments of this application Figure 1 .like Figure 1As shown, the AC resistance measurement system for this cable includes: a power supply unit, a zero-phase closing switch unit, a transition circuit unit, the cable under test, and a cable measurement circuit unit.

[0076] The following implementation instructions apply to this AC resistance measurement system for cables:

[0077] 1) The zero-phase closing switch unit is connected to the transition circuit unit and the cable measurement circuit unit respectively, and is used to control the connection or disconnection between the transition circuit unit and the power supply unit, and to control the connection or disconnection between the cable measurement circuit unit and the power supply unit.

[0078] For example, the zero-phase closing switch unit is connected to the transition circuit unit and the cable measurement circuit unit respectively, and precisely controls the connection status of the two circuits with the power supply unit. It can connect or disconnect the transition circuit unit and the power supply unit separately, and can also independently control the connection between the cable measurement circuit unit and the power supply unit, ensuring that the two circuits will not be connected to the power supply at the same time and cause conflict.

[0079] In one possible implementation, the zero-phase closing switch unit mainly adopts a double-contact zero-phase switch, with two independently controlled contact channels inside the switch, corresponding to the transition circuit unit and the cable measurement circuit unit respectively. Furthermore, it can automatically switch the contact state according to the phase of the voltage detection signal, achieving orderly switching of the transition circuit unit and the cable measurement circuit unit, while maintaining voltage phase consistency during the switching process without any abrupt changes.

[0080] 2) The power supply unit is connected to the zero-phase closing switch unit and is used to supply power to the transition circuit unit when the zero-phase closing switch control transition circuit unit is connected to the power supply unit, or to supply power to the cable measurement circuit unit when the zero-phase closing switch control cable measurement circuit unit is connected to the power supply unit.

[0081] For example, the power supply unit is connected to the zero-phase closing switch unit only through a single interface and is not directly connected to other circuits. Its power supply direction is entirely determined by the control state of the zero-phase closing switch unit. When the zero-phase closing switch unit controls the transition circuit unit to connect with the power supply unit, the power output of the power supply unit is directed to the transition circuit unit; when the zero-phase closing switch unit switches to connect the cable measurement circuit unit with the power supply unit, the power supply unit then provides stable power to the cable measurement circuit unit.

[0082] In one possible implementation, the power supply unit uses a 220V industrial frequency AC power supply, providing a sinusoidal voltage with an effective value of 220V-1% to 220V+1% and a frequency of 50Hz. It is fixedly connected to the input terminal of the zero-phase closing switch unit through a wire, without the need for additional manual wiring. The power supply object can be switched simply by switching the contacts of the zero-phase closing switch.

[0083] The power supply unit can also be equipped with a feedthrough transformer with an adjustable turns ratio, which can be used to adjust the voltage supplied by the power supply unit by adjusting the turns ratio.

[0084] 3) The transition circuit unit is connected to the zero-phase closing switch and is used to smoothly transition the closing overvoltage generated by the power supply unit to the preset voltage when the zero-phase closing switch controls the transition circuit unit to connect with the power supply unit.

[0085] For example, one end of the transition circuit unit is connected to the zero-phase closing switch unit to alleviate closing overvoltage. When the zero-phase closing switch unit connects the power supply unit and the transition circuit unit, the instantaneous closing overvoltage generated at the moment the power supply unit closes will enter the transition circuit unit. The transition circuit unit gradually absorbs the overvoltage energy through its own impedance regulation characteristics, and smoothly reduces the voltage to a preset safe voltage value, providing a stable power supply foundation for the subsequent cable measurement circuit connection.

[0086] In one possible implementation, the transition circuit unit adopts an RC series structure, consisting of a current-limiting resistor and a filter capacitor. When an overvoltage is applied, the filter capacitor first absorbs electrical energy to charge, and the current-limiting resistor limits the charging current to avoid impact. Together, they gradually reduce the voltage from the peak value at the moment of closing to a preset stable value of 220V. After the voltage stabilizes, the circuit remains in the conducting state, waiting for the zero-phase closing switch unit to switch the circuit.

[0087] 4) The cable measurement circuit unit is connected to the zero-phase closing switch and the cable under test respectively. It is used to determine the AC resistance of the cable under test when the zero-phase closing switch controls the transition circuit unit to disconnect from the power supply unit according to the preset voltage, and when the cable measurement circuit unit is connected to the power supply unit.

[0088] For example, the cable measurement circuit unit is connected at one end to the zero-phase closing switch unit and at the other end directly to the cable under test. When the zero-phase closing switch unit detects that the voltage after the transition reaches the preset voltage standard, it will simultaneously disconnect the transition circuit unit from the power supply unit and connect the cable measurement circuit unit to the power supply unit. At this time, a stable power supply is connected, and the cable measurement circuit unit collects the current and voltage data of the cable under test and calculates the AC resistance value through a built-in algorithm.

[0089] In one possible implementation, the cable measurement loop unit incorporates a current transformer and a voltage sampling unit, which are connected to both ends of the cable under test via clip-on test terminals. After power is supplied, the current transformer and voltage sampling unit collect real-time data on the operating current and voltage at both ends of the cable under test, transmitting this data to the built-in signal processing unit. Based on Ohm's law, the AC resistance is calculated, and the measurement results are finally output through a visual display interface. The entire process is completed under stable voltage conditions, ensuring data accuracy.

[0090] Furthermore, in this embodiment, the cable under test is a cable with a cross-sectional area ranging from 800mm² to 2000mm². This application embodiment uses a cable with a cross-sectional area of ​​1200mm² for illustration, and its structure is required to be free of mechanical damage and have an intact insulation layer.

[0091] The operating environment conditions for the cable AC resistance measurement system are: temperature 19℃-21℃, humidity 45%RH-5%RH to 45%RH+5%RH, in order to reduce the influence of temperature and humidity on the cable AC resistance measurement.

[0092] The cable AC resistance measurement system provided in this application includes: a power supply unit, a zero-phase closing switch unit, a transition circuit unit, a cable under test, and a cable measurement circuit unit. The zero-phase closing switch unit is connected to both the transition circuit unit and the cable measurement circuit unit, and is used to control the connection or disconnection between the transition circuit unit or the cable measurement circuit unit and the power supply unit. The power supply unit is connected to the zero-phase closing switch unit and is used to supply power to the transition circuit unit or the cable measurement circuit unit. The transition circuit unit is connected to the zero-phase closing switch and is used to smoothly transition the closing overvoltage generated by the power supply unit to a preset voltage. The cable measurement circuit unit is connected to both the zero-phase closing switch and the cable under test, and is used to determine the AC resistance of the cable under test. By applying the technical solution of this application embodiment, the influence of closing overvoltage in the circuit can be avoided, and the AC resistance of the cable under test can be accurately obtained.

[0093] Based on the above embodiments, Figure 2 Schematic diagram of the structure of the cable AC resistance measurement system provided in the embodiments of this application Figure 2 .like Figure 2 As shown, the zero-phase closing switch unit also includes: a voltage sensor, a phase analysis unit, and an execution unit;

[0094] The following implementation instructions apply to this AC resistance measurement system for cables:

[0095] 1) The voltage sensor is connected to the power supply unit to collect the first voltage data of the power supply unit in real time;

[0096] For example, the voltage sensor is directly connected to the power supply unit to collect the first voltage data of the power supply unit in real time, providing the raw signal for subsequent voltage phase determination.

[0097] In one possible implementation, the voltage sensor acquires the voltage waveform on the secondary side of the transformer in the power supply unit in real time, mainly by using a high-speed sampling analog-to-digital converter module to acquire the instantaneous voltage signal.

[0098] 2) The phase resolution unit is connected to the voltage sensor and is used to determine the voltage phase of the first voltage data;

[0099] For example, the phase analysis unit is connected to the voltage sensor, receives the first voltage data transmitted by the voltage sensor, extracts the phase information of the voltage waveform (such as the zero-crossing time and phase angle) through the algorithm, determines the phase state of the current power supply unit voltage, and provides accurate timing basis for zero-phase closing switch switching.

[0100] In one possible implementation, a digital signal processor can be used as the phase analysis unit, with a built-in zero-crossing detection algorithm.

[0101] For example, after receiving the 0-5V voltage signal output by the voltage sensor, the digital signal processor identifies the zero-crossing point of the voltage waveform (phase 0° or 180°) in real time, calculates the phase angle change rate, converts the phase information into a switch execution command, and instructs the zero-phase closing switch unit to perform loop switching.

[0102] 3) The execution unit is connected to the transition circuit unit and the cable measurement circuit unit respectively, and is used to control the on and off of the transition circuit unit and the cable measurement circuit unit according to the voltage phase.

[0103] For example, the execution unit is connected to the transition circuit unit and the cable measurement circuit unit respectively, and controls the switching of the two circuits at the voltage zero crossing point (phase 0°) according to the voltage phase information provided by the phase analysis unit, so as to avoid the closing impact caused by the phase change and ensure a smooth power supply transition.

[0104] In one possible implementation, the execution unit is connected to the phase resolution unit and receives voltage phase information provided by the phase resolution unit.

[0105] In one possible implementation, the execution unit employs a solid-state relay or thyristor, with its control terminal connected to the phase analysis unit. When the phase analysis unit detects a voltage zero-crossing, it outputs a trigger signal, and the relay immediately actuates: disconnecting the transition circuit unit from the power supply unit while simultaneously closing the cable measurement circuit unit from the power supply unit. The entire switching process is completed within 10ms, and the switching time is synchronized with the voltage zero-crossing, achieving zero-phase shockless switching.

[0106] In this embodiment, the zero-phase closing switch unit collects the first voltage data of the power supply unit in real time through a voltage sensor and transmits the first voltage data to the phase analysis unit. The phase analysis unit analyzes the phase angle of the first voltage data. When it detects that the instantaneous voltage value is close to zero, it triggers the execution unit to switch the power supply circuit from the transition circuit unit to the cable test circuit unit, ensuring that the closing operation is completed near the zero point of the voltage and reducing residual voltage jumps.

[0107] In one possible implementation, the zero-phase closing switch unit closes the circuit under the condition that the instantaneous voltage value is zero at the phase point, thereby controlling the sequential switching of the transition circuit unit and the cable measurement circuit unit.

[0108] Secondary voltage of transformer in power supply unit A wave whose relationship with time satisfies a standard sine wave is expressed as follows:

[0109]

[0110] Considering the error and delay time of the closing phase, meaning that the actual closing phase will have a corresponding residual peak voltage, the constraint reference value is the ratio of the residual peak voltage to the maximum peak voltage, referred to as the residual voltage percentage, which satisfies the following formula:

[0111]

[0112]

[0113] in, Indicates the percentage of residual voltage. This represents the secondary voltage of the transformer, i.e., the residual peak voltage corresponding to the actual closing phase. This indicates the maximum peak voltage.

[0114] In one possible implementation, since the AC resistance of a large-section cable is on the order of magnitude small, it can be equivalent to an unloaded line. If the overvoltage caused by closing the unloaded line is considered, the cable measurement circuit unit can be equivalent to a T-shaped equivalent circuit model including a combination of equivalent inductance and equivalent capacitance.

[0115] For the equivalent T-shaped circuit model, the voltage across the equivalent capacitor is... The calculation is as follows:

[0116]

[0117]

[0118]

[0119] in, The effective value of the voltage across the equivalent capacitance can be represented as the voltage amplitude across the cable measurement circuit unit. This represents the oscillation frequency of the equivalent circuit. This indicates the amplitude of the voltage in the power supply unit. This indicates the value of the equivalent inductance. This indicates the capacitance value of the equivalent capacitance.

[0120] Due to practical engineering needs, the effective voltage value of the equivalent capacitance does not need to be substituted with the specific values ​​of the equivalent capacitance and equivalent inductance when calculating the equivalent capacitance; it can be equivalently represented as... The power supply voltage amplitude is times that of the power supply voltage. Represents the oscillation coefficient, the effective value of the voltage across the equivalent capacitance. The calculation is as follows:

[0121]

[0122] in, This represents the oscillation coefficient, which is related to the line parameters. In an unloaded cable line, it is taken as 1.5, resulting in the residual voltage percentage satisfying the following:

[0123]

[0124] Based on the above calculation formula, the zero-phase closing switch unit can achieve relatively precise on / off control at the zero-phase point according to the residual voltage percentage, and control the voltage regulated by the zero-phase closing switch unit within a very small range, thereby preventing overcurrent during circuit switching.

[0125] Determine the percentage of residual voltage Does it meet the requirements? ≤1%, ensuring the voltage is almost zero at the moment of closing. If this condition is met, the zero-phase closing switch unit is directly triggered to perform the switching action, switching from the transition circuit unit to the cable measurement circuit unit; if this condition is not met, the system waits until the next voltage cycle to re-acquire the voltage signal for judgment.

[0126] If the residual voltage percentage If the set range is met, the circuit breaker is considered successfully closed, and the cable AC resistance measurement system can operate normally; if... Too large, such as If the value exceeds 5%, triggering a "closing failure" alarm, the switch must be forcibly disconnected to activate the protection, preventing damage to the equipment in the cable AC resistance measurement system due to inrush current. The cause of the failure should then be checked and analyzed.

[0127] The cable AC resistance measurement system provided in this application includes a zero-phase closing switch unit, which further comprises a voltage sensor, a phase analysis unit, and an execution unit. The voltage sensor is connected to the power supply unit and is used to acquire the first voltage data of the power supply unit in real time. The phase analysis unit is connected to the voltage sensor and is used to determine the voltage phase of the first voltage data. The execution unit is connected to the transition circuit unit and the cable measurement circuit unit respectively and is used to control the switching on and off of the transition circuit unit and the cable measurement circuit unit according to the voltage phase. Applying the technical solution of this application, the first voltage data of the power supply unit is acquired by the voltage sensor, and the phase, frequency, and harmonic distortion rate of the sine wave corresponding to the first voltage data are analyzed by the phase analysis unit. The zero-phase closing switch unit accurately captures the optimal closing time, significantly reducing the impact of residual voltage jumps on the cable under test and system equipment. By setting the zero-phase closing switch unit, the phase shift problem caused by power grid fluctuations or changes in cable parameters can be effectively addressed, further suppressing transient harmonics and inrush currents, improving the stability and safety of the testing process, and extending the service life of the equipment.

[0128] Based on the above embodiments, Figure 3 Schematic diagram of the structure of the cable AC resistance measurement system provided in the embodiments of this application Figure 3 .like Figure 3 As shown, the transition circuit unit also includes: a current-limiting resistor and a filter capacitor;

[0129] The following implementation instructions apply to this AC resistance measurement system for cables:

[0130] 1) The current-limiting resistor is used to control the current amplitude of the transition loop unit to be less than the first preset threshold.

[0131] For example, a current-limiting resistor is used to limit the maximum amplitude of the loop current to ensure that it does not exceed a first preset threshold, thereby preventing excessive current from impacting circuit components or affecting the smooth transition of voltage.

[0132] The current-limiting resistor mainly consumes some electrical energy through its own impedance characteristics, reduces the circuit current intensity, and provides safe conditions for the smooth charging and voltage transition of the filter capacitor.

[0133] In one possible implementation, a power-type metal film resistor is selected as the current-limiting resistor, and the resistance value is calculated and determined based on the power supply output voltage and a first preset threshold.

[0134] For example, when the power supply output is 220V, if the preset current threshold is 5A, a 44Ω / 50W resistor can be selected. The current-limiting resistor is connected in series between the power input terminal of the transition circuit unit and the filter capacitor. When current flows through, its impedance will limit the current peak. Even if there is a sudden current change at the moment of closing, the current can be quickly suppressed within the threshold. At the same time, it has good heat dissipation performance to avoid overheating damage.

[0135] 2) The filter capacitor is used to filter out high-frequency harmonics in the voltage data of the transition circuit unit.

[0136] For example, the filter capacitor is a harmonic suppression element in the transition circuit unit, mainly used to filter out high-frequency harmonic components of the voltage data in the transition circuit, making the voltage waveform smoother and more stable.

[0137] The voltage signal generated when the power supply unit is closed may contain high-frequency interference harmonics. These harmonics can affect the smoothness of voltage transition. The filter capacitor forms a path for the high-frequency signal through its capacitive reactance characteristics, absorbing or bypassing the harmonic energy and retaining a stable fundamental voltage.

[0138] In one possible implementation, a non-polar polypropylene capacitor is used as the filter capacitor, with a capacitance of 10μF and a withstand voltage higher than 1.5 times the power supply output voltage (e.g., 350V) to ensure safe operation in overvoltage scenarios.

[0139] The filter capacitor and the current-limiting resistor are connected in series in the transition circuit. When a voltage containing high-frequency harmonics is applied, the filter capacitor presents a low impedance to the high-frequency components, allowing the harmonic current to be filtered out through the capacitor circuit. Finally, a stable fundamental voltage is output, providing a clean power supply signal for the subsequent cable measurement circuit.

[0140] The cable AC resistance measurement system provided in this application embodiment further includes a current-limiting resistor and a filter capacitor in the transition circuit unit. The current-limiting resistor is used to control the current amplitude of the transition circuit unit to be less than a first preset threshold, and the filter capacitor is used to filter out high-frequency harmonics in the voltage data of the transition circuit unit. By applying the technical solution of this application embodiment, a smooth voltage transition is achieved and overvoltage during closing is suppressed through the series connection of the current-limiting resistor and the filter capacitor; the current-limiting resistor limits the current amplitude to avoid inrush current; and the filter capacitor absorbs high-frequency harmonics and smooths voltage fluctuations.

[0141] Based on the above embodiments, Figure 4 Schematic diagram of the structure of the cable AC resistance measurement system provided in the embodiments of this application Figure 4 .like Figure 4 As shown, the transition loop unit also includes: a parameter adjustment unit;

[0142] The following implementation instructions apply to this AC resistance measurement system for cables:

[0143] The parameter adjustment unit is used to adjust the first parameter of the current-limiting resistor and the second parameter of the filter capacitor.

[0144] For example, based on system operating conditions (such as power supply voltage fluctuations and changes in the characteristics of the cable under test), the first parameter (such as resistance value) of the current-limiting resistor and the second parameter (such as capacitance value) of the filter capacitor are adjusted in real time to ensure that the transition circuit can always effectively suppress inrush current, filter out harmonics, and maintain a smooth voltage transition.

[0145] In one possible implementation, the parameter adjustment unit uses a variable resistor and an adjustable capacitor to adjust the values ​​of the current-limiting resistor and the filter capacitor in real time based on the equivalent capacitance and inductance of the cable under test and the ambient temperature and humidity.

[0146] For example, if the capacitance of the cable under test is large, the resistance of the current-limiting resistor can be reduced to shorten the charging time, or the filter capacitor can be increased to enhance the filtering effect when the ambient humidity is high.

[0147] In one possible implementation, the parameter calculation process for the current-limiting resistor and filter capacitor in the transition loop unit includes the following steps:

[0148] Step 1: Determine the test signal parameters for the cable under test;

[0149] For example, to ensure power supply consistency after switching, the effective value of the input stable voltage in the transition loop unit is set to 220V.

[0150] The rated current of the cable test circuit unit is determined based on the cross-sectional area and current carrying capacity of the cable under test. For example, a copper cable with a cross-sectional area of ​​1200 mm² has a rated current of 400 A; an aluminum core cable with a cross-sectional area of ​​2000 mm² has a rated current of 550 A. In this embodiment, a 1200 mm² copper cable with a rated current of 400 A is used.

[0151] The maximum allowable charging time for the transition circuit is set to 1 minute to balance test time and charging stability, avoid lengthy processes, and meet cable test time requirements.

[0152] Step 2: Determine the parameters of the current-limiting resistor;

[0153] First, the parameters of the current-limiting resistor must be chosen to ignore the influence of capacitive reactance on the loop current. With a filter capacitor of 4700μF and operating at power frequency, the corresponding capacitive reactance is 0.68Ω. When the current-limiting resistor's resistance is greater than 4.809Ω, the capacitive reactance will account for less than 14%, and at this point, the influence of capacitive reactance on the loop current can be ignored.

[0154] Secondly, based on the overcurrent protection principle, the current-limiting resistor can be calculated. Lower limit of the value.

[0155] To avoid current overload, the ratio of overload current to the current carrying capacity of the cable under test is... It needs to meet the following requirements: within a certain range, among which The current safety factor is typically set to 1.2 in engineering practice to provide a 20% safety margin and accommodate the operating thresholds of most protective devices. Overload current can be calculated using Ohm's law, as shown in the following formula:

[0156]

[0157] Then the current limiting resistor The lower limit of the value satisfies:

[0158]

[0159] in, This represents the current safety factor, which is typically taken as 1.2 in engineering. This indicates the rated current of the cable test circuit unit.

[0160] when When the value is 400A, the current limiting resistor The lower limit of the value is 0.458Ω, which is insufficient to ignore the influence of capacitive reactance on the steady-state current. Therefore, the current-limiting resistor is determined to be... The lower limit of the value is 4.809Ω.

[0161] Finally, based on the charging efficiency, the resistance can be calculated. Upper limit of possible values.

[0162] According to circuit theory, charging the filter capacitor to 95% of its steady-state voltage requires 3-5 time constants τ. The time constant determines the charging speed, and in engineering, it is typically chosen as... Ensure the battery is fully charged. Also, avoid prolonged charging times; charging time should be less than 0.2 seconds. (The current-limiting resistor should be used.) The upper limit of the value satisfies:

[0163]

[0164]

[0165] in, Represents the time constant. Indicates the maximum charging time. This indicates the capacitance value of the filter capacitor.

[0166] When the capacitance of the filter capacitor When the current limiting resistor is 4700μF, The upper limit of its value is 14.184Ω.

[0167] In summary, when the filter capacitor has a capacitance of 4700μF, the current-limiting resistor... The value range is 4.809Ω-14.184Ω.

[0168] Step 3: Determine the parameters of the filter capacitor;

[0169] For example, the parameters of the filter capacitor need to meet the requirements of voltage tolerance and charging time, while also taking into account the filtering effect to suppress higher frequency harmonics.

[0170] Transition loop steady voltage peak Considering the potential for voltage fluctuations of ±10% and capacitor aging, the rated voltage of the filter capacitor must be no less than 400V to prevent capacitor breakdown.

[0171] The value of the filter capacitor can be determined by the current-limiting resistor. The upper limit of the value is calculated using the formula. Based on standard capacitor specifications, a filter capacitor within the range of 4700μF to 8500μF is selected. This embodiment uses a 4700μF capacitor, which can accommodate a wider range of current-limiting resistor values, while also exhibiting low capacitive reactance and excellent filtering performance.

[0172] In summary, by combining cable current-carrying capacity standards, charging time constraints, and overcurrent protection principles, the range of values ​​for the current-limiting resistor and the filter capacitor is derived. Furthermore, based on the parameter calculation formulas for the current-limiting resistor and filter capacitor in the aforementioned transition circuit unit, the resistance value of the current-limiting resistor and the capacitance value of the filter capacitor are adjusted.

[0173] The cable AC resistance measurement system provided in this application embodiment further includes a parameter adjustment unit for adjusting the first parameter of the current-limiting resistor and the second parameter of the filter capacitor. By applying the technical solution of this application embodiment, the parameter adjustment module enables the transition circuit unit to adapt to the electrical characteristics and environmental conditions of different cables under test, overcoming the performance limitations of traditional fixed-parameter designs under complex operating conditions. This optimizes the stability and efficiency of the charging process and reduces the risk of equipment damage due to parameter mismatch.

[0174] Based on the above embodiments, Figure 5 Schematic diagram of the structure of the cable AC resistance measurement system provided in the embodiments of this application Figure 5 .like Figure 5 As shown, the cable measurement circuit unit also includes: a cable fixing unit, a current transformer, and a data acquisition and processing unit;

[0175] The following implementation instructions apply to this AC resistance measurement system for cables:

[0176] 1) The cable fixing unit is connected to the cable under test and is used to fix the cable under test;

[0177] For example, the cable fixing unit is directly connected to the cable under test, which can stabilize the position of the cable under test and avoid signal interference or data errors caused by cable shaking or poor contact during the measurement process, thus ensuring the stability of current and voltage acquisition.

[0178] In one possible implementation, a stainless steel mechanical clamp is used to ensure that the large cross-section cable under test is in a straight state, thus avoiding cable deformation that could introduce additional contact resistance.

[0179] 2) The current transformer is connected to the cable under test to control the current data of the cable under test;

[0180] For example, the current transformer is connected to the cable under test, mainly to adjust the current in the cable under test, while achieving electrical isolation between the cable side and the data acquisition side to ensure system safety.

[0181] In one possible implementation, the turns ratio of the current transformer is adjustable, and the transformer passes through the transmission wires of the cable measurement circuit unit connected to the cable under test to adjust the magnitude of the current flowing into the cable under test.

[0182] 3) The data acquisition and processing unit is connected to the current transformer and the cable under test respectively, and is used to acquire and process the voltage and current data of the cable under test.

[0183] For example, one end of the data acquisition and processing unit is connected to a current transformer to obtain the converted current signal, and the other end is directly connected to the cable under test to collect the voltage signal. It is responsible for converting the analog signal into a digital signal and calculating the AC resistance.

[0184] In one possible implementation, the data acquisition and processing unit has a built-in digital signal processor and microprocessor. After the current signal is input through the current transformer, it is synchronously acquired with the voltage signal at both ends of the cable. After being converted into a digital quantity, the AC resistance is calculated using Ohm's law (resistance = voltage / current).

[0185] Based on Shannon's sampling theorem, the data sampling frequency of the data acquisition and processing unit is set to 20,000 times per cycle to realize the analog-to-digital conversion of current and voltage signals, as well as the calculation of the resistance to be measured.

[0186] In one possible implementation, when the zero-phase closing switch unit switches the circuit to the cable measurement circuit unit, the current of the cable test circuit unit is adjusted to the target value using a current transformer, the temperature of the cable under test is controlled according to the experimental environment requirements, and multiple sets of voltage and current data are recorded.

[0187] After all temperature point tests are completed, first reduce the current of the cable test circuit unit to zero, switch the zero-phase closing switch unit back to the transition circuit unit, and then turn off the power supply unit.

[0188] Finally, the AC resistance of the cable under test is calculated based on multiple sets of voltage and current data.

[0189] The cable AC resistance measurement system provided in this application includes a cable measurement circuit unit further comprising: a cable fixing unit, a current transformer, and a data acquisition and processing unit. The cable fixing unit is connected to the cable under test and is used to fix the cable under test. The current transformer is connected to the cable under test and is used to control the current data of the cable under test. The data acquisition and processing unit is connected to both the current transformer and the cable under test and is used to acquire and process the voltage and current data of the cable under test. By applying the technical solution of this application embodiment, the cable under test is fixed in the cable measurement circuit unit by the cable fixing unit, the current of the cable under test is adjusted by the current transformer, and the voltage and current data of the cable under test are acquired and processed by the data acquisition and processing unit, significantly improving the completeness and accuracy of the measurement data.

[0190] Based on the above embodiments, Figure 6 Schematic diagram of the structure of the cable AC resistance measurement system provided in the embodiments of this application Figure 6 .like Figure 6 As shown, the data acquisition and processing unit also includes: a first digital signal processor, a second digital signal processor, and a data processing unit;

[0191] The following implementation instructions apply to this AC resistance measurement system for cables:

[0192] 1) The first digital signal processor is connected to the current transformer to collect the first current data of the cable under test;

[0193] For example, the first digital signal processor is connected to the output of the current transformer, receives the current signal converted by the current transformer, and accurately acquires it as the first current data. Its independent working mode can avoid resource conflicts with other signal acquisition, ensuring the real-time performance and integrity of the current data.

[0194] In one possible implementation, the first digital signal processor uses a 16-bit fixed-point digital signal processing chip and is connected to the output of the current transformer via an analog input interface.

[0195] 2) The second digital signal processor is connected to the cable under test and is used to acquire the second voltage data of the cable under test;

[0196] For example, the second digital signal processor is directly connected to the voltage measurement terminal of the cable under test to acquire the second voltage data at both ends of the cable. Its independent operation avoids interference from current acquisition on the voltage signal, ensuring the sampling accuracy and synchronization of the voltage data.

[0197] In one possible implementation, the second digital signal processor uses a 16-bit fixed-point digital signal processing chip of the same model as the first digital signal processor, and its sampling frequency is consistent with that of the first digital signal processor. This ensures that the current and voltage data correspond one-to-one in the time dimension. At the same time, isolation circuits are used to prevent the high voltage of the cable under test from affecting the processor.

[0198] 3) The data processing unit is connected to the first digital signal processor and the second digital signal processor, and is used to convert and process the first current data and the second voltage data.

[0199] For example, the data processing unit is connected to two digital signal processors respectively. After receiving the first current data and the second voltage data, it performs format conversion, synchronization calibration and calculation processing, and outputs the resistance value of the cable under test.

[0200] In one possible implementation, the data processing unit uses an ARM microprocessor and communicates with two digital signal processors through a Serial Peripheral Interface (SPI) interface. After reading the raw data, it first ensures the synchronization of current and voltage data through timestamp calibration, and then calculates the resistance according to the formula "resistance = voltage / current". At the same time, it executes a temperature compensation algorithm to correct the error and outputs the resistance value of the cable under test. The processing delay is controlled within 10ms.

[0201] The cable AC resistance measurement system provided in this application embodiment further includes a data acquisition and processing unit comprising: a first digital signal processor, a second digital signal processor, and a data processing unit. The first digital signal processor is connected to a current transformer and is used to acquire first current data of the cable under test. The second digital signal processor is connected to the cable under test and is used to acquire second voltage data of the cable under test. The data processing unit is connected to both the first and second digital signal processors and is used to perform conversion processing on the first current data and the second voltage data. Applying the technical solution of this application embodiment, current and voltage data are acquired independently by two digital signal processors, avoiding time differences caused by single-processor "time-division acquisition" (such as voltage sampling lagging current), and ensuring the time synchronization of the two types of data. The dedicated data processing unit centrally processes the two types of data, and can uniformly perform calibration algorithms, error compensation, format standardization, and other operations to ensure the consistency of the final output data and avoid format confusion or calibration deviation caused by decentralized processing.

[0202] Figure 7 This is a schematic flowchart illustrating the method for measuring the AC resistance of a cable provided in an embodiment of this application. Figure 7 As shown, the method for measuring the AC resistance of a cable is applied to the cable measurement circuit unit in the aforementioned cable AC resistance measurement system. The method for measuring the AC resistance of a cable includes the following steps:

[0203] S710: Acquire the first current data and the second voltage data of the cable under test;

[0204] In this step, in order to determine the AC resistance of the cable under test, the first current data and the second voltage data of the cable under test can be obtained first.

[0205] In one possible implementation, the current of the cable measurement circuit unit connected to the cable under test can be collected by the current transformer of the cable measurement circuit unit in the above-mentioned cable AC resistance measurement system. The first digital signal processor is connected to the output terminal of the current transformer, receives the current signal converted by the current transformer, and obtains the first current data.

[0206] The second digital signal processor of the data acquisition and processing unit in the above-mentioned cable AC resistance measurement system is directly connected to the voltage measurement terminal of the cable under test to acquire the second voltage data at both ends of the cable under test.

[0207] S720. Adjust the first current data until the first current data is equal to the current carrying capacity of the cable under test, and determine at least one second current data and at least one corresponding third voltage data of the cable under test.

[0208] In this step, by adjusting the power supply parameters (such as power output), the first current data is calibrated to the actual current carrying capacity of the cable (such as rated current) to eliminate the acquisition error. At the same time, the stable current (second current data) and the corresponding voltage (third voltage data) at this time are recorded. In order to improve the accuracy of resistance calculation, multiple sets of current and voltage data under different current carrying capacities need to be obtained.

[0209] In one possible implementation, the magnitude of the first current data is controlled by adjusting the current transformer of the cable measurement circuit unit in the above-mentioned cable AC resistance measurement system, and the power output is gradually increased so that the first current data rises from the initial value to the current carrying capacity value of the cable under test.

[0210] For example, adjust the first current data to 400A, control the temperature of the cable under test to 40℃, and after stabilizing for 0.5 hours, collect one set of voltage and current data every 1 minute, for a total of 10 sets of data.

[0211] S730. Determine the AC resistance data of the cable under test based on at least one second current data and at least one corresponding third voltage data.

[0212] In one possible implementation, step S730 may further include the following steps:

[0213] Step 1: Determine at least one first AC resistance data of the cable under test based on at least one second current data and at least one corresponding third voltage data;

[0214] For example, based on each set of second current data and corresponding third voltage data, multiple first AC resistance data are obtained by calculating them one by one using the resistance calculation formula (resistance = voltage / current).

[0215] Step 2: Sum and average all the first AC resistance data to determine the AC resistance data of the cable under test.

[0216] For example, the average value of multiple first AC resistance data is taken after summing them to reduce the impact of random errors (such as instantaneous voltage fluctuations) and obtain more stable and reliable AC resistance data.

[0217] In one possible implementation, the method for measuring the AC resistance of the cable further includes the following steps:

[0218] Step 1: Convert the first current data and the second voltage data to obtain the first current waveform data and the second voltage waveform data.

[0219] For example, the data acquisition and processing unit in the above-mentioned cable AC resistance measurement system can perform format processing (such as time domain conversion and waveform reconstruction) on the acquired first current data and second voltage data to generate first current waveform data and second voltage waveform data that can reflect the signal change trend.

[0220] Waveform data can intuitively present the fluctuation characteristics of current and voltage over time, providing a visual basis for subsequent analysis.

[0221] Step 2: Visualize the first current waveform data and the second voltage waveform data.

[0222] For example, the first current waveform data and the second voltage waveform data are presented in graphical form through a visual display interface, which makes it easier to determine whether the data is abnormal (such as whether there are harmonics, excessive fluctuations, etc.) and provides a visual basis for the reliability of the measurement results.

[0223] In one possible implementation, the first current waveform data and the second voltage waveform data are superimposed and displayed as curves, with the current waveform curve marked in blue and the voltage waveform curve marked in red. The horizontal axis is marked with time scale and the vertical axis is marked with physical quantity scale.

[0224] For example, the visualized first current waveform data is compared with the actual current carrying capacity of the cable to determine whether there is an inrush current, and at the same time, it is detected whether there is a significant fluctuation in the current.

[0225] Observe whether the voltage of the cable circuit is stable at 220V based on the visualized second voltage waveform data, that is, the voltage fluctuation amplitude does not exceed 3% within 1 minute.

[0226] The cable AC resistance measurement method provided in this application is applied to the cable measurement circuit unit of the aforementioned cable AC resistance measurement system. First, it acquires first current data and second voltage data of the cable under test. Then, it adjusts the first current data until it equals the current-carrying capacity of the cable under test. Next, it determines at least one second current data and at least one corresponding third voltage data of the cable under test. Finally, based on the at least one second current data and the corresponding at least one third voltage data, it determines the AC resistance data of the cable under test. In this embodiment, by measuring and adjusting the current value at multiple points (under different currents and voltages), the accuracy of the resistance data can be effectively improved. By adjusting the current value to the current-carrying capacity, the resistance performance of the cable under test under operating conditions can be more accurately simulated, thereby accurately measuring the AC resistance of the cable under test.

[0227] Based on the above embodiments, the following is a cable AC resistance measuring device provided in the embodiments of this application, which can perform the method provided in the above method embodiments.

[0228] Figure 8 This is a schematic diagram of the structure of the cable AC resistance measuring device provided in an embodiment of this application. Figure 8 As shown, the cable AC resistance measuring device 800 is used in the cable measuring circuit unit of the aforementioned cable AC resistance measuring system, and includes:

[0229] The acquisition module 810 is used to acquire the first current data and the second voltage data of the cable under test;

[0230] The processing module 820 is used to adjust the first current data until the first current data is equal to the current carrying value of the cable under test, and to determine at least one second current data and at least one corresponding third voltage data of the cable under test.

[0231] The determination module 830 is used to determine the AC resistance data of the cable under test based on at least one second current data and at least one corresponding third voltage data.

[0232] In one or more embodiments, the determining module 830 is specifically used for:

[0233] Based on at least one second current data and at least one corresponding third voltage data, determine at least one first AC resistance data of the cable under test;

[0234] The AC resistance data of the cable under test are determined by summing and averaging all the first AC resistance data.

[0235] In one or more embodiments, the processing module 820 is further configured to:

[0236] The first current data and the second voltage data are converted and processed to obtain the first current waveform data and the second voltage waveform data.

[0237] The first current waveform data and the second voltage waveform data are visualized.

[0238] The cable AC resistance measuring device provided in this embodiment can perform the method provided in the above method embodiment. Its implementation principle and technical effect are similar, and will not be described in detail here.

[0239] Figure 9 This is a schematic diagram of the structure of an electronic device provided in an embodiment of this application. Figure 9 As shown, the electronic device includes: the aforementioned cable AC resistance measuring system;

[0240] Or / and, the electronic equipment includes: a cable measurement circuit unit in a cable AC resistance measurement system, the cable measurement circuit unit being used to perform the above-described method.

[0241] This application also provides a computer program product, including a computer program that, when executed by a processor, implements the above-described method.

[0242] This application also provides a computer-readable storage medium storing computer-executable instructions, which, when executed by a processor, implement the above-described method.

[0243] The aforementioned readable storage medium can be implemented by any type of volatile or non-volatile storage device or a combination thereof, such as Static Random-Access Memory (SRAM), Electrically Erasable Programmable Read-Only Memory (EEPROM), Erasable Programmable Read-Only Memory (EPROM), Programmable Read-Only Memory (PROM), Read-Only Memory (ROM), magnetic storage, flash memory, magnetic disk, or optical disk. The readable storage medium can be any available medium accessible to a general-purpose or special-purpose computer.

[0244] An exemplary readable storage medium is coupled to a processor, enabling the processor to read information from and write information to the readable storage medium. Of course, the readable storage medium can also be a component of the processor. The processor and the readable storage medium can reside in an application-specific integrated circuit (ASIC). Alternatively, the processor and the readable storage medium can exist as discrete components in the device.

[0245] The division of units is merely a logical functional division; in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be indirect coupling or communication connection through some interfaces, devices, or units, and may be electrical, mechanical, or other forms.

[0246] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0247] In addition, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit.

[0248] If a function is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this invention, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods of the various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory, random access memory (RAM), magnetic disks, or optical disks.

[0249] Those skilled in the art will understand that all or part of the steps of the above-described method embodiments can be implemented by hardware related to program instructions. The aforementioned program can be stored in a computer-readable storage medium. When executed, the program performs the steps of the above-described method embodiments; and the aforementioned storage medium includes various media capable of storing program code, such as ROM, RAM, magnetic disks, or optical disks.

[0250] Finally, it should be noted that other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein, and is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. A system for measuring the ac resistance of a cable, characterized by, The application relates to a zero-phase closing switch unit for a cable resistance tester. The zero-phase closing switch unit is connected with a power supply unit, a transition loop unit, a cable under test and a cable measurement loop unit. The zero-phase closing switch unit is connected with the transition loop unit and the cable measurement loop unit. The zero-phase closing switch unit controls the connection or disconnection of the transition loop unit and the power supply unit and controls the connection or disconnection of the cable measurement loop unit and the power supply unit. The power supply unit is connected with the zero-phase closing switch unit. The power supply unit supplies power to the transition loop unit when the zero-phase closing switch controls the connection of the transition loop unit and the power supply unit.

2. The system of claim 1, wherein, The power supply unit supplies power to the cable measurement loop unit when the zero-phase closing switch controls the connection of the cable measurement loop unit and the power supply unit. The transition loop unit is connected with the zero-phase closing switch. The transition loop unit smoothly transits the closing overvoltage generated by the power supply unit to a preset voltage when the zero-phase closing switch controls the connection of the transition loop unit and the power supply unit. The cable measurement loop unit is connected with the zero-phase closing switch and the cable under test.

3. The system of claim 1, wherein, The cable measurement loop unit determines the AC resistance of the cable under test when the zero-phase closing switch controls the disconnection of the transition loop unit and the power supply unit and controls the connection of the cable measurement loop unit and the power supply unit according to the preset voltage. The zero-phase closing switch unit further comprises a voltage sensor, a phase analysis unit and an execution unit. The voltage sensor is connected with the power supply unit.

4. The system of claim 3, wherein, The voltage sensor collects first voltage data of the power supply unit in real time. The phase analysis unit is connected with the voltage sensor.

5. The system of claim 1, wherein, The phase analysis unit determines the voltage phase of the first voltage data. The execution unit is connected with the transition loop unit and the cable measurement loop unit. The execution unit controls the on-off of the transition loop unit and the cable measurement loop unit according to the voltage phase. The transition loop unit further comprises a current-limiting resistor and a filter capacitor.

6. The system of claim 5, wherein, The current-limiting resistor controls the current amplitude of the transition loop unit to be less than a first preset threshold. The filter capacitor filters the high-frequency harmonics of the voltage data in the transition loop unit. The transition loop unit further comprises a parameter adjustment unit. The parameter adjustment unit adjusts the first parameter of the current-limiting resistor and the second parameter of the filter capacitor. The cable measurement loop unit further comprises a cable fixing unit, a current transformer and a data acquisition and processing unit. The cable fixing unit is connected with the cable under test. The cable fixing unit fixes the cable under test. The current transformer is connected with the cable under test. The current transformer controls the current data of the cable under test. The data acquisition and processing unit is connected with the current transformer and the cable under test. The data acquisition and processing unit acquires and processes the voltage data and the current data of the cable under test. The data acquisition and processing unit further comprises a first digital signal processor, a second digital signal processor and a data processing unit. The first digital signal processor is connected with the current transformer. The first digital signal processor acquires first current data of the cable under test. The second digital signal processor is connected with the cable under test. The second digital signal processor acquires second current data of the cable under test. The data processing unit is connected with the first digital signal processor and the second digital signal processor. The data processing unit processes the first current data and the second current data. The data processing unit determines the AC resistance of the cable under test according to the first current data and the second current data. The second digital signal processor is connected with the cable to be measured, and is used for collecting second voltage data of the cable to be measured; The data processing unit is connected with the first digital signal processor and the second digital signal processor, and is used for converting and processing the first current data and the second voltage data.

7. A method of measuring the ac resistance of a cable, characterized by, The method is applied to a cable measurement loop unit in the cable AC resistance measurement system of any one of claims 1-6, and the method comprises: obtaining first current data and second voltage data of a cable to be measured; adjusting the first current data until the first current data is equal to a current-carrying value of the cable to be measured, determining at least one second current data and corresponding at least one third voltage data of the cable to be measured; determining AC resistance data of the cable to be measured according to the at least one second current data and the corresponding at least one third voltage data.

8. The method of claim 7, wherein, The method further comprises: converting and processing the first current data and the second voltage data to obtain first current waveform data and second voltage waveform data; visually displaying the first current waveform data and the second voltage waveform data.

9. The method of claim 7, wherein, The electronic device comprises the cable AC resistance measurement system of any one of claims 1-6; Or / and, the electronic device comprises a cable measurement loop unit in the cable AC resistance measurement system, and the cable measurement loop unit is used for executing the method of any one of claims 7-10. ​ 10. An electronic device, comprising: ​ ​

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