A cable conductor ac resistance testing device and method

Abstract

The application discloses a cable conductor AC resistance testing device and method, which directly supplies a large current to a cable conductor, measures the temperature, current and voltage of the powered cable conductor, adopts the measured data and a function relationship between the interference voltage value and the cable conductor radius which is fitted in advance, and obtains the cable conductor AC resistance, so that the reverse current is not applied to the cable metal shielding layer, and the proximity effect between the cable conductor and the shielding layer is avoided to influence the test result.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of cable conductor ac resistance testing device and method, belong to ac resistance test field. BACKGROUND

[0002] When ac transmission, the existence of skin effect makes the current density distribution in cable conductor uneven, presents the phenomenon that conductor surface current density is large, center current density is small, the larger the cross section of conductor, the more obvious the skin effect, and the skin effect reduces the effective cross section of conductor, and increases the resistance of conductor.Cable conductor ac resistance is closely related to cable single wire twisting mode, insulation between single wire, the segmentation of cable conductor, and accurate measurement of cable conductor ac resistance is the basis of cable structure design and optimization.

[0003] At present, foreign public has disclosed a variety of ac resistance test methods, among which the most widely used is the electrical measurement method, which calculates the ac resistance by testing the voltage, current and phase difference between the two points of the conductor.

[0004] At present, cable usually adopts copper conductor or aluminum conductor, and its resistance value is only a few micro-ohms or tens of micro-ohms per meter, so the test voltage signal is very small, usually in millivolt level, and the electromagnetic interference coupled from the measured cable in this case cannot be ignored.In order to eliminate electromagnetic interference, reverse current is applied to the metal shielding layer of cable, so that the electromagnetic interference generated by cable conductor and metal shielding layer to the test loop is offset each other, but the proximity effect between cable conductor and shielding layer will affect the test result, resulting in that the ac resistance test precision cannot meet the design requirements. SUMMARY

[0005] The present application provides a kind of cable conductor ac resistance testing device and method, solves the problems existing in the prior art test technology.

[0006] In order to solve the above technical problems, the technical scheme adopted by the present application is:

[0007] A kind of large cross section cable conductor ac resistance testing device, including current source, first voltage probe, second voltage probe, current probe, processor and display;

[0008] Current source is used to pass large current to large cross section cable conductor;Wherein, the large cross section cable conductor is the cable conductor with a cross section greater than a threshold value;

[0009] The first voltage probe and the second voltage probe measure the voltage of point A and point B of the large cross section cable conductor respectively, and send the voltage measured by each to the processor;

[0010] The current probe measures the current of the large cross section cable conductor, and sends the measured current to the processor;

[0011] The processor receives the measured voltage and current, calculates the AC resistance of the large-section cable conductor according to the function relationship between the interference voltage value and the radius of the small-section cable conductor conductor which is previously fitted, the measured voltage and current, and sends the AC resistance of the large-section cable conductor to the display for display.

[0012] The temperature probe is further included; when calculating the AC resistance of the large-section cable conductor, the temperature probe is used to measure the temperature of the large-section cable conductor and send the measured temperature to the processor, and the processor sends the measured temperature to the display for display.

[0013] When fitting the function relationship, the current source is used to pass a large current to the small-section cable conductor; the temperature probe is used to measure the temperature of the small-section cable conductor and send the measured temperature to the processor; the first voltage probe and the second voltage probe respectively measure the A-point voltage and the B-point voltage of the small-section cable conductor and send the respective measured voltages to the processor; the current probe measures the current of the small-section cable conductor and sends the measured current to the processor; and the processor receives the temperature, current, A-point voltage and B-point voltage of the plurality of small-section cable conductors, and fits the function relationship between the interference voltage value and the radius of the small-section cable conductor.

[0014] The A-point and the B-point are symmetrical along the midpoint of the cable conductor on which the A-point and the B-point are located, and the A-point and the B-point are each around a wire, and the first voltage probe and the second voltage probe are respectively connected to the wire of the A-point and the wire of the B-point.

[0015] The first voltage probe and the second voltage probe are both connected to the processor through the test line; the test line is attached to the surface of the cable conductor and is arranged from the measurement point to the midpoint, at the midpoint, the test line for measuring the A-point voltage and the test line for measuring the B-point voltage are twisted in opposite directions along the vertical direction of the cable conductor, and the test lines after being twisted in opposite directions are connected to the processor.

[0016] The current probe is installed at the midpoint between the B-point and the end of the cable conductor close to the B-point; and the temperature probe is installed at the midpoint between the A-point and the end of the cable conductor close to the A-point.

[0017] A method for testing the AC resistance of a large-section cable conductor, which is tested by using a large-section cable conductor AC resistance testing device, and comprises the following steps:

[0018] Passing a large current to the large-section cable conductor, measuring the current, A-point voltage and B-point voltage of the large-section cable conductor;

[0019] According to the function relationship between the interference voltage value and the radius of the small-section cable conductor which is previously fitted, and the radius of the large-section cable conductor, calculating the interference voltage value of the large-section cable conductor;

[0020] According to the interference voltage value, the current, the A-point voltage and the B-point voltage of the large-section cable conductor, the alternating current resistance of the large-section cable conductor is calculated.

[0021] The formula for calculating the alternating current resistance of the large-section cable conductor is:

[0022]

[0023] wherein R is the alternating current resistance of the large-section cable conductor, I is the current of the large-section cable conductor, L is the length of the large-section cable conductor between the A-point and the B-point, U is the measured voltage difference of the A-point and the B-point of the large-section cable conductor, and θ is the phase difference between U and I. AC 测量 测量 干扰 is the interference voltage value of the large-section cable conductor.

[0024] The function relationship between the fitted interference voltage value and the radius of the small-section cable conductor includes:

[0025] A plurality of small-section cable conductor samples are selected, each sample having a different radius;

[0026] For each sample, a large current is passed through the sample, the temperature, the current, the A-point voltage and the B-point voltage of the sample are measured, the theoretical voltage difference of the A-point and the B-point of the sample is calculated according to the radius, the temperature and the current of the sample, and the interference voltage value is obtained according to the measured voltage of the A-point and the B-point of the sample and the theoretical voltage difference of the A-point and the B-point of the sample;

[0027] According to the interference voltage values and the radii of all the samples, the function relationship between the interference voltage value and the radius of the small-section cable conductor is fitted.

[0028] A device for testing the alternating current resistance of a cable conductor at a preset temperature, comprising a temperature control box, a current source, a first voltage probe, a second voltage probe, a temperature probe, a current probe, a processor and a display;

[0029] The temperature control box is internally provided with a support for placing the cable conductor to be tested, and the cable conductor to be tested is heated by using heated air;

[0030] The temperature probe is used to measure the temperature of the cable conductor to be tested during the heating process of the cable conductor to be tested, and sends the measured temperature to the processor;

[0031] When the temperature of the cable conductor to be tested meets the preset requirements, the current source passes a large current through the cable conductor to be tested, the first voltage probe and the second voltage probe measure the A-point voltage and the B-point voltage of the cable conductor to be tested respectively, and send the measured voltages to the processor, and the current probe measures the current of the cable conductor to be tested and sends the measured current to the processor;

[0032] ​​​The processor receives the measured temperature and sends the measured temperature to the display for display; receives the measured voltage and current, calculates the AC resistance of the cable conductor to be measured according to the function relationship between the interference voltage value and the radius of the cable conductor sample, the measured voltage and the current, and sends the AC resistance of the cable conductor to be measured to the display for display.

[0033] The temperature control box comprises a box capable of shielding external electromagnetic interference, an electric heating wire and an air blower are arranged at the bottom of the inner cavity of the box, the electric heating wire generates heat and heats the surrounding air after being electrified, and the air blower diffuses the heated air to the whole inner cavity of the box.

[0034] When fitting the function relationship, the temperature control box is used to heat the cable conductor sample;

[0035] The current source is used to pass a large current to the cable conductor sample; the temperature probe is used to measure the temperature of the cable conductor sample and send the measured temperature to the processor; the first voltage probe and the second voltage probe measure the voltages at points A and B of the cable conductor sample respectively and send the measured voltages to the processor; the current probe measures the current of the cable conductor sample and sends the measured current to the processor; the processor receives the temperature, current, voltage at point A and voltage at point B of multiple cable conductor samples and fits the function relationship between the interference voltage value and the radius of the cable conductor sample.

[0036] A method for testing the AC resistance of a cable conductor at a preset temperature, which is tested by using a device for testing the AC resistance of a cable conductor at a preset temperature, and comprises the following steps:

[0037] Placing the cable conductor to be measured into a temperature control box;

[0038] Starting the temperature control box to measure the temperature of the cable conductor to be measured in real time;

[0039] When the displayed temperature of the cable conductor to be measured reaches a preset requirement, passing a large current to the cable conductor, measuring the current, the voltage at point A and the voltage at point B of the cable conductor;

[0040] According to the function relationship between the interference voltage value and the radius of the cable conductor sample, the current of the cable conductor to be measured, the voltage at point A and the voltage at point B of the cable conductor to be measured, the AC resistance of the cable conductor to be measured is calculated.

[0041] Fitting the function relationship between the interference voltage value and the radius of the cable conductor sample, comprising:

[0042] Selecting multiple cable conductor samples, each sample having a different radius;

[0043] For each sample, the sample is placed in a temperature control chamber, a large current is applied to the sample, and the sample temperature, current, voltage at point A and voltage at point B are measured. Based on the sample radius, temperature and current, the theoretical voltage difference between points A and B of the sample is calculated. Based on the measured voltages at points A and B of the sample and the theoretical voltage difference between points A and B of the sample, the interference voltage value is obtained.

[0044] Based on the interference voltage values ​​and radii of all samples, a functional relationship between the interference voltage values ​​and the radius of the cable conductor samples was fitted.

[0045] The beneficial effects achieved by this invention are as follows: This invention directly applies a large current to the cable conductor, measures the temperature, current, and voltage at two points of the energized cable conductor, and obtains the AC resistance of the cable conductor by using the measured data and the pre-fitted functional relationship between the interference voltage value and the radius of the cable conductor. It does not require applying a reverse current to the cable's metal shielding layer, thus avoiding the proximity effect between the cable conductor and the shielding layer from affecting the test results. Attached Figure Description

[0046] Figure 1 A schematic diagram of a device for testing the AC resistance of large cross-section cable conductors;

[0047] Figure 2 This is a schematic diagram of a cable conductor AC resistance testing device at a preset temperature. Detailed Implementation

[0048] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0049] like Figure 1 As shown, a large cross-section cable conductor AC resistance testing device includes a current source 12, a first voltage probe 4, a second voltage probe 5, a current probe 6, a temperature probe 3, a temperature acquisition module 7, a current acquisition module 9, a voltage acquisition module 8, a processor 10, and a display 11.

[0050] Current source 12 connects to the cable conductor to supply a large current. The cable conductor length is 3-8m, typically 5m. The distance between the cable conductor and current source 12 is 2-3m, typically 2m. Current source 12 outputs a current of 0-200A, a frequency of 45-60Hz, an output current accuracy better than 0.5%, and a current ripple factor less than 0.5%. The connecting wire between current source 12 and the cable conductor is soft copper wire or braided copper wire, with a cross-section of 50-100mm². 2 Generally 50mm 2 .

[0051] The cable conductor is marked with A point and B point with distance L, L is 1-6m, generally 2m, the two points are voltage measurement points, A point and B point are symmetrical along the midpoint of the cable conductor, A point and B point are respectively 0.5-1m, generally 1.5m, away from the cable conductor end. A point and B point are both around a wire, specifically using thin copper wire, diameter less than 0.5mm, generally 0.4mm, so that A point cable cross section circumference is equipotential, B point cable cross section circumference is equipotential.

[0052] The first voltage probe 4 and the second voltage probe 5 are both voltage differential probes, can adjust the amplification multiple of the differential signal, suppress the common mode component of the differential signal in the test circuit, reduce the background noise, improve the signal to noise ratio, the first voltage probe 4 and the second voltage probe 5 are respectively connected with the A point thin copper wire and the B point thin copper wire of the cable conductor. The first voltage probe 4 and the second voltage probe 5 are both connected with the voltage acquisition module 8 through the test line, the test line is attached to the surface of the cable conductor and is arranged from the measurement point to the midpoint, at the midpoint, the test line for measuring A point voltage and the test line for measuring B point voltage are twisted in opposite directions along the vertical direction of the cable conductor, the twisted length is 200-400mm, the test line after opposite twisting is connected with the voltage acquisition module 8. There is magnetic flux between the cable conductor and the voltage test line, the magnetic flux will generate induced electromotive force on the test line, thereby affecting the test accuracy, therefore, here the opposite twisting can effectively reduce the gap and reduce the interference.

[0053] The temperature probe 3 adopts a thermal resistance thermometer, which has high measurement accuracy and good reproducibility, or can also adopt a thermal couple with large test range and fast thermal response time, the temperature probe 3 is installed at the midpoint between A point and the cable conductor end close to A point, and the temperature probe 3 is connected with the temperature acquisition module 7 through the test line.

[0054] The current probe 6 adopts a Rogowski coil, compared with the current transformer, the Rogowski coil has no magnetic saturation limit, no secondary side open circuit danger, and can be conveniently connected, the current probe 6 is installed at the midpoint between B point and the cable conductor end close to B point, and the current probe 6 is connected with the current acquisition module 9 through the test line.

[0055] The temperature acquisition module 7, the current acquisition module 9, the voltage acquisition module 8, the processor 10 and the display 11 are all integrated in one terminal, and the temperature acquisition module 7, the current acquisition module 9, the voltage acquisition module 8 and the display 11 are all connected with the processor 10.

[0056] The above device can mainly implement two processes, one is alternating current resistance test, and the other is function relationship fitting.

[0057] In the AC resistance test, the current source 12 is used to pass a large current (in A) to the large cross-section cable conductor 13, generally 10 A; wherein the large cross-section cable conductor 13 is a cable conductor with a cross-section greater than a threshold value, and the cross-section is 400 mm 2 ; the first voltage probe 4 and the second voltage probe 5 measure the voltages at points A and B of the large cross-section cable conductor 13 respectively, and send the measured voltages to the processor 10; the current probe 6 measures the current of the large cross-section cable conductor 13 and sends the measured current to the processor 10; the temperature probe 3 is used to measure the temperature of the large cross-section cable conductor 13 and sends the measured temperature to the processor 10; the processor 10 sends the measured temperature to the display 11 for display, and the processor 10 receives the measured voltages and currents, calculates the AC resistance of the large cross-section cable conductor 13 according to the function relationship between the previously fitted interference voltage value and the radius of the small cross-section cable conductor, and sends the AC resistance of the large cross-section cable conductor 13 to the display 11 for display; wherein the small cross-section cable conductor is a cable conductor with a cross-section not greater than a threshold value, and the interference voltage is a voltage induced by the coupling of the cable conductor and the voltage test line.

[0058] In fitting the function relationship, the current source 12 is used to pass a large current (in A) to the small cross-section cable conductor, generally 10 A; the temperature probe 3 is used to measure the temperature of the small cross-section cable conductor and sends the measured temperature to the processor 10; the first voltage probe 4 and the second voltage probe 5 measure the voltages at points A and B of the small cross-section cable conductor respectively, and send the measured voltages to the processor 10; the current probe 6 measures the current of the small cross-section cable conductor and sends the measured current to the processor 10; the processor 10 receives the temperatures, currents, voltages at points A and B of multiple small cross-section cable conductors, and fits the function relationship between the interference voltage value and the radius of the small cross-section cable conductor.

[0059] The above device performs the method for testing the AC resistance of the large cross-section cable conductor 13, which comprises:

[0060] 1) passing a large current to the large cross-section cable conductor 13, measuring the current, voltage at point A and voltage at point B of the large cross-section cable conductor 13;

[0061] 2) calculating the interference voltage value of the large cross-section cable conductor 13 according to the function relationship between the previously fitted interference voltage value and the radius of the small cross-section cable conductor, and the radius of the large cross-section cable conductor 13;

[0062] 3) calculating the AC resistance of the large cross-section cable conductor 13 according to the interference voltage value, current, voltage at point A and voltage at point B of the large cross-section cable conductor 13.

[0063] Wherein, the formula for calculating the AC resistance of the large cross-section cable conductor 13 is:

[0064]

[0065] wherein R AC is the AC resistance of the large cross-section cable conductor 13, I is the current of the large cross-section cable conductor 13, L is the length of the large cross-section cable conductor 13 between point A and point B, U 测量 is the difference between the measured voltage at point A and the measured voltage at point B of the large cross-section cable conductor 13, and θ is the phase difference between U 测量 and I. 干扰 is the interference voltage value of the large cross-section cable conductor 13.

[0066] The function relationship between the fitted interference voltage value and the radius of the small cross-section cable conductor includes:

[0067] A1) selecting a plurality of small cross-section cable conductor samples, each sample having a different radius;

[0068] Specifically, five samples are selected, each having a cross-section of 50mm 2 , 95mm 2 , 120mm 2 , 240mm 2 , and 400mm 2 , and a length of 5m.

[0069] A2) for each sample, passing a large current through the sample, measuring the temperature, current, voltage at point A, and voltage at point B of the sample, based on GB / T 10181.1, calculating the theoretical value of the AC resistance of the sample according to the radius of the sample and the temperature of the sample, using Ohm's law to calculate the theoretical voltage difference between point A and point B of the sample according to the theoretical value of the AC resistance and the current of the sample, and obtaining the interference voltage value according to the measured voltage at point A and point B of the sample and the theoretical voltage difference between point A and point B of the sample;

[0070] A3) fitting the function relationship between the interference voltage value and the radius of the small cross-section cable conductor according to the interference voltage values and radii of all the samples.

[0071] Based on the same principle, the application also discloses a cable conductor AC resistance testing device under a preset temperature, as shown in Figure 2 The cable conductor AC resistance testing device under a preset temperature comprises a temperature control box 1, a current source 12, a first voltage probe 4, a second voltage probe 5, a temperature probe 3, a current probe 6, a temperature acquisition module 7, a current acquisition module 9, a voltage acquisition module 8, a processor 10, and a display 11.

[0072] The current source 12 is connected to the cable conductor to pass a large current to the cable conductor, the length of the cable conductor is 3-8m, generally 5m, the distance between the cable conductor and the current source 12 is 2-3m, generally 2m, the current source 12 outputs a current of 0-200A, a frequency of 45-60Hz, an output current accuracy better than 0.5%, a current ripple coefficient less than 0.5%, and the connecting wire between the current source 12 and the cable conductor is soft copper wire or braided copper wire, and the cross section of the connecting wire is 50-100mm 2 , generally 50mm 2 .

[0073] The temperature control box 1 includes a box body capable of shielding external electromagnetic interference, the box body is made of ferromagnetic material or higher magnetic permeability material, the box body is a cuboid structure, the length is 0.5-1m longer than the cable conductor 2 to be measured, the width and height are 0.8-0.1m, the wall thickness is 2-3mm, the inner wall is provided with a 10-20mm thermal insulation layer, the upper part of the box body is a cover plate which can be opened and closed, and the cover plate is connected by hinges, the front panel, rear panel, left panel, right panel and bottom panel of the box body are welded seamlessly, the left, middle and right of the front panel of the box body are provided with through holes, the left panel and the right panel of the box body are provided with through holes, and the box body is provided with a plurality of built-in supports which are insulating supports, the height of the insulating support is 0.5m, the interval is 1m, and the insulating supports are arranged along the length direction at the bottom of the box body, and the insulating supports are used to place the cable conductor.

[0074] The working principle of the temperature control box 1 is similar to that of the air blowing oven, the inner cavity of the box body is provided with an electric heating wire and a blower, the electric heating wire generates heat and heats the surrounding air after being electrified, the blower diffuses the heated air to the whole inner cavity of the box body, so that the temperature in the temperature control box 1 is uniformly distributed, thereby heating the cable conductor on the insulating support, and the temperature control box 1 can control the temperature of the internal air by controlling the temperature of the electric heating wire.

[0075] By directly heating the cable conductor through the temperature control box 1, the cable conductor does not need to pass a heating current, the conductor heating and temperature stabilization time is short, is not affected by the external environment temperature, the temperature control precision is high, the temperature adjustment is simple and convenient, the test efficiency is high, a large-capacity power supply system and a special cable conductor connecting fitting are not needed, and the equipment cost is low.

[0076] and Figure 1 , mark A point and B point with a distance of L on the cable conductor 2, L is 1-6m, generally 2m, the two points are voltage measurement points, A point and B point are symmetrical along the midpoint of the cable conductor, A point and B point are 0.5-1m away from the end of the cable conductor, generally 1.5m, the A point and B point of the cable conductor are wound around a wire, which is made of thin copper wire with a diameter of less than 0.5mm, generally 0.4mm, so that the A point cable cross section is circumferentially equipotential, and the B point cable cross section is circumferentially equipotential.

[0077] The first voltage probe 4 and the second voltage probe 5 are both differential voltage probes, which can adjust the amplification of the differential signal, suppress the common mode component of the differential signal in the test circuit, reduce the background noise, and improve the signal-to-noise ratio. The first voltage probe 4 and the second voltage probe 5 are respectively connected to the fine copper wires of the A point and the B point of the cable conductor 2 to be tested. The first voltage probe 4 and the second voltage probe 5 are connected to the voltage acquisition module 8 through test lines, which are arranged from the measurement point to the midpoint along the surface of the cable conductor. At the midpoint, the test line for measuring the voltage of the A point and the test line for measuring the voltage of the B point are twisted in opposite directions along the vertical direction of the cable conductor, and the twisted length is 200-400 mm. The test lines after being twisted in opposite directions are passed out from the middle through hole of the front panel, and the passed-out test lines are connected to the voltage acquisition module 8.

[0078] The temperature probe 3 is a thermal resistance thermometer, which has high measurement accuracy and good reproducibility, or a thermal couple with large test range and fast thermal response time. The temperature probe 3 is installed at the midpoint between the A point and the end of the cable conductor close to the A point. The temperature probe 3 is connected to the temperature acquisition module 7 through a test line, which is passed out from the left through hole of the front panel.

[0079] The current probe 6 is a Rogowski coil, which has no magnetic saturation limit, no secondary side open circuit danger, and can be conveniently connected. The current probe 6 is installed at the midpoint between the B point and the end of the cable conductor close to the B point. The current probe 6 is transmitted to the current acquisition module 9 through a test line, which is passed out from the right through hole of the front panel.

[0080] The temperature acquisition module 7, the current acquisition module 9, the voltage acquisition module 8, the processor 10 and the display 11 are integrated in one terminal. The temperature acquisition module 7, the current acquisition module 9, the voltage acquisition module 8 and the display 11 are connected to the processor 10.

[0081] The above device can mainly implement two processes, one is AC resistance test, and the other is function relationship fitting.

[0082] In the AC resistance test, the temperature control box uses hot air to heat the cable conductor 2 to be tested; the temperature probe 3 is used to measure the temperature of the cable conductor 2 to be tested during the heating process and send the measured temperature to the processor 10; when the temperature of the cable conductor 2 to be tested meets the preset requirements (stabilized at 90℃±0.5℃ within 5min), the current source 12 passes a large current to the cable conductor 2 to be tested, the first voltage probe 4 and the second voltage probe 5 measure the voltages at points A and B of the cable conductor 2 to be tested respectively, and send the measured voltages to the processor 10, the current probe 6 measures the current of the cable conductor 2 to be tested and sends the measured current to the processor 10; the processor 10 receives the measured temperature and sends the measured temperature to the display 11 for display; the measured voltage and current are received, and the AC resistance of the cable conductor 2 to be tested is calculated according to the function relationship between the interference voltage value and the radius of the cable conductor sample, the measured voltage and current, and the AC resistance of the cable conductor 2 to be tested is sent to the display 11 for display.

[0083] In the process of fitting the function relationship, the temperature control box is used to heat the cable conductor sample; the current source 12 is used to pass a large current to the cable conductor sample; the temperature probe 3 is used to measure the temperature of the cable conductor sample and send the measured temperature to the processor 10; the first voltage probe 4 and the second voltage probe 5 measure the voltages at points A and B of the cable conductor sample respectively, and send the measured voltages to the processor 10; the current probe 6 measures the current of the cable conductor sample and sends the measured current to the processor 10; the processor 10 receives the temperature, current, voltage at point A and voltage at point B of multiple cable conductor samples, and fits the function relationship between the interference voltage value and the radius of the cable conductor sample.

[0084] Based on the above device, the AC resistance test of the cable conductor at the rated operating temperature is divided into two processes: heating and AC resistance test.

[0085] Heating process: place the cable conductor 2 to be tested in the temperature control box 1, use the heating wire and the air blower to heat the air in the temperature control box 1, and then use the hot air to heat the cable conductor.

[0086] AC resistance test process: the current on the conductor generates an induced electromotive force interference on the test wire, and the size of the interference depends on the radius of the cable conductor, the current, and the length of the cable test. When the current and the length are constant, the size of the interference only depends on the radius of the cable conductor. According to JB / T 10181.1, when the cross-section of the conductor is less than 400mm 2 , the theoretical calculation result of the AC cable is reliable (with very small error), so various specifications of cross-sections less than 400mm 2 (such as 50mm 2 , 95mm 2 , 120mm 2 , 240mm2 400mm 2 Using cable conductor samples (e.g., the interference voltage value and the radius of the cable conductor sample are fitted to obtain a functional relationship, and then the AC resistance of the cable conductor is calculated.

[0087] The specific testing method is as follows:

[0088] 1) Place the conductor 2 of the cable to be tested into the temperature control chamber 1; specifically, select a 1200mm² conductor. 2 The cable conductor 2 to be tested can also be a small cross-section cable conductor with a length of 5m;

[0089] 2) Set the temperature inside temperature control box 1 to 90℃, start temperature control box 1, and measure the temperature of the conductor 2 of the cable under test in real time;

[0090] 3) When the displayed temperature of the cable conductor 2 under test reaches the preset requirement, that is, the temperature stabilizes at 90℃±0.5℃ within 5 minutes, apply a current of 50A to the cable conductor 2 under test, and measure the current of the cable conductor 2 under test and the voltage at points A and B of the cable conductor 2 under test.

[0091] 4) Based on the pre-fitted functional relationship between the interference voltage value and the radius of the cable conductor sample, the current of the cable conductor 2 under test, and the voltages at points A and B of the cable conductor 2 under test, calculate the AC resistance of the cable conductor 2 under test. The specific calculation formula is as follows:

[0092]

[0093] Among them, R′ AC Let I' be the AC resistance of conductor 2 of the cable under test, I' be the current in conductor 2 of the cable under test, L' be the length of conductor 2 of the cable under test between points A and B, and U' be the current in conductor 2 of the cable under test. 测量 Measure the voltage difference between points A and B of conductor 2 of the cable under test, where θ′ is U′. 测量 The phase difference with I′, U′ 干扰 The interference voltage value is calculated based on the functional relationship between the interference voltage value and the radius of the cable conductor sample, and the radius of the cable conductor 2 under test.

[0094] The above-fitted functional relationship between interference voltage and cable conductor radius includes:

[0095] S1) Select a variety of cable conductor samples, each with a different radius;

[0096] Small cross-section (400mm) can be selected 2 The following samples have conductor cross-sections of 50mm. 2 95mm 2 120mm 2 240mm 2 400mm2 , each with a length of 5m;

[0097] S2) for each sample, put the sample into the temperature control box 1, apply a 10A current to the sample, measure the sample temperature, current, A point voltage and B point voltage, calculate the theoretical value of the sample ac resistance according to GB / T 10181.1, known sample cross section and temperature, further calculate the theoretical voltage difference of the sample A point and B point according to Ohm's law, according to the measured voltage of the sample A point and B point, obtain the measured voltage difference, subtract the theoretical voltage difference from the measured voltage difference, obtain the interference voltage value;

[0098] S3) according to the interference voltage value and the radius of all samples, a function relationship between the interference voltage value and the radius of the cable conductor sample is fitted;

[0099] Each sample of a certain radius has one interference voltage value, and the function relationship between the interference voltage value and the radius of the cable conductor sample can be further fitted, and the corresponding interference voltage value of the to-be-tested cable conductor 2 can be calculated through the relationship.

[0100] The present application directly applies a large current to the cable conductor, measures the temperature, current and voltage of the energized cable conductor, uses the measured data and the function relationship between the interference voltage value and the radius of the cable conductor fitted in advance to obtain the ac resistance of the cable conductor, without applying a reverse current to the cable metal shielding layer, avoiding the influence of the proximity effect between the cable conductor and the shielding layer on the test result, with high test precision, high stability and good repeatability, and being suitable for the test of the ac resistance of the cable round tight conductor, special-shaped conductor and split conductor.

[0101] The above only describes the preferred embodiments of the present application, and it should be noted that for ordinary skilled persons in the art, several improvements and modifications can be made without departing from the technical principles of the present application, and these improvements and modifications should also be considered as the protection scope of the present application.

Claims

1. A large cross-section cable conductor AC resistance testing device, characterized by, The device comprises a current source, a first voltage probe, a second voltage probe, a current probe, a processor and a display. The current source is used to pass a large current through the large-section cable conductor; wherein the large-section cable conductor is a cable conductor with a cross section greater than a threshold value; The first voltage probe and the second voltage probe respectively measure the voltages at points A and B of the large-section cable conductor, and send the measured voltages to the processor; The current probe measures the current of the large-section cable conductor, and sends the measured current to the processor; The processor receives the measured voltages and current, calculates the AC resistance of the large-section cable conductor according to the function relationship between the previously fitted interference voltage value and the radius of the small-section cable conductor, the measured voltages and current, and sends the AC resistance of the large-section cable conductor to the display for display. The small-section cable conductor is a cable conductor with a cross section not greater than a threshold value; the interference voltage is a voltage induced by the coupling of the cable conductor and the voltage test line; the formula for calculating the AC resistance of the large-section cable conductor is: ； wherein R AC is the AC resistance of the large cross-section cable conductor, I is the current of the large cross-section cable conductor, L is the length of the large cross-section cable conductor between point A and point B, U 测量 is the measured voltage difference between point A and point B of the large cross-section cable conductor, θ is the phase difference between U 测量 and I U 干扰 is the interference voltage value of the large cross-section cable conductor.​ 2. An apparatus for testing the AC resistance of a large cross-section cable conductor as defined in claim 1, wherein It also comprises a temperature probe; when calculating the AC resistance of the large-section cable conductor, the temperature probe is used to measure the temperature of the large-section cable conductor, and sends the measured temperature to the processor; the processor sends the measured temperature to the display for display.

3. An apparatus for testing the AC resistance of a large cross-section cable conductor as defined in claim 2, wherein, When fitting the function relationship, the current source is used to pass a large current through the small-section cable conductor; the temperature probe is used to measure the temperature of the small-section cable conductor, and sends the measured temperature to the processor; the first voltage probe and the second voltage probe respectively measure the voltages at points A and B of the small-section cable conductor, and send the measured voltages to the processor; the current probe measures the current of the small-section cable conductor, and sends the measured current to the processor; the processor receives the temperatures, currents, voltages at points A and B of multiple small-section cable conductors, and fits the function relationship between the interference voltage value and the radius of the small-section cable conductor.

4. An apparatus for testing the AC resistance of a large cross-section cable conductor as claimed in claim 1 or 3, wherein, Points A and B are symmetrical along the midpoint of the cable conductor on which they are located, and there is a wire around each of points A and B; the first voltage probe and the second voltage probe are respectively connected to the wire at point A and the wire at point B; The first voltage probe and the second voltage probe are both connected to the processor through test lines; the test lines are arranged along the surface of the cable conductor from the measurement points to the midpoint; at the midpoint, the test line for measuring the voltage at point A and the test line for measuring the voltage at point B are twisted in opposite directions along the vertical direction of the cable conductor, and the twisted test lines are connected to the processor.

5. An apparatus for testing the AC resistance of a large cross-section cable conductor as defined in claim 1, wherein, The current probe is installed at the midpoint between point B and the end of the cable conductor close to point B; the temperature probe is installed at the midpoint between point A and the end of the cable conductor close to point A.

6. A method of testing the AC resistance of a large cross-section cable conductor, characterized by, The device of any one of claims 1-5 is used for testing, comprising: Passing a large current through the large-section cable conductor, measuring the current, voltage at point A and voltage at point B of the large-section cable conductor; According to the function relationship between the previously fitted interference voltage value and the radius of the small-section cable conductor, and the radius of the large-section cable conductor, calculating the interference voltage value of the large-section cable conductor; According to the interference voltage value, current, voltage at point A and voltage at point B of the large-section cable conductor, calculating the AC resistance of the large-section cable conductor.

7. A method of testing the AC resistance of a large cross-section cable conductor as defined in claim 6, wherein The fitted function relationship between the interference voltage value and the radius of the small-section cable conductor comprises: Select a plurality of small cross-section cable conductor samples, each sample having a different radius; For each sample, pass a large current through the sample, measure the sample temperature, current, A point voltage and B point voltage, calculate the theoretical voltage difference of the sample A point and B point according to the sample radius, sample temperature and sample current, and obtain the interference voltage value according to the measured voltage of the sample A point and B point and the theoretical voltage difference of the sample A point and B point; According to the interference voltage value and the radius of all samples, the functional relationship between the interference voltage value and the radius of the small cross-section cable conductor is fitted.

8. A device for testing the AC resistance of a cable conductor at a predetermined temperature, characterized in that It comprises a temperature control box, a current source, a first voltage probe, a second voltage probe, a temperature probe, a current probe, a processor and a display; The temperature control box is internally provided with a support for placing the cable conductor to be measured, and the cable conductor to be measured is heated by using heated air; The temperature probe is used to measure the temperature of the cable conductor to be measured during heating of the cable conductor to be measured, and sends the measured temperature to the processor; When the temperature of the cable conductor to be measured meets the preset requirement, the current source passes a large current through the cable conductor to be measured, the first voltage probe and the second voltage probe measure the A point voltage and the B point voltage of the cable conductor to be measured respectively, and send the measured voltages to the processor, and the current probe measures the current of the cable conductor to be measured and sends the measured current to the processor; The processor receives the measured temperature and sends the measured temperature to the display for display, receives the measured voltage and current, calculates the AC resistance of the cable conductor to be measured according to the previously fitted functional relationship between the interference voltage value and the radius of the cable conductor sample, the measured voltage and current, and sends the AC resistance of the cable conductor to be measured to the display for display; wherein the interference voltage is the voltage induced by the coupling of the cable conductor and the voltage test line; The formula for calculating the AC resistance of the large cross-section cable conductor is: ； wherein R AC is the AC resistance of the large cross-section cable conductor, I is the current of the large cross-section cable conductor, L is the length of the large cross-section cable conductor between point A and point B, U 测量 is the measured voltage difference between point A and point B of the large cross-section cable conductor, θ is the phase difference between U 测量 and I U 干扰 is the interference voltage value of the large cross-section cable conductor.​ 9. The device of claim 8, wherein the device is configured to test the AC resistance of the cable conductor at a pre-determined temperature. The temperature control box comprises a box body capable of shielding external electromagnetic interference, an electric heating wire and a blower are arranged at the bottom of the inner cavity of the box body, the electric heating wire generates heat and heats the surrounding air after being powered on, and the blower diffuses the heated air to the entire inner cavity of the box body.

10. The device of claim 8, wherein the device is configured to test the AC resistance of the cable conductor at a pre-determined temperature. When fitting the functional relationship, the temperature control box is used to heat the cable conductor sample; The current source is used to pass a large current through the cable conductor sample; the temperature probe is used to measure the temperature of the cable conductor sample and send the measured temperature to the processor; the first voltage probe and the second voltage probe measure the A point voltage and the B point voltage of the cable conductor sample respectively and send the measured voltages to the processor; the current probe measures the current of the cable conductor sample and sends the measured current to the processor; the processor receives the temperature, current, A point voltage and B point voltage of a plurality of cable conductor samples, and fits the functional relationship between the interference voltage value and the radius of the cable conductor sample.

11. A method of testing the AC resistance of a cable conductor at a predetermined temperature, characterised by, The device of any one of claims 8-10 is used for testing, comprising: placing the cable conductor to be measured into the temperature control box; starting the temperature control box to measure the temperature of the cable conductor to be measured in real time; when the displayed temperature of the cable conductor to be measured reaches the preset requirement, passing a large current through the cable conductor, measuring the current, A point voltage and B point voltage of the cable conductor; According to the function relationship between the interference voltage value and the cable conductor sample radius, the to-be-tested cable conductor current, the to-be-tested cable conductor A point voltage and the B point voltage, the to-be-tested cable conductor AC resistance is calculated.

12. The method of claim 11, wherein the method is performed at a predetermined temperature. The function relationship between the interference voltage value and the cable conductor sample radius is fitted, including: A plurality of cable conductor samples are selected, and the radius of each sample is different; For each sample, the sample is placed into a temperature control box, a large current is supplied to the sample, the sample temperature, the current, the A point voltage and the B point voltage are measured, the theoretical voltage difference of the A point and the B point of the sample is calculated according to the sample radius, the temperature and the current, and the interference voltage value is obtained according to the measured voltage of the A point and the B point of the sample and the theoretical voltage difference of the A point and the B point of the sample; The function relationship between the interference voltage value and the cable conductor sample radius is fitted according to the interference voltage value and the radius of all the samples.

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