This standard specifies the test equipment, sample preparation, test steps, test result evaluation and precautions for impulse voltage tests on cables and their accessories. This standard is applicable to impulse voltage tests on various types of power cables and their accessories. GB/T 3048.13-1992 Wire and Cable Impulse Voltage Test Method GB/T3048.13-1992 Standard Download Decompression Password: www.bzxz.net

National Standard of the People's Republic of China
Electric cables and wires
Method for Impulse voitage testGB/T 3048. 13—92
This standard adopts the relevant provisions of IEC60-160-4 (1973) "High Voltage Test Technology" and IEC230 (1966) for impulse voltage test of cables and their accessories.
1 Subject content and scope of application
This standard specifies the test equipment, sample preparation, test procedures, test result evaluation and precautions for impulse voltage test of cables and their accessories.
This standard is applicable to impulse voltage test of various types of power cables and their accessories. 2 Reference standards
GB311.2~311.6 High voltage test technology
G32900.10 Electrical terminology Wire and cable GB 2900.19 Electrical terminology High voltage test technology and insulation coordination 3 Test equipment
The test equipment should meet the following requirements.
3.1 Test voltage
3.1.1 Test voltage value
The test voltage value generally refers to the peak value of the impulse voltage wave. For some test circuits, there may be oscillation or overshoot at the peak value of the impulse voltage wave (for overshoot or oscillation near the peak value, it is only allowed when the amplitude of its single wave peak does not exceed 5% of the peak value). If the frequency of such oscillation is not less than 0.5 MHz or the duration of the overshoot is not more than 1 μs, an average curve should be drawn. When measuring, the maximum amplitude of this average curve can be taken as the test voltage value.
The test voltage value is selected according to the corresponding product standard. 3.1.2 Test voltage waveform
3.1.2.1 Lightning impulse voltage wave
The apparent wavefront time T of the lightning impulse voltage wave is 1 ~ 5 μs, and the standard half-wave peak time T is 40 ~ 60 μs, as shown in Figure 1. The allowable deviation between the standard value of the peak value and the measured value is ± 3%. Approved by the State Administration of Technical Supervision on February 19, 1992
Implementation on October 1, 1992
3.1.2.2 Switching impulse voltage wave
GB/T3048.13-92
Figure 1 Lightning impulse voltage wave
T, = 1. 67 I
T'=0.3 T, = 0.5T
The wavefront time T of the switching impulse voltage wave is 250 μus, and the half-peak time T is 250 μs. 2 500 μs, as shown in Figure 2. The allowable deviation between the standard value and the measured value is as follows: peak value
pre-time
half peak time ± 60%
Figure 2 switching impulse voltage wave
3.2 Generation of test voltage
lightning impulse voltage and switching impulse voltage are generally generated by impulse voltage generator. The impulse voltage generator is mainly composed of many capacitors GB/T 3048.13-92
, which are first charged in parallel by a high-voltage DC charging power supply, and then discharged in series to the circuit connected with the sample. The high-voltage DC charging power supply should be adjustable so that the corresponding charging voltage value can be adjusted according to the required test voltage value. 3.3 Measurement of test voltage and waveform
3.3.1 Use the impulse voltage measurement system in accordance with Article 4 of GB311.4, including analyzer, oscilloscope and bee value voltmeter (or approved state recorder that meets the requirements of the corresponding standards), high-voltage lead, damping resistor, commercial frequency cable and its end matching and grounding loop to measure the test voltage peak value and waveform parameters.
3.3.2 For lightning impulse voltage, the test voltage value can also be measured by measuring the ball gap in accordance with GB311.6. 4 Sample preparation
4.1 Treatment of electric braided samples According to the relevant product standards, if only the impulse voltage test is carried out on the cable accessories, the electric rope samples matching the cable accessories do not need to undergo the bending test. 4.2 Unless otherwise specified in the product standards, the length of the cable sample should be selected according to the following provisions. . The sample has only two cable terminals, and the length of the cable between the bottom of the two terminals is at least 5m; b. There is one cable connector in the sample, and the length of free cable between the bottom of each cable terminal and the connector is at least 5㎡; c. There is more than one cable connector in the sample, and the length of free cable between the bottom of each cable terminal and the connector is at least 5m, and the length of free cable between adjacent connectors is at least 3m. 4.3 The sample should be placed under the test pressure (oil pressure or air pressure) and test temperature conditions specified in the corresponding product standard. 4.4 If the product standard stipulates that the sample needs to be subjected to impulse voltage test under conductor heating conditions, before making the terminal of the sample, the cable sample should be passed through the through-type induction heating transformer, and the copper or aluminum busbar (the cross-sectional area of ​​the busbar should be determined according to the conductor heating current value expected to be applied by the closed loop formed by the cable sample) should be connected between the two terminals of the sample to apply the conductor heating current. 5 Test steps
5.1 Withstand impulse voltage test
5.1.1 Calibration of positive polarity impulse voltage value and waveform The two terminals of the sample are connected to the impulse voltage generator, and the measuring system is connected in parallel with it. Under this condition, the output voltage value of the impulse voltage generator and the corresponding charging voltage value are calibrated at 50%, 65% and 80% of the withstand impulse voltage value specified by the sample, and a relationship curve between the two is drawn. This curve should generally be a straight line, and then the charging voltage value corresponding to the withstand impulse voltage value specified by the sample is determined by extrapolation, and this charging voltage value is used as a reference for applying the withstand impulse voltage value. The impulse voltage value is measured by the impulse voltage measurement system (the impulse voltage value can also be measured by the measuring ball) and the oscillogram of the impulse voltage waveform is recorded. The oscillogram should include the time scale and calibration amplitude. According to the oscillogram, it is judged whether the impulse voltage waveform meets the provisions of Article 3.1.2. If not, the wavefront and wavetail resistance parameters of the impulse voltage generator should be adjusted and the calibration should be repeated.
5.1.2 Unless otherwise specified in the product standard, the positive polarity corresponding withstand impulse voltage value is applied continuously for 10 times when the sample is under the test pressure and temperature conditions specified in the corresponding product standard. The time interval between two adjacent impulse voltages should be sufficient to ensure that the impulse voltage generator has been charged to the corresponding charging voltage value. If the withstand impulse voltage value applied is lower than the lower limit of the allowable deviation specified in Article 3.1.2.1, this time will not be counted. The charging voltage value should be adjusted appropriately and the withstand impulse voltage value should be applied accordingly. 5.1.3 After applying the corresponding withstand impulse voltage value of positive polarity 10 times, immediately calibrate the negative polarity impulse voltage value and waveform according to Article 5.1.1, and then apply the same withstand impulse voltage value of negative polarity to the sample continuously for 10 times. Similarly, if the withstand impulse voltage value applied is lower than the lower limit of the allowable deviation specified in Article 3.1.2.1, this time will not be counted, the charging voltage value should be adjusted appropriately and the withstand impulse voltage value should be applied accordingly. 5.1.4 When the withstand impulse voltage of positive and negative polarity is applied continuously, at least the 1st and 10th impulse voltage oscillograms should be recorded respectively. The oscillogram should include time scale and calibration amplitude. 5.1.5 During the test, the ambient temperature and sample temperature should be checked, and the oil pressure or air pressure of the sample should also be included if necessary. 5.2 Lightning impulse voltage margin test
GB/T3048.13-92
5.2.1 When the lightning impulse voltage margin test is carried out for research purposes or at the request of the user department, it is recommended to apply the impulse voltage in the following order: 8. After the sample has passed the test of 10 times of positive and negative polarity withstand impulse voltage value (U), apply negative polarity impulse voltage to the sample continuously for 10 times, and its value is 1.05Uw
b. Apply positive polarity impulse voltage continuously for 5 times, and its values ​​are 0.5U0.6U, 0.7U#, 0.8U and 0.85Uw; c. Apply positive polarity impulse voltage 10 times continuously, the value is 1.05U, d. Apply positive polarity impulse voltage 10 times continuously, the value is 1.10Uwe, apply negative polarity impulse voltage 5 times continuously, the values ​​are 0.55Uw0.65Uw, 0.75Uw, 0.85Uw and 0.90Uw
Apply negative polarity impulse voltage 10 times continuously, the value is 1.10Uw: Apply negative polarity impulse voltage 10 times continuously, the value is 1.15Uw,
Apply 5 times continuously The positive polarity impulse voltage is applied 10 times, and its value is 1.15Uw; the positive polarity impulse voltage is applied 10 times continuously, and its value is 1.20UjWww.bzxZ.net
Apply negative polarity impulse voltage 5 times continuously, and its value is 0.65Vw, 0.75Uw, 0.85Uw0.95U and 1.0 respectively. k.
1.Apply negative polarity impulse voltage 10 times continuously, and its value is 1.200W; m. Apply impulse voltage step by step in the above order, and increase the voltage by 5% at each level until the sample is broken down or the terminal head flashes over. 5.2.2 At least the first and tenth impulse voltage oscillograms should be recorded for each test, and the waveform of the oscillogram should be used to determine whether the sample has passed the impulse voltage test at this voltage level. If the waveform of the oscillogram is distorted or shows a truncated wave, it can generally be considered that the sample has been broken down or the terminal head has flashed over.
3 In general, it is not necessary to calibrate the impulse voltage value and waveform repeatedly during a test. The charging voltage value corresponding to the impulse voltage value can be determined from the original calibration curve by extrapolating 5.2.3
. If the difference between the maximum calibrated impulse voltage value used in the original calibration curve and the impulse voltage value to be applied is large, in order to obtain more accurate test results, it must be recalibrated according to Article 5.1.1. 6 Evaluation of test results
6.1 Unless otherwise specified in the product standard, when positive or negative polarity impulse voltage is applied continuously for 10 times at the specified test voltage value, if the waveform of the 10th impulse voltage oscillogram recorded is not distorted or does not show clipping, it is considered that the sample has passed the corresponding impulse voltage test.
6.2 If the 10th impulse voltage oscillogram recorded cannot be clearly displayed, the same withstand impulse voltage value can be applied again to obtain a clear oscillogram, and the oscillogram can be used to determine whether the sample has passed the corresponding withstand impulse voltage test. 7 Precautions
7.1 The impulse voltage generator should be equipped with a fast overcurrent protection device to ensure that the test power supply can be quickly cut off when the sample breaks down or the sample end or terminal head flashes along its surface or breaks down internally. 7.2 There should be metal grounding cabinets, import and export door interlocks, signal indicators and "high voltage danger" warning signs and other safety measures around the test area. 7.3 There should be a grounding electrode and a grounding grid connected to it under the floor of the test area, and its grounding resistance should generally be less than 0.5. The grounding terminals of the impulse voltage generator, measurement system and sample, as well as the grounding terminal of the through-type induction heating transformer (if used), should be reliably connected to the grounding grid.
7.4 The high-voltage terminals of the impulse voltage generator, measurement system and sample should maintain a sufficient safety distance from the surrounding grounding bodies to prevent air discharge.
7.5 In order to prevent the high voltage generated by ground discharge or breakdown during the test from damaging the power supply system, it is generally required that all power supplies in the impulse voltage test area be powered by a separate insulation isolation transformer. GB/T 3048.13-92
This standard was proposed by the Ministry of Machinery and Electronics Industry of the People's Republic of China. This standard is under the jurisdiction of Shanghai Cable Research Institute of the Ministry of Machinery and Electronics Industry. 15
This standard was drafted by Shanghai Cable Research Institute of the Ministry of Machinery and Electronics Industry. The main drafter of this standard is Yang Wencai.
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