This standard specifies the test equipment, sample preparation, test steps, test results, calculations and precautions for AC voltage test. This standard applies to the test of wire and cable products withstanding power frequency AC voltage, but does not apply to winding wire products. GB/T 3048.8-1994 Test methods for electrical properties of wires and cables AC voltage test GB/T3048.8-1994 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Test methods for determining electrical properties of ciectric cables and wires
AC voltage test
GH/T 3048.8---94
G15 3018,583
Test methods for determining electrical properties of ciectric cables and wiresA. C. voltage tests
This standard adopts the high voltage test technology of IEC60 (1989) with reference. 1 Subject content and scope of application
This standard specifies the test equipment, sample preparation, test procedures, test results and design considerations for AC voltage test. This standard applies to the test of wire and cable products to withstand power frequency AC voltage, and does not apply to dry porcelain wire products: the general requirements, definitions and periodic calibration requirements of the electrical performance test of wires and cables are specified in GB/I3018.1! 2 Reference standards
GB/T3048.1 General principles for test methods for electrical properties of wires and cables 3 Test equipment
Should meet the following requirements.
3.1 Test voltagebzxZ.net
3.1.1 The test voltage should be an AC voltage with a frequency of 40 to 60 Hz. The waveform of the voltage should be close to a sine wave, with two half-wave bases 1 phase apart, and the ratio of the monthly peak value to the effective value is 2±5%.
3.1.2 The test voltage value and withstand voltage time of the sample shall be in accordance with the product standards. 3.2 Generation of test voltage
In addition to using a voltage regulator and a step-up transformer to generate the required test voltage, according to the characteristics of wire and cable products, the test voltage can also be generated by a series resonant circuit specified in Appendix A, that is, it is composed of the capacitance of the sample and the adjustable inductance connected in parallel with it and the feeding power supply. Changing the inductance value can generate resonance at the power supply frequency. Regardless of which method is used, the test power supply should meet the voltage and capacitance current requirements required for the sample test. 3.3 Test voltage measurement
The measurement error of the effective value or peak value of the test voltage should not exceed 3%. The following three methods can meet the requirements: 3.3.1 Voltage transformer (connected in parallel with the high-voltage output end of the step-up transformer): The measurement error of the voltage transformer should not exceed 1%, and the error of the voltmeter connected to it should not exceed +2%. 3.3.2 High-voltage electrostatic voltmeter (connected to the commercial voltage output end of the step-up transformer): The measurement error of the commercial voltage electrostatic voltmeter should not exceed ±2%.
3.3.3 Capacitor voltage divider (connected in parallel with the high-voltage output end of the step-up transformer): The voltage divider ratio error of the capacitor voltage divider should not exceed +1%, and the low-voltage arm of the voltage divider is connected to the low-voltage electrostatic voltmeter with a measurement error of no more than +2% through a coaxial cable. 4 Sample preparation
4.1 Selection of samples should be randomly selected unless otherwise specified in the product standard. Approved by the State Administration of Technical Supervision on May 19, 1994, and implemented on 199501-01
4.2 The number of samples shall be in accordance with the product standards. GB/T 3048.8 94
4.3 The length of the sample shall be in accordance with the product standards. 4.4 The length of the terminal part of the sample and the method of making the terminal head shall ensure that no flashover discharge or internal breakdown occurs along its surface under the specified test voltage.
4.5 When testing in a water tank, the length of the two ends of the sample protruding from the water surface shall not be less than 200mm, and it shall be ensured that no flashover discharge occurs along its surface under the specified test voltage. 4.6 The requirements for the oil pressure or air pressure of the oil-filled or air-filled cable samples shall be in accordance with the product standards. 5 Test steps
5.1 Unless otherwise specified in the product standard, the wiring shall be in accordance with the following wiring methods. 5.1.1 Power cables and electrical equipment wires and cables shall be wired in accordance with Table 1. Table 1
Test sample wiring method (high voltage end → grounding end》Test sample core teaching
Test sample structure diagram
5.1.2 Communication cables shall be wired as specified in Table 2. Without metal sheath, metal screen,
armor and without additional special electrodes
(1)1→2+3
(2)2→3+1
(1)1→2+3+4
(2)2→3+4+1
(3)3-+4+1+2
With metal sheath, metal screen,
armor or with additional special electrodes
(1)12+0
(2)2-110
1212+3- 0
(2)2 -1 F3--0
(3)31-2-0
(1)1+2--3+4+0
(2)2-1+3+4+0
(3)3→1+2+4+0
(4)4→1+2+3+0
Twisted element
Single core
Pair wire group
Blue wire group
Four-wire knot
Element structure diagram
GB/T 3048.8—94
Sample wiring method (high voltage end grounding end) without gold sleeve, metal shielding,
armor and no additional special electrode
All conductors a-
All conductors b
(1) All conductors a
All conductors b+c
(2) All conductors b
All conductors
(1) All conductors aFb-
All conductors c+d
(2) All conductors a+c.
All conductors btd
Certification: (In the table, 1.2, 3, 4 and ab, the center represents the core conductor number. ② The center of the table represents the metal sheath, metal shield, armor or additional special electrode. ③ In the table, +*+\ represents mutual electrical connection. () Additional pole refers to water tank, metal bead chain, stone wall coating, wrapped metal foil, etc. There is a metal sheath. Metal shield.
Armor or additional special electrode
Each conductor is connected to the ground of all other conductors and metal sheaths, shields, armors
(1) All conductors a→
All conductors b
(2) All conductors a+b→0
(1) All conductors 8-
All conductors b-1c
(2) All conductors h→
All conductors ac
(3) All conductors a+b+c -0
(1) All conductors white + b--
All conductors cd
(2) All conductors a+c
All conductors b+d
(3) All conductors a+b+c+d→0
Other wiring methods are allowed, but it must be ensured that each core of the sample is subjected to the industrial AC voltage test required by the product standard. 5.1.3 When testing the insulating sheath between the metal sheath (shield) and armor of the sample, all cores should be connected to the metal sheath (shield) and connected to the high voltage end of the stop transformer, and the armor is connected to the ground terminal. 5.1.4 When testing the insulating sheath (no armor) outside the metal sheath (shield) of the sample, all cores should be connected to the metal sheath (shield) and connected to the high voltage end of the step-up transformer, and the electrode (such as water or other electrode) is connected to the ground terminal. 5.1.5 When testing the insulating sheath outside the armor of the sample, all cores should be connected to the metal sheath (shield) and armor, and connected to the high ratio end of the step-up transformer, and the electrode (such as water pump or other electrode) should be connected to the ground terminal. 5.1.6 For multi-core cables with 5 cores or more, the wiring method should be such that each core and its adjacent cores are subjected to at least one power frequency AC voltage test specified in the product standard. Usually, the following tests are carried out: first, the voltage is applied between the odd-numbered cores (in parallel) in each layer of cores to the even-numbered cores (in parallel); second, the voltage is applied between the cores (in parallel) of all odd-numbered layers to the cores (in parallel) of the slow-numbered layers. If the number of cores in the same layer of the cable is odd, the specified voltage test should be carried out again between the adjacent layers or adjacent cores that have not been subjected to the voltage test.
5.1.7 For each shielding unit composed of multiple cores, the wiring method of the test is the same as the principle specified in Article 5.1.6. 5.2 During the test, the temperature difference between the sample and the ambient temperature should not exceed 3°C. GB/T3048.8-94
5.3 During the test, the voltage should start from a lower value (should not exceed 40% of the test voltage value specified in the product standard), slowly and steadily increase to the specified test voltage value, and maintain the specified time, then reduce the voltage to 40% of the specified test voltage value, and then cut off the power supply. It is not allowed to suddenly cut off the power supply at high voltage to avoid overvoltage. 5.4 The test voltage value applied to the sample should not exceed 3% of the specified value within the withstand voltage time. 6 Test results and calculations
6.1 If the sample does not have any breakdown phenomenon within the specified test voltage and duration, it can be considered that the sample has passed the power frequency AC voltage withstand test.
6.2 If during the test, the end or terminal of the sample has flashover discharge along its surface or internal breakdown, it is allowed to make another terminal and repeat the test. Unless otherwise specified in the product standard, the time must be re-timed. 6.3 If the test is continued after a power outage due to some reason during the test, the time should be re-timed unless otherwise specified in the product standard. ·7 Precautions
7.1 The test circuit should have a fast protection device to ensure that the test power supply can be quickly cut off when the sample breaks down or the end or terminal of the sample has flashover discharge along its surface or internal breakdown.
7.2 There should be metal grounding fences around the test area, interlocking of import and export doors, signal indicators and "high voltage danger" warning signs and other safety measures. 7.3 There should be a grounding electrode in the test area, and the grounding resistance should be less than 40. The grounding terminal of the step-up transformer and the grounding terminal of the sample or the additional electrode should be reliably connected to the grounding electrode
A1 Power frequency series resonance test circuit
CB/T 3048.8-94
Appendix A
Generate test voltage using power frequency series resonance test circuit (supplement)
Figure A1
T-frequency series resonance test circuit
TC·Single-phase voltage regulator + TF·Feeding transformer, RV-adjustable reactor; TT step-up transformer iC. Sample
Equivalent circuit
L: adjustable inductance, μH: C—sample inductance+μF; R--loop equivalent resistance (including the resistance of the adjustable reactor, the loss of the step-up transformer and the feeder transformer, the corona loss of the high-voltage conductor and the sample dielectric loss, etc.) A2
Resonance condition
According to the sample capacitance value, adjust the inductance value of the reactor to meet the resonance condition wl.=
In the formula: a=2 yuanf, f=50 Hz.
When the resonance is achieved, the current flowing through the high-voltage circuit L reaches the maximum value, that is: U
In the formula: U—the power supply voltage required during the test. The loop quality factor Q-
(AI)
(A3)
Q value is generally large, Q>12.
A3 Parameter selection
GB/T3048.8—94
A3.1 Output voltage U of the power transformer, select the advanced, D. is the maximum test voltage value required by the sample. De
A3.2 Output current of the feeder transformer 1. is equal to the maximum capacitance current value required by the sample A3.3 The rated capacity of the voltage regulator is the same as that of the feeder transformer. A3.4 The step-up transformer can be selected according to the maximum test voltage and maximum capacitance current value required for the actual test, A3.5 The inductance adjustment range of the adjustable reactor is selected according to the maximum capacitance and minimum capacitance value of the sample, and the condition of L=- is met
Additional instructions:
This standard is proposed by the Ministry of Machinery and Electronics Industry of the People's Republic of China. This standard is under the jurisdiction of the Shanghai Electric Relay Research Institute of the Ministry of Machinery and Electronics Industry. This standard was drafted by the Shanghai Cable Research Institute of the Ministry of Machinery and Electronics Industry, etc. The main drafters of this standard are Yang Wencai and Jin Biaoyi. This standard was first issued in 1965, revised for the first time in November 1983, and revised for the second time in May 1994 (A4
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