This standard specifies the test equipment, test preparation, test steps, test results, calculation and precautions for measuring insulation resistance by the voltage-current method. This standard is applicable to measuring the insulation resistance of wires and cables. The measurement range is: 10 to the 4th power ~ 10 to the 16th power Ω; the measurement voltage is 100, 250, 500, 1000V four levels, and the selection and specification are made according to the measurement field strength in the product standard. GB/T 3048.6-1994 Electrical performance test method for wires and cables Insulation resistance test voltage-current method GB/T3048.6-1994 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Test methods for determining electrical properties of eletric cables and wires
Insulation resistance test voltage-current method
GB/T 3048. 6—94
Test methods for determining electrical properties of eletric cables and wiresGeneration GR g48.68sDetermining insulation resistanceVoltneter-ammeter method
1 Subject content and scope of application
This standard specifies the test equipment, sample preparation, test steps, test results, calculation and precautions for measuring insulation resistance using the voltage-current method.
This standard is applicable to measuring the insulation resistance of wires and cables, and its measurement range is: 101~10160; the measuring voltage is 100, 250.5001000V level. The selection and selection shall be made according to the measurement field strength in the product standard. Unless otherwise specified in the wire and cable product standard, the measurement shall be carried out indoors or in water with an ambient temperature of 20±5℃ and relative air humidity not exceeding 80%.
TThe test temperature of insulation resistance under working temperature shall be specified in the relevant product standards, and the temperature error shall not exceed 2°C. The temperature error during arbitration test is ±1°C. When this test method is used for testing, if the measured voltage and current are directly expressed as resistance in the same instrument, it is also called "isolation meter method".
The general requirements, definitions and periodic calibration requirements of the electrical performance test of wires and cables are specified in: GB/T3048.1. 2 Reference standards
GB/T3048.1 General principles for electrical performance test methods of wires and cables 3 Test equipment
The wiring schematic diagram of the measurement system is shown in Figure 1, and the main components shall meet the following requirements: 3.1 The accuracy of the DC voltmeter shall not be less than Class 1.0. 3.2 The zero drift of the commercial impedance DC amplifier, galvanometer or microammeter under the rated working voltage within 8 hours shall not exceed 4% of the full length of the instrument scale
3.3 The input resistance of the DC amplifier shall be at least 100 times smaller than the insulation resistance of the sample. 3.4 When using a rectified DC power supply, the voltage must be stable. Any charging and discharging of the sample due to power supply voltage fluctuations should be small enough to be ignored compared to the leakage current when measuring the insulation voltage. At the same time, the ripple factor of the output voltage should not exceed 0.1%.
3.5 The connecting wire should be well shielded, and its insulation resistance to ground should be at least 100 times that of the input voltage of the amplifier. Approved by the State Administration of Technical Supervision on May 19, 1994, and implemented on January 1, 1995
4 Sample preparation
GB/T 3048. 6-94
Figure 1 Schematic diagram of the wiring of the voltage-current method (high impedance meter method) measurement system E-high impedance DC power supply; AD-high impedance DC amplifier; V-DC voltage drop; G-galvanometer or microammeter: R, DC amplifier input resistance, R sample insulation resistance,. AC input power supply voltage, DC output voltage amplifier input resistance voltage drop 4.1 Unless otherwise specified in the product standard, the effective length of the sample should not be less than 10m, and the covers outside the insulation at both ends of the sample should be carefully stripped off, and be careful not to damage the insulation surface.
4.2 The sample should be placed in the test environment for a long enough time to balance the sample temperature with the test temperature and keep it stable. 4.3 When testing in water, the length of the two ends of the sample exposed to the water surface should be not less than 250mm, and the length of the insulation part exposed should be not less than 150mme
When testing in air, the length of the insulation part exposed at the end of the sample should be not less than 100tmm, and the exposed insulation surface should be kept dry and clean. 5 Test steps
5.1 The general provisions are as follows:
5.1.1 For metal sheathed cable, screen-type cable or armored cable samples, for single-core cables, the insulation resistance between the conductor and the metal sheath or shielding layer or armoring layer should be measured; for multi-core cables, the insulation resistance of each conductor pair connected to the metal sheath or shielding layer or armoring layer should be measured separately. For non-metallic sheathed cable, non-shielded cable or unarmored cable samples, they should be immersed in water, and for single-core cables, the insulation resistance between the conductor and water should be measured; for multi-core cables, the insulation resistance of each conductor pair connected to the test rod should be measured separately. The sample can also be tightly wound around the metal test rod, and for single-core cables, the insulation resistance between the conductor and the test rod should be measured; for multi-core cables, the insulation resistance of each conductor pair connected to the test rod should be measured. The outer diameter of the test rod shall be as specified in the product standard.
5.1.2 Measurement error:
For the measured resistance value of 1×10\ and below, it shall not be greater than ±10%; for the measured resistance value of 1×101°2 and above, it shall not be greater than ±20%. 5.2 Connect the sample to the measuring system. The effective length measurement error of the sample shall not exceed ±1%. 5.3 Measure the insulation resistance R of the sample.
5.3.1 The measurement voltage of the sample shall be selected in the range specified in Chapter 1. 5.3.2 The charging time during measurement shall be sufficient to achieve basic stability of the measurement. Unless otherwise specified in the product standard, the charging time is specified as min.
5.3.3 Record the temperature during the test.
5.3.4 When repeating the test, the sample shall be short-circuited and discharged before powering on. The discharge time shall be no less than 4 times the charging time of the sample. 6 Test results and calculations
6.1 The insulation resistance of the sample is calculated according to the following formula:
Where: R——insulation resistance of the sample, MO;
U.—DC output voltage V;
R, input resistance, Mn.
U.\R: voltage drop, V.
GB/T3048.6—94
6.2 The insulation resistance per kilometer length is calculated according to the following formula: U.
Where: R.—insulation resistance per kilometer length, MQ·km; L—effective measurement length of the sample, km,
6.3 The insulation resistance per kilometer length at 20°C is calculated according to the following formula: R—KRL
Where: R2-
-20°C insulation resistance per kilometer length, MQ·kmtK insulation resistance temperature correction coefficient, specified by special documents. 6.4 The number of significant digits taken in the calculation result should be consistent with the product standard. 7 Precautions
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7.1 When necessary, it is allowed to add protective rings on the insulating surface of both ends of the sample. The protective ring should be close to the insulating surface and connected to the shield of the measurement system. bzxz.net
7.2 If the insulation resistance of the sample is greater than 1×1013 and the friction caused by the external electromagnetic field or the movement of the sample during measurement will cause unstable measurement, the measurement can be carried out under the condition that the sample is shielded as a whole. However, the insulation resistance of the measurement circuit to ground is at least 100 times greater than the input resistance of the amplifier. The shield must be reliably grounded. 7.3 If there is a significant difference in the measurement results due to residual charge on the sample, it must be fully discharged. 7.4 When using a high resistance meter with the output end suspended to the ground to measure the insulation resistance, it is recommended to connect the measuring end (low voltage end) of the high resistance meter to the conductor of the insulated wire core to be measured. If the other pole of the sample is measured with a non-floating high resistance meter with the output end to the ground, the sample must be insulated from the ground: otherwise, the high voltage end of the high resistance meter will be short-circuited to the ground and damaged. Additional remarks:
This standard is proposed by the Ministry of Machinery and Electronics Industry of the People's Republic of China. This standard is submitted by the Shanghai Cable 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. The main drafters of this standard are Zhu Zhongzhu 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.
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