Ningbo Qiaopu Electric Co., Ltd. power line insulation resistance test, comparison galvanometer

Ningbo Qiaopu Electric Co., Ltd. power line test equipment
Measurement system wiring diagram, the main components should meet the following requirements:
Galvanometer current constant is not greater than 10-9Ω/mm.
Shunt shunt factor should be able to 1 / 10000 to 1 / 1 to range, and adjust the series less than five, should be equal to or slightly greater than the critical resistance galvanometer external critical resistance, but not more than 20% .
Standard resistance is not less than 105Ω, the relative error of less than ± 5%.
DC output voltage, output voltage does not exceed ± 1%.
Shielding galvanometer, shunt, standard resistor, measuring cable and line components and shielding should be connected to the base, was shielded components and shielding than standard insulation resistance between the resistance of at least 200 times larger.
Galvanometer with a battery for the lighting power, the power supply must be placed within the shielding system. If AC power supply, it must be step-down transformer and low voltage side of the shield connected at one end.
Qiaopu power line power line sample preparation
Except as otherwise provided in the product standards, the effective length of the specimen is not less than 10m, outside of the insulation at both ends of the specimen should be carefully stripped cover, pay attention to not damage the insulation surface.
Sample should be placed in the test environment long enough time to allow the sample temperature and test temperature balance and stability.
Immersed in water test, the sample both ends above the surface of the length should be not less than 250mm, the length of exposed insulation should be not less than 150mm.
In the air tests, the sample exposed ends of the insulation jacket length should be not less than 100mm.
Exposed insulation surface should be kept dry and clean.
Ningbo Qiaopu Electric Co., Ltd. of test procedure
A general rule is as follows:
Metal sheath power cable, shielded power cable or power cable armored sample, single-core, should be measured on the metal conductor sets or armor, or shield between the insulation resistance; multi-core, should be separately on each The remaining lines of the core conductor and metal sleeve or shield or armor layer connection be measured.
Non-metallic sheathed power cable, unshielded power cord or power cable without armor sample shall be immersed in water, single-core conductor by measuring the insulation resistance between the water; multi-core conductor should be separately on each of the remaining lines core measurements and water connections. Samples can also be tightly wrapped around the metal rod on trial, single-core conductors of the power cord measuring the insulation resistance between the test bar; multi-core power cord cable measuring the remaining core of each conductor of the connecting rod with the insulation resistance test. Diameter test bar according to product standards.
Measurement error:
Measured resistance value of 1 * 1010Ω or less, not more than ± 10%
Measured resistance value of 1 * 1010Ω more, no more than ± 20%
2 access to the sample measurement system. The effective sample length measurement error should not exceed ± 5%.
3 measure resistance RN. Closed switch S2, and then close S1, appropriate adjustments shunt diversion coefficient P, the galvanometer G has a significant deflection readings. Record deflection readings αN and the split ratio nN.
Insulation resistance measurement sample 4 RX:
Disconnect switch S2, step by step adjustment factor shunt diversion of P, so that the galvanometer G has a significant deflection readings. Record deflection readings αX, split ratio nX and the charging time t.
Measuring the charging time should be sufficient to achieve stable measurement. In addition to the product standards as otherwise provided, the charging time of 1min.
5 record time of the test temperature.
4 repeat tests, the applied voltage, before closing switch S2, the sample short-circuit discharge, the discharge time should be no less than four times the sample charging time.
5 Ningbo Qiaopu Electric Co., Ltd. The results and calculations
1 specimen insulation resistance calculated as follows:
RX = RN · (αNnX / αXnN) (1)
Where: RX - sample insulation resistance, MΩ;
RN - standard resistance, MΩ;
αN - measure resistance galvanometer deflection readings;
nN - measure the shunt shunt resistance coefficient;
αX - measuring specimen deflection galvanometer readings;
nX - when measuring the sample coefficient of shunt diversion.
1.5.2 Insulation resistance per kilometer length of the formula:
RL = RXL (2)
Where: RL - per kilometer length of the insulation resistance, MΩ · km;
L - effective measurement of the length of the sample, km.
1.5.3 20 ℃ when the insulation resistance per kilometer length of the formula:
R20 = K RL (3)
Where: R20 - 20 ℃ per kilometer length of the insulation resistance, MΩ · km;
K - insulation resistance temperature correction factor, provided by the special file.
1.5.4 The results obtained by the number of significant figures should be consistent with product standard requirements.