gui chao cable news: wire and cable finished voltage withstand test
from：guichao author：admin click： 630 addtime：2017-04-22 14:33:41
1 ac voltage test
the voltage withstand test of the product is ac voltage test.
ac withstand voltage test is on the wire and cable insulation
applying a voltage higher than the operating voltage (rated voltage),
keep a certain amount of time without insulation breakdown.
insulated wires and cables for power transmission,
each product must be tested before leaving the factory.
the purpose of the pressure test is to check the product at the operating voltage
reliability of operation and serious defects found in insulation,
but the most important thing is to find defects in the production process,
for example: the damage of the insulation, the conductor has a serious distortion of the electric field distortion.
voltage test voltage selection principle is: it is necessary to be able to find a serious defect in insulation,
at the same time without damage to good insulation, resulting in insulation injury.
general wire and cable withstand time is 5 minutes.
2 test equipment requirements
the test voltage should be 40 ~ 60 hz ac voltage,
the waveform of the voltage is close to the sine wave.
the test voltage and pressure time of the sample shall be carried out according to the relevant product standards.
3 test methods
3.1 preparation of test samples
length of sample terminal part and method for making terminal,
it shall ensure that no flashover discharge or internal breakdown occurs along the surface of the test voltage.
when the test is carried out in the flume, the length of the two ends of the sample extending out of the water surface shall not be less than 200mm,
it should be ensured that the flashover discharge does not occur along the surface of the test voltage.
3.2 test procedure
the test procedure is carried out according to the operating rules of the pressure test. (field operation)
the difference between the temperature of the test and the ambient temperature should not exceed 3.
during the test, the voltage should be lower
(should not exceed 40% of the test voltage specified in the product standard),
slowly and steadily rise to the specified test voltage value, and maintain the specified pressure time,
reduce the voltage until the specified test voltage value of 40%, and then cut off the power supply,
do not allow to cut off the power supply under high pressure in order to avoid over voltage.
3.3 voltage test evaluation
the sample has no breakdown in the specified test voltage and duration,
it can be considered that the sample is tested by the power frequency withstand voltage test.
if in the course of the experiment,
the end or end of the sample occurs along its surface flashover discharge or internal breakdown,
allow other end connections, and repeat the test.
in addition to the special provisions in the product standards, must be re timed.
in the course of the experiment, the test was continued after the blackout,
unless otherwise specified in the product standard, it must be re timed.
3.4 ac withstand voltage test notes
(a) test equipment shall be calibrated periodically;
(b) test circuit shall have a fast overcurrent protection device,
to ensure that when the test breakdown or end or end of the sample occurs
when the surface flashover discharge or internal breakdown, the power supply can be rapidly removed.
c) there should be a metal grounding fence around the test area,
signal indicator and safety measures such as "high voltage danger".
d) the test area shall have a ground wire and the grounding resistance shall be less than 4 ohms,
the earthing end of the step-up transformer and the earthing end or additional electrode of the sample should be connected reliably with the grounding electrode.