Because the equivalent frequency of operating voltage is higher than the power frequency voltage, duration is shorter than a minute frequency. Insulation structure in the operating voltage of the discharge characteristics, the breakdown mechanism and frequency, the impact is not the same. The operation does not cause the effect of wave oscillation, a long time, for the same voltage, the coil will be more severe than the impulse test. Compared to frequency voltage,operation wave is directly caused by the oil gap breakdown. The small oil cylinder gap thin insulation structure of transformer is more necessary.
If insulation level is reduced, the power frequency and frequency test may cause partial damage. This residual weakness in the test is not easy to find. But under the long term working voltage, it will gradually develop to lead to the breakdown of insulation. Generally partial discharge occurs in operation wave , it will not caused residual damage.
The operating waveform is close to the voltage in the operation. The authenticity is strong. The equivalent power frequency voltage is more reasonable, and the main longitudinal insulation are all evaluated, which has the advantages of portable equipment, sensitive display, no large power supply and so on.
The frequency or frequency test, ready to spend huge sums of equipment, heavy workload, the scene often give the test of safety equipment will be without clear aims. It is necessary and feasible to test the insulation of the transformer by using the operating wave test.
Inductance operating impulse waveform
Wave front length; Tf ≥100μs
Wave tail length; Tt ≥100μs
90% amplitude duration: ≥200μs
peak reverse voltage:U2M≤0.5 UM
≥－[100×1000(0)×200(90)]μs
Circuit of inductance operating impulse wave
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