10kv High Tension Power Cables Test Notes
1. DC voltage cable insulation volume resistivity of the electric field distribution depends on the material, and the electric field distribution depends on the AC voltage of each of the dielectric constant of the medium, especially in the DC cable terminal head, connector boxes and other cable accessories in alternating electric field intensity distribution and the distribution of the field strength is completely different, and the mechanism and the mechanism of aging DC voltage AC voltage insulation aging is not the same. Therefore, the DC voltage test can not simulate high voltage cable operating conditions.
2. 10Kv High tension power cable in the DC voltage will have a "memory" effect, unipolar accumulation of residual charge storage. Once you have the test because the DC voltage caused by "memory", that will take a long time to release the DC bias. If the DC cable before the release of residual charge is not fully operational, it will be superimposed on the DC bias power frequency voltage peak, the cable so that the voltage value far exceeds its rated voltage, which may cause the cable insulation breakdown.
3. DC voltage test, there will be injected into the polymer inside the electronic media, the formation of space charge, so reducing the electric field strength of the premises, making it difficult to breakdown occurs. Semiconductor contamination and projections at the point of high-voltage cables, etc. prone to space charge. However, if the cable terminal head occurs when the surface flashover test cable attachment or breakdown will cause the cable core line generated wave oscillation, has been the accumulation of space charge of the place, since the oscillation voltage polarity is rapidly changing different polarity, so that the at a field strength significantly increased, it may damage the insulation, resulting in more clicks to wear.
4. The 10kV high tension power cable fatal weakness is easy to produce water tree inside insulation, once the water branch, in the DC voltage will be rapidly converted into electrical trees, and the formation of discharge and accelerated the deterioration of insulation, so after running frequency voltage is formed under the action breakdown. And pure water trees in the AC operating voltage can remain fairly voltage value, and can be maintained for a period of time.
