1. The background of high voltage power cable partial discharge test

1.1 high voltage power cable application

XLPE cable with its good characters on high electrical property, big capacity in transmission line, light weight, easy installation and maintain, they play great important role in high voltage transmission line.

2. Malfunction on high voltage power cable

The main problem happened on high voltage transmission line is cable quality and installed skill, and above 90% problem happened due to cable accessory. The poor design or wrong material used, scrappy skill on cable termination and jointing make cable problem happened in high rate.

3. The necessity for partial discharge test on high voltage power cable

With requirement of Standard for Hand-Over Test of Electric Equipment Electric Equipment Installation Engineering -GB 50150, any project when finished should have voltage withstand test, AC cable voltage withstand test.

2. The causes of partial discharge happened in cables
   • partial discharge

In electrical engineering, partial discharge (PD) is a localized dielectric breakdown of a small portion of a solid or fluid electrical insulation system under high voltage stress, which does not bridge the space between two conductors.

• location in partial discharge

XLPE cables are insulated with a solid plastic structure.In the manufacturing process such as mixed with metal impurities, the appearance of air holes, or due to the inside, outside the semiconductor layer irregular process caused by the high voltage field intensity is not uniform, or insulation in the electric tree, etc., in these parts are likely to appear.With the development of cable manufacturing technology and the continuous improvement of quality control level, the bureau caused by the above reasons in the field test has been very small.Local discharge points detected in cross-linked polyethylene cables are generally found in intermediate joints and terminal heads

• the damage if partial discharge happened

The partial discharge energy is very small and usually does not affect the short term insulation strength of the cable.However, partial discharge exists for a long time, which can slowly damage the insulation and eventually lead to insulation breakdown.In addition, due to the chemical properties, the performance of cross-linked polyethylene insulated cable is poor in partial discharge resistance. The long partial discharge will accelerate the insulation degradation and eventually cause its failure.