Abstract:
—For high voltage dc cable insulation, LDPE is
considered as a prospective material. With increasing voltage
levels of power transmission, the need for understanding high
filed phenomena is also increasing. In general a strong interrelation
among leakage current, space charge, breakdown and
ageing of insulation is believed to exist. The leakage or
conduction current in LDPE is very important due to the fact
that it is linked to charge accumulation in it. It is of very
interesting to observe current dynamics in LDPE at high fields
due to the fact that charge packets emerge from electrodes and
move into the insulation - a phenomena known as packet charge
formation. In the present paper authors report long-term current
measurements on thin LDPE samples under different types of
electric field application. The measurements are performed using
a guarded three-terminal electrode system. The difference in
current profiles between short duration voltage application and
long duration application has been examined. A significant
difference has been observed in the leakage current profiles for
different voltage time durations and different history of voltage
application which may indicate different type of charge
formation.
