Reproduction of fault causing flashovers.
Laboratory test with UV camera on insulators removed from power line
by: Ildiko Fogarasi, Dr.
Ottó Gúntner, Dr. László Varga
Damage of a 5 years old polymer insulator on
a power line.
On this power line, outages occured during
wet foggy weather due to flashovers caused by a damaged composite
insulator.
The insulator was located at the middle line of a three-part chain.
This damaged insulator was removed from the line and sent to our
laboratory where we tried to reproduce
the mechanism of failure in dry and wet conditions.
We found that in dry conditions, flashover does
not occur and corona cannot be seen. In wet conditions, however,
corona effect was observed with UV camera before flashover occurred
at the rated voltage.
Chain of three parts – the length is shorter probably in
order to keep the original length as it was with the porcelain insulator.
Porcelain replaced with polymer insulator
Note the carbonization signs on the central defective insulator
Insulator damage
The puncture of the polymer is on the area of the live end.
As humidity started penetrating the rod the boiling water pressure
and the prolonged corona and arcing cracked the insulator
Please note the carbonization signs
Damage under the lowest shed
Broken silicone rubber covering
between sheds
Damaged Silicone Rubber Covering
Damaged Core
Reproduction
of a fault by laboratory tests on new insulators
Generation of supposed fault: Dielectric strength test under wet condition
Test carried out with the original insulators
The voltage was stable - 140kV
Humidity was raised – please note the way the failure evolves
up to the evolution of the flashover
Fault detection with UV and infrared
camera
Detection of damage with UV camera
Detection of temperature rise with IR camera
These
images were taken after accelerated aging test of two years.
Corona detection could detect the fault long before the polymer is
punctured. This is also shown in the STRI
tests on UGM 2. The early detection of the fault is the advantage
of the UV detection.
